Tin sulfide thin films by spin coating of laser ablated nanocolloids for UV–Vis–NIR photodetection

Abstract

Tin sulfide (SnS) has emerged in the field of layered metal chalcogenides (LMCs) as one of the preferred semiconductors due to its prominent optical properties and high absorption coefficient. In this work, SnS nanocolloids were obtained by pulsed laser ablation in liquid (PLAL) using Nd:YAG laser wavelengths of 532 and 1064 nm. Furthermore, thin films of SnS were spin-coated using nanocolloids and annealed in vacuum at 350 and 450 ℃. Morphology and crystal structure of SnS nanoparticles (NPs) were studied using Transmission electron microscopy and particle sizes calculated were in the range of 8–12 nm. X-ray diffraction results reproduced the same orthorhombic crystal structure for the SnS films as that of SnS NPs. The elemental composition and chemical states were analyzed by X-ray photoelectron spectroscopy. Morphological analysis of the films by scanning electron microscopy reveals surfaces having interconnected spherical grains. The energy bandgap values of the nanocolloids were 1.9, 2.8 eV and the films were between 1.4 and 2.1 eV. The photodetection abilities of the films exhibit wavelength response in the UV–Visible as well as NIR (785, 840 and 980 nm) regions. The photodetector shows a specific detectivity of 106 Jones. Photodetector parameters such as sensitivity, responsivity, noise equivalent power (NEP), rise time and decay time were also estimated. The study of thin films fabricated from nanocolloids by combining the aspects of PLAL and spin-coating provides a new insight to synthesize reproducible semiconducting thin films for optoelectronics.