Influence of ZnO buffer layer on microstructure and Raman scattering of ZnO:Ag film on Si substrate

Pure ZnO and Ag-doped ZnO (ZnO:Ag) films were deposited on ZnO buffer layer and p-Si (1 0 0) substrate by radio frequency reactive magnetron sputtering. ZnO buffer layer was deposited at lower power. The microstructures of the films were investigated by X-ray diffraction (XRD) and scanning electron microscopy (SEM) analysis techniques. The results indicated that ZnO:Ag film had a stronger preferred orientation toward the c-axis, a more uniform grain size and smoother surface after using ZnO buffer layer, and the residual strain was reduced. In addition, stronger Raman scattering was observed from ZnO:Ag film on ZnO buffer layer than that on Si substrate. It was because the ZnO buffer layer effectively relaxed the partial stress induced by the large lattice mismatch between the film and Si. Two additional local vibrational modes (LVMs) at 245 and 495.8 cm−1 induced by Ag dopant in ZnO:Ag films were observed by Raman spectra, corresponding to Ag atoms located at O sites (LVM of Zn-Ag) and Ag atoms in the films. It meant that the LVMs could act as an indication of Ag incorporation into ZnO:Ag film.