Day 1 :
Michigan State University, USA
Time : 09:30-10:15
Subhendra Dev Mahanti obtained his BSc from Utkal University in 1961; MSc from Allahabad University in 1963; PhD in Theoretical Condensed Matter Physics from the University of California, Riverside (USA) in 1968. After two years at Bell Telephone Laboratories, he joined Michigan State University in 1970, where he has been a Full Professor since 1982 and is currently an Emeritus Professor. His research is in the area of magnetism, high Tc superconductors, multi-ferroics, physical systems showing colossal magnetic resistance, thermoelectrics, and topological insulators. He has published nearly 300 papers in reputed journals.
Global energy issues have created a pressure to increase both the use of renewable sources of energy and the efficiency of current power generation and utilization. In the latter context thermoelectricity can play an important role in addressing the problems of energy utilization and management. The major challenge facing the thermoelectric research is to improve the efficiency which depends on dimensionless figure of merit (is thermopower, is electrical conductivity, is total thermal conductivity usually dominated by the phonons and is the operating temperature). To achieve higher efficiency, ideas like quantum confinement, electron crystal phonon glass, nanostructuring, hierarchical structures, energy filtering, low-dimensional charge transport created by highly anisotropic electronic band structure, etc. have impacted the field of thermoelectrics during the last several decades. In this talk I will review some of the recent advances in the field and discuss how ab initio theoretical calculations are contributing to and clarifying these ideas. Some of the systems I will discuss are (i) thermoelectric materials with intrinsically low thermal conductivity such as layered SnSe and bulk systems with effective superlattice structure Bi(CuSe)O and Sr(AgSe)F where CuSe(AgSe) layers are sandwiched between Bi-O (Sr-F) layers; (ii) 3-dimensional systems with highly anisotropic electronic bands as in Heusler systems. I will also briefly discuss recent work on computationally guided discovery of novel thermoelelctric materials for example, n-type Zintl compounds.
Cheongju University, Republic of South Korea
Time : 10:15-11:00
Sang Yeol Lee obtained his BS Degree in the Department of Electrical Engineering at Yonsei University (Republic of South Korea) in 1986; MS and PhD Degrees in the Department of Electrical and Computer Engineering from State University of New York at Buffalo (USA) in 1990 and 1992, respectively. He has been a Full Professor in the Department of Semiconductor Engineering at the Cheongju University; Full Professor and Director of Research Institute of Advanced Semiconductor Convergence Technology. He was invited as a Visiting Scholar in Electronic Device Team, Los Alamos National Lab (USA) in 2002–2003. His research areas are ZnO electronics including oxide TFTs, LEDs, transparent conducting oxides, semiconductor processing, nanoelectronics, memory devices and displays. He is mainly interested in Materials Science.
Amorphous oxide thin film transistors (AOTFT) have been fabricated by RF (Radio Frequency) magnetron sputtering with the bottom gate structure. AOTFTs exhibited to change stability under the bias and temperature stress and electrical properties strongly depending on Si ratio, mainly because Si atom can act as a good carrier suppressor. Therefore, the threshold voltage (Vth) of AOTFTs could be easily controlled by changing the Si ratio. Depletion load inverter model has been consisted by using only n-type AOTFTs. This inverter model is operated by difference of Vth between depletion mode (D-mode) and enhancement mode (E-mode) controlled by Si ratio. Furthermore, the conventional NMOS logic circuit models was adopted for the realization of AOTFT-based logic circuits such as NAND, NOR and ELSE. The proposed logic circuit composed by only n-type AOTFTs could be promising in terms of high performance and simply controllable thin film type for next generation integrated circuit applications.