A DFT perspective analysis of optical properties of defected germanene mono-layer

Abstract

Abstract Germanene, germanium version of graphene, is a novel member in the two-dimensional (2D) materials family. In this present study, a theoretical analysis involving optical properties of defected free standing (FS) germanene layer has been performed within density functional theory (DFT) framework. FS buckled germanene exhibits many fascinating and unconventional optical properties due to introductions of adatoms and voids. Arsenic (As), gallium (Ga) and beryllium (Be) are chosen as doping elements. Doping sites (same or different sub-lattice positions) play a crucial role to improve various optical properties. While Be doping, concentrations of Be are increased up to 18.75 % and void concentrations are increased up to 15.62 % (keeping fixed 3.12 % Be concentration). Emergence of several plasma frequencies occur in case of both parallel and perpendicular polarizations for defected germanene layers. Energy positions of peaks corresponding to maximum of imaginary parts of dielectric constants are red shifted for some As and Ga incorporated systems compared to pristine germanene. Absorption spectra peaks are more prominent for Be doped systems rather than void added systems. In addition, conductivity in infrared (IR) region is very high for the Be doped configurations in case of parallel polarization. Along with these, changes in other optical properties like refractive index, reflectivity, electron energy loss spectroscopy etc. are also analyzed briefly in this present study. We hope, this theoretical investigation may be regarded as an important tool to design novel opto-electronic tuning devices involving germanene in near future.