Impact of ambient oxygen pressure on the structural and optical properties of NiO thin films deposited using pulsed laser deposition and the performance of self-driven p-NiO/n-Si as UV–Visible-NIR photodetectors

The stoichiometry of a metal oxide thin film has excellent potential to modify the material’ s physical properties and hence, the device’ s performance. In this paper, an in-depth investigation has been conducted to understand the impact of ambient oxygen pressure (AOP) during Pulsed laser deposition on the structural and optical properties of NiO thin films and its consequences on the self-driven UV–Visible-NIR photodetection properties of the NiO/Si heterostructure. X-ray photoelectron spectroscopy results confirm that the Ni vacancy increases with the increase of AOP. Furthermore, a comparative study of spectroscopic ellipsometry and first-principles density functional theory + U calculations is conducted to better understand the impact of different AOP conditions. Our experimental and theoretical results show that while nickel vacancy is an efficient acceptor in NiO, it also reduces transparency in the visible region of the material. In addition, the effects of AOP on the NiO/Si heterojunction-based photodetector's performance were studied in the broad range from UV to NIR. The stability of the broadband self-powered photodetectors are ensured by periodically switching the photo-illumination at regular time intervals. After tuning the AOP during growth, a highly stable and fast-switching self-biased p-NiO/n-Si photodiode is achieved with the highest responsivity of 32 mA/W upon exposure to 455 nm wavelength.