Speaker: Melvin Vopson, Senior Lecturer in Physics at the University of Portsmouth
Title: Ferroelectric and Antiferroelectric Oxides for Memories
Abstract: Polarization dynamics in polar and anti-polar dielectrics is a very complex process that is the subject of intensive theoretical and experimental research. Besides the necessity to advance our fundamental understanding of these materials, a unifying model that explains the polarization dynamics in polar and anti-polar dielectrics is extremely beneficial for their technological applications, including non-volatile digital memories. In this lecture, a new theoretical approach to the physics of polarization dynamics is introduced together with its experimental confirmation. The presented model is universally applicable to bulk and thin film dielectrics. It will be shown that the model accounts successfully for the applied electric field, time, and temperature contributions, simultaneously, to produce comprehensive analytical relations for the reversed polarization, switching time, switching current, coercive field, remanent polarization, domain wall velocity and Curie law in ferroelectrics. Moreover, there is recent evidence that the model is applicable not only to polar dielectrics, but also to anti-polar dielectrics, i.e. antiferroelectric materials. These findings will be discussed in the context of their applications to non-volatile memory devices, and a novel concept of antiferroelectric non-volatile random access memory will be presented.
Bio: Dr. Melvin M. Vopson is Senior Lecturer in Physics at the University of Portsmouth, where he was appointed permanent academic staff in 2012. He has over 16 years postdoctoral experience in condensed matter research, has published 71 articles, achieving 1258 citations and an h-index of 19. Previously he worked as postdoctoral research fellow of the University of York, followed by a senior R&D scientist appointment at Seagate Technology and Higher Research Scientist with the UK National Physical Laboratory, where he worked for over six years. Melvin is a Chartered Physicist, Fellow of the Institute of Physics and Fellow of the UK Higher Education Academy. Melvin’s main scientific contributions are: the development of a new plasma sputtering process for grain size control in thin films; the first experimental demonstration of the magneto-refractive effect; the development of a novel model of polarization dynamics; the discovery of the multicaloric effect and the co-discovery of the memory effect in antiferroelectrics. Currently his research involves studies of multiferroic materials, development of flexible multi-functional thin films, and development of non-contact non-destructive optical testing of magnetic and magnetotransport properties in solids.
MSE Seminar Host: Xiaoli Tan