Influence of O-2/Ar flow ratio on the structure, optical and electrical properties of DC reactively magnetron-sputtered face-centered cubic NiO films at room temperature

摘要

Single-phase NiO films with high carrier mobility and low electrical resistivity are crucial for NiO-based heterojunction solar cells. Herein, a series of face-centered cubic (fcc) nickel oxide (NiO) films was room-temperature prepared at different O-2/Ar flow ratio (R-oa) values through low-cost DC reactive magnetron sputtering. With increase of R-oa, the film crystallization is initially improved, and the film's free carrier concentration increases, thereby resulting in a slight blue shift in optical absorption edge. The oxygen-rich state in the form of nickel vacancies and interstitial oxygen enlarges the film's lattice distortion and thus leads to a red shift in optical absorption edge. The reduced film transmittance with increase of R-oa is due to the enhanced point defect scattering. The free carrier concentration of the films reaches the maxima of 3.17 x 10(19)/cm(3) at 3:1 R-oa and the hole mobility reaches the maxima of 1.53 cm(2)/Vs at 2:1 R-oa.