Friday, June 19th, 2015

Emmanuel Kioupakis
Materials Science and Engineering, University of Michigan, USA
Electronic and Optical Properties of Ultrathin Materials from First Principles
Department of Physics Bldg., Voutes, 3rd floor Seminar Room

We use first-principles calculations based on density functional and many-body perturbation theory to analyze the effects of quantum confinement on the band gap, excitons, and optical properties of two-dimensional materials, as well as ultrathin nitride nanowires and quantum wells. Our calculations for single-layer and double-layer SnSe and GeSe show that these materials exhibit an unusually high absorbance (approaching 40-50%) in the visible range and that they are promising for ultrathin photovoltaic applications. Moreover, our results for few-layer PbI2 reveal the intermediate nature of excitons between the Wannier and Frenkel picture in this material [1]. We also examined the optical properties of ultrathin InN nanowires and GaN quantum wells. Our results show that InN nanostructures with a dimension of ~1 nm can be applied for efficient green-light emission [2], while ultrathin GaN quantum wells with a thickness of 1-4 monolayers can be used for deep ultraviolet LEDs for germicidal applications.

[1] A. S. Toulouse, B. P. Isaacoff, G. Shi, M. Matuchov, E. Kioupakis, and R. Merlin, Phys. Rev. B 91, 165308 (2015).

[2] D. Bayerl and E. Kioupakis, Nano Lett. 14, 3709–3714 (2014).

See text.