The Department of Physics and Astronomy invites all to a colloquium featuring Dr. Yi Gu, department of Physics & Astronomy at Washington State University. Dr. Gu will present his talk, “Phase-Defined Van der Waals Metal-Semiconductor Junction”, Tuesday, March 28 at 4:10 p.m. in Webster 17.
Meet for refreshments before the lecture at 3:45 – 4:10 p.m. in the foyer on floor G above the lecture hall.
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 significantly enhanced in these junctions, by more than 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
