Improved sensing response of nanostructured CuO thin films towards sweat rate monitoring: Effect of Cr doping

In this research, we have studied the effect of chromium doping of CuO on the main physical properties and hydration level sensing ability of thin-film samples synthesized by SILAR method on soda-lime glass substrates. The structural, morphological and optical properties as well as hydration level sensing behavior of pristine and Cr_xCu_1-xO (x = 0.01 and 0.02) films were investigated under different Cr concentrations. Optical and structural analysis verified the Cr-doping into CuO films without degrading the uniformity of the metal oxide semiconductor structure. It was shown that the resistivity increases with Cr-doping, which was attributed to the additional holes introduced to the semiconductor crystal. Sweat sensing response of the metal oxide films improved significantly with doping (sensing response from 0.45 to 8.50 for heavy doping). Transient analysis of the sweat response also showed that response time is less than 60 s. We conclude that Cr-doping improves the sensing performance of CuO thin films and offers to be implemented in sweat sensing devices as the sensing material.