VLADIMIR FALKO \’Electronic and Optical Properties of Monolayer and Few-Layer Films of InSe and GaSe\’
We present the analysis of electronic band structure of InSe (and other III-VI semiconductors) films, from the stoichiometric mono- to N-layer films, and we describe the resulting optical properties of these 2D materials [1,2] and conduction/valence band parameters. This study is based on the ab initio DFT and related multi-orbital tight-binding model analysis of the electronic band structure and wave functions in the two-dimensional N-layer InSe crystals, and it is compared to the results of luminescence spectroscopy of this material. We show [1-3] that the band gap in InSe (and GaSe) strongly depend on the number of layers, with a strong (more than twice) reduction from the monolayer to crystals with N>6. We find that the conduction-band-edge electron mass in few-layer InSe is quite light (comparable to Si), which suggests opportunities for high-mobility devices and the development of nanocircuits. In contrast, the valence band in mono-, bi- and trilayer InSe is flat, opening possibilities for strongly correlated hole gases in p-doped films. We also propose a model to describe electronic properties of misaligned layers of InSe. Using the band structure and wave functions, we analyse optical transitions in thin films of InSe, identify their polarisation and compare the results of modelling to the measurements performed on hBN-encapsulated atomically thin InSe crystals.
Seminar, November 8, 2017, 12:00. ICFO Blue Lecture Room
Hosted by Prof. Adrian Bachtold and Prof. Frank Koppens