Probing the properties of nanoscale materials using first-principles modeling

Speaker: Hartwin Peelaers, Materials Department, University of California, Santa Barbara, CA 93106-5050
Date & Time: October 16th, 2:00 PM
Location: AMPEL 311
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In this talk I will show how advanced first-principles calculations can be used to describe, explain, and predict the properties of nanoscale materials.

I will first discuss my research on MoS₂, a two-dimensional (2D) layered material with a band gap, and interesting (opto)electronic applications. Bulk MoS₂ has an indirect band gap, while a single layer has a direct band gap. First-principles calculations based on density functional theory, that explicitly include van der Waals interactions, are used to shed light on this indirect-to-direct band-gap transition.

In the second part of my talk I will focus on a new, unconventional 2D material: Ga₂O₃. In its bulk form this material is a wide-band-gap transparent conducting oxide, which is used as transparent contact and in high-power electronics. It is not a layered material, since its monoclinic crystal structure does not contain van der Waals gaps. Nevertheless it is possible to create extremely thin nanolayers. Surprisingly, the electronic structure of these nanolayers does not seem to show signs of quantum confinement. Closer inspection reveals that the effect of quantum confinement is exactly canceled by surface interactions through the nanolayer, as is also confirmed by embedding the nanolayers in a material with a large conduction-band offset.