Highly sensitive thermoelectric touch sensor based on p-type SnO _x thin film

Here, the ability of using p-type tin oxide (SnO _x ) thin films as a thermal sensor has been investigated. Firstly, the thermoelectric performance was optimized by controlling the thickness of the SnO _x film from 60 up to 160 nm. A high Seebeck coefficient of +263 μV K^-1 and electrical conductivity of 4.1 × 10² (S m^-1) were achieved in a 60 nm thick SnO _x film, due to a compact nanostructured film and the absence of the Sn metallic phase, which was observed for the thicker SnO _x film leading to a typical thermoelectric transport properties of a n-type Sn film. Moreover, x-ray photoelectron spectroscopy revealed the co-existence of SnO (79.7%) and SnO₂ (20.3%) phases in the 60 nm thick SnO _x film, while the optical measurements revealed an indirect gap of 1.8 eV and a direct gap of 2.7 eV, respectively. The 60 nm-SnO _x thin film have been tested as a thermoelectric touch sensor, achieving a V_signal /V_noise  ≈ 20, with a rise time <1 s. Therefore, this work provides an efficient way for developing highly efficient thermal sensors with potential use in display technologies.