Each year, the Institute for Materials Research Distinguished Lecture Series brings world renowned materials researchers to The Ohio State University campus to share the latest developments in materials-allied fields and discuss their research with Ohio State students, faculty and staff. IMR Distinguished Lecturers include the top scientists in their fields.
All IMR Distinguished Lectures are free and open to the entire Ohio State materials community – faculty, staff and students. For detailed listings of all past IMR Colloquia as part of the former IMR Colloquia Series, click here.
High-K Dielectrics: A Perspective on Applications from Silicon to 2-D Materials
Robert M. Wallace, professor of Materials Science and Engineering and Erik Jonsson Distinguished Chair in the Erik Jonson School of Engineering and Computer Science at the University of Texas at Dallas.
Tuesday, March 27, 2018, 2 p.m.
E100 Scott Laboratory
201 W. 19th Ave., Columbus, Ohio
In the 1990s, research accelerated on addressing the limits of the industry standard gate dielectric: SiO2. With the most aggressive integrated circuit scaling, it became clear that standby power for MOSFETs required the insertion of a gate dielectric material that reduced tunneling leakage while enabling performance expectations. Leveraging prior dielectric research and after exploring several dielectric material candidates, [1,2] Hf-based dielectrics became the dominant choice and were established in commercial Si technology fabrication processes in 2007 after at least a decade of research.  Although perhaps forgotten among today’s 3-D FET technologies, the introduction of a new gate dielectric, simultaneously with metal gate materials, was considered quite revolutionary in its day, and this development, in conjunction with other device engineering aspects like strain, enabled the continued march of the industry along Moore’s original predictions. Since that time, the research on incorporating high-k dielectrics has expanded to address alternative channel materials including Ge, III-V, wide band gap semiconductors, and, most recently, perhaps the ultimate limit in channel scaling – atomically thin 2-D materials.  This talk, from the author’s perspective, will review some of these developments and provide some context on the resilience of the materials research as well as the challenges and opportunities that lie ahead. 
This work is supported in part by the US-Ireland R&D Partnership (UNITE) under the NSF award ECCS-1407765, and (iv) the Erik Jonsson Distinguished Chair in the Erik Jonson School of Engineering and Computer Science at the University of Texas at Dallas.
 J. Robertson and R.M.Wallace, Materials Science and Engineering R, 88, 1-41 (2015).
 G.D.Wilk, R.M.Wallace, and J.M.Anthony, Journal of Applied Physics 89 5243 (2001).
 M.T. Bohr, R.S. Chau, T. Ghani, K. Mistry, IEEE Spectrum. 44 (29) (2007).
 S.J. McDonnell and R.M.Wallace, Thin Solid Films, 616, 482 (2016).
 R.M.Wallace, ECS Transactions 80(1), 17 (2017).
Robert M. Wallace received his B.S. in Physics and Applied Mathematics in 1982 at the University of Pittsburgh where he also earned his M.S. (1984) and Ph.D. (1988) in Physics, under Prof. W. J. Choyke. From 1988 to 1990, he was a postdoctoral research associate in the Department of Chemistry at the Pittsburgh Surface Science Center under the late Prof. John T. Yates, Jr.
In 1990, he joined Texas Instruments Central Research Laboratories as a Member of Technical Staff (MTS) in the Materials Characterization Branch of the Materials Science Laboratory, and was elected as a Senior MTS in 1996. Dr. Wallace was then appointed in 1997 to manage the Advanced Technology branch in TI’s R&D, which focused on advanced device concepts and the associated material integration issues. In 2003, he joined the faculty in the Erik Jonsson School of Engineering and Computer Science at the University of Texas at Dallas (UTD) as a professor of Electrical Engineering and Physics. He is a founding member of the Materials Science and Engineering program at UTD and served as an interim head for the program. Dr. Wallace also has appointments in the Departments of Electrical Engineering, Mechanical Engineering, and Physics.
Research in the Wallace group focuses on the study of surfaces and interfaces, particularly with applications to electronic materials and the resultant devices fabricated from them. Current interests include materials systems leading to concepts that may enable further scaling of integrated circuit technology and beyond CMOS-based logic. These include the study of the surfaces and interfaces of compound semiconductor systems, including arsenides (e.g. InGaAs), nitrides (e.g. GaN), phosphides (e.g. InP), as well as antimondies (e.g. GaSb), and most recently 2-D materials, such as graphene and transition metal dichalcogenides. He has authored or co-authored over 375 publications in peer-reviewed journals and proceedings with over 20000 (29000) citations according to Scopus (Google Scholar).
Dr. Wallace is also an inventor on 45 U.S. and 27 international patents/applications, and a co-inventor of the Hf-based, high-k gate dielectric materials now used by the semiconductor industry for advanced high performance logic in microprocessors. He was named Fellow of the AVS in 2007 and an IEEE Fellow in 2009 for his contributions to the field of high-k dielectrics in integrated circuits.
The Influence of Fields and Dopants on Grain Boundary Mobility
Wayne D. Kaplan, Professor in the Department of Materials Science and Engineering, Technion – Israel Institute of Technology
Thursday, October 12, 2017
E100 Scott Laboratory,
Controlling grain size is a fundamental part of Materials Science and Engineering. While the driving force for grain growth is thought to be understood, the mechanism by which grain boundaries migrate, and how microscopic parameters affect grain boundary mobility, are less understood. This presentation focuses on the mobility of grain boundaries and how dopants and external fields influence the kinetics of grain growth.
The first part of the talk will address the concept of solute-drag, where conventional wisdom indicates that moving a solute cloud with a grain boundary should either slow down grain boundary motion (e.g. Mg in Al2O3), or not affect it. Model experiments at dopant levels below the experimentally determined solubility limit clearly show that some adsorbates reduce grain boundary mobility (the accepted solute-drag effect) whereas other increase grain boundary mobility (solute-acceleration). Reasons for the varying behavior are discussed within the framework of grain boundary disconnections as the mechanism by which grain boundaries move, and current approaches to understanding Gibbsian adsorption.
The second part of the talk reviews model experiments designed to probe the influence of external fields on grain boundary mobility. As a model system, polycrystalline SiC underwent conventional annealing, and annealing using spark plasma sintering (SPS) without pressure, and the grain size as a function of annealing time was characterized. From these experiments, the grain boundary mobility of SiC at 2100°C under conventional versus SPS annealing was determined. SPS annealing resulted in a grain boundary mobility which is three orders of magnitude larger than that resulting from conventional annealing. This indicates that the same (or similar) mechanism which promotes rapid sintering during SPS also significantly increases the rate of grain growth. This mechanism will be discussed in light of the “solute-acceleration” effect presented in the first part of the talk.
Wayne D. Kaplan is a full professor in the Department of Materials Science and Engineering at the Technion – Israel Institute of Technology, where he holds the Karl Stoll Chair in Advanced Materials. Kaplan currently serves as the Executive Vice President for Research at the Technion. He completed his BSc in Mechanical Engineering, and his MSc and DSc in Materials at the Technion after immigrating to Israel from the U.S. He then spent a year as a Humboldt Fellow at the Max-Planck Institute in Stuttgart Germany before joining the Technion faculty in 1995.
During the past 20 years Kaplan’s research activities at the Technion have focused on the structure, chemistry and energy of interfaces between metals and ceramics, with a focus on the correlation between thermodynamics (continuum) approaches and the atomistic structure and chemistry of interfaces. In addition to his fundamental research in materials science, Kaplan works on the development of electron microscopy techniques for characterization at the sub-nanometer length-scale.
Kaplan is the author of more than 130 reviewed and archived scientific articles, as well as two textbooks: Joining Processes and Microstructural Characterization of Materials. In 2006 he received the Henry Taub Prize for Academic Excellence. He is a fellow of the American Ceramic Society, a member of the Israel Microscopy Society, and was an editor of the Journal of Materials Science (Springer).
From Mobile Phones to Russian Dolls to MASERs
Neil Alford, Head of Department of Materials, Imperial College London
Friday, January 20, 2017
Smith Seminar Room, 1080 Physics Research Building
In this talk we will look at the problem of dielectric loss (the tan δ) in oxides and how this led us to the world’s first room temperature MASER. Why are we interested in dielectric loss? Almost all of us have a mobile phone and dielectric resonators form essential parts of communications systems. The term “Dielectric Resonator” was first used by Richtmeyer(1) in 1939 who showed that a dielectric ring could confine high frequency electromagnetic waves and thus form a resonator. The idea of a dielectric material confining EM radiation dates back to 1897 when Lord Rayleigh described a dielectric waveguide(2) and in 1909 when Debye described dielectric spheres(3). With the astonishing growth in the cellular communications industry the market is now very approximately 2BN sales of mobile phones each year (that’s about 60 each second) the market for microwave ceramics is huge.
One of the key properties is the dielectric loss or tan delta. The inverse of this is called the Quality factor or Q. Imagine a tuning fork. When you strike it, it resonates for a long time – it has a high Q and if it were made from e.g. wood it would be damped severely, would not resonate and have a very low Q. Now imagine hitting a dielectric (like alumina or sapphire) with an electromagnetic wave – a microwave – it resonates and what we need is a very high Q so that we can build good filters. The dielectric loss is limited by the dielectric loss of the material – the dielectric limit – but suppose you could exceed this. This is what we did by some cunning engineering using a Bragg reflector (a bit like a Russian doll) in which the sapphire layers of the Russian doll (called Bragg layers) are not the usual equal thickness but are aperiodic. Remarkably, if the layers are aperiodic in thickness the Q factor rises quadratically to reach extraordinarily high values of Q=0.6×106 at 30GHz (world record)(4).
This result suggested that it might be possible to reach the threshold for masing and indeed we demonstrated that in P-terphenyl doped with pentacene when located inside a very high Q sapphire resonator maser action can be observed. This is the first time a solid state maser has been demonstrated at room temperature and in the earth’s magnetic field(5). Recent work(6) has shown that miniaturisation is feasible and considerable reduction in pumping power is possible by using a strontium titanate resonator which by virtue of a higher relative permittivity leads to a factor of over 5 in size reduction. Importantly, the Purcell factor which is the ratio of the Q factor to the mode volume, remains high and this is a key factor in the ability to exceed the threshold for masing.
Professor Neil Alford MBE FREng is a materials scientist and Associate Provost for Academic Planning at Imperial College London. He worked in industry for 15 years and then in University research at Queen Mary College, Oxford and South Bank University. His work has focused on materials from high-strength cement to High Temperature Superconductors, nanotechnology and room temperature MASERs. Technology transfer is a key focus and Neil’s discoveries been applied widely in industry, including cellular communications. Having held various academic posts at Imperial (including HoD of Materials), Neil is closely involved in the College’s new White City Campus. Spanning 23 acres, the campus will provide a new research and innovation district, where Imperial and its partners work to tackle the world’s greatest challenges. It will provide space for new types of multidisciplinary research, collaboration with corporations, institutions and start-ups, as well as activities to engage and inspire the community in White City.
1. R. D. Richtmeyer, J Appl. Phys. 10, 391-398 (1939)
2. Lord Rayleigh, Phil. Mag. S.5 43, 125-132 (1897)
3. P. Debye, Ann. D. Physik, 30, 57-136 (1909)
4. Better than Bragg: Optimizing the quality factor of resonators with aperiodic dielectric reflectors Breeze Jonathan; Oxborrow Mark; Alford Neil McN APPLIED PHYSICS LETTERS Volume: 99 Issue: 11 Number: 113515 2011
5. Room Temperature Maser NATURE, 16 August 2012 Mark Oxborrow, Jonathan Breeze and Neil Alford
6. Enhanced magnetic Purcell effect in room-temperature masers Jonathan Breeze, Ke-Jie Tan, Benjamin Richards, Juna Sathian, Mark Oxborrow and Neil Alford Nature Comms DOI 10.1038/ncomms7215 (2015)
2015-2016 IMR Distinguished Lecture Series
21.25% World Efficiency Record with Multi-Crystalline p-type Silicon Solar Cells: Closing the Gap with n-type Mono
Friday, June 17, 2016
10:00 AM (Reception to follow)
E525 Scott Laboratory, 201 West 19th Avenue
Multicrystalline Silicon technologies represents more than 65% of 2015 global shipments. Over the last two years, the best p-type multicrystalline silicon solar cells developed by Trina Solar have reached new efficiency records, up to 20.86% in 2014 and 21.25% in 2015. These achievements result from improvements of all aspects of the solar cell fabrication: contamination control, development of high-performance multi-crystalline silicon wafers, cell design and process optimization. Analysis show that efficiencies above 22% are possible with p-type multicrystalline and could be reached in the next few years.
Pierre J. Verlinden is Vice-President and Chief Scientist at Trina Solar, the world’s largest PV manufacturer. He is also Vice-Chair of the State Key Laboratory of PV Science and Technology. Dr. Verlinden has been working in the field of photovoltaics for more than 35 years and has published over 170 technical papers and contributed to a number of books. Before joining Trina Solar, Dr. Verlinden served as Chief Scientist or head of R&D department in several other PV companies in USA and Australia, including SunPower, Origin Energy, Amrock and Solar Systems.
Antimonide Materials for Mid-Infrared Photonic Detectors and Focal Plane Arrays
Tuesday, April 12, 2016
9:45 AM (reception to follow)
E100 Scott Laboratory, 201 West 19th Avenue
Infrared imaging (3-25mm) has been an important technological tool for the past sixty years since the first report of infrared detectors in 1950s. There has been a dramatic progress in the development of infrared antimonide based detectors and low power electronic devices in the past decade with new materials like InAsSb, InAs/GaSb superlattices and InAs/InAsSb superlattices demonstrating very good performance. One of the unique aspects of the 6.1A family of semiconductors (InAs, GaSb and AlSb) is the ability to engineer the bandstructure to obtain designer band-offsets. Our group (www.krishnairlab.com) has been involved with the vision of the 4th generation of infrared detectors and is one of two university laboratories in the country that can undertake “Design to Camera” research and realize focal plane arrays.
This talk will revolve around three research themes:
The first theme involves the fundamental investigation into the material science and device physics of the antimonide systems. I will describe some of the challenges in these systems including the identification of defects that limit the performance of the detector. The use of “unipolar barrier engineering” to realize high performance infrared detectors and focal plane arrays will be discussed.
The second theme will involve the vision of the 4th Gen infrared imaging systems. Using the concept of a bio-inspired infrared retina, I will make a case for an enhanced functionality in the pixel. The key idea is to engineer the pixel such that it not only has the ability to sense multimodal data such as color, polarization, dynamic range and phase but also the intelligence to transmit a reduced data set to the central processing unit. The design and demonstration of meta-infrared detectors will be discussed.
In the final theme, I will describe the role of infrared imaging in bio-medical diagnostics. In particular, I will highlight some work on using infrared imaging in the early detection of skin cancer and for detection of flow in cerebral shunts. Using dynamic thermal imaging on over 100 human subjects, a sensitivity >95% and specificity >83% has been demonstrated. Commercialization of this technology will also be discussed.
Sanjay Krishna is the Director of the Center for High Technology Materials and Professor and Regents Lecturer in the Department of Electrical and Computer Engineering at the University of New Mexico. Sanjay received his M.S. from IIT, Madras, MS in Electrical Engineering in 1999 and PhD in Applied Physics in 2001 from the University of Michigan. He joined UNM as a tenure track faculty member in 2001. He currently heads a group of 15 researchers involved with the development of next generation infrared imagers. Sanjay received the Gold Medal from IIT, Madras, Ralph Powe Junior Faculty Award, IEEE Outstanding Engineering Award, ECE Department Outstanding Researcher Award, School of Engineering Jr Faculty Teaching Excellence Award, NCMR-DIA Chief Scientist Award for Excellence, the NAMBE Young Investigator Award, IEEE-NTC, SPIE Early Career Achievement Award and the ISCS Young Scientist Award. He was also awarded the UNM Teacher of the Year and the UNM Regents Lecturer award. Sanjay has more than 200 peer-reviewed journal articles (h-index=42), two book chapters and seven issued patents. He is the co-founder and CTO of Skinfrared, a UNM start-up involved with the use of IR imaging for dual use applications including early detection of skin cancer. He is a Fellow of IEEE, OSA and SPIE.
2014-2015 IMR Distinguished Lecture Series
Joan F. Brennecke, Keating-Crawford Professor of Chemical Engineering, Department of Chemical and Biomolecular Engineering, University of Notre Dame
Wednesday, February 18, 2015
Ionic liquids (ILs) present intriguing possibilities for removal of carbon dioxide from a wide variety of different gas mixtures, including post-combustion flue gas, pre-combustion gases, air, and raw natural gas streams. Even by physical absorption, many ILs provide sufficient selectivity over N2, O2, CH4 and other gases. However, when CO2 partial pressures are low, the incorporation of functional groups to chemically react with the CO2 can dramatically increase capacity, while maintaining or even enhancing selectivity. We will demonstrate several major advances in the development of ILs for CO2 capture applications. First, we will show how the reaction stoichiometry can be doubled over conventional aqueous amine solutions to reach one mole of CO2 per mole of IL by incorporating the amine on the anion. Second, we will show how we have been able to virtually eliminate any viscosity increase upon complexation of the IL with CO2, by using aprotic heterocyclic anions (AHA ILs) that eliminate the pervasive hydrogen bonding and salt bridge formation that is the origin of the viscosity increase. Third, we will describe the discovery of AHA ILs whose melting points when reacted with CO2 are more than 100 °C below the melting point of the unreacted material. These materials allow one to dramatically reduce the energy required for CO2 release and regeneration of the absorption material because a significant amount of the energy needed for the regeneration comes from the heat of fusion as the material releases CO2 and turns from liquid to solid.
Joan F. Brennecke is the Keating-Crawford Professor of Chemical Engineering at the University of Notre Dame and was the founding Director of the Center for Sustainable Energy at Notre Dame. She joined Notre Dame after completing her Ph.D. and M.S. (1989 and 1987) degrees at the University of Illinois at Urbana-Champaign and her B. S. at the University of Texas at Austin (1984).
Her research interests are primarily in the development of less environmentally harmful solvents. These include supercritical fluids and ionic liquids. In developing these solvents, Dr. Brennecke’s primary interests are in the measurement and modeling of thermodynamics, thermophysical properties, phase behavior and separations. Major awards include the 2001 Ipatieff Prize from the American Chemical Society, the 2006 Professional Progress Award from the American Institute of Chemical Engineers, the J. M. Prausnitz Award at the Eleventh International Conference on Properties and Phase Equilibria in Greece in May, 2007, the 2008 Stieglitz Award from the American Chemical Society, the 2009 E. O. Lawrence Award from the U.S. Department of Energy, and the 2014 E. V. Murphree Award in Industrial and Engineering Chemistry from the American Chemical Society. She serves as Editor-in-Chief of the Journal of Chemical & Engineering Data. Her 130+ research publications have garnered over 12,000 citations. She was inducted into the National Academy of Engineering in 2012.
The Automotive Industry, Vehicle Electrification, and Industrial Research
Mark W. Verbrugge, Chemical and Materials Systems Laboratory, General Motors Research and Development
Tuesday, October 14, 2014
This talk will begin with a review of automotive vehicle electrification: trends and drivers. The life of lithium-ion batteries is related to the mechanical expansion and contraction of the active materials along with solvent decomposition at the active material surfaces—lithium-ion batteries would not work if a protective shell did not cover the electroactive core of the positive and negative electrode materials. Exposure of the active core leads to cell degradation. These observations hold for current and next-generation lithium-ion batteries. Under what conditions are the protective (outer shell) materials compromised? In addition to reviewing literature that is relevant to answering this question, the speaker intends to overview research results to render a qualitative response to this question and identify open questions that limit the quantitative application of modeling results to these systems. Last, we will close with a brief perspective on “what is useful industrial research?”
Mark Verbrugge is the Director of GM’s Chemical and Materials Systems Laboratory, which maintains global research programs—enabled by the disciplines of chemistry, physics, and materials science—and targets the advanced development of structural subsystems, energy storage and conversion devices, and various technologies associated with fuels, lubricants, and emissions.
Mark is a Board Member of the United States Automotive Materials Partnership LLC and the United States Advanced Battery Consortium LLC. Mark has received a number of GM internal awards as well as external awards including the Norman Hackerman Young Author Award and the Energy Technology Award from the Electrochemical Society, and the Lifetime Achievement Award from the United States Council for Automotive Research. Mark is a Fellow of the Electrochemical Society and a member of the National Academy of Engineering.
2013-2014 IMR Distinguished Lecture Series
Silicon Photovoltaics: Power Source for the Future?
Prof. Martin A. Green, Australian Centre for Advanced Photovoltaics, School of Photovoltaic and Renewable Energy Engineering, University of New South Wales, Australia
Monday, October 7, 2013
The last few years has seen photovoltaics (PV) emerge from relative obscurity to becoming one of the top three sources of new electricity generation capacity internationally. The vast majority of photovoltaic solar cells produced to date have been based on silicon wafers, with this dominance likely to continue well into the future. The surge in manufacturing volume over the last decade has resulted in greatly decreased costs. Multiple companies are now producing at costs much lower than the US$1/Watt module manufacturing cost benchmark once regarded as the lowest possible with this technology. Despite these huge cost reductions, there is clear scope for much more, as the polysilicon source material becomes more competitively priced, new “high-performance” directional solidification processes for producing increasingly large and better-performing silicon ingots are brought on-line, wafer slicing switches to much quicker diamond impregnated approaches and cell conversion efficiencies increase towards 25% and increasing effort is placed on the development of even higher performance silicon-based tandem cell stacks. Photovoltaics are increasingly seen as a viable green energy source of the future, meeting growing energy demands on a large scale without adding to the carbon burden.
Dr. Martin Green is currently Scientia Professor at the University of New South Wales, Sydney and Director of the Australian Centre for Advanced Photovoltaics. His group’s contributions to photovoltaics include development of the world’s highest efficiency silicon cells and commercialization of several different cell technologies. He is the author of several books on solar cells and numerous papers. His work has been recognised by major international awards including the 2002 Right Livelihood Award, also known as the Alternative Nobel Prize, the 2007 SolarWorld Einstein Award and the 2010 Eureka Prize for Leadership. In 2012, he was appointed as a Member of the Order of Australia in recognition of his contributions to photovoltaics and photovoltaics education.