Studies On Surface Electronic Structure Of Nano-La_0.8Sr_0.2FeO₃ And Nano-ZnO

The transition metal complex oxide nano-La_0.8Sr_0.2FeO₃ was synthesized with citrate method; the nano-ZnO and nano-α-Fe₂O₃ were prepared by solid reaction, respectively. The photoexcited transition mechanism and the energy conversion behaviors of both nano-semiconductors p-La_0.8Sr_0.2FeO₃ and n-ZnO were studied in this article by Photoacoustic Spectroscopy (PAS) and Surface Photovoltage Spectroscopy (SPS). The surface electron structure was investigated based on the experimental results. The band structure and state density distribution of the samples at ideal situation were simulated by CASTEP program. The photoexcited charge transfer transiton characters and the surface electron structure of nano-La₍0.80Sr_0.2FeO₃ were explained by PAS, SPS and EFISPS. The results show that the difference between PAS and SPS of the sample attributes to the different energy transform on the surface. At the same time, the band structure and states density distribution of La_1-xSr_xFeO₃ (x=0⁰.4) and α-Fe2O3 were simulated by CASTEP program, the influnce of x to the properties of the nano-material was analyzed carefully. The similar experimental method had been used to ZnO. The results show that the PAS of nano-La_0.8Sr_0.2FeO₃ and α-Fe₂O₃ is similar, even though an obvious difference appears in SPS of them, which results from different size and impurity. Both results of experiment and computer simulation indicate that x=0.2 is a special dope value with respect to La_1-xSr_xFeO₃ (x=0⁰.4). The band structure of La_1-xSr_xFeO₃ (x=0⁰.4) is different to α-Fe₂O₃ because of the doped impurity. The existences of the surface states and shallow level in the body were approved by SPS,SPC,PAS and electric field induced SPS (EFISPS). The states density distribution of ZnO simulated by CASTEP relates to the independent level at some appropriate situation in between the band gap. The EFISPS of nano-La_0.8Sr_0.2FeO₃ and nano-ZnO indicates the special variation properties which are different from normal semiconductors because of the adsorbiton of O^2- at the surface.