Structural and opto-electrical properties of Cu–Al–O thin films prepared by magnetron sputtering method

• Cu–Al–O thin film mainly composed of CuAlO2 phase has been obtained.
• The annealed film shows better hydrophobicity than the as-deposited film.
• The annealed film exhibits good antireflection effect in infrared region.

Multi-functional Cu–Al–O thin films were deposited on silicon and quartz substrates by using radio frequency (RF) magnetron sputtering method. The structural characteristics, electrical properties, optical transmittance, in visible and infrared regions, of the films have been investigated. The X-ray diffraction patterns reveal that the as-deposited film is mainly composed of amorphous phase and post-annealing treatment leads to crystallization. After annealed at 950 °C in air, only CuO diffraction peaks have been detected, while after annealed in argon ambience the film is composed predominantly of CuAlO2 phase and its hydrophobicity improves markedly due to the crystallization and increase of surface roughness. The argon-annealed film shows p-type conductivity with electrical resistivity being 92.0 Ω cm at room temperature. The optical transmittance in the visible region (390–780 nm) varies in the range of 65–70%, with the corresponding direct band gaps being 3.4 and 4.7 eV. Moreover, the film annealed in argon ambience exhibits remarkable antireflection effect in the wavenumber range 920–4000 cm−1.