Strategy to improve the electrical and optical properties of NiO thin films by reactive pulsed laser ablation of Ni under oxygen ambient

Stoichiometry of Nickel Oxide (NiO) plays an important role in simultaneously enhancing the electrical conductivity and optical transparency of thin films. In this study, we have focused on depositing NiO films by reactive pulsed laser ablation of Ni metallic target under the variation of ambient oxygen pressure. The deposited films have an average optical transparency of nearly 50 %. The band gap of the films is in the range of 3.25-3.55 eV, determined by using the Tauc plot. Excess oxygen during deposition helps to create Ni vacancies. X-ray photoelectron spectroscopy reveals that increased Ni3+ maintains charge neutrality in NiOx films, enhancing ptype conductivity by generating holes. The minimum resistivity of 6.7 Omega-cm at room temperature has been achieved for the film deposited under the 70 mTorr oxygen pressure. Carrier concentration and mobility are obtained from Hall experiments. UV detection properties of p- NiOx/n-Si thin films have also been investigated. Sample deposited under 50 mTorr oxygen pressure has maximum detectivity of 2.58 x 1011 Jones due to lower dark current and highest responsivity 12.1 mA/W at 0 V. The ambient oxygen pressure has been meticulously optimized to simultaneously enhance the electrical conductivity and optical transparency of p-type NiOx thin films.