semiconductor technology (4)

Cooling Computer Chips...

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An electron microscopy image of a gallium nitride-boron arsenide heterostructure interface at atomic resolution. Courtesy: The H-Lab/UCLA

Topics: Materials Science, Nanotechnology, Semiconductor Technology

A novel semiconducting material with high thermal conductivity can be integrated into high-power computer chips to cool them down and so improve their performance. The material, boron arsenide, is better at removing heat than the best thermal-management devices available today, according to the US-based researchers who developed it.

The size of computer chips has been shrinking over the years and has now reached the nanoscale, meaning that billions of transistors can be squeezed onto a single computer chip. This increased density of chips has enabled faster, more powerful computers, but it also generates localized hot spots on the chips. If this extra heat is not dealt with properly during operation, computer processors begin to overheat. This slows them down and makes them inefficient.

Defect-free boron arsenide

Researchers led by Yongjie Hu at the University of California, Los Angeles, recently developed a new thermal-management material that is much more efficient at drawing out and dissipating heat than other known metals or semiconducting materials such as diamond and silicon carbide. This new material is known as defect-free boron arsenide (BAs), and Hu and colleagues have now succeeded in interfacing it with computer chips containing wide-bandgap high-electron-mobility gallium nitride (GaN) transistors for the first time.

Using thermal transport measurements, the researchers found that processors interfaced with BAs and running at near maximum capacity had much lower hot-spot temperatures than other heat-management materials at the same transistor power density. During the experiment, the temperature of the BAs-containing devices increased from room temperature to roughly 360 K, compared to around 410 K and 440 K, respectively, for diamond and silicon carbide.

New semiconductor cools computer chips, Isabelle Dumé, Physics World

 

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Stop-Motion Efficiency...

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A team of researchers created a new method to capture ultrafast atomic motions inside the tiny switches that control the flow of current in electronic circuits. Pictured here are Aditya Sood (left) and Aaron Lindenberg (right). Courtesy: Greg Stewart/SLAC National Accelerator Laboratory

Topics: Applied Physics, Electrical Engineering, Nanotechnology, Semiconductor Technology

A new ultrafast imaging technique that captures the motion of atoms in nanoscale electronic devices has revealed the existence of a short-lived electronic state that could make it possible to develop faster and more energy-efficient computers. The imaging technique, which involves switching the devices on and off while taking snapshots of them with an electron diffraction camera, could also help researchers probe the limits of electronic switching.

“In general, we know very little about the intermediate phases materials pass through during electronic switching operations,” explains Aditya Sood, a postdoctoral researcher at the US Department of Energy’s SLAC National Accelerator Laboratory and lead author of a paper in Science about the new method. “Our technique allows for a new way to visualize this process and therefore address what is arguably one of the most important questions at the heart of computing – that is, what are the fundamental limits of electronic switches in terms of speed and energy consumption?”

Ultrafast electron diffraction camera

Sood and colleagues at SLACStanford UniversityHewlett Packard LabsPennsylvania State University, and Purdue University chose to study devices made from vanadium dioxide (VO2) because the material is known to transition between insulating and electrically conducting states near room temperature. It thus shows promise as a switch, but the exact pathway underlying electric field-induced switching in VOhas long been a mystery, Sood tells Physics World.

To take snapshots of VO2’s atomic structure, the team used periodic voltage pulses to switch an electronic device made from the material on and off. The researchers synchronized the timing of these voltage pulses with the high-energy electron pulses produced by SLAC’s ultrafast electron diffraction (UED) camera. “Each time a voltage pulse excited the sample, it was followed by an electron pulse with a delay that we could tune,” Sood explains. “By repeating this process many times and changing the delay each time, we created a stop-motion movie of the atoms moving in response to the voltage pulse.”

This is the first time that anyone has used UED, which detects tiny atomic movements in a material by scattering a high-energy beam of electrons off a sample, to observe an electronic device during operation. “We started thinking about this subject three years ago and soon realized that existing techniques were simply not fast enough,” says Aaron Lindenberg, a professor of materials science and engineering at Stanford and the study’s senior author. “So we decided to construct our own.”

‘Stop-motion movie of atoms’ reveals short-lived state in nanoscale switch, Isabelle Dumé, Physics World

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Integrated Nanodiamonds...

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Nanophotonic integration for simultaneously controlling a large number of quantum mechanical spins in nanodiamonds. (Image: P. Schrinner/AG Schuck)

Topics: Nanotechnology, Quantum Computer, Quantum Mechanics, Semiconductor Technology

(Nanowerk News) Physicists at Münster University have succeeded in fully integrating nanodiamonds into nanophotonic circuits and at the same time addressing several of these nanodiamonds optically. The study creates the basis for future applications in the field of quantum sensing schemes or quantum information processors.

The results have been published in the journal Nano Letters ("Integration of Diamond-Based Quantum Emitters with Nanophotonic Circuits").

Using modern nanotechnology, it is possible nowadays to produce structures that have feature sizes of just a few nanometers.

This world of the most minute particles – also known as quantum systems – makes possible a wide range of technological applications, in fields which include magnetic field sensing, information processing, secure communication, or ultra-precise timekeeping. The production of these microscopically small structures has progressed so far that they reach dimensions below the wavelength of light.

In this way, it is possible to break down hitherto existent boundaries in optics and utilize the quantum properties of light. In other words, nanophotonics represents a novel approach to quantum technologies.

Controlling fully integrated nanodiamonds, Westfälische Wilhelms-Universität Münster

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Diamond Nanoneedles...

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Credit: Z. Shi et al., Proc. Natl. Acad. Sci. USA 117, 24634 (2020)

Topics: Materials Science, Modern Physics, Nanotechnology, Semiconductor Technology

If you ever manage to deform a diamond, you’re likely to break it. That’s because the hardest natural material on Earth is also inelastic and brittle. Two years ago, Ming Dao (MIT), Subra Suresh (Nanyang Technological University in Singapore), and their collaborators demonstrated that when bulk diamonds are etched into fine, 300-nm-wide needles, they become nearly defect-free. The transformation allows diamonds to elastically bend under the pressure of an indenter tip, as shown in the figure, and withstand extremely large tensile stresses without breaking.

The achievement prompted the researchers to investigate whether the simple process of bending could controllably and reversibly alter the electronic structure of nanocrystal diamond. Teaming up with Ju Li and graduate student Zhe Shi (both at MIT), Dao and Suresh have now followed their earlier study with numerical simulations of the reversible deformation. The team used advanced deep-learning algorithms that reveal the bandgap distributions in nanosized diamond across a range of loading conditions and crystal geometries. The new work confirms that the elastic strain can alter the material’s carbon-bonding configuration enough to close its bandgap from a normally 5.6 eV width as an electrical insulator to 0 eV as a conducting metal. That metallization occurred on the compression side of a bent diamond nanoneedle.

Diamond nanoneedles turn metallic, R. Mark Wilson, Physics Today

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