Spectroscopic ellipsometry modeling of ZnO thin films with various O ₂ partial pressures

ZnO films were deposited on thermally oxidized SiO ₂/p-type Si (100) substrates and glass substrates by DC magnetron sputtering using a metal Zn target. Three types of samples were prepared with various O ₂/(Ar + O ₂) ratios (O ₂ partial pressure) of 20%, 50%, and 80%. The properties of these ZnO thin films were investigated using X-ray diffraction (XRD), optical transmittance, atomic force microscopy (AFM), and spectroscopic ellipsometry in the spectral region of 1.7-3.1 eV. The structural and optical properties of ZnO thin films were affected by O ₂ partial pressure. Relationships between crystallinity, the ZnO surface roughness layer, and the refractive index (n) were investigated with varying O ₂ partial pressure. It was shown that the spectroscopic ellipsometry extracted parameters well represented the ZnO thin film characteristics for different O ₂ partial pressures.