Laser processing of thin film sputtered MoS2: Thinning, oxidation, and crystallization

Abstract

The interest in thin film 2D materials has brought renewed attention to the compound molybdenum disulfide (MoS2). As a 2D material, MoS2 can exhibit high transport mobility and transitions to a direct-gap semiconductor when thinned down to a few atomic layers. Consequently, it has both electronic and photonic device applications. The bulk of research on crystalline MoS2 is via exfoliated and chemical vapor deposited material. In this work, we present a laser processing approach that offers flexibility in the types of composite materials that can be produced. We demonstrate laser crystallization of sputter-deposited amorphous MoS2 (∼10 nm) and subsequent thinning down to a few atomic layers that result in direct bandgap emission. With further laser processing under inert gas purge (argon) and low vacuum air, we fabricate composite nano-materials comprised of metallic and molybdenum oxides. Material characterization is done by optical interferometry, atomic force microscopy, SEM, Auger, and Raman diagnostics, but the ongoing physics of the laser thinning process is elucidated by XPS measurements.