Electronic and optical properties of stanane and armchair stanane nanoribbons

In this study, we performed a density functional theory based investigation of the structural, electronic, and optical properties of a stanane, fully hydrogenated stanene SnH, and armchair stanane nanoribbons ASnHNRs. Our full geometry optimization calculations show stanane has 0.84 angstrom buckled height and the buckled structure is preserved in ASnHNRs. The optimized lattice parameter of stanane, Sn-Sn, and Sn-H bond length are 4.58 angstrom, 2.75 angstrom, and 1.73 angstrom, respectively. Electronic structure calculations show that stanane is a moderate-band-gap semiconductor with a direct band gap of 1.2 eV and ASnHNRs are wide-band-gap semiconductors. The band gap of ASnHNRs decreases as the ribbons width increases. We investigated the optical properties for two directions of polarization. For perpendicular-polarized light, the imaginary part of dielectric function epsilon 2(omega) of stanane peaks between 5 and 10 eV; while for the parallel-polarized light, the peaks are seen in a wide range of energy. According to the results, stanane is a good absorptive matter, especially for visible regions of the electromagnetic spectrum. The presence of anisotropy with respect to the type of light polarization is observed in ASnHNRs also. In these structures, the main peak of epsilon 2(omega) is located at 3.4 eV for parallel- and in 6-8 eV for perpendicular-polarized light.