Interplay between Growth Mechanism, Materials Chemistry, and Band Gap Characteristics in Sputtered Thin Films of Chalcogenide Perovskite BaZrS <sub>3</sub>
Soham Mukherjee, Stefania Riva, Corrado Comparotto, Fredrik O. L. Johansson, Gabriel Man, Dibya Phuyal, Konstantin A. Simonov, Justus Just, Konstantin Klementiev, Sergei M. Butorin, Jonathan J. S. Scragg, Håkan Rensmo
Abstract
High Resolution Image Download MS PowerPoint Slide The prototypical chalcogenide perovskite BaZrS 3, characterized by its direct band gap, exceptionally strong light-harvesting ability, and good carrier transport properties, provides fundamental prerequisites for a promising photovoltaic material. This inspired the synthesis of BaZrS 3 in the form of thin films, using sputtering and rapid thermal processing, aimed at device fabrication for future optoelectronic applications. Using a combination of short- and long-range structural information from X-ray absorption spectroscopy (XAS) and X-ray diffraction (XRD), we have elucidated how, starting from a random network of Ba, Zr, and S atoms, thermal treatment induces crystallization and growth of BaZrS 3 and explained its impact on the observed photoluminescence (PL) properties. We also provide a description of the electronic structure and substantiate the surface material chemistry using a combination of depth-dependent photoelectron spectroscopy (PES) using hard X-ray (HAXPES) and traditional Al K α radiation. From the knowledge of the optical band gap of BaZrS 3 thin films, synthesized at an optimal temperature of 900 °C, and our estimation of the valence band edge position with respect to the Fermi level, one may conclude that these semiconductor films are intrinsic in nature with a slight n -type character. A detailed understanding of the growth mechanism and electronic structure of BaZrS 3 thin films helps pave the way toward their utilization in photovoltaic applications.