Substrate-tilt angle effect on structural and optical properties of sputtered ZnO film

A new one-step method utilizing a special holder for a direct current magnetron sputtering system has enabled simultaneous deposition of ZnO films with different substrate tilt angles on quartz and silicon substrates. Observation from scanning electron microscopy shows that a typical columnar structure is obtained and the column inclination angle varies from 0° to 34°. From X-ray diffraction analysis, the strains in the ZnO films decrease with increasing substrate tilt angle, which is confirmed by the variation of the longitude optical phonon vibration in the Raman spectra. The band-gap energies decrease from 3.19 eV to 3.07 eV mainly due to the changes of strain relaxation induced by the defect variations in the films. Photoluminescence spectra revealed that the generation, type and concentration of the complex defects are influenced by the substrate tilt angle.