Highly sensitive, selective and stable NO2 gas sensors with a ppb-level detection limit on 2D-platinum diselenide films

Unlike common TMDCs such as MoS2, PtSe2 can be fabricated at temperatures below 600 degrees C, or even as low as 300 degrees C, while still maintaining high quality. By varying the selenization temperature from 300 degrees C to 600 degrees C, the electrical properties were changed significantly, resulting in superior gas sensing performance. Through comprehensive material analysis, an interesting phenomenon was found, namely that strain along the [001] direction existed in films grown at a low temperature rather than at a high temperature. Moreover, due to the layer-dependent property of PtSe2, a phase transition from metal-to-semiconductor occurs as the thickness is reduced. Hybridization of phase engineering and thermal strain engineering significantly enhances the gas sensing performance, resulting in PtSe2 with a dramatic increase in the response to 1 ppm NO2 from 25% to 550% once the thickness was reduced from 10 to 5 layers. In addition, PtSe2 showed good stability during exposure to not only 1 ppm but also 50 ppb NO2 for more than 5 cycles with responses of over 550% and 60%, respectively.