Characterization of sol gel Zn1-xCaxO thin layers deposited on p-Si substrate by spin-coating method

Abstract Thin films Zn1-xCaxO (0 ≤ x ≤ 6%) on a p-Si substrate are elaborated by sol-gel process and spin coating. X-ray diffraction displays a hexagonal wurtzite structure with an increase of lattice parameters confirming the substitution of Zn2+ by Ca2+. The estimation of crystallite sizes along the three main crystallographic planes is practically constant (22 nm) suggesting a spherical symmetry shape of the crystallites which is confirmed by SEM. UV–visible reflectance spectra attest a band gap tuning from 3.144 to 3.262 eV which is confirmed by the PL measurement at 2 K for Zn0.94Ca0.06O sample by the appearance of a broad band around 3.508 eV. Although the luminescence of the samples is weak, we well distinguish the free exciton emission (FXA) positioned at 3.376 eV and the bound exciton recombination (D0X) around 3.362 eV.