Structural, surface morphological, and optical properties of nanocrystalline Cu2O and CuO films formed by RF magnetron sputtering: Oxygen partial pressure effect

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Abstract
Copper oxide films were deposited on glass and silicon substrates held at 473 K by radio‐frequency (RF) magnetron sputtering of copper target under different oxygen partial pressure in the range 5 × 10−3–8 × 10−2 Pa. The influence of oxygen partial pressure on the compositional, chemical binding configuration, structural, morphological, electrical, and optical properties of the deposited films was investigated. The films grown at low oxygen partial pressures < 2 × 10−2 Pa, showed mixed phase of Cu2O and Cu. At an oxygen partial pressure of 2 × 10−2 Pa the grown films were single‐phase Cu2O. The films formed at oxygen partial pressure of 2 × 10−2 Pa showed a core level binding energy peak of Cu 2p3/2 at 932.3 eV, confirmed the growth of Cu+ state of copper in Cu2O. The films formed at higher oxygen partial pressure of 5 × 10−2 Pa, films showed mixed phase of Cu2O and CuO. While those formed at 8 × 10−2 Pa were of CuO. Atomic force micrographs showed that the grain size of the films was increased from 40 to 110 nm with increase of oxygen partial pressure from 8 × 10−3 to 2 × 10−2 Pa. Single‐phase Cu2O films grown at oxygen partial pressure of 2 × 10−2 Pa showed electrical resistivity of 10 Ω cm and optical bandgap of 2.36 eV. The CuO films formed at higher oxygen partial pressure of 8 × 10−2 Pa exhibited an electrical resistivity of 3 × 102 Ω cm and optical bandgap of 1.96 eV.

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