Novel approach for improving electrochromic and mechanical properties of NiO film: Experiment and molecular dynamics simulation

In this paper, we systematically studied the effect of substrate surface roughness on the electrochromic and mechanical properties of NiO films deposited on FTO conductive glass by magnetron sputtering. Results showed that increasing substrate surface roughness led to an increase in optical contrast of the film and decreased response time. The NiO film deposited on FTO (Ra 20 nm) had the largest optical contrast (54.7 % at 600 nm) and fastest response time (7.0 s and 1.7 s). Moreover, SEM, XPS, and EDS analyses revealed that the resultant increase in nanoporosity with increasing surface roughness was the main reason for this occurrence. The growth process of the NiO film was simulated by molecular dynamics, and the mechanism of the nanoporous structure was explained theoretically. The mechanical test showed that the composite hardness of FRa20 was 4.2 GPa, while the elastic modulus of the NiO film deposited on it was 74.9 GPa, which was better than all the other films. Thus, this study provides a novel and convenient approach for improving the electrochromic and mechanical prop-erties of NiO films.