Conduction and Photoconduction Mechanisms in Two-Dimensional SnS2 Field-Effect Transistor

We report on the synthesis, fabrication, and optoelectronic characterization of a field-effect transistor (FET) based on a multilayer SnS2 flake. The device was fabricated by mechanical exfoliation of single crystals grown via chemical vapor transport and transferred onto SiO2/Si substrates. Electrical measurements under vacuum reveal nearly symmetric output curves, indicating low Schottky barriers, and an n-type behavior with an ON/OFF ratio ~100. Photodetection measurements under monochromatic laser illumination (from 420 to 800 nm) show a highly wavelength-dependent responsivity, peaking at ~100 A/W. Under ambient conditions the device behavior changes dramatically, showing strong asymmetry in output curves and increased hysteresis are observed due to oxygen-enhanced Schottky barriers and trap states. A power-law fitting of the photocurrent reveals α ≈ 1.23 in vacuum, indicative of efficient photogeneration, and α ≈ 0.63 in air, highlighting the role of trap-assisted processes. Time-resolved measurements reveal how this trap states induce gate-tunable persistent photoconductivity, which demonstrate the strong versatility of SnS2-based devices for tunable optoelectronic applications.