Tagged: Perovskites Toggle Comment Threads | Keyboard Shortcuts

  • richardmitnick 8:20 am on September 20, 2021 Permalink | Reply
    Tags: "A simple way to get complex semiconductors to assemble themselves", , , , Entirely new and unexpected properties could emerge at the interfaces where layers meet., Growing 2D perovskites precisely layered with other 2D materials to produce crystals with a wide range of electronic properties., Layering perovskites with other materials could combine their properties in ways that improve their performance in specific applications., Perovskites, , Stacking extremely thin films of material on top of each other can create new materials with exciting new properties., The new method lays the foundation for making a wide array of complex semiconductors in a much more deliberate way.   

    From DOE’s SLAC National Accelerator Laboratory (US) : “A simple way to get complex semiconductors to assemble themselves” 

    From DOE’s SLAC National Accelerator Laboratory (US)

    September 15, 2021
    Glennda Chui

    Much like crystallizing rock candy from sugar syrup, the new method grows 2D perovskites precisely layered with other 2D materials to produce crystals with a wide range of electronic properties.

    1
    A diagram shows how layers of two 2D materials – a perovskite (blue) and a metal halide (yellow) – assemble themselves out of chemicals tumbling around in water (left). The assembly is directed by linker molecules that look like barbells. Each end of a barbell (blue or yellow) carries a chemical template for growing one of the layers, and as the layers grow, the barbells link them together in the correct order. The new self-assembly technique, developed by SLAC and Stanford researchers, produces large crystals with a wide range of electronic properties. Credit: Jiayi Li/Stanford University (US).

    Stacking extremely thin films of material on top of each other can create new materials with exciting new properties. But the most successful processes for building those stacks can be tedious and imperfect, and not well suited for large-scale production.

    Now a team led by Stanford Professor Hemamala Karunadasa has created a much simpler and faster way to do it. They grew 2D layers of one of the most sought-after materials, known as perovskites, interleaved with thin layers of other materials in large crystals that assemble themselves.

    The assembly takes place in vials where the chemical ingredients for the layers tumble around in water, along with barbell-shaped molecules that direct the action. Each end of a barbell carries a template for growing one type of layer. As the layers crystallize – a process similar to making rock candy — the barbells automatically link them together in the proper order.

    “What’s really cool is that these complex layered materials spontaneously crystallize,” said Michael Aubrey, who was a postdoctoral researcher in Karunadasa’s lab at the time of the study.

    The researchers say their method lays the foundation for making a wide array of complex semiconductors in a much more deliberate way, including combinations of materials that have not been known to pair up in crystals before. They described the work in a paper published in Nature today.

    “We are pretty thrilled about this general strategy that can be expanded to so many kinds of materials,” said Karunadasa, who is an investigator with the Stanford Institute for Materials and Energy Sciences (SIMES) at the Department of Energy’s SLAC National Accelerator Laboratory.

    “Rather than manipulating materials one layer at time,” she said, “we’re just throwing the ions into a pot of water and letting the ions assemble the way they want to assemble. We can make grams of this stuff, and we know where the atoms are in the crystals. This level of precision allows me to know what the interfaces between the layers really look like, which is important for determining the material’s electronic structure – how its electrons behave”

    Easy to make, hard to stack

    Halide perovskites – materials that have the same octahedral structure as naturally occurring perovskite minereals – have been assembled in water since the 1900s, Aubrey said. They have a lot of potential for efficiently absorbing sunlight in solar cells and converting it to electricity, but they’re also notoriously unstable, especially in the hot, brilliantly lit environments that photovoltaics operate in.

    Layering perovskites with other materials could combine their properties in ways that improve their performance in specific applications. But an even more exciting prospect is that entirely new and unexpected properties could emerge at the interfaces where layers meet; for instance, scientists have previously discovered that stacking thin films of two different types of insulators can create an electrical conductor.

    It’s hard to predict which combinations of materials will turn out to be interesting and useful. What’s more, making thinly layered materials has been a slow, painstaking process. Layers are generally made by peeling films just one or two atoms thick, one at a time, from a bigger chunk of material. That’s how graphene is made from graphite, a pure form of carbon used in pencil leads. In other cases, these thinly layered materials are made in tiny batches at very high temperatures.

    “The way they’re made has not been scalable and sometimes even difficult to reproduce from one batch to another,” Karunadasa said. “Peeling off layers that are just one or two atoms thick is specialized work; it is not something you and I can just go into the lab and do. These sheets are like a very flexible deck of cards; when you take one out, it can crumple or buckle. So it is hard to know the exact structure of the final stack. There is very little precedent for materials that look like the ones we created in this study.”

    2
    This animation shows how a 2D layer of material that’s being interwoven with a 2D perovskite (which is not shown) has to distort slightly to form a tight interface with the perovskite’s atomic lattice. Both types of layers assemble themselves from chemicals in water with the help of molecules shaped like barbells. These barbells carry templates that direct the assembly and link the finished layers in the correct order. The new self-assembly technique, developed by SLAC and Stanford researchers, produces large crystals with a wide range of electronic properties. (Michael Aubrey/Stanford University.)

    Rock candy synthesis

    This work grew out of research by study co-author Abraham Saldivar Valdes, a graduate student in Karunadasa’s group at the time. Over the course of several years, he developed the new method for getting the layered structures to assemble themselves, which was further expanded by graduate student Bridget Connor. Meanwhile, Aubrey discovered that their atomically thin layers had the same structure as 3D blocks of similar materials whose properties were already known, and he tracked how the two different layers have to slightly distort to share an interface. He also studied the optical properties of the final products with the help of graduate student Kurt Lindquist.

    Creating the layered structures “is the same exact process as making rock candy, where you drop a wooden dowel into saturated sugar solution and the candy crystals seed themselves onto the dowel,” Aubrey said. “But in this case the starting materials are different and you don’t need a dowel – crystals will start forming in water or on the surface of the glass vial.”

    The team made six of the self-assembled materials, interleaving perovskites with metal halides or metal sulfides, and examined them with X-rays at the Advanced Light Source at DOE’s Lawrence Berkeley National Laboratory (US).

    DOE’s Lawrence Berkeley National Laboratory (US) Advanced Light Source.

    In most of the structures, the barbell molecules held the layers slightly apart. But in one of them the barbell molecules brought the layers directly into contact with each other so they could form chemical bonds.

    3
    The way 2D layers are linked in self-assembled crystals can have a big impact on their electronic structure, which determines their properties. In the material at top left, the links hold the layers slightly apart (see inset). When this material is hit with light to free electrons and create positively charged holes (in orange at top right), both concentrate in the perovskite layers. In contrast, the links in the material at bottom left (see inset) hold the layers so closely together that they can form direct chemical bonds. When this material is hit with light (bottom right), electrons stay mostly in one type of layer and holes in the other. Such emergent properties are a particularly exciting consequence of interfaces between two different types of structures. (Michael Aubrey/Stanford University.)

    “We are particularly excited about this type of structure where the layers are connected because it could lead to emergent properties, like electronic excitations that are distributed across both layers,” Karunadasa said.

    “And in this particular case, when we hit the material with light to free electrons and create positively charged holes, we found the electrons mostly in one type of layer and the holes mostly in the other. This is important in our field, because it allows you to tune those two environments to get the electronic behavior you want.”

    With the new technique in hand, Aubrey said, “We’re doing a lot of exploration now to discover what kinds of structures can be made with it.”

    Marina Filip and Jeffrey Neaton from The University of California-Berkeley (US) and DOE’s Lawrence Berkeley National Laboratory (US) performed the electronic structure calculations in this work. This research was funded by the DOE Office of Science. ALS is an Office of Science user facility, as are two other facilities where computing was done for this research: the National Energy Research Scientific Computing Center (NERSC) and the Oak Ridge Leadership Computing Facility.

    See the full article here .


    five-ways-keep-your-child-safe-school-shootings
    Please help promote STEM in your local schools.

    Stem Education Coalition

    SLAC National Accelerator Laboratory (US) originally named Stanford Linear Accelerator Center, is a Department of Energy (US) National Laboratory operated by Stanford University (US) under the programmatic direction of the Department of Energy (US) Office of Science and located in Menlo Park, California. It is the site of the Stanford Linear Accelerator, a 3.2 kilometer (2-mile) linear accelerator constructed in 1966 and shut down in the 2000s, which could accelerate electrons to energies of 50 GeV.
    Today SLAC research centers on a broad program in atomic and solid-state physics, chemistry, biology, and medicine using X-rays from synchrotron radiation and a free-electron laser as well as experimental and theoretical research in elementary particle physics, astroparticle physics, and cosmology.

    Founded in 1962 as the Stanford Linear Accelerator Center, the facility is located on 172 hectares (426 acres) of Stanford University-owned land on Sand Hill Road in Menlo Park, California—just west of the University’s main campus. The main accelerator is 3.2 kilometers (2 mi) long—the longest linear accelerator in the world—and has been operational since 1966.

    Research at SLAC has produced three Nobel Prizes in Physics

    1976: The charm quark—see J/ψ meson
    1990: Quark structure inside protons and neutrons
    1995: The tau lepton

    SLAC’s meeting facilities also provided a venue for the Homebrew Computer Club and other pioneers of the home computer revolution of the late 1970s and early 1980s.

    In 1984 the laboratory was named an ASME National Historic Engineering Landmark and an IEEE Milestone.

    SLAC developed and, in December 1991, began hosting the first World Wide Web server outside of Europe.

    In the early-to-mid 1990s, the Stanford Linear Collider (SLC) investigated the properties of the Z boson using the Stanford Large Detector.

    As of 2005, SLAC employed over 1,000 people, some 150 of whom were physicists with doctorate degrees, and served over 3,000 visiting researchers yearly, operating particle accelerators for high-energy physics and the Stanford Synchrotron Radiation Laboratory (SSRL) [below] for synchrotron light radiation research, which was “indispensable” in the research leading to the 2006 Nobel Prize in Chemistry awarded to Stanford Professor Roger D. Kornberg.

    In October 2008, the Department of Energy announced that the center’s name would be changed to SLAC National Accelerator Laboratory. The reasons given include a better representation of the new direction of the lab and the ability to trademark the laboratory’s name. Stanford University had legally opposed the Department of Energy’s attempt to trademark “Stanford Linear Accelerator Center”.

    In March 2009, it was announced that the SLAC National Accelerator Laboratory was to receive $68.3 million in Recovery Act Funding to be disbursed by Department of Energy’s Office of Science.

    In October 2016, Bits and Watts launched as a collaboration between SLAC and Stanford University to design “better, greener electric grids”. SLAC later pulled out over concerns about an industry partner, the state-owned Chinese electric utility.

    Accelerator

    The main accelerator was an RF linear accelerator that accelerated electrons and positrons up to 50 GeV. At 3.2 km (2.0 mi) long, the accelerator was the longest linear accelerator in the world, and was claimed to be “the world’s most straight object.” until 2017 when the European x-ray free electron laser opened. The main accelerator is buried 9 m (30 ft) below ground and passes underneath Interstate Highway 280. The above-ground klystron gallery atop the beamline, was the longest building in the United States until the LIGO project’s twin interferometers were completed in 1999. It is easily distinguishable from the air and is marked as a visual waypoint on aeronautical charts.

    A portion of the original linear accelerator is now part of the Linac Coherent Light Source [below].

    Stanford Linear Collider

    The Stanford Linear Collider was a linear accelerator that collided electrons and positrons at SLAC. The center of mass energy was about 90 GeV, equal to the mass of the Z boson, which the accelerator was designed to study. Grad student Barrett D. Milliken discovered the first Z event on 12 April 1989 while poring over the previous day’s computer data from the Mark II detector. The bulk of the data was collected by the SLAC Large Detector, which came online in 1991. Although largely overshadowed by the Large Electron–Positron Collider at CERN, which began running in 1989, the highly polarized electron beam at SLC (close to 80%) made certain unique measurements possible, such as parity violation in Z Boson-b quark coupling.

    European Organization for Nuclear Research [Organisation européenne pour la recherche nucléaire](CH) LEP Collider

    Presently no beam enters the south and north arcs in the machine, which leads to the Final Focus, therefore this section is mothballed to run beam into the PEP2 section from the beam switchyard.

    The SLAC Large Detector (SLD) was the main detector for the Stanford Linear Collider. It was designed primarily to detect Z bosons produced by the accelerator’s electron-positron collisions. Built in 1991, the SLD operated from 1992 to 1998.

    SLAC National Accelerator Laboratory(US)Large Detector

    PEP

    PEP (Positron-Electron Project) began operation in 1980, with center-of-mass energies up to 29 GeV. At its apex, PEP had five large particle detectors in operation, as well as a sixth smaller detector. About 300 researchers made used of PEP. PEP stopped operating in 1990, and PEP-II began construction in 1994.

    PEP-II

    From 1999 to 2008, the main purpose of the linear accelerator was to inject electrons and positrons into the PEP-II accelerator, an electron-positron collider with a pair of storage rings 2.2 km (1.4 mi) in circumference. PEP-II was host to the BaBar experiment, one of the so-called B-Factory experiments studying charge-parity symmetry.

    SLAC National Accelerator Laboratory(US) BaBar

    SLAC National Accelerator Laboratory(US)/SSRL

    Fermi Gamma-ray Space Telescope

    SLAC plays a primary role in the mission and operation of the Fermi Gamma-ray Space Telescope, launched in August 2008. The principal scientific objectives of this mission are:

    To understand the mechanisms of particle acceleration in AGNs, pulsars, and SNRs.
    To resolve the gamma-ray sky: unidentified sources and diffuse emission.
    To determine the high-energy behavior of gamma-ray bursts and transients.
    To probe dark matter and fundamental physics.


    KIPAC

    The Stanford PULSE Institute (PULSE) is a Stanford Independent Laboratory located in the Central Laboratory at SLAC. PULSE was created by Stanford in 2005 to help Stanford faculty and SLAC scientists develop ultrafast x-ray research at LCLS.

    The Linac Coherent Light Source (LCLS)[below] is a free electron laser facility located at SLAC. The LCLS is partially a reconstruction of the last 1/3 of the original linear accelerator at SLAC, and can deliver extremely intense x-ray radiation for research in a number of areas. It achieved first lasing in April 2009.

    The laser produces hard X-rays, 10^9 times the relative brightness of traditional synchrotron sources and is the most powerful x-ray source in the world. LCLS enables a variety of new experiments and provides enhancements for existing experimental methods. Often, x-rays are used to take “snapshots” of objects at the atomic level before obliterating samples. The laser’s wavelength, ranging from 6.2 to 0.13 nm (200 to 9500 electron volts (eV)) is similar to the width of an atom, providing extremely detailed information that was previously unattainable. Additionally, the laser is capable of capturing images with a “shutter speed” measured in femtoseconds, or million-billionths of a second, necessary because the intensity of the beam is often high enough so that the sample explodes on the femtosecond timescale.

    The LCLS-II [below] project is to provide a major upgrade to LCLS by adding two new X-ray laser beams. The new system will utilize the 500 m (1,600 ft) of existing tunnel to add a new superconducting accelerator at 4 GeV and two new sets of undulators that will increase the available energy range of LCLS. The advancement from the discoveries using this new capabilities may include new drugs, next-generation computers, and new materials.

    FACET

    In 2012, the first two-thirds (~2 km) of the original SLAC LINAC were recommissioned for a new user facility, the Facility for Advanced Accelerator Experimental Tests (FACET). This facility was capable of delivering 20 GeV, 3 nC electron (and positron) beams with short bunch lengths and small spot sizes, ideal for beam-driven plasma acceleration studies. The facility ended operations in 2016 for the constructions of LCLS-II which will occupy the first third of the SLAC LINAC. The FACET-II project will re-establish electron and positron beams in the middle third of the LINAC for the continuation of beam-driven plasma acceleration studies in 2019.

    The Next Linear Collider Test Accelerator (NLCTA) is a 60-120 MeV high-brightness electron beam linear accelerator used for experiments on advanced beam manipulation and acceleration techniques. It is located at SLAC’s end station B.

    SSRL and LCLS are DOE Office of Science user facilities.

    Stanford University (US)

    Leland and Jane Stanford founded the University to “promote the public welfare by exercising an influence on behalf of humanity and civilization.” Stanford opened its doors in 1891, and more than a century later, it remains dedicated to finding solutions to the great challenges of the day and to preparing our students for leadership in today’s complex world. Stanford, is an American private research university located in Stanford, California on an 8,180-acre (3,310 ha) campus near Palo Alto. Since 1952, more than 54 Stanford faculty, staff, and alumni have won the Nobel Prize, including 19 current faculty members.

    Stanford University, officially Leland Stanford Junior University, is a private research university located in Stanford, California. Stanford was founded in 1885 by Leland and Jane Stanford in memory of their only child, Leland Stanford Jr., who had died of typhoid fever at age 15 the previous year. Stanford is consistently ranked as among the most prestigious and top universities in the world by major education publications. It is also one of the top fundraising institutions in the country, becoming the first school to raise more than a billion dollars in a year.

    Leland Stanford was a U.S. senator and former governor of California who made his fortune as a railroad tycoon. The school admitted its first students on October 1, 1891, as a coeducational and non-denominational institution. Stanford University struggled financially after the death of Leland Stanford in 1893 and again after much of the campus was damaged by the 1906 San Francisco earthquake. Following World War II, provost Frederick Terman supported faculty and graduates’ entrepreneurialism to build self-sufficient local industry in what would later be known as Silicon Valley.

    The university is organized around seven schools: three schools consisting of 40 academic departments at the undergraduate level as well as four professional schools that focus on graduate programs in law, medicine, education, and business. All schools are on the same campus. Students compete in 36 varsity sports, and the university is one of two private institutions in the Division I FBS Pac-12 Conference. It has gained 126 NCAA team championships, and Stanford has won the NACDA Directors’ Cup for 24 consecutive years, beginning in 1994–1995. In addition, Stanford students and alumni have won 270 Olympic medals including 139 gold medals.

    As of October 2020, 84 Nobel laureates, 28 Turing Award laureates, and eight Fields Medalists have been affiliated with Stanford as students, alumni, faculty, or staff. In addition, Stanford is particularly noted for its entrepreneurship and is one of the most successful universities in attracting funding for start-ups. Stanford alumni have founded numerous companies, which combined produce more than $2.7 trillion in annual revenue, roughly equivalent to the 7th largest economy in the world (as of 2020). Stanford is the alma mater of one president of the United States (Herbert Hoover), 74 living billionaires, and 17 astronauts. It is also one of the leading producers of Fulbright Scholars, Marshall Scholars, Rhodes Scholars, and members of the United States Congress.

    Stanford University was founded in 1885 by Leland and Jane Stanford, dedicated to Leland Stanford Jr, their only child. The institution opened in 1891 on Stanford’s previous Palo Alto farm.

    Jane and Leland Stanford modeled their university after the great eastern universities, most specifically Cornell University. Stanford opened being called the “Cornell of the West” in 1891 due to faculty being former Cornell affiliates (either professors, alumni, or both) including its first president, David Starr Jordan, and second president, John Casper Branner. Both Cornell and Stanford were among the first to have higher education be accessible, nonsectarian, and open to women as well as to men. Cornell is credited as one of the first American universities to adopt this radical departure from traditional education, and Stanford became an early adopter as well.

    Despite being impacted by earthquakes in both 1906 and 1989, the campus was rebuilt each time. In 1919, The Hoover Institution on War, Revolution and Peace was started by Herbert Hoover to preserve artifacts related to World War I. The Stanford Medical Center, completed in 1959, is a teaching hospital with over 800 beds. The DOE’s SLAC National Accelerator Laboratory(US)(originally named the Stanford Linear Accelerator Center), established in 1962, performs research in particle physics.

    Land

    Most of Stanford is on an 8,180-acre (12.8 sq mi; 33.1 km^2) campus, one of the largest in the United States. It is located on the San Francisco Peninsula, in the northwest part of the Santa Clara Valley (Silicon Valley) approximately 37 miles (60 km) southeast of San Francisco and approximately 20 miles (30 km) northwest of San Jose. In 2008, 60% of this land remained undeveloped.

    Stanford’s main campus includes a census-designated place within unincorporated Santa Clara County, although some of the university land (such as the Stanford Shopping Center and the Stanford Research Park) is within the city limits of Palo Alto. The campus also includes much land in unincorporated San Mateo County (including the SLAC National Accelerator Laboratory and the Jasper Ridge Biological Preserve), as well as in the city limits of Menlo Park (Stanford Hills neighborhood), Woodside, and Portola Valley.

    Non-central campus

    Stanford currently operates in various locations outside of its central campus.

    On the founding grant:

    Jasper Ridge Biological Preserve is a 1,200-acre (490 ha) natural reserve south of the central campus owned by the university and used by wildlife biologists for research.
    SLAC National Accelerator Laboratory is a facility west of the central campus operated by the university for the Department of Energy. It contains the longest linear particle accelerator in the world, 2 miles (3.2 km) on 426 acres (172 ha) of land.
    Golf course and a seasonal lake: The university also has its own golf course and a seasonal lake (Lake Lagunita, actually an irrigation reservoir), both home to the vulnerable California tiger salamander. As of 2012 Lake Lagunita was often dry and the university had no plans to artificially fill it.

    Off the founding grant:

    Hopkins Marine Station, in Pacific Grove, California, is a marine biology research center owned by the university since 1892.
    Study abroad locations: unlike typical study abroad programs, Stanford itself operates in several locations around the world; thus, each location has Stanford faculty-in-residence and staff in addition to students, creating a “mini-Stanford”.

    Redwood City campus for many of the university’s administrative offices located in Redwood City, California, a few miles north of the main campus. In 2005, the university purchased a small, 35-acre (14 ha) campus in Midpoint Technology Park intended for staff offices; development was delayed by The Great Recession. In 2015 the university announced a development plan and the Redwood City campus opened in March 2019.

    The Bass Center in Washington, DC provides a base, including housing, for the Stanford in Washington program for undergraduates. It includes a small art gallery open to the public.

    China: Stanford Center at Peking University, housed in the Lee Jung Sen Building, is a small center for researchers and students in collaboration with Beijing University [北京大学](CN) (Kavli Institute for Astronomy and Astrophysics at Peking University(CN) (KIAA-PKU).

    Administration and organization

    Stanford is a private, non-profit university that is administered as a corporate trust governed by a privately appointed board of trustees with a maximum membership of 38. Trustees serve five-year terms (not more than two consecutive terms) and meet five times annually.[83] A new trustee is chosen by the current trustees by ballot. The Stanford trustees also oversee the Stanford Research Park, the Stanford Shopping Center, the Cantor Center for Visual Arts, Stanford University Medical Center, and many associated medical facilities (including the Lucile Packard Children’s Hospital).

    The board appoints a president to serve as the chief executive officer of the university, to prescribe the duties of professors and course of study, to manage financial and business affairs, and to appoint nine vice presidents. The provost is the chief academic and budget officer, to whom the deans of each of the seven schools report. Persis Drell became the 13th provost in February 2017.

    As of 2018, the university was organized into seven academic schools. The schools of Humanities and Sciences (27 departments), Engineering (nine departments), and Earth, Energy & Environmental Sciences (four departments) have both graduate and undergraduate programs while the Schools of Law, Medicine, Education and Business have graduate programs only. The powers and authority of the faculty are vested in the Academic Council, which is made up of tenure and non-tenure line faculty, research faculty, senior fellows in some policy centers and institutes, the president of the university, and some other academic administrators, but most matters are handled by the Faculty Senate, made up of 55 elected representatives of the faculty.

    The Associated Students of Stanford University (ASSU) is the student government for Stanford and all registered students are members. Its elected leadership consists of the Undergraduate Senate elected by the undergraduate students, the Graduate Student Council elected by the graduate students, and the President and Vice President elected as a ticket by the entire student body.

    Stanford is the beneficiary of a special clause in the California Constitution, which explicitly exempts Stanford property from taxation so long as the property is used for educational purposes.

    Endowment and donations

    The university’s endowment, managed by the Stanford Management Company, was valued at $27.7 billion as of August 31, 2019. Payouts from the Stanford endowment covered approximately 21.8% of university expenses in the 2019 fiscal year. In the 2018 NACUBO-TIAA survey of colleges and universities in the United States and Canada, only Harvard University(US), the University of Texas System(US), and Yale University(US) had larger endowments than Stanford.

    In 2006, President John L. Hennessy launched a five-year campaign called the Stanford Challenge, which reached its $4.3 billion fundraising goal in 2009, two years ahead of time, but continued fundraising for the duration of the campaign. It concluded on December 31, 2011, having raised a total of $6.23 billion and breaking the previous campaign fundraising record of $3.88 billion held by Yale. Specifically, the campaign raised $253.7 million for undergraduate financial aid, as well as $2.33 billion for its initiative in “Seeking Solutions” to global problems, $1.61 billion for “Educating Leaders” by improving K-12 education, and $2.11 billion for “Foundation of Excellence” aimed at providing academic support for Stanford students and faculty. Funds supported 366 new fellowships for graduate students, 139 new endowed chairs for faculty, and 38 new or renovated buildings. The new funding also enabled the construction of a facility for stem cell research; a new campus for the business school; an expansion of the law school; a new Engineering Quad; a new art and art history building; an on-campus concert hall; a new art museum; and a planned expansion of the medical school, among other things. In 2012, the university raised $1.035 billion, becoming the first school to raise more than a billion dollars in a year.

    Research centers and institutes

    DOE’s SLAC National Accelerator Laboratory(US)
    Stanford Research Institute, a center of innovation to support economic development in the region.
    Hoover Institution, a conservative American public policy institution and research institution that promotes personal and economic liberty, free enterprise, and limited government.
    Hasso Plattner Institute of Design, a multidisciplinary design school in cooperation with the Hasso Plattner Institute of University of Potsdam [Universität Potsdam](DE) that integrates product design, engineering, and business management education).
    Martin Luther King Jr. Research and Education Institute, which grew out of and still contains the Martin Luther King Jr. Papers Project.
    John S. Knight Fellowship for Professional Journalists
    Center for Ocean Solutions
    Together with UC Berkeley(US) and UC San Francisco(US), Stanford is part of the Biohub, a new medical science research center founded in 2016 by a $600 million commitment from Facebook CEO and founder Mark Zuckerberg and pediatrician Priscilla Chan.

    Discoveries and innovation

    Natural sciences

    Biological synthesis of deoxyribonucleic acid (DNA) – Arthur Kornberg synthesized DNA material and won the Nobel Prize in Physiology or Medicine 1959 for his work at Stanford.
    First Transgenic organism – Stanley Cohen and Herbert Boyer were the first scientists to transplant genes from one living organism to another, a fundamental discovery for genetic engineering. Thousands of products have been developed on the basis of their work, including human growth hormone and hepatitis B vaccine.
    Laser – Arthur Leonard Schawlow shared the 1981 Nobel Prize in Physics with Nicolaas Bloembergen and Kai Siegbahn for his work on lasers.
    Nuclear magnetic resonance – Felix Bloch developed new methods for nuclear magnetic precision measurements, which are the underlying principles of the MRI.

    Computer and applied sciences

    ARPANETStanford Research Institute, formerly part of Stanford but on a separate campus, was the site of one of the four original ARPANET nodes.

    Internet—Stanford was the site where the original design of the Internet was undertaken. Vint Cerf led a research group to elaborate the design of the Transmission Control Protocol (TCP/IP) that he originally co-created with Robert E. Kahn (Bob Kahn) in 1973 and which formed the basis for the architecture of the Internet.

    Frequency modulation synthesis – John Chowning of the Music department invented the FM music synthesis algorithm in 1967, and Stanford later licensed it to Yamaha Corporation.

    Google – Google began in January 1996 as a research project by Larry Page and Sergey Brin when they were both PhD students at Stanford. They were working on the Stanford Digital Library Project (SDLP). The SDLP’s goal was “to develop the enabling technologies for a single, integrated and universal digital library” and it was funded through the National Science Foundation, among other federal agencies.

    Klystron tube – invented by the brothers Russell and Sigurd Varian at Stanford. Their prototype was completed and demonstrated successfully on August 30, 1937. Upon publication in 1939, news of the klystron immediately influenced the work of U.S. and UK researchers working on radar equipment.

    RISCARPA funded VLSI project of microprocessor design. Stanford and UC Berkeley are most associated with the popularization of this concept. The Stanford MIPS would go on to be commercialized as the successful MIPS architecture, while Berkeley RISC gave its name to the entire concept, commercialized as the SPARC. Another success from this era were IBM’s efforts that eventually led to the IBM POWER instruction set architecture, PowerPC, and Power ISA. As these projects matured, a wide variety of similar designs flourished in the late 1980s and especially the early 1990s, representing a major force in the Unix workstation market as well as embedded processors in laser printers, routers and similar products.
    SUN workstation – Andy Bechtolsheim designed the SUN workstation for the Stanford University Network communications project as a personal CAD workstation, which led to Sun Microsystems.

    Businesses and entrepreneurship

    Stanford is one of the most successful universities in creating companies and licensing its inventions to existing companies; it is often held up as a model for technology transfer. Stanford’s Office of Technology Licensing is responsible for commercializing university research, intellectual property, and university-developed projects.

    The university is described as having a strong venture culture in which students are encouraged, and often funded, to launch their own companies.

    Companies founded by Stanford alumni generate more than $2.7 trillion in annual revenue, equivalent to the 10th-largest economy in the world.

    Some companies closely associated with Stanford and their connections include:

    Hewlett-Packard, 1939, co-founders William R. Hewlett (B.S, PhD) and David Packard (M.S).
    Silicon Graphics, 1981, co-founders James H. Clark (Associate Professor) and several of his grad students.
    Sun Microsystems, 1982, co-founders Vinod Khosla (M.B.A), Andy Bechtolsheim (PhD) and Scott McNealy (M.B.A).
    Cisco, 1984, founders Leonard Bosack (M.S) and Sandy Lerner (M.S) who were in charge of Stanford Computer Science and Graduate School of Business computer operations groups respectively when the hardware was developed.[163]
    Yahoo!, 1994, co-founders Jerry Yang (B.S, M.S) and David Filo (M.S).
    Google, 1998, co-founders Larry Page (M.S) and Sergey Brin (M.S).
    LinkedIn, 2002, co-founders Reid Hoffman (B.S), Konstantin Guericke (B.S, M.S), Eric Lee (B.S), and Alan Liu (B.S).
    Instagram, 2010, co-founders Kevin Systrom (B.S) and Mike Krieger (B.S).
    Snapchat, 2011, co-founders Evan Spiegel and Bobby Murphy (B.S).
    Coursera, 2012, co-founders Andrew Ng (Associate Professor) and Daphne Koller (Professor, PhD).

    Student body

    Stanford enrolled 6,996 undergraduate and 10,253 graduate students as of the 2019–2020 school year. Women comprised 50.4% of undergraduates and 41.5% of graduate students. In the same academic year, the freshman retention rate was 99%.

    Stanford awarded 1,819 undergraduate degrees, 2,393 master’s degrees, 770 doctoral degrees, and 3270 professional degrees in the 2018–2019 school year. The four-year graduation rate for the class of 2017 cohort was 72.9%, and the six-year rate was 94.4%. The relatively low four-year graduation rate is a function of the university’s coterminal degree (or “coterm”) program, which allows students to earn a master’s degree as a 1-to-2-year extension of their undergraduate program.

    As of 2010, fifteen percent of undergraduates were first-generation students.

    Athletics

    As of 2016 Stanford had 16 male varsity sports and 20 female varsity sports, 19 club sports and about 27 intramural sports. In 1930, following a unanimous vote by the Executive Committee for the Associated Students, the athletic department adopted the mascot “Indian.” The Indian symbol and name were dropped by President Richard Lyman in 1972, after objections from Native American students and a vote by the student senate. The sports teams are now officially referred to as the “Stanford Cardinal,” referring to the deep red color, not the cardinal bird. Stanford is a member of the Pac-12 Conference in most sports, the Mountain Pacific Sports Federation in several other sports, and the America East Conference in field hockey with the participation in the inter-collegiate NCAA’s Division I FBS.

    Its traditional sports rival is the University of California, Berkeley, the neighbor to the north in the East Bay. The winner of the annual “Big Game” between the Cal and Cardinal football teams gains custody of the Stanford Axe.

    Stanford has had at least one NCAA team champion every year since the 1976–77 school year and has earned 126 NCAA national team titles since its establishment, the most among universities, and Stanford has won 522 individual national championships, the most by any university. Stanford has won the award for the top-ranked Division 1 athletic program—the NACDA Directors’ Cup, formerly known as the Sears Cup—annually for the past twenty-four straight years. Stanford athletes have won medals in every Olympic Games since 1912, winning 270 Olympic medals total, 139 of them gold. In the 2008 Summer Olympics, and 2016 Summer Olympics, Stanford won more Olympic medals than any other university in the United States. Stanford athletes won 16 medals at the 2012 Summer Olympics (12 gold, two silver and two bronze), and 27 medals at the 2016 Summer Olympics.

    Traditions

    The unofficial motto of Stanford, selected by President Jordan, is Die Luft der Freiheit weht. Translated from the German language, this quotation from Ulrich von Hutten means, “The wind of freedom blows.” The motto was controversial during World War I, when anything in German was suspect; at that time the university disavowed that this motto was official.
    Hail, Stanford, Hail! is the Stanford Hymn sometimes sung at ceremonies or adapted by the various University singing groups. It was written in 1892 by mechanical engineering professor Albert W. Smith and his wife, Mary Roberts Smith (in 1896 she earned the first Stanford doctorate in Economics and later became associate professor of Sociology), but was not officially adopted until after a performance on campus in March 1902 by the Mormon Tabernacle Choir.
    “Uncommon Man/Uncommon Woman”: Stanford does not award honorary degrees, but in 1953 the degree of “Uncommon Man/Uncommon Woman” was created to recognize individuals who give rare and extraordinary service to the University. Technically, this degree is awarded by the Stanford Associates, a voluntary group that is part of the university’s alumni association. As Stanford’s highest honor, it is not conferred at prescribed intervals, but only when appropriate to recognize extraordinary service. Recipients include Herbert Hoover, Bill Hewlett, Dave Packard, Lucile Packard, and John Gardner.
    Big Game events: The events in the week leading up to the Big Game vs. UC Berkeley, including Gaieties (a musical written, composed, produced, and performed by the students of Ram’s Head Theatrical Society).
    “Viennese Ball”: a formal ball with waltzes that was initially started in the 1970s by students returning from the now-closed Stanford in Vienna overseas program. It is now open to all students.
    “Full Moon on the Quad”: An annual event at Main Quad, where students gather to kiss one another starting at midnight. Typically organized by the Junior class cabinet, the festivities include live entertainment, such as music and dance performances.
    “Band Run”: An annual festivity at the beginning of the school year, where the band picks up freshmen from dorms across campus while stopping to perform at each location, culminating in a finale performance at Main Quad.
    “Mausoleum Party”: An annual Halloween Party at the Stanford Mausoleum, the final resting place of Leland Stanford Jr. and his parents. A 20-year tradition, the “Mausoleum Party” was on hiatus from 2002 to 2005 due to a lack of funding, but was revived in 2006. In 2008, it was hosted in Old Union rather than at the actual Mausoleum, because rain prohibited generators from being rented. In 2009, after fundraising efforts by the Junior Class Presidents and the ASSU Executive, the event was able to return to the Mausoleum despite facing budget cuts earlier in the year.
    Former campus traditions include the “Big Game bonfire” on Lake Lagunita (a seasonal lake usually dry in the fall), which was formally ended in 1997 because of the presence of endangered salamanders in the lake bed.

    Award laureates and scholars

    Stanford’s current community of scholars includes:

    19 Nobel Prize laureates (as of October 2020, 85 affiliates in total)
    171 members of the National Academy of Sciences
    109 members of National Academy of Engineering
    76 members of National Academy of Medicine
    288 members of the American Academy of Arts and Sciences
    19 recipients of the National Medal of Science
    1 recipient of the National Medal of Technology
    4 recipients of the National Humanities Medal
    49 members of American Philosophical Society
    56 fellows of the American Physics Society (since 1995)
    4 Pulitzer Prize winners
    31 MacArthur Fellows
    4 Wolf Foundation Prize winners
    2 ACL Lifetime Achievement Award winners
    14 AAAI fellows
    2 Presidential Medal of Freedom winners

    Stanford University Seal

     
  • richardmitnick 5:40 pm on February 5, 2021 Permalink | Reply
    Tags: "UCLA Material Scientists Discover New Ways to Power Up Nanomaterials for Electronic Applications", , , , Perovskite materials have a crystal-lattice structure of inorganic molecules like that of ceramics along with organic molecules that are interlaced throughout., Perovskites, , UCLA Samueli School of Engineering, When the organic molecules are designed properly they not only can maintain the crystal lattice structure but also contribute to the materials’ electronic properties.   

    From UCLA Samueli School of Engineering at UCLA: “UCLA Material Scientists Discover New Ways to Power Up Nanomaterials for Electronic Applications” 

    From UCLA Samueli School of Engineering

    at

    UCLA bloc

    UCLA

    Feb 4, 2021

    1
    Schematic of perovskite material with organic molecules that can add to its electronic properties.
    Credit: Jingjing Xue and Rui Wang/UCLA Samueli.

    UCLA materials scientists and colleagues have discovered that perovskites, a class of promising materials that could be used for low-cost, high-performance solar cells and LEDs, have a previously unutilized molecular component that can further tune the electronic property of perovskites.

    Named after Russian mineralogist Lev Perovski, perovskite materials have a crystal-lattice structure of inorganic molecules like that of ceramics, along with organic molecules that are interlaced throughout. Up to now, these organic molecules appeared to only serve a structural function and could not directly contribute to perovskites’ electronic performance.

    Led by UCLA, a new study shows that when the organic molecules are designed properly, they not only can maintain the crystal lattice structure, but also contribute to the materials’ electronic properties. This discovery opens up new possibilities to improve the design of materials that will lead to better solar cells and LEDs. The study detailing the research was recently published in Science.

    “This is like finding an old dog that can play new tricks,” said Yang Yang, the Carol and Lawrence E. Tannas Jr. Professor of Engineering at the UCLA Samueli School of Engineering, who is the principal investigator on the research. “In materials science, we look all the way down to the atomic structure of a material for efficient performance. Our postdocs and graduate students didn’t take anything for granted and dug deeper to find a new pathway.”

    On its exterior, the positively charged ammonium molecule connected to molecules of pyrene — a quadruple ring of carbon atoms. This molecular design offered additional electronic tunability of perovskites.

    “The unique property of perovskites is that they have the advantage of high-performance inorganic semiconductors, as well as easy and low-cost processability of polymers,” said study co-lead author Rui Wang, a UCLA postdoctoral scholar in materials science and engineering. “This newly enhanced perovskite material now offers opportunities for improved design concepts with better efficiency.”

    To demonstrate perovskites’ added effectiveness, the team built a photovoltaic (PV) cell prototype with the materials, and then tested it under continuous light for 2,000 hours. The new cell continued to convert light to energy at 85% of its original efficiency. This contrasts with a PV cell made of the same materials, but without the added altered organic molecule, which retained only 60% of its original efficiency.

    The other co-lead authors on the study are Jingjing Xue, a materials science postdoctoral scholar at UCLA; and Xihan Chen of the U.S. Department of Energy’s National Renewable Energy Laboratory (NREL) in Colorado. The other corresponding authors include Matthew Beard, a senior research fellow at NREL and the director of its Center for Hybrid Organic Inorganic Semiconductors for Energy; and Yanfa Yan, a professor of physics and astronomy at the University of Toledo.

    Other authors are from UCLA; NREL; the University of Toledo; Yangzhou University (CN); Soochow University (CN); Monash University (AU) and Lawrence Berkeley National Laboratory (US).

    The research was funded in part by the U.S. Department of Energy.

    See the full article here .


    five-ways-keep-your-child-safe-school-shootings
    Please help promote STEM in your local schools.

    Stem Education Coalition

    The UCLA Henry Samueli School of Engineering and Applied Science (HSSEAS), informally known as UCLA Engineering, is the school of engineering at the University of California, Los Angeles (UCLA). It opened as the College of Engineering in 1945, and was renamed the School of Engineering in 1969.[2] Since its initial enrollment of 379 students, the school has grown to approximately 6,100 students. The school is ranked 16th among all engineering schools in the United States.[3] The school offers 28 degree programs and is home to eight externally funded interdisciplinary research centers, including those in space exploration, wireless sensor systems, and nanotechnology.

    UC LA Campus

    For nearly 100 years, UCLA has been a pioneer, persevering through impossibility, turning the futile into the attainable.

    We doubt the critics, reject the status quo and see opportunity in dissatisfaction. Our campus, faculty and students are driven by optimism. It is not naïve; it is essential. And it has fueled every accomplishment, allowing us to redefine what’s possible, time after time.

    This can-do perspective has brought us 12 Nobel Prizes, 12 Rhodes Scholarships, more NCAA titles than any university and more Olympic medals than most nations. Our faculty and alumni helped create the Internet and pioneered reverse osmosis. And more than 100 companies have been created based on technology developed at UCLA.

     
  • richardmitnick 1:41 pm on February 1, 2021 Permalink | Reply
    Tags: "Squeezing a rock-star material could make it stable enough for solar cells", A promising lead halide perovskite is great at converting sunlight to electricity but it breaks down at room temperature., , , , Now scientists have discovered how to stabilize the lead halide perovskite with pressure from a diamond anvil cell., Perovskites, , Simply place the useless version of the material in a diamond anvil cell and squeeze it at high temperature., , This is the first study to use pressure to control this stability and it really opens up a lot of possibilities.   

    From DOE’s SLAC National Accelerator Laboratory and Stanford University: “Squeezing a rock-star material could make it stable enough for solar cells” 

    From DOE’s SLAC National Accelerator Laboratory

    and

    Stanford University Name

    Stanford University

    January 21, 2021 [Just now in social media.]
    By Glennda Chui

    A promising lead halide perovskite is great at converting sunlight to electricity, but it breaks down at room temperature. Now scientists have discovered how to stabilize it with pressure from a diamond anvil cell.

    1
    Scientists at SLAC National Accelerator Laboratory and Stanford University discovered that squeezing a promising lead halide material in a diamond anvil cell (left) produces a so-called “black perovskite” (right) that’s stable enough for solar power applications.
    Credit: Greg Stewart/ SLAC National Accelerator Laboratory.

    Among the materials known as perovskites, one of the most exciting is a material that can convert sunlight to electricity as efficiently as today’s commercial silicon solar cells and has the potential for being much cheaper and easier to manufacture.

    There’s just one problem: Of the four possible atomic configurations, or phases, this material can take, three are efficient but unstable at room temperature and in ordinary environments, and they quickly revert to the fourth phase, which is completely useless for solar applications.

    Now scientists at Stanford University and the Department of Energy’s SLAC National Accelerator Laboratory have found a novel solution: Simply place the useless version of the material in a diamond anvil cell and squeeze it at high temperature. This treatment nudges its atomic structure into an efficient configuration and keeps it that way, even at room temperature and in relatively moist air.

    The researchers described their results in Nature Communications.

    “This is the first study to use pressure to control this stability, and it really opens up a lot of possibilities,” said Yu Lin, a SLAC staff scientist and investigator with the Stanford Institute for Materials and Energy Sciences (SIMES).

    “Now that we’ve found this optimal way to prepare the material,” she said, “there’s potential for scaling it up for industrial production, and for using this same approach to manipulate other perovskite phases.”

    A search for stability

    Perovskites get their name from a natural mineral with the same atomic structure. In this case the scientists studied a lead halide perovskite that’s a combination of iodine, lead and cesium.

    One phase of this material, known as the yellow phase, does not have a true perovskite structure and can’t be used in solar cells. However, scientists discovered a while back that if you process it in certain ways, it changes to a black perovskite phase that’s extremely efficient at converting sunlight to electricity. “This has made it highly sought after and the focus of a lot of research,” said Stanford Professor and study co-author Wendy Mao.

    Unfortunately, these black phases are also structurally unstable and tend to quickly slump back into the useless configuration. Plus, they only operate with high efficiency at high temperatures, Mao said, and researchers will have to overcome both of those problems before they can be used in practical devices.

    There had been previous attempts to stabilize the black phases with chemistry, strain or temperature, but only in a moisture-free environment that doesn’t reflect the real-world conditions that solar cells operate in. This study combined both pressure and temperature in a more realistic working environment.

    Pressure and heat do the trick

    Working with colleagues in the Stanford research groups of Mao and Professor Hemamala Karunadasa, Lin and postdoctoral researcher Feng Ke designed a setup where yellow phase crystals were squeezed between the tips of diamonds in what’s known as a diamond anvil cell. With the pressure still on, the crystals were heated to 450 degrees Celsius and then cooled down.

    Under the right combination of pressure and temperature, the crystals turned from yellow to black and stayed in the black phase after the pressure was released, the scientists said. They were resistant to deterioration from moist air and remained stable and efficient at room temperature for 10 to 30 days or more.

    Examination with X-rays and other techniques confirmed the shift in the material’s crystal structure, and calculations by SIMES theorists Chunjing Jia and Thomas Devereaux provided insight into how the pressure changed the structure and preserved the black phase.

    The pressure needed to turn the crystals black and keep them that way was roughly 1,000 to 6,000 times atmospheric pressure, Lin said ­– about a tenth of the pressures routinely used in the synthetic diamond industry. So one of the goals for further research will be to transfer what the researchers have learned from their diamond anvil cell experiments to industry and scale up the process to bring it within the realm of manufacturing.

    Wendy Mao and Hemamala Karunadasa are also SIMES investigators. Parts of this work were performed at the Advanced Photon Source at Argonne National Laboratory and the Advanced Light Source at Lawrence Berkeley National Laboratory. It also used resources of the National Energy Research Scientific Computing Center (NERSC). All three are DOE Office of Science user facilities. Major funding came from the DOE Office of Science.

    ANL Advanced Photon Source.

    LBNL ALS .

    National Energy Research Scientific Computing Center (NERSC) at Lawrence Berkeley National Laboratory

    NERSC Cray Cori II supercomputer, named after Gerty Cori, the first American woman to win a Nobel Prize in science.

    NERSC Hopper Cray XE6 supercomputer, named after Grace Hopper, One of the first programmers of the Harvard Mark I computer.

    NERSC Cray XC30 Edison supercomputer.

    NERSC GPFS for Life Sciences.


    The Genepool system is a cluster dedicated to the DOE Joint Genome Institute’s computing needs. Denovo is a smaller test system for Genepool that is primarily used by NERSC staff to test new system configurations and software.

    NERSC PDSF computer cluster in 2003.

    PDSF is a networked distributed computing cluster designed primarily to meet the detector simulation and data analysis requirements of physics, astrophysics and nuclear science collaborations.

    Future:

    Cray Shasta Perlmutter SC18 AMD Epyc Nvidia pre-exascale supeercomputer

    NERSC is a DOE Office of Science User Facility.

    See the full article here .


    five-ways-keep-your-child-safe-school-shootings
    Please help promote STEM in your local schools.

    Stem Education Coalition

    Stanford University campus. No image credit

    Stanford University

    Leland and Jane Stanford founded the University to “promote the public welfare by exercising an influence on behalf of humanity and civilization.” Stanford opened its doors in 1891, and more than a century later, it remains dedicated to finding solutions to the great challenges of the day and to preparing our students for leadership in today’s complex world. Stanford, is an American private research university located in Stanford, California on an 8,180-acre (3,310 ha) campus near Palo Alto. Since 1952, more than 54 Stanford faculty, staff, and alumni have won the Nobel Prize, including 19 current faculty members

    Stanford University Seal

    SLAC is a multi-program laboratory exploring frontier questions in photon science, astrophysics, particle physics and accelerator research. Located in Menlo Park, California, SLAC is operated by Stanford University for the DOE’s Office of Science.

    SLAC National Accelerator Lab


    SLAC/LCLS


    SLAC/LCLS II projected view

    SLAC LCLS-II Undulators The Linac Coherent Light Source’s new undulators each use an intricately tuned series of magnets to convert electron energy into intense bursts of X-rays. The “soft” X-ray undulator stretches for 100 meters on the left side of this hall, with the “hard” x-ray undulator on the right. Credit: Alberto Gamazo/SLAC National Accelerator Laboratory.

    SSRL and LCLS are DOE Office of Science user facilities.

     
  • richardmitnick 1:13 pm on February 1, 2021 Permalink | Reply
    Tags: "Study shows tweaking one layer of atoms on a catalyst’s surface can make it work better", , Building materials one atomic layer at a time., , Catalysts help molecules react without being consumed in the reaction so they can be used over and over., , , Perovskites, Scientists crafting a nickel-based catalyst used in making hydrogen fuel built it one atomic layer at a time to gain full control over its chemical properties., Splitting water to make hydrogen fuel., Tuning a catalyst’s surface for better performance.   

    From DOE’s SLAC National Accelerator Laboratory: “Study shows tweaking one layer of atoms on a catalyst’s surface can make it work better” 

    From DOE’s SLAC National Accelerator Laboratory

    January 11, 2021 [Just now in social media.]
    Glennda Chui

    The surprising results offer a way to boost the activity and stability of catalysts for making hydrogen fuel from water.

    1
    Credit: SLAC.

    2
    An illustration combines two possible types of surface layers for a catalyst that performs the water-splitting reaction, the first step in making hydrogen fuel. The gray surface, top, is lanthanum oxide. The colorful surface is nickel oxide; a rearrangement of its atoms while carrying out the reaction made it twice as efficient, a phenomenon researchers hope to harness to design better catalysts. Lanthanum atoms are depicted in green, nickel in blue and oxygen in red. Credit: CUBE3D Graphic.

    3
    A new study shows how tweaking the surface layer of a catalyst can make it work better. This particular catalyst is used to split water, the first step in making hydrogen fuel. It consists of alternating layers of materials rich in nickel (blue spheres) and lanthanum (green spheres; the red spheres represent oxygen atoms). When the material is grown at relatively cool temperatures so a nickel-rich layer is on top (left), the atoms on that surface layer rearrange during the water-splitting reaction (middle) in a way that allows them to carry out the reaction more efficiently (right). This surprising result gives scientists a new way to tune catalytic activity and engineer better catalysts. Credit:Tomas Duchon/Jülich Research Centre [Forschungszentrum Jülichs] (FZJ)(DE)[DE]).

    Scientists crafting a nickel-based catalyst used in making hydrogen fuel built it one atomic layer at a time to gain full control over its chemical properties. But the finished material didn’t behave as they expected: As one version of the catalyst went about its work, the top-most layer of atoms rearranged to form a new pattern, as if the square tiles that cover a floor had suddenly changed to hexagons.

    But that’s ok, they reported today, because understanding and controlling this surprising transformation gives them a new way to turn catalytic activity on and off and make good catalysts even better.

    The research team, led by scientists from Stanford University and the Department of Energy’s SLAC National Accelerator Laboratory, described their study in Nature Materials today.

    “Catalysts can change very quickly during the course of a reaction, and understanding how they transform from an inactive phase to an active one is crucial to designing more efficient catalysts,” said Will Chueh, an investigator with the Stanford Institute for Materials and Energy Sciences (SIMES) at SLAC who led the study. “This transformation gives us the equivalent of a knob we can turn to fine-tune their behavior.”

    Splitting water to make hydrogen fuel

    Catalysts help molecules react without being consumed in the reaction, so they can be used over and over. They’re the backbone of many green-energy devices.

    This particular catalyst, lanthanum nickel oxide or LNO, is used to split water into hydrogen and oxygen in a reaction powered by electricity. It’s the first step in generating hydrogen fuel, which has enormous potential for storing renewable energy from sunlight and other sources in a liquid form that’s energy-rich and easy to transport. In fact, several manufacturers have already produced electric cars powered by hydrogen fuel cells.

    But this first step is also the most difficult one, said Michal Bajdich, a theorist at the SUNCAT Center for Interface Science and Catalysis at SLAC, and researchers have been searching for inexpensive materials that will carry it out more efficiently.

    Since reactions take place on a catalyst’s surface, researchers have been trying to precisely engineer those surfaces so they promote only one specific chemical reaction with high efficiency.

    Building materials one atomic layer at a time

    The LNO investigated in this study belongs to a class of promising catalytic materials known as perovskites, named after a natural mineral with a similar atomic structure.

    Christoph Baeumer, who came to SLAC as a Marie Curie Fellow from RWTH Aachen University [Rheinisch-Westfälische Technische Hochschule Aachen] (DE) to carry out the study, prepared LNO in what’s known as an epitaxial thin film – a film grown in atomically thin layers in a way that creates an extraordinarily precise arrangement of atoms.

    Dividing his time between California and Germany, Baeumer made two versions of the film at different temperatures ­­– one with a nickel-rich surface and another with a lanthanum-rich surface. Then the research team ran all the versions through the water-splitting reaction to compare how well they performed.

    “We were surprised to discover that the films with nickel-rich surfaces carried out the reaction twice as fast,” Baeumer said.

    Tuning a catalyst’s surface for better performance

    To find out why, the team took the films to DOE’s Lawrence Berkeley National Laboratory, where a group led by Slavomír Nemšák looked at their atomic structure with X-rays at the Advanced Light Source.

    LBNL ALS .

    “It was surprising that the difference between the ‘good’ and the ‘bad’ catalyst was only in the last atomic layer of the films,” Nemšák said. Those investigations also revealed that in films with nickel-rich surface layers that were prepared at cooler temperatures, the top layer of atoms transformed at some point during the water-splitting reaction, and this new arrangement boosted the catalytic activity.

    Meanwhile, Jiang Li, a postdoctoral researcher and theorist at SUNCAT, performed computational studies of this very complex system using Berkeley Lab’s National Energy Research Scientific Computing Center (NERSC).

    National Energy Research Scientific Computing Center (NERSC) at Lawrence Berkeley National Laboratory

    NERSC Cray Cori II supercomputer, named after Gerty Cori, the first American woman to win a Nobel Prize in science.

    NERSC Hopper Cray XE6 supercomputer, named after Grace Hopper, One of the first programmers of the Harvard Mark I computer.

    NERSC Cray XC30 Edison supercomputer.

    NERSC GPFS for Life Sciences.


    The Genepool system is a cluster dedicated to the DOE Joint Genome Institute’s computing needs. Denovo is a smaller test system for Genepool that is primarily used by NERSC staff to test new system configurations and software.

    NERSC PDSF computer cluster in 2003.

    PDSF is a networked distributed computing cluster designed primarily to meet the detector simulation and data analysis requirements of physics, astrophysics and nuclear science collaborations.

    Future:

    Cray Shasta Perlmutter SC18 AMD Epyc Nvidia pre-exascale supeercomputer

    NERSC is a DOE Office of Science User Facility.

    His conclusions agreed with the experimental results, predicting that the version of the catalyst with the transformed surface – from a cubic pattern to a hexagonal one – would be the most active and stable one.

    Bajdich said, “Is the transformation of the nickel-rich surface driven by the way the catalyst is prepared, or by changes it undergoes while it carries out the water-splitting reaction? That’s very hard to answer. It looks like both have to occur.”

    Although this particular catalyst is not the best in the world for splitting water into hydrogen and oxygen, he said, discovering how a surface transformation boosts its activity is important and could potentially apply to other materials too.

    “If we can unlock the secrets of this transformation so we can accurately tune it,” he said, “then we can leverage this phenomenon to make much better catalysts in the future.”

    See the full article here .


    five-ways-keep-your-child-safe-school-shootings
    Please help promote STEM in your local schools.

    Stem Education Coalition

    SLAC is a multi-program laboratory exploring frontier questions in photon science, astrophysics, particle physics and accelerator research. Located in Menlo Park, California, SLAC is operated by Stanford University for the DOE’s Office of Science.

    SLAC National Accelerator Lab


    SLAC/LCLS


    SLAC/LCLS II projected view

    SLAC LCLS-II Undulators The Linac Coherent Light Source’s new undulators each use an intricately tuned series of magnets to convert electron energy into intense bursts of X-rays. The “soft” X-ray undulator stretches for 100 meters on the left side of this hall, with the “hard” x-ray undulator on the right. Credit: Alberto Gamazo/SLAC National Accelerator Laboratory.

    SSRL and LCLS are DOE Office of Science user facilities.

     
  • richardmitnick 10:25 am on February 25, 2019 Permalink | Reply
    Tags: "Quantum dots can spit out clone-like photons", , , It’s a new phenomenon and will require much work to develop to a practical level, , , Perovskite quantum dots still have a long way to go until they become applicable in real applications, Perovskites, , , Such coherent photons could also be used for quantum-encrypted communications applications, The ability to produce individual photons with precisely known and persistent properties including a wavelength or color that does not fluctuate at all could be useful for many kinds of proposed quant, They need to achieve 100 percent indistinguishability in the photons produced   

    From MIT News: “Quantum dots can spit out clone-like photons” 

    MIT News
    MIT Widget

    From MIT News

    February 21, 2019
    David L. Chandler

    1
    Scanning Transmission Electron Microscope image (STEM) of single perovskite quantum dots. New study shows that single perovskite quantum dots could be a fundamental building block for quantum-photonic technologies for computing or communications. Image courtesy of the authors.

    System that generates coherent single particles of light could help pave the way for quantum information processors or communications.

    In the global quest to develop practical computing and communications devices based on the principles of quantum physics, one potentially useful component has proved elusive: a source of individual particles of light with perfectly constant, predictable, and steady characteristics. Now, researchers at MIT and in Switzerland say they have made major steps toward such a single photon source.

    The study, which involves using a family of materials known as perovskites to make light-emitting particles called quantum dots, appears today in the journal Science. The paper is by MIT graduate student in chemistry Hendrik Utzat, professor of chemistry Moungi Bawendi, and nine others at MIT and at ETH Zürich, Switzerland.

    The ability to produce individual photons with precisely known and persistent properties, including a wavelength, or color, that does not fluctuate at all, could be useful for many kinds of proposed quantum devices. Because each photon would be indistinguishable from the others in terms of its quantum-mechanical properties, it could be possible, for example, to delay one of them and then get the pair to interact with each other, in a phenomenon called interference.

    “This quantum interference between different indistinguishable single photons is the basis of many optical quantum information technologies using single photons as information carriers,” Utzat explains. “But it only works if the photons are coherent, meaning they preserve their quantum states for a sufficiently long time.”

    Many researchers have tried to produce sources that could emit such coherent single photons, but all have had limitations. Random fluctuations in the materials surrounding these emitters tend to change the properties of the photons in unpredictable ways, destroying their coherence. Finding emitter materials that maintain coherence and are also bright and stable is “fundamentally challenging,” Utzat says. That’s because not only the surroundings but even the materials themselves “essentially provide a fluctuating bath that randomly interacts with the electronically excited quantum state and washes out the coherence,” he says.

    “Without having a source of coherent single photons, you can’t use any of these quantum effects that are the foundation of optical quantum information manipulation,” says Bawendi, who is the Lester Wolfe Professor of Chemistry. Another important quantum effect that can be harnessed by having coherent photons, he says, is entanglement, in which two photons essentially behave as if they were one, sharing all their properties.

    Previous chemically-made colloidal quantum dot materials had impractically short coherence times, but this team found that making the quantum dots from perovskites, a family of materials defined by their crystal structure, produced coherence levels that were more than a thousand times better than previous versions. The coherence properties of these colloidal perovskite quantum dots are now approaching the levels of established emitters, such as atom-like defects in diamond or quantum dots grown by physicists using gas-phase beam epitaxy.

    One of the big advantages of perovskites, they found, was that they emit photons very quickly after being stimulated by a laser beam. This high speed could be a crucial characteristic for potential quantum computing applications. They also have very little interaction with their surroundings, greatly improving their coherence properties and stability.

    Such coherent photons could also be used for quantum-encrypted communications applications, Bawendi says. A particular kind of entanglement, called polarization entanglement, can be the basis for secure quantum communications that defies attempts at interception.

    Now that the team has found these promising properties, the next step is to work on optimizing and improving their performance in order to make them scalable and practical. For one thing, they need to achieve 100 percent indistinguishability in the photons produced. So far, they have reached 20 percent, “which is already very remarkable,” Utzat says, already comparable to the coherences reached by other materials, such as atom-like fluorescent defects in diamond, that are already established systems and have been worked on much longer.

    “Perovskite quantum dots still have a long way to go until they become applicable in real applications,” he says, “but this is a new materials system available for quantum photonics that can now be optimized and potentially integrated with devices.”

    It’s a new phenomenon and will require much work to develop to a practical level, the researchers say. “Our study is very fundamental,” Bawendi notes. “However, it’s a big step toward developing a new material platform that is promising.”

    The work was supported by the U.S. Department of Energy, the National Science Foundation, and the Swiss Federal Commission for Technology and Innovation.

    See the full article here .


    five-ways-keep-your-child-safe-school-shootings
    Please help promote STEM in your local schools.


    Stem Education Coalition

    MIT Seal

    The mission of MIT is to advance knowledge and educate students in science, technology, and other areas of scholarship that will best serve the nation and the world in the twenty-first century. We seek to develop in each member of the MIT community the ability and passion to work wisely, creatively, and effectively for the betterment of humankind.

    MIT Campus

     
  • richardmitnick 11:17 am on January 8, 2016 Permalink | Reply
    Tags: , , , Perovskites, Silicon and solar materials   

    From MIT Tech Review: “Promising New Solar Material Boosts Performance of Silicon” 

    MIT Technology Review
    M.I.T Technology Review

    January 7, 2016
    Mike Orcutt

    Silicon probably won’t be replaced as the dominant solar material anytime soon, but it might not be too long before it gets a partner from a promising class of materials called perovskites.

    A group led by Henry Snaith, a physicist at the University of Oxford and leading perovskite researcher, has demonstrated what it says is a viable pathway to a device that combines a conventional silicon cell with a perovskite cell to boost the efficiency of that silicon cell by several percentage points.

    Perovskites, which have captured the interest of solar researchers and energy policy experts because of their rapidly improving performance and low cost, are distinguished by a chemical structure that gives rise to unique electronic properties that make them attractive for solar technology (see “Could a New Solar Material Outperform Silicon?”). Snaith and his colleagues say the new composition they’ve developed overcomes a fundamental obstacle to designing a highly efficient device that combines the light-absorbing characteristics of silicon with those of a perovskite material.

    The researchers say the result suggests it should be possible to make a silicon-perovskite “tandem” device that is more than 25 percent efficient, higher than the performance of today’s commercially available silicon cells, which are about 17 to 20 percent efficient. The measurements they took were in a laboratory environment, but the approach could eventually be used to achieve significantly higher efficiencies than the best silicon panels on the market today.

    High-performance tandem devices made of semiconductors other than perovskite have already achieved efficiencies in the lab of over 40 percent, but they are extremely expensive because they require very technically complex manufacturing processes. Making perovskite solar cells is much simpler and cheaper, and the process could be integrated into existing silicon panel manufacturing lines by adding a few steps. Many experts believe the most realistic near-term commercial application of perovskites will be a tandem device with silicon.

    Several groups have demonstrated working tandem devices made of a silicon cell and a perovskite cell, but the efficiencies have been limited because the range of the solar spectrum the perovskite absorbed did not fully complement the range that silicon absorbs. Attempts to tweak the range of light the perovskite absorbs led to instabilities within the material’s structure that compromised performance. Snaith and his colleagues came up with a method, which relies on substituting certain ions in the material with cesium ions, to achieve the desired photovoltaic properties while maintaining the material’s structural stability.

    The researchers have only demonstrated the new composition at a small scale, and a lot of work would be needed before we might see it in commercially available panels. But a company Snaith cofounded, Oxford PV, is also focused on developing silicon-perovskite tandem devices.

    Chris Case, chief technology officer of Oxford PV, says results like this reflect how quickly researchers are addressing the inherent challenges to making reliable, high-performing tandem cells. Case won’t reveal the specifics of his company’s technology, but says Oxford PV is close to demonstrating full-size devices that are 23 percent efficient and could hit 25 percent shortly thereafter. Case says it’s not unrealistic to think 28 or even 30 percent efficiency is possible within just a few years.

    Perovskite-based technologies still face challenges due to the material’s sensitivity to moisture and air, and questions remain about whether perovskite cells can be made durable enough to survive the long lifetimes required of power systems. Still, Case says Oxford PV is on track to deliver a commercial product—aimed at silicon panel manufacturers who want to “upgrade” the efficiency of their products—in 2017.

    See the full article here .

    Please help promote STEM in your local schools.

    STEM Icon

    Stem Education Coalition

    The mission of MIT Technology Review is to equip its audiences with the intelligence to understand a world shaped by technology.

     
c
Compose new post
j
Next post/Next comment
k
Previous post/Previous comment
r
Reply
e
Edit
o
Show/Hide comments
t
Go to top
l
Go to login
h
Show/Hide help
shift + esc
Cancel
%d bloggers like this: