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The pattern of arrangement of atoms in a crystal, called the crystal lattice, can have a huge effect on the properties of solid materials. Controlling and harnessing these properties is a challenge that promises rewards in applications such as novel sensors and new solid-state devices. An international research collaboration, including researchers from Osaka University, has reported the induction of an interesting type of magnetic order, called helimagnetism, in a cobalt oxide material by expanding its lattice structure. Their findings were published in Physical Review Materials.

This is a schematic illustration of the helimagnetic-ferromagnetic transition driven by the lattice expansion/compression in the cubic perovskite Sr1-xBaxCoO3. Credit: S. Ishiwata and H. Sakai

Magnetic behavior results from the order of the magnetic moments of the many individual atoms in a material. In helimagnetism, instead of the magnetic moments being aligned–as they are in permanent magnets, producing ferromagnetism–the moments arrange themselves in a helical pattern. This behavior is generally only observed in complicated lattice structures where different types of magnetic interactions compete with each other, therefore the report of induced helimagnetism in a simple cubic cobalt oxide structure, is highly significant.

“We have shown emergent helical spin order in a cubic perovskite-type material, which we achieved simply by expanding the lattice size,” study first author Hideaki Sakai says. “We were able to control the size of the lattice expansion by using a high-pressure technique to grow a series of single crystals with particular chemical compositions. Changing the amount of different ions in our materials provided us with sufficient control to investigate the magnetic properties.”

Systematically replacing strontium ions in the structure with larger barium ions caused the lattice to continually expand until the regular ferromagnetic magnetic order present at room temperature was disrupted, resulting in helimagnetism. These experimental findings were successfully supported by calculations.

“The fact that we were able to largely reproduce our findings by first principles calculations verifies that the magnetic interactions in the materials are highly sensitive to the lattice constant,” Sakai says. “The more we can understand about the magnetic behavior of crystalline materials, the closer we move towards translating their properties into useful functions. We hope that our findings will pave the way for novel sensor applications.

The control of magnetic order simply by changing the lattice chemistry, as demonstrated by this research, provides a foundation for investigating the properties of many other crystalline materials.

The ideal optoelectronic semiconductor material should be a strong light emitter i.e. should emit light very efficiently upon optical excitation as well as be an efficient charge conductor to allow for electrical injection in devices. These two conditions when met can lead to highly efficient light emitting diodes as well as to solar cells with the possibility to approach the Shockley-Queisser limit. Until now the materials that have come close to meeting these conditions have been based on epitaxially-grown costly III-V semiconductors that cannot be monolithically integrated to CMOS electronics.

The ICFO team has reported a solution processed nanocomposite system comprising infrared colloidal quantum dots that also meets these criteria and at the same time offers low cost and facile CMOS integration. Colloidal Quantum Dots (CQDs) are extremely small semiconductor particles or crystals, as small as a few nanometers in size, and because of their size they are capable of having unique optical and electronic properties. They are excellent absorbers and emitters of light, having their properties change as a function of their size and shape: smaller quantum dots emit in the blue range while larger quantum dots emit in the red.

The use of colloidal quantum dot (CQD) light-emitting diodes (LEDs) has become one of the key ingredients in leading technologies such as, for example, 3rd generation, solution processed, and inorganic solar cells. The implementation of these nanocrystals in devices for optical sensing in the short-wave and mid- infrared have triggered a vast number of applications including surveillance, night vision, product, process and environmental monitoring and spectroscopy.

In this recent study published in Nature Nanotechnology, ICFO researchers Santanu Padhan, Francesco Di Stasio, Yu Bi, Shuchi Gupta, Sotirios Christodoulou, and Alexandros Stavrinadis, led by ICREA Prof. at ICFO Gerasimos Konstantatos, have developed CQD infrared emitting LEDs, which have achieved unprecedented values in the infrared range, with an external quantum efficiency of 7.9% and a power conversion efficiency of 9.3%, a value never attained before with these type of devices.

The key feature of this work has been the development of a CQD composite structure engineered at the suprananocrystalline level to reach unprecedently low electronic defect density. Prior efforts in suppressing electronic defects in CQD solids have been primarily been based on chemical passivation of the CQD surface, something that could not solve the problem in PbS QDs. The researchers at ICFO took an alternative path of creating the appropriate matrix in which they embedded the emitting QDs, to serve as a remote electronic passivant for the emitter CQDs. Moreover, the energetic landscape of the matrix was engineered in order to facilitate efficient charge funnelling into the QD emitters in order to achieve efficient electrical injection.

With these new blend devices, the team of researchers took a step further and constructed solar cells to test their performance in the infrared range. In doing so they discovered that the effective passivation achieved in these nanocomposites along with the modulation of the electronic density of states has resulted in solar cells that deliver open circuit voltage very close to the theoretical limit. The open circuit voltage (VOC), which is the maximum voltage available from a solar cell, increased from 0.4 V for a single QD configuration, up to ~0.7 V for the ternary blend configuration, an impressive value considering the lower bandgap of the cell at ~0.9 eV.

As ICREA Prof at ICFO Gerasimos Konstantatos comments, “The most surprising finding of this study is the extremely low electronic trap density that can be achieved in a conductive QD material system that is full of chemical defects arising on the surface of the dots, the very high quantum efficiency of those LEDs has been the consequence of this passivation strategy we demonstrate. The other exciting outcome has been the potential to reach so high Voc values for QD solar cells that was synergistically achieved thanks to the very low trap density as well as to a novel engineering approach of the density of states in a semiconductor film”. Santanu Pradhan, the first author of this study adds: “Next we will focus on how to further exploit this reduction of electronic density of states synergistically with other means to allow for simultaneous achievement of high Voc and current production, thereby targeting record power conversion efficiencies in solar cell devices”.

The results obtained in this study prove that the engineering of QCD infrared-emitting LEDs at the nanoscale integrated in solar cells can significantly improve the performance efficiency of these devices in the infrared range. Such results open the pathway into a range of the spectra that is still to be fully exploited and offers amazing new applications, such as on-chip spectrometers for food inspection, environmental monitoring, manufacturing process monitoring as well as active imaging systems for biomedical or night vision applications.

A team of scientists from Arizona State University’s School of Molecular Sciences and Germany have published in Science Advances online today an explanation of how a particular phase-change memory (PCM) material can work one thousand times faster than current flash computer memory, while being significantly more durable with respect to the number of daily read-writes.

PCMs are a form of computer random-access memory (RAM) that store data by altering the state of the matter of the “bits”, (millions of which make up the device) between liquid, glass and crystal states. PCM technology has the potential to provide inexpensive, high-speed, high-density, high-volume, nonvolatile storage on an unprecedented scale.

The basic idea and material were invented by Stanford Ovshinsky, long ago, in1975, but applications have lingered due to lack of clarity about how the material can execute the phase changes on such short time scales and technical problems related to controlling the changes with necessary precision. Now high tech companies like Samsung, IBM and Intel are racing to perfect it.

The semi-metallic material under current study is an alloy of germanium, antimony and tellurium in the ratio of 1:2:4. In this work the team probes the microscopic dynamics in the liquid state of this PCM using quasi-elastic neutron scattering (QENS) for clues as to what might make the phase changes so sharp and reproducible.

On command, the structure of each microscopic bit of this PCM material can be made to change from glass to crystal or from crystal back to glass (through the liquid intermediate) on the time scale of a thousandth of a millionth of a second just by a controlled heat or light pulse, the former now being preferred. In the amorphous or disordered phase, the material has high electrical resistance, the “off” state; in the crystalline or ordered phase, its resistance is reduced 1000 fold or more to give the “on” state.

These elements are arranged in two dimensional layers between activating electrodes, which can be stacked to give a three dimension array with particularly high active site density making it possible for the PCM device to function many times faster than conventional flash memory, while using less power.

“The amorphous phases of this kind of material can be regarded as “semi-metallic glasses”,” explains Shuai Wei, who at the time was conducting postdoctoral research in SMS Regents’ Professor Austen Angell’s lab, as a Humboldt Foundation Fellowship recipient.

“Contrary to the strategy in the research field of “metallic glasses”, where people have made efforts for decades to slow down the crystallization in order to obtain the bulk glass, here we want those semi-metallic glasses to crystallize as fast as possible in the liquid, but to stay as stable as possible when in the glass state. I think now we have a promising new understanding of how this is achieved in the PCMs under study.”

A Deviation from the expected

Over a century ago, Einstein wrote in his Ph.D. thesis that the diffusion of particles undergoing Brownian motion could be understood if the frictional force retarding the motion of a particle was that derived by Stokes for a round ball falling through a jar of honey. The simple equation: D (diffusivity) = kBT/6??r where T is the temperature, ? is the viscosity and r is the particle radius, implies that the product D?/T should be constant as T changes, and the surprising thing is that this seems to be true not only for Brownian motion, but also for simple molecular liquids whose molecular motion is known to be anything but that of a ball falling through honey!

“We don’t have any good explanation of why it works so well, even in the highly viscous supercooled state of molecular liquids until approaching the glass transition temperature, but we do know that there are a few interesting liquids in which it fails badly even above the melting point,” observes Angell.

“One of them is liquid tellurium, a key element of the PCM materials. Another is water which is famous for its anomalies, and a third is germanium, a second of the three elements of the GST type of PCM. Now we are adding a fourth, the GST liquid itself..!!! thanks to the neutron scattering studies proposed and executed by Shuai Wei and his German colleagues, Zach Evenson (Technical University of Munich, Germany) and Moritz Stolpe (Saarland University, Germany) on samples prepared by Shuai with the help of Pierre Lucas (University of Arizona).”

Another feature in common for this small group of liquids is the existence of a maximum in liquid density which is famous for the case of water. A density maximum closely followed, during cooling, by a metal-to semiconductor transition is also seen in the stable liquid state of arsenic telluride, (As2Te3), which is first cousin to the antimony telluride (Sb2Te3 ) component of the PCMs all of which lie on the “Ovshinsky” line connecting antimony telluride (Sb2Te3 ) to germanium telluride (GeTe) in the three component phase diagram. Can it be that the underlying physics of these liquids has a common basis?

It is the suggestion of Wei and coauthors that when germanium, antimony and tellurium are mixed together in the ratio of 1:2:4, (or others along Ovshinsky’s “magic” line) both the density maxima and the associated metal to non-metal transitions are pushed below the melting point and, concomitantly, the transition becomes much sharper than in other chalcogenide mixtures.

Then, as in the much-studied case of supercooled water, the fluctuations associated with the response function extrema should give rise to extremely rapid crystallization kinetics. In all cases, the high temperature state (now the metallic state), is the denser.

“This would explain a lot,” enthuses Angell “Above the transition the liquid is very fluid and crystallization is extremely rapid, while below the transition the liquid stiffens up quickly and retains the amorphous, low-conductivity state down to room temperature. In nanoscopic “bits”, it then remains indefinitely stable until instructed by a computer-programmed heat pulse to rise instantly to a temperature where, on a nano-second time scale, it flash crystallizes to the conducting state, the “on” state.

Lindsay Greer at Cambridge University has made the same argument couched in terms of a “fragile-to-strong” liquid transition”.

A second slightly larger heat pulse can take the “bit” instantaneously above its melting point and then, with no further heat input and close contact with a cold substrate, it quenches at a rate sufficient to avoid crystallization and is trapped in the semi-conducting state, the “off” state.

“The high resolution of the neutron time of flight-spectrometer from the Technical University of Munich was necessary to see the details of the atomic movements. Neutron scattering at the Heinz Maier-Leibnitz Zentrum in Garching is the ideal method to make these movements visible,” states Zach Evenson.

EV Group (EVG), a supplier of wafer bonding and lithography equipment for the MEMS, nanotechnology and semiconductor markets, today introduced the all new BONDSCALE™ automated production fusion bonding system. BONDSCALE is designed to fulfill a wide range of fusion/molecular wafer bonding applications, including engineered substrate manufacturing and 3D integration approaches that use layer-transfer processing, such as monolithic 3D (M3D). With BONDSCALE, EVG is bringing wafer bonding to front-end semiconductor processing and helping to address long-term challenges for “More Moore” logic device scaling identified in the International Roadmap for Devices and Systems (IRDS). Incorporating an enhanced edge alignment technology, BONDSCALE provides a significant boost in wafer bond productivity and lower cost of ownership (CoO) compared to existing fusion bonding platforms. It is already being shipped to customers.

BONDSCALE is being sold alongside EVG’s industry benchmark GEMINI® FB XT automated fusion bonding system, with each platform targeting different applications. While BONDSCALE will primarily focus on engineered substrate bonding and layer-transfer processing, the GEMINI FB XT will support applications requiring higher alignment accuracies, such as memory stacking, 3D systems on chip (SoC), backside illuminated CMOS image sensor stacking, and die partitioning.

Direct wafer bonding key to driving semiconductor performance scaling

According to the IRDS Roadmap, parasitic scaling will become a dominant driver of logic device performance in the coming years, requiring new transistor architectures and materials. The IRDS Roadmap also notes that new 3D integration approaches such as M3D will be necessary to support the long-term transition from 2D to 3D VLSI, including backside power distribution, N&P stacking, logic-on-memory, clustered functional stacks and beyond-CMOS adoption. Layer-transfer processes and engineered substrates are enabling technologies for logic scaling by helping to deliver significant improvements in device performance, functionality and power consumption. Direct wafer bonding with plasma activation is a proven solution for enabling heterogeneous integration of different materials, high-quality engineered substrates as well as thin-silicon-layer-transfer applications.

“As a pioneer and market leader in wafer bonding, EVG has been at the forefront in helping customers bring new semiconductor technologies from early R&D to full-scale manufacturing,” stated Paul Lindner, executive technology director at EV Group. “Nearly 25 years ago, EVG introduced the industry’s first silicon-on-insulator (SOI) wafer bonder to support the production of high-frequency and radiation-hard devices for niche applications. Since then, we have continuously enhanced the performance and CoO of our direct bonding platforms to help our customers bring the benefits of engineered substrates to a wider range of applications. Our new BONDSCALE solution takes this to the next level, boosting productivity to fulfill the growing need for engineered substrates and layer-transfer processing to enable continued performance, power and area scaling of next-generation logic and memory devices in the ‘More Moore’ era.”

BONDSCALE is a high-volume production system for fusion/direct wafer bonding needed for front-end-of-line applications. Featuring EVG’s LowTemp™ plasma activation technology, the BONDSCALE system combines all essential steps for fusion bonding — including cleaning, plasma activation, alignment, pre-bonding and IR inspection — in a single platform that is suitable for a wide range of fusion/molecular wafer bonding applications. Capable of processing both 200-mm and 300-mm wafers, the system ensures a void-free, high-throughput, and high-yield production process.

BONDSCALE incorporates next-generation fusion/direct bonding modules, a new wafer handling system and optical edge alignment to provide significantly higher throughput and productivity to support the needs of its customers to ramp up engineered substrate wafer production and M3D integration.

Thermal Engineering Associates, Inc. (TEA) announces that its Thermal Test Chip (TTC) will soon be available in 8″ (200mm) diameter wafers. This conversion is taking place because –

  • Industry is better able to handle 8″ wafers for bumping, thinning, and sawing
  • Number of available Unit Cells per wafer is more than doubled
  • Wafers can be offered up to 725µm thick to better simulate application chips
  • The larger wafer produces more large cell array chips
  • Cost per Unit Cell is lowered

For a limited time, TEA is accepting preorders for the 8″ wafer products – both TTC-1001 (1mm x 1mm Unit Cell) and TTC-1002 (2.54mm x 2.54mm Unit Cell) versions – and is offering a price discount on orders of 5 or more wafers of either version. Both versions will be available in Wire Bond or Flip Chip (Bumped) types. Initial delivery is scheduled for February 2019.

Professor Michelle Simmons’ team at UNSW Sydney has demonstrated a compact sensor for accessing information stored in the electrons of individual atoms – a breakthrough that brings us one step closer to scalable quantum computing in silicon.

The research, conducted within the Simmons group at the Centre of Excellence for Quantum Computation and Communication Technology (CQC2T) with PhD student Prasanna Pakkiam as lead author, was published today in the prestigious journal Physical Review X (PRX).

Quantum bits (or qubits) made from electrons hosted on single atoms in semiconductors is a promising platform for large-scale quantum computers, thanks to their long-lasting stability. Creating qubits by precisely positioning and encapsulating individual phosphorus atoms within a silicon chip is a unique Australian approach that Simmons’ team has been leading globally.

But adding in all the connections and gates required for scale up of the phosphorus atom architecture was going to be a challenge – until now.

“To monitor even one qubit, you have to build multiple connections and gates around individual atoms, where there is not a lot of room,” says Professor Simmons. “What’s more, you need high-quality qubits in close proximity so they can talk to each other – which is only achievable if you’ve got as little gate infrastructure around them as possible.”

Compared with other approaches for making a quantum computer, Simmons’ system already had a relatively low gate density. Yet conventional measurement still required at least 4 gates per qubit: 1 to control it and 3 to read it.

By integrating the read-out sensor into one of the control gates the team at UNSW has been able to drop this to just two gates: 1 for control and 1 for reading.

“Not only is our system more compact, but by integrating a superconducting circuit attached to the gate we now have the sensitivity to determine the quantum state of the qubit by measuring whether an electron moves between two neighbouring atoms,” lead author Pakkiam states.

“And we’ve shown that we can do this real-time with just one measurement – single shot – without the need to repeat the experiment and average the outcomes.”

“This represents a major advance in how we read information embedded in our qubits,” concludes Simmons. “The result confirms that single-gate reading of qubits is now reaching the sensitivity needed to perform the necessary quantum error correction for a scalable quantum computer.”

Australia’s first quantum computing company

Since May 2017, Australia’s first quantum computing company, Silicon Quantum Computing Pty Limited (SQC), has been working to create and commercialise a quantum computer based on a suite of intellectual property developed at the Australian Centre of Excellence for Quantum Computation and Communication Technology (CQC2T).

Co-located with CQC2T on the UNSW Campus in Sydney, SQC is investing in a portfolio of parallel technology development projects led by world-leading quantum researchers, including Australian of the Year and Laureate Professor Michelle Simmons. Its goal is to produce a 10-qubit demonstration device in silicon by 2022 as the forerunner to a commercial scale silicon-based quantum computer.

SQC believes that quantum computing will ultimately have a significant impact across the global economy, with possible applications in software design, machine learning, scheduling and logistical planning, financial analysis, stock market modelling, software and hardware verification, climate modelling, rapid drug design and testing, and early disease detection and prevention.

Created via a unique coalition of governments, corporations and universities, SQC is competing with some of the largest tech multinationals and foreign research laboratories.

As well as developing its own proprietary technology and intellectual property, SQC will continue to work with CQC2T and other participants in the Australian and International Quantum Computing ecosystems, to build and develop a silicon quantum computing industry in Australia and, ultimately, to bring its products and services to global markets.

The European Research Council (ERC) has just published the list of 27 projects it selected out of the 299 submitted to the ERC Synergy 2018 call for projects. Among them, the CEA’s laboratories have 3 winners.  In order to ensure Europe’s long-term competitiveness, the ERC’s mission is to support world-class frontier research of excellence through highly competitive calls for projects. With a budget of 250 million euros, the “Synergy” category supports two to four researchers and their teams from different laboratories to jointly carry out an ambitious research project over a six-year period. With 35 million euros in European subsidies granted to these three projects, this is a strong recognition of the expertise of the CEA and its partners within the European Research Area.

ReNewQuantum (for Recursive and Exact New Quantum)

While quantum physics is omnipresent in most recent science and technology, quantum theory needs mathematical tools. These are currently somewhat lacking, in particular for complex quantum systems and approximation methods.

This is why the ReNewQuantum project is aiming to develop a mathematical method of semi-classical approximation[1] of quantum theories, which could benefit the entire scientific community, whether it is working on chaotic systems, quantum field theories or string theory. Building on concrete success already achieved in some quantum systems, ReNewQuantum proposes using modern geometry to reinterpret quantum theories and, in particular, to reinterpret semi-classical corrections as geometric objects. The project aims for a better understanding of the entire set of corrections, which would enable more effective computing. The objective is therefore to generalize these geometric methods to create a mathematical applicable to almost all quantum theories.

QuCube (for 3D integration technology for silicon spin qubits)[2]

Applied to the field of computing, quantum physics could revolutionize high performance computing, theoretically solving problems that conventional supercomputers are unable to solve. All major industries (transport, finance, energy, chemistry, pharmaceuticals, etc.) could benefit from quantum computing. In practice, this research has produced the first proofs of concept for quantum bits – the quantum equivalent of the most basic bit in elementary computing – but it is not yet certain that these first demonstrations can be reproduced on a large scale. In this context, the QuCube project aims to develop a quantum processor based on silicon, the base material already used in what is known as classical electronics. The processor will support at least one hundred quantum bits, or qubits, currently a first in terms of qubit numbers. The success of the project requires technological breakthroughs, including architecture implementation, the control of quantum bit variability or the implementation of quantum error correction processes, and finally a thorough understanding of conventional control electronics, for example on issues related to thermal dissipation.

Whole Sun (for The Whole Sun Project: Untangling the complex physical mechanisms behind our eruptive magnetic star and its twins)[3]

Our Sun is an active magnetic star that, due to its variable and eruptive behavior, has a direct impact on our technological society. However, despite decades of research, many questions remain unanswered. While this research into solar physics has so far focused on either the structure and dynamics of the inside of the Sun or, separately, on the surface and atmosphere of the Sun, the Whole Sun project aims to understand the Sun as a whole by consolidating research into these two major solar regions. A detailed study of the (thermo) dynamic and magnetic interaction between the deep solar interior, the surface of the Sun and the highly stratified atmosphere is absolutely vital if we hope to tackle the fundamental problems of solar physics (such as the origin of sunspots and the 11-year cycle; the presence of a warm atmosphere, etc.). In conjunction with the development of what is known as ‘exascale’ computers[4], Whole Sun will deliver the most advanced multi-resolution solar code in order to jointly address global and local, macrophysical and microphysical aspects of solar dynamics. Finally, extending this integrated approach led by Whole Sun to solar analogue stars that have different rotational speeds and chemical compositions will also provide a deeper understanding of stellar magnetism and activity.

[1] That is, starting from a classical system and calculating the successive quantum corrections.

[2] With CNRS and the participation of teams from the Université Grenoble Alpes.

[3] With the Max Planck Institute for Solar System Research (Germany), the University of Oslo (Norway) and the University of St Andrews (United Kingdom).

[4] Exascale computers are capable of performing a billion billion calculations per second. CEA is actively involved in working to develop this new generation of supercomputers.

[5] Not including these three new Synergy projects.

SUNY Polytechnic Institute (SUNY Poly) announced today that two professors have been selected to receive a total of $330,000 via the awarding of two separate nanoscience and nanoengineering-focused grants:

  • Professor of Nanoscience Dr. Serge Oktyabrsky has been awarded $200,000 from the U.S. Department of Energy (DOE) for research aiming to demonstrate a novel type of scintillation detector that upon detection of small particles, can emit measurable light with unsurpassed speed and yield. This greater sensitivity and speed is essential for several DOE High Energy Physics areas of research, and could help to detect the interaction of quantum particles to better understand their properties and actions, for example, in addition to the potential for medical and nuclear security applications; and
  • Assistant Professor of Nanoengineering Dr. Spyros Gallis (Spyridon Galis) was awarded $130,000 by the National Science Foundation (NSF) — Directorate of Engineering for research which will help develop critical physical properties and provide a fundamental understanding of new silicon carbide photonic nanostructures that have erbium ions added to them for the realization of high-temperature CMOS-compatible quantum emitters at telecommunications wavelengths. The emission from erbium ions at telecommunication wavelengths can be controlled and amplified by these photonic nanostructures and can improve light-based devices, with applications in areas such as biological imaging and sensing, quantum storage of single-photons, and long-distance quantum communications.

“I am proud to congratulate Professors Serge Oktyabrsky and Spyros Gallis for being awarded these grants which will support research that could help us to better understand the behavior of fundamental particles through improved detection capabilities, in addition to providing us with further knowledge about how photonic nanostructures, combined with erbium ions, can be used to improve a variety of quantum-based applications,” said SUNY Poly Interim President Dr. Grace Wang. “We are thankful to the Department of Energy and National Science Foundation for recognizing the exciting potential of these research projects being led by our outstanding faculty members who continue to push the boundaries of knowledge as they provide hands-on educational opportunities for our students.”

Both research projects will provide hands-on learning opportunities to SUNY Poly students. In Dr. Oktyabrsky’s lab, a graduate student will build the scintillation detector and perform its initial testing, along with support from two SUNY Poly staff scientists. Dr. Gallis’ research project will provide first-hand laboratory experience for both undergraduate and graduate students at SUNY Poly, as well as summer interns, who will simulate with numerical calculations the theoretical behavior of erbium emissions in the photonic nanostructures.

“These two grants are the latest example of how SUNY Poly’s faculty are driving research that can impact a wide range of applications and enhance our understanding of the world around us,” said SUNY Poly Interim Provost Dr. Steven Schneider. “The DOE and NSF grants will allow SUNY Poly students to take an active, hands-on role in these important areas of research, and I congratulate Drs. Oktyabrsky and Gallis on this news.”

Dr. Oktyabrsky Research Grant—”Performance of scintillation detectors based on quantum dots in a semiconductor matrix”

The DOE award supports the development of quantum dots (QD’s), semiconducting Indium Arsenide (InAs) particles approximately 10 nanometers in size, embedded into a Gallium Arsenide (GaAs) matrix. This arrangement enables the QD’s to act as artificial luminescence centers, which, when struck by gamma rays or other particles, emit luminescence, thereby acting as a measurable detector of such particles. If successful, the research will lead to the development of scintillation detectors with unsurpassed speed and light yield.

The main goal of the proposed research is to develop and test a novel scientific approach and technology for a QD semiconductor scintillation detector, develop a physical understanding of the underlying processes, and establish credible performance parameters of the detector. As supported by the DOE, Office of Science, High Energy Physics (HEP) Program, the technology would mostly be focused on HEP applications, such as using the detectors to identify multiple primary interactions, for example, at the Tevatron or Large Hadron Collider. In addition, the development of an ultra-high rate photon counting detector could be used for muon-to-electron conversion experiments, and because they are expected to have unprecedented energy resolution at high counting rates, the QD semiconductor scintillators could also be useful for non-accelerator dark matter searches and searches for new physics phenomena.

Eventually, by taking advantage of the picosecond-range timing (one trillionth of a second) and energy resolution of single X-ray photons, these detectors could also be used to reduce the radiation doses that patients receive via medical imaging/tomography applications, such as those used in X-ray computed tomography, or CT Scans, as well as positron emission tomography, or PET scans, in addition to improving spectroscopic accuracy in nuclear security applications.

“I am thrilled to congratulate Dr. Oktyabrsky, whose research, supported by the Department of Energy, can lay a strong foundation for being able to detect and measure quantum particle behavior through this enhanced scintillation detector. This can enable a more detailed understanding of high-energy physics, with ramifications for how we comprehend the universe around us. Dr. Oktyabrsky’s research is just one great example of what our faculty are working on each day in collaboration with students, who are able to engage by using SUNY Poly’s world-class capabilities to design and deploy new tools for obtaining new information,” said SUNY Poly Interim Dean of the College of Nanoscale Sciences; Empire Innovation Professor of Nanoscale Science; and Executive Director, Center for Nanoscale Metrology Dr. Alain Diebold.

“I am thankful to the Department of Energy for this grant which will support Quantum Dot semiconductor scintillators that could provide about 5x higher light yield and 20x faster decay time, potentially opening a pathway for the development of very low mass tracking detectors with picosecond-scale time-of-flight resolution, along with gamma detectors with energy resolution close to 1% at 1 million electron volts and room temperature, which would be capable of sustaining counting rates greater than 100 megahertz, or one million cycles per second,” said Dr. Oktyabrsky. “In addition to my gratitude for this DOE award, I am also thankful to Fermi National Accelerator Laboratory (Fermilab) for providing inspirational guidance in high-energy physics applications and support with detectors testing.”

Dr. Spyros Gallis Research Grant—“EAGER: On-Demand Silicon Carbide Photonic Nanostructures for Quantum Optoelectronics at Telecom Wavelengths”

Dr. Gallis’ research project aims to address fundamental questions pertaining to the material and physical behaviors of erbium-doped silicon carbide (SiC) photonic nanostructures. By deterministically integrating rare-earth erbium ions and by being able to engineer the ion’s emission properties in these photonic nanostructures, Dr. Gallis expects to develop potentially disruptive advances in single-photon emission at low-loss telecom C-band wavelength region ~1540 nm. The light emitted by a single-photon emitter is fundamentally different from laser or thermally produced light. The key distinction relates to the time intervals between the emitted photons in the light beam. Photons can either cluster together in bunches or they can have regular gaps between them. In the latter case, an ion cannot emit two photons at once, which can lead to a non-classical light (single-photon emission) source. This is a required property for the development of future quantum optoelectronics and long-distance quantum communication applications using existing fiber-optical-based infrastructures. Applications that could also benefit include, for example, telecom quantum memories and repeaters, to enable the storage of information based on quantum bits, which are the more complex version of today’s bits that can have more than an on (1) or off (0) state.

“I am proud to congratulate Dr. Gallis on this NSF research grant, which can drive advancements in the burgeoning quantum computing and communication space, with opportunities to develop these cutting-edge technologies while allowing our students to gain first-hand skills that can serve them well for a lifetime of learning,” said SUNY Poly Interim Dean of the College of Nanoscale Engineering and Technology Innovation and Associate Professor of Nanoengineering Dr. Michael Carpenter.

“I am grateful to the NSF Electronics, Photonics and Magnetic Devices (EPMD) Program for the support of this research, which can pave pathways in the uncharted territories of quantum optoelectronics and communication at telecom C-band wavelengths, empowering me and my research team to innovate and educate,” said Dr. Gallis. “I am also excited that this research can further attract students to our globally recognized College of Nanoscale Engineering and Technology Innovation, inspiring them to work in new quantum photonics research programs that can lead to game-changing technological developments.”

News of these latest grants follows other recent research funding announcements by SUNY Poly, including:

  •  Associate Professor of Nanoengineering Dr. Woongje Sung was selected to receive $2,078,000 in total federal funding from the U.S. Army Research Laboratory (ARL) for advancing the “MUSiC,” or the Manufacturing of Ultra-high-voltage Silicon Carbide devices for more robust power electronics chips with a range of military and commercial applications;
  •   Professor of Nanobioscience Dr. Nate Cady was recently awarded $500,000 in funding from the National Science Foundation to develop advanced computing systems based on a novel approach to the creation of non-volatile memory architecture;
  • Associate Professor of Nanobioscience Dr. Janet Paluh was recently awarded more than $970,000 from the New York State Health Department—Spinal Cord Injury Research Board (NYSCIRB) for collaborative research using nanotechnology and human stem cell-derived neural cell therapies to create an effective treatment platform for spinal cord injuries in patients, in addition to a $162,000 sub-award from the New York State Health Department—NYSTEM Innovative, Developmental, or Exploratory Activities (IDEA) program for collaborative research with the University at Albany to identify new types of injury and repair biomarkers based on cell communication to benefit prognosis or diagnosis of traumatic brain injuries; and
  • Associate Professor of Nanobioscience Dr. Michael Fasullo was awarded $446,000 by the National Institutes of Health National Institute of Environmental Health Sciences (NIH-NIEHS) to investigate with a number of partners how genetics can increase the risk of diet-associated colon cancer.

As new methods have become available for understanding and manipulating matter at its most fundamental levels, researchers working in the interdisciplinary field of materials science have been increasingly successful in synthesizing new kinds of materials. Often the goal of researchers in the field is to design materials that incorporate properties that can be useful for performing specific functions. Such materials can, for example, be more chemically stable or resistant to physical breakage, have advantageous electromagnetic characteristics, or react in predictable ways to specific environmental conditions.

Artist’s rendering of organic molecules adsorbing on a silicon surface. Credit: Image: Aaron Beller

Dr. Ralf Tonner and his research group at the University of Marburg are addressing the challenge of designing functional materials in an unusual way — by applying approaches based on computational chemistry. Using computing resources at the High-Performance Computing Center Stuttgart (HLRS), one of three German national supercomputing centers that make up the Gauss Centre for Supercomputing, Tonner models phenomena that happen at the atomic and subatomic scale to understand how factors such as molecular structure, electronic properties, chemical bonding, and interactions among atoms affect a material’s behavior.

“When you study how, for example, a molecule adsorbs on a surface,” Tonner explains, “other scientists will often describe that phenomenon with methods from physics, solid state theory, or band structures. We think it can also be very helpful to ask, how would a chemist look at what’s happening here?” From this perspective, Tonner is interested in exploring whether understanding chemical reactions — how atoms bond together into molecules and react when brought into contact with one another — can offer new and useful insights.

In a new publication in WIREs Computational Molecular Science, Tonner and his collaborator Lisa Pecher highlight the ability of computational chemistry approaches using high-performance computing to reveal interesting phenomena that occur between organic molecules and surfaces. They also demonstrate more generally how these interactions can be understood with respect to the molecular and solid state world. The knowledge they gained could be useful in designing patterned surfaces, a goal of scientists working on the next generation of more powerful, more efficient semiconductors.

Bringing computation to chemistry

Atoms bond together to form molecules and compounds when they approach one another and then trade or share electrons orbiting around their nuclei. The specific atoms involved, the physical shapes that the molecules take, their energetic properties, and how they interact with other nearby molecules are all properties that give a compound its unique properties. Such characteristics can determine whether compounds are likely to remain stable, or whether stresses such as changes in temperature or pressure could affect their reactivity.

Tonner uses a computational approach called density functional theory (DFT) to explore such characteristics at the quantum scale; that is, at the scale where Newtonian mechanics becomes replaced by the much stranger world of quantum mechanics (at distances of less than 100 nanometers). DFT uses information about variations in the density of electrons within a molecule — a quantity that can also be experimentally measured using a widely used technology called x-ray diffraction — to derive the energy of the system. This, in turn, enables the researchers to infer interactions among nuclei as well as interactions between electrons and nuclei, factors that are critical to understanding chemical bonds and reactions.

DFT can provide useful, though static, information about the energy profiles of the compounds they study. To gain a better understanding of how systems of molecules actually behave when interacting with a surface, Tonner’s group also uses high-performance computing at HLRS to perform molecular dynamics simulations. Here, the scientists look at how the system of molecules develops over time, at the level of atoms and electrons and at time scales of picoseconds (one picosecond is one trillionth of a second).

Such calculations typically use 2,000-3,000 computing cores, running on a problem for a week, and Tonner has been budgeted approximately 30 million CPU hours at HLRS for the current two-year funding cycle.

“Increasing computing power has made it possible for computational chemistry and quantum chemistry to describe real molecular systems. Just 15-20 years ago, people could only look at small molecules and had to make rather strong approximations,” Tonner explains. “In the last few years, the computational chemistry and solid state theory communities have solved the problem of parallelizing their codes to operate efficiently on high-performance computing systems. As supercomputers get bigger, we anticipate being able to develop increasingly realistic models for experimental systems in materials science.”

Toward light-based semiconductors

One area in which Tonner is currently using computational chemistry is to study ways to improve silicon for use in new kinds of semiconductors. This problem has gained urgency in recent years, as it has become clear that the microelectronics industry is reaching the limits of its ability to improve semiconductors using silicon alone.

As Tonner and experimental colleagues report in a recent paper in the Beilstein Journal of Organic Chemisty, functionalizing silicon with compounds such as gallium phosphide (GaP) or gallium arsenide (GaAs) could enable the design of new kinds of semiconductors. This research, based in a field called silicon photonics, posits that such new materials would make it possible to use light instead of electrons for signal transport, supporting the development of improved electronic devices.

“To do this,” Tonner explains, “we really need to understand how the interfaces between silicon and these organic compounds look and behave. The reaction between these two material classes needs to proceed in a very controlled manner so that the interface is as perfect as possible. With computational chemistry we can look at the elemental details of these interactions and processes.”

For example, to cover a slab of silicon, liquid precursor molecules for the constituent atoms of gallium arsenide are placed in a bubbler, where they are then brought into the gas phase. These precursor molecules are composed of the atoms required for the new material (gallium, arsenic) and ions or molecules called ligands to stabilize them in the liquid and gas phase. These ligands are subsequently lost in the deposition process and when silicon is placed in the system, the precursor molecules are adsorbed onto the solid silicon surface. After adsorption and loss of the ligands, gallium and arsenide atoms attach to the silicon, forming a GaAs film.

How atoms are arranged when they adsorb to a surface is determined by chemical bonding. The strength of these bonds and the density with which the GaAs precursor molecules are adsorbed is affected not only by the distance between them and the silicon surface but also by interactions among the precursor molecules themselves. In one type of interaction, called Pauli repulsion, clouds of electrons overlap and repel each other, causing the available energy for bonding to decline. In another, called attractive dispersion interaction, changes in the electronic positions in one atom cause electrons to be redistributed in other atoms, bringing the electron movements into harmony and lowering the energy of the total system.

Previously, it had been suggested that repulsive relationships among atoms is the most important factor in “steering” atoms into place when they adsorb on a surface. By using density functional theory and looking at intriguing features of how electrons are distributed, the researchers determined that the ability of atoms to steer other atoms into place on the surface can also result from attractive dispersive interactions.

Gaining a better understanding of these fundamental interactions should help designers of optically active semiconductors to improve adsorption of the precursor molecules onto silicon. This, in turn, would make it possible to combine light signal conduction with silicon based microelectonics, bringing together the best of both worlds in optical and electronic conduction.

For Tonner, using first principles methods in chemistry for materials science applications holds great promise. “Theory today is very often taken as a complement to experimental investigation,” he says. “Although experimentation is extremely important, our ultimate goal is for theory to be predictive in ways that enable us to make the first steps in first principles-inspired materials design. I see this as a long term goal.”

A team of researchers from Siberian Federal University (SFU) obtained thin copper/gold and iron/palladium films and studied the reactions that take place in them upon heating. Knowing these processes, scientists will be able to improve the properties of materials currently used in microelectronics. The article of the scientists was published in the Journal of Solid State Chemistry.

Materials based on thin metal films are widely used in microelectronics (e.g. copper and gold – in the manufacture of electrical contacts). Nanomaterials based on iron and palladium have unique magnetic properties and potentially can be used for high-density magnetic recording of information. One of the main factors that affects the properties of thin film materials is alteration of the phase composition as a result of chemical reactions and atomic structure realignment. The work of the researchers covers solid phase reactions in two-layer thin metal films – copper/gold (Cu/Au) and iro/palladium (Fe/Pl).

The scientists obtained the Cu/Au and Fe/Pd films in SFU common use center. To do so, they used the method of electron-beam deposition in high vacuum, i.e. evaporated the alloy using a beam of electrons and then deposited it on a carrying base as a thin layer. The thickness of the layer could be regulated. After obtaining the films the scientists made an experiment to study the course of chemical reactions in the interface region of the initial elements. For the reactions to take place, materials had to be heated to high temperatures which was done directly in the column of a transmission electron microscope. The team used a special sample holder that allowed for controlled heating of each sample from room temperature to 1,000 °. Along with the heating, the team registered electron diffraction images and measured the temperature. Thus, the scientists managed to combine the initiation of the reaction and the registration of changes in a solid-phase reaction within one experiment and to secure high data precision.

“We’ve established the value of the long-range order parameter and the temperature of the order-disorder transition in atomically ordered phases formed in the course of the reaction. The atoms of such phases form ordered structures of certain shapes. We also suggested a mechanism for the formation of such ordered structures. For instance, in the case of the Cu/Au system we demonstrated how mutual diffusion of copper and gold on the initial stages of the reaction leads to the refinement of grains of the initial materials and the formation of Cu-Au solid solution nanocrystallites within the material. Later on, a new ordered structure occurs and starts to grow on the basis of these components,” explains Evgeny Moiseenko, a co-author of the work, candidate of physics and mathematics, and a research assistant at SFU.

The work of the scientists will help identify the features of the studied thin film systems that may be used in the design of microelectronic devices.