Tin telluride quantum dot thin films: Size dependent structural, optical and electrical properties

Abstract

In the current study, efforts have been made to acquire tin telluride quantum dot (QD) thin films that work at room temperature and in the region of visible and near-infrared (NIR). SnTe ingot and thin films were formed using the solid solution and inert gas condensation (IGC) techniques respectively. A cubic polymorph structure was identified using XRD for the prepared SnTe ingot, while grazing incident in-plane X-ray diffraction (GIIXD) and HR-TEM electron diffraction was used for identifying the thin films. The average particle size was found to increase from 2.3 to 9.6 nm with increasing film thickness from 5 to 25 nm. The optical gap of thin film QDs is wider than those of bulk samples; this is attributable to the quantum confinement effect. As a result of quantum confinement, SnTe thin films have optical gap values in the visible and NIR region (2–0.85 eV) instead of being in the infrared region (0.19 eV) of their bulk materials counterpart. The electronic transition was described by studying various important optical parameters such as optical conductivity (σop), interband transition strength (JCV), and surface and volume energy loss functions (SELF, VELF). Electrical conductivity shows a degenerate semiconductor performance. I–V characteristic show symmetric nonlinear behavior for 10 and 15 nm film thickness.