Impact of Al2O3 stress liner on two-dimensional SnS2 nanosheet for photodetector application

Layered tin disulfide (SnS2) nanosheets are gradually coming into people's vision as an emerging twodimensional material for the potential application majority in optoelectronic field. We investigate a sample of ultra-thin SnS2 nanosheets (-5 nm) on SiO2/Si substrates and the photodetectors performance based on it with and without high-k ALD-A1203 stress liner. By means of temperature-dependent Raman spectroscopy, both a red-shift of Raman frequency from 313.1 cm1 to 311.2 cm-1 as well as a reduction of the first order temperature coefficient from -0.01232 cm -1/K to -0.00895 cm -1/K are measured. For device, compared to SnS2 photodetector, A1203/SnS2 photodetector shows enhancement with 7 -times light current, 10-times responsivity, 25%-off rising time and 70%-off falling time under 365 nm illumination. The phenomena can be rationalized by factors that the SnS2 sample suffers a tensile strain and passivation effect exerted by capped A1203 layer. Meanwhile, the first principle calculations assist the study from an angle of verification. The analogue stress treatment operated in this work improves the properties of SnS2 and enhances the performances of SnS2-based photodetectors, aiming at expanding the thin-film materials applications in optoelectronic devices. (C) 2020 Elsevier B.V. All rights reserved.