Synthesis, structure and femtosecond nonlinear absorption properties of Ce-ZnO films

Abstract

In this work, Ce-ZnO (CZO) films with excellent nonlinear absorption (NA) properties were successfully prepared via the magnetron sputtering process, where the conditions depended morphology were characterized. The cluster surface appeared with the increased sputtering time at low power, and disappeared at high power. Energy dispersive spectrometer and X-ray photoelectron spectroscopy analysis confirmed the presence of Ce ions into ZnO lattice. The functional groups, optical bandgap value and NA properties were revealed by Raman spectroscopy studies, UV–Visible absorption spectra and Z-scan technique, respectively. By adjusting the direct current sputtering power and excitation intensities, the NA mechanism of samples was converted from saturable absorption (SA) to reverse saturable absorption (RSA) behavior. Under different laser excitation intensities, the NA mechanism of samples was that TPA induced RSA. Furthermore, the results show that the order of magnitude of the NA coefficient for samples is ~10−8 m/W. In addition, the ultrafast carrier dynamics was studied using two-color pump-probe technique. When excited with 380 and 400 nm pumps and probed over a broad range in the visible region, the biexponential decay of positive signal is same to the mechanism of pump-induced deep-level or excited state absorption. CZO films will be promising candidate for developing optoelectronic devices.