Zhang Yueli

Optical Study of Sol-gel Processed Nd-doped BiFeO3 Multiferroic Films by Spectroscopic Ellipsometry

We have prepared undoped and Nd-doped BiFeO3 films on Si(100) by sol-gel method. XRD measurements show that all the films are single perovskite structure and a phase transition appeared in Nd doping BiFeO3 films. Dense microstructure with evenly distributed grains about 100 nm is observed by SEM. The ellipsometric measurements were carried out in the UV-visible region and the corresponding experimental data were fitted by using a model consisting of air/roughness/BNFO/Si(100). It has been found that the optical constants tend to increase with Nd content increasing, however, the optical band gap decreases as Nd content increasing.

TWO-WAVE COUPLING IN PHOTOREFRACTIVE TRANSITION METAL DOPED POTASSIUM SODIUM BARIUM STRONTIUM NIOBATE CRYSTALS

Large values of the exponential gain coefficient are obtained (Γ = 8-20 cm-1) in photorefractive potassium sodium barium strontium niobate crystals doped with transition metal elements: Co, Cu, Fe, Cr and Ni by using two-wave coupling experiments with argon ion laser (λ = 488 nm). The response time is measured to be 60-1000 ms at an intensity of 5W/cm2 for various samples. We find that in all the crystals electrons are the dominant photorefractive charge carriers, and the typical density of carriers is 1016-1017 cm-3.