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  • richardmitnick 10:19 am on December 14, 2020 Permalink | Reply
    Tags: "Researchers Pinpoint More Precise Method for Atomic-Level Manufacturing", , Hydrogen depassivation lithography (HDL), , , The University of Texas at Dallas   

    From The University of Texas at Dallas: “Researchers Pinpoint More Precise Method for Atomic-Level Manufacturing” 

    From The University of Texas at Dallas

    Dec. 11, 2020
    Kim Horner

    1
    Building a silicon-based qubit, or quantum bit, the basic unit of information in a quantum computer, starts with an atomically flat silicon surface (left) coated with a layer of hydrogen. On the right, areas where UT Dallas researchers removed hydrogen atoms are highlighted.

    Quantum computers have the potential to transform fields such as medicine, cybersecurity and artificial intelligence by solving hard optimization problems that are beyond the reach of conventional computing hardware.

    But the technology to manufacture the devices on a large scale does not yet exist.

    Researchers at The University of Texas at Dallas have developed a technique that could remove one of the challenges to scaling the production of silicon quantum devices. The researchers outlined their method, which provides greater control and precision during the fabrication process, in a study published in the July print edition of the Journal of Vacuum Science & Technology B. Silicon is the preferred material for the base of quantum devices because of its compatibility with conventional semiconductor technology.

    The study’s corresponding author, Dr. Reza Moheimani, the James Von Ehr Distinguished Chair in Science and Technology and a professor of systems engineering in the Erik Jonsson School of Engineering and Computer Science, received a $2.4 million U.S. Department of Energy grant in 2019 to develop technology for atomically precise manufacturing, the process of building new materials and devices atom by atom.

    Moheimani’s team is addressing a range of challenges to quantum device fabrication.

    “Our latest work increases the precision of the fabrication process,” Moheimani said. “We’re also working to increase throughput, speed and reliability.”

    The researchers’ method for building a silicon-based qubit, or quantum bit, the basic unit of information in a quantum computer, starts with an atomically flat silicon surface coated with a layer of hydrogen, which prevents other atoms or molecules from getting absorbed into the surface. Next, researchers use a scanning tunneling microscope (STM), which features a probe with an atomically sharp tip, functioning as a micro-robotic arm, to remove atoms of hydrogen selectively from the surface. The STM was designed for imaging atomic features on a surface, however, researchers also use the device to manipulate atoms in a mode called hydrogen depassivation lithography (HDL).

    The painstaking process involves positioning the tip over an atom of hydrogen, adding a high-frequency signal to the tip-sample bias voltage and ramping up the amplitude of the high-frequency signal until the atom of hydrogen detaches from the surface, revealing silicon underneath. After a predetermined number of hydrogen atoms are selectively removed from the surface, phosphine gas is introduced in the environment and after a specific process, atoms of phosphorus are adsorbed to the surface, where each functions as a qubit.

    The problem with conventional HDL is that it can be easy for the operator to pluck the wrong atom of hydrogen resulting in creation of qubits at unwanted locations. Using the STM for HDL requires a higher voltage than for imaging, which too often causes the tip to crash into the surface sample, forcing the operator to start over.

    The researchers were working on their solution to the STM tip-crash problem when they discovered a more precise method for manipulating the surface atoms.

    “Conventional lithography cannot achieve the requisite atomic precision,” Moheimani said. “The issue is that we are using a microscope to do lithography; we’re using a device to do something it’s not designed for.”

    The researchers found that they could achieve higher precision by performing HDL in imaging mode, rather than the conventional lithography mode, with some adjustments to the voltage and a change to the STM’s feedback control system.

    “We realized that we could actually use this method to remove hydrogen atoms in a controlled fashion,” Moheimani said. “This came as a surprise. It’s one of those things that happens during experiments, and you try to explain it and take advantage of it.”

    Quantum computers are expected to be able to store more information than current computers. Current transistors, which relay information, cannot be made any smaller, said Hamed Alemansour, a mechanical engineering doctoral student and lead author of the study.

    “The kind of technology that’s used now for making transistors has reached its limit. It’s difficult to decrease the size any more through conventional methods,” Alemansour said.

    While a conventional computer uses the precise values of 1s and 0s to make calculations, the fundamental logic units of a quantum computer are more fluid, with values that can exist as a combination of 1s and 0s at the same time or anywhere in between. The fact that a qubit can represent two numbers at the same time allows the quantum computer to process information much faster.

    One of the next challenges, Moheimani said, will be to develop technology to operate multiple STM tips at a time.

    “What if we can use 10 or 100 tips in parallel with each other so we can do the same lithography multiplied by 100 times? What if we can do it 10 times faster? If we can manufacture 100 qubits 10 times faster, we’re 1,000 times better off already,” Moheimani said.

    Other researchers involved with the current study include scientists at Richardson, Texas-based nanotechnology company Zyvex Labs: Dr. John Randall, president and CEO, who co-chairs the Jonsson School’s Industrial Advisory Council and is on the adjunct faculty at UT Dallas; Dr. James Owen, director of anatomically precise manufacturing; and Dr. Ehud Fuchs, research scientist.

    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 University of Texas at Dallas is a Carnegie R1 classification (Doctoral Universities – Highest research activity) institution, located in a suburban setting 20 miles north of downtown Dallas. The University enrolls more than 27,600 students — 18,380 undergraduate and 9,250 graduate —and offers a broad array of bachelor’s, master’s, and doctoral degree programs.

    Established by Eugene McDermott, J. Erik Jonsson and Cecil Green, the founders of Texas Instruments, UT Dallas is a young institution driven by the entrepreneurial spirit of its founders and their commitment to academic excellence. In 1969, the public research institution joined The University of Texas System and became The University of Texas at Dallas.

    A high-energy, nimble, innovative institution, UT Dallas offers top-ranked science, engineering and business programs and has gained prominence for a breadth of educational paths from audiology to arts and technology. UT Dallas’ faculty includes a Nobel laureate, six members of the National Academies and more than 560 tenured and tenure-track professors.

     
  • richardmitnick 8:19 am on October 19, 2020 Permalink | Reply
    Tags: "Physicists Create Tiny Thermoelectric Generators with Plenty of Power", , Internet of Things (IoT) devices are embedded with sensors; communications electronics; and other software that connect remotely and exchange data with other devices and systems., , Texas Instruments, The University of Texas at Dallas   

    From The University of Texas at Dallas: “Physicists Create Tiny Thermoelectric Generators with Plenty of Power” 

    From The University of Texas at Dallas

    Oct. 2, 2020 [Just now in social media.]
    Stephen Fontenot

    TI Partnership Produces Practical, Cost-Effective Silicon-Germanium Generator.

    1
    Dr. Mark Lee (pictured in 2019), professor of physics in the School of Natural Sciences and Mathematics at UT Dallas, and his team have been working with Texas Instruments to create practical, cost-effective thermoelectric generators. Their most recent generator can power an Internet of Things device by recycling ambient waste heat from a warm copper rod.

    Electronic sensors can report data from a variety of remote locations as long as they have power. The challenge is providing safe, reliable power when there’s no wall plug, no light for solar panels and no access to replace a battery.

    Researchers at The University of Texas at Dallas, in partnership with Texas Instruments, are using a combination of silicon and germanium in a way that harnesses waste heat to provide enough power to run commercial electronic devices.

    In a study published Aug. 31 in Nature Communications, they show that their tiny thermoelectric generators can provide a practical, cost-effective and mass-producible solution for producing power from only a relatively small difference in temperature.

    “These new results meet a metric that’s quite important for actual practical applications,” said Dr. Mark Lee, professor of physics in the School of Natural Sciences and Mathematics and senior author of the paper. “By incorporating 3% germanium into a silicon-based microelectronic thermoelectric generator, we can generate enough voltage and current to power a commercial Internet of Things device using nothing more than a warm copper rod as the energy source.”

    Defined broadly, Internet of Things (IoT) devices are embedded with sensors, communications electronics and other software that connect remotely and exchange data with other devices and systems.

    “These devices are made with the understanding that they will be deployed somewhere without much energy available,” Lee said. “As such, they’ve been designed to operate at the lowest possible energy level.”

    Thermoelectric generators recycle ambient waste heat — such as the warmth that comes off an asphalt road in the sunlight or due to the friction from cars driving on the road — into electrical power.

    “The great potential for these generators is in recovery and utilization of waste heat from other electronic devices,” said Prabuddha Madusanka, a UT Dallas physics doctoral student and co-lead author of the study.

    Existing thermoelectric generators are bulky, contain rare or toxic elements, and are incompatible with silicon integrated circuit fabrication technology, all of which prevent their large-scale use in microelectronics, said Ruchika Dhawan, a UT Dallas physics doctoral student and co-lead author of the study.

    Although silicon has many advantageous electrical properties that make it the workhorse material in today’s microchips, it also has a high thermal conductivity, which means it transfers heat very well. “This property is its drawback for use in the generation of electricity,” Dhawan said.

    What is needed is a thermoelectric generator that contains a material that works well with silicon to reduce its thermal conductivity, is inexpensive and can be easily incorporated into the standard industrial device-making process.

    Lee said that IoT devices generally require a minimum of 1.6 to 1.8 volts and a minimum current of about 2 microamps. The team’s new silicon-germanium thermoelectric generators can produce this operating in an environment at ordinary room temperature (about 23 degrees Celsius or 73 degrees Fahrenheit) from a copper rod warmed to as low as 45 C (113 F).

    “That’s where we’ve crossed a new threshold: by demonstrating commercial viability of this technology,” Lee said.

    The design and fabrication of IoT devices incorporating thermoelectric generators was handled by the Texas Instruments team, led by Hal Edwards, a TI Fellow at the company. He explained that hundreds of individual thermoelectric generators, each about the size of a grain of salt, are combined to form what he referred to as a macroscopic harvester.

    “By stacking hundreds of tiny harvesters electrically in series, like tiny batteries, we achieved a high enough voltage to turn on actual microchips — in this case, a commercially purchased low-power ambient light sensor and a power management integrated circuit,” Edwards said. “It’s a nice demonstration that this exploratory research project actually generated useful power, making it a real technological proof of concept. There’s no reason we couldn’t make the generator even larger if needed.”

    Lee described UT Dallas’ alliance with TI as critical: “No university can truly replicate modern industrial silicon fabrication, which is an integral part of proving the feasibility of a proposed method.

    “Researchers might fabricate a single item with a method that is, in principle, compatible with silicon CMOS (complementary metal-oxide-semiconductor) technology. In our case, however, TI fabricated this on an existing production line, and we followed all the rules — not in just principle — it’s compatible in practice.”

    UT Dallas alumnus Gangyi Hu PhD’19 is also among the paper’s authors, along with researchers from Texas Instruments. The work was supported by the National Science Foundation through the Grant Opportunities for Academic Liaison with Industry (GOALI) program and by TI.

    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 University of Texas at Dallas is a Carnegie R1 classification (Doctoral Universities – Highest research activity) institution, located in a suburban setting 20 miles north of downtown Dallas. The University enrolls more than 27,600 students — 18,380 undergraduate and 9,250 graduate —and offers a broad array of bachelor’s, master’s, and doctoral degree programs.

    Established by Eugene McDermott, J. Erik Jonsson and Cecil Green, the founders of Texas Instruments, UT Dallas is a young institution driven by the entrepreneurial spirit of its founders and their commitment to academic excellence. In 1969, the public research institution joined The University of Texas System and became The University of Texas at Dallas.

    A high-energy, nimble, innovative institution, UT Dallas offers top-ranked science, engineering and business programs and has gained prominence for a breadth of educational paths from audiology to arts and technology. UT Dallas’ faculty includes a Nobel laureate, six members of the National Academies and more than 560 tenured and tenure-track professors.

     
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