Oxygen partial pressure effects on nickel oxide thin films and NiO/Si diode performance

Abstract

In this work, nickel oxide thin films were grown on glass and n-type Si substrates using RF-magnetron sputtering in an oxygen-rich environment. The effects of elevated oxygen on the optical properties, electrical properties, ionic states, compositional analysis, surface morphology, and crystal structure are investigated. The X-ray diffraction data, which also demonstrate the presence of two phases in all samples: NiO and Ni₂O₃, indicate that the highly crystalline Ni₂O₃ phase in the nickel oxide thin film structure has a (002) growth orientation. According to X-ray photoelectron spectroscopy, the ratio of Ni³⁺ (Ni₂O₃ phase) to Ni²⁺ (NiO) states increases as the oxygen concentration increases. In the nickel oxide thin films, the ratio of Ni³⁺ states is substantially higher than that of Ni²⁺ states. The optical band gap is around 3.4 eV, as determined from UV-Vis transmission spectroscopy, and the average transmittance of nickel oxide thin films exceeds 50% in the visible spectrum. The nickel oxide thin films demonstrate a substantial carrier concentration between 2.33 × 10¹⁹ and 7.46 × 10¹⁹ cm⁻³, with a minimum resistivity of 0.28 Ω cm. Furthermore, the p–n heterojunctions of the p-nickel oxide/n-silicon substrates revealed the optimal diode characteristic parameters at a 30% oxygen gas ratio. The results have been promising for further industrial development and fabrication of diodes.