Everyone is welcome to attend!
February 16 @ 11 a.m. – noon, ETRL 101
Refreshments will begin at 10:30 a.m. in ETRL 119
The School of Mechanical and Materials Engineering is hosting a seminar presented by Dr. Yi Gu, Associate Professor of Physics, Department of Physics and Astronomy, Washington State University
Abstract: Metal-semiconductor junctions (MSJs) are a fundamental component in electronic circuits, and the capability to control the behaviors of MSJs (Schottky vs. Ohmic) is central to realizing various device functions. Such a control, in principle, can be achieved by varying the junction energy barrier height, via using metals with different work functions relative to the semiconductor’s band edges. However, in conventional MSJs, the Fermi level is often pinned to a certain position within the semiconductor bandgap, rendering the energy barrier height insensitive to the metal work function. In this talk, we demonstrate a novel van der Waals Schottky junction defined by chemically identical and structurally similar crystalline phases of multilayer In2Se3. Besides ideal diode behaviors and the gate-tunable current rectification, the thermoelectric power (Seebeck coefficient) is greatly enhanced in these junctions, by ~ 2 – 3 orders of magnitude, compared to single-phase multilayer In2Se3, with the thermoelectric figure-of-merit approaching ~ 1 at room temperature. Interestingly, these significantly improved thermoelectric properties are not due to the two-dimensional (2D) quantum confinement effects, but instead are a consequence of the Schottky barrier at the junction interface, which leads to hot carrier transport and shift the balance between thermally and field-driven currents. This “bulk” effect extends the advantages of van der Waals materials beyond the typical few-layer limit. Adopting such an approach of using energy barriers between van der Waals materials, where the interface states are minimal, is expected to enhance the thermoelectric performance in other 2D materials as well.
Biography: Prof. Gu conducted his PhD research at Columbia University (Applied Physics) on optical properties of semiconductor nanostructures, using primarily photoluminescence spectroscopy techniques. He then performed his postdoctoral research at Northwestern University (Materials Science and Engineering), studying the carrier transport properties in semiconductor nanowires. He joined the Department of Physics and Astronomy at Washington State University as an Assistant Professor in 2007, and was promoted to Associate Professor in 2013.
