Growth and characterization of Cu2O and CuO thin films

Crystalline Cu2O and CuO thin films were synthesized by pulsed laser deposition on fused silica substrates at three O-2 partial pressures (0.1 Pa, 1 Pa and 10 Pa) and the effects of O-2 pressure on the phase formation, structural, optical, surface morphology, wettability and electrical properties of films were characterized by grazing-incidence X-ray diffraction (GIXRD), field emission scanning electron microscopy (FESEM), atomic force microscopy (AFM), UV-visible, FTIR, Raman and photoluminescence (PL) spectroscopy, water contact angle measurements and two-probe electrical studies. GIXRD and Raman studies revealed that the film prepared at 0.1 Pa is a mixed phase of Cu and Cu2O, while the films prepared at higher O-2 pressure of 1 Pa and 10 Pa are single-phase CuO. The optical bandgap of the films decreases from 3.00 eV to 2.82 eV with the conversion of Cu2O into CuO. PL studies show strong luminescence peaks at 486 nm (blue), 503 nm (green) and 613 nm (red). The surface roughness of the films decreases with an increase in O-2 pressure from 0.1 Pa to 10 Pa. All films are hydrophilic and the hydrophilicity decreases with an increase in O-2 pressure. The surface electrical resistivities of films deposited at 0.1 Pa, 1 Pa and 10 Pa O-2 pressure are 1.6 x 10(2), 6.4 x 10(4) and 1.0 x 10(4) omega cm, respectively. It is found that copper oxide phase formation and its properties can be significantly modified by varying O-2 pressure during PLD.