Vacuum-Free Liquid-Metal-Printed 2D Semiconducting Tin Dioxide: The Effect of Annealing

Thin film transistors (TFTs) offer unparalleled opportunities for the fabrication of multifunctional electronic and optoelectronic devices. In this work, we report a vacuum-free liquid metal exfoliation technique for rapidly printing ∼2 nm-thick layer of oxide from molten tin. We explore the effect of rapid thermal annealing at 450 °C on the stoichiometry, morphology, and crystal structure of the resulting tin oxide nanosheets. The annealed samples exhibit a dominant SnO2 phase and a high degree of transparency (>99%) in the visible spectra. Field-effect transistors based on the two-dimensional (2D) SnO2 films show typical n-channel conduction with a field-effect mobility of ∼7.5 cm2 V–1 s–1. Photodetectors utilizing annealed tin dioxide demonstrate significant improvement in photoresponsivity reaching a value of 5.2 × 103 A W–1 compared to that found in an unannealed sample at an ultraviolet wavelength of 285 nm. We demonstrate that the improvement in device performance is due to nanocrystalline changes within the oxide layers during the annealing process. This work offers a straightforward and ambient air-compatible method for depositing ultrathin, large-area semiconducting oxides as potential candidates for enabling emerging applications in transparent nanoelectronics and optoelectronics.