Multiferroic bismuth ferrite (BiFeO3) thin films were prepared by pulsed laser deposition (PLD) technique. Electronic structures of the film have been studied by in situ photoemission spectroscopy (PES) and x-ray absorption spectroscopy (XAS). Both the Fe 2p PES and XAS spectra show that Fe ion is formally in +3 valence state. The Fe 2p and O K edge XAS spectra indicate that the oxygen octahedral crystal ligand field splits the unoccupied Fe 3d state to t2g and eg states. Valence band Fe 2p-3d resonant photoemission results indicate that hybridization between Fe 3d and O 2p plays important role in the multiferroic BiFeO3 thin films.

Multiferroic Bi1−xGdxFeO3 (0≤x≤0.15) samples were prepared using the solid-state reaction method. The influence of Gd substitution on the crystal, the electronic structure, and the magnetic properties of Bi1−xGdxFeO3 was studied. X-ray diffraction spectra show that Gd substitution changes the crystal structure of the Bi1−xGdxFeO3 system from a rhombohedral to an orthorhombic phase. According to Fe L-edge X-ray absorption spectra (XAS), Fe ions are found to be formally trivalent for any value of x in Bi1−xGdxFeO3. Based on a careful examination of Fe L and O K-edge XAS spectra, it was found that the enhanced magnetization which results from increasing Gd content is attributed to a reduced degree of hybridization between Fe 3d-O 2p orbitals. The crystal and electronic structures exhibit a causal relationship between themselves and demonstrated intrinsic mutual dependence in their corresponding variations.

The electronic structure of BiFe1-xMnxO3 (0 <= x <= 0.3) thin films has been investigated by in situ near edge X-ray absorption fine structure (NEXAFS) and photoemission spectroscopy. Fe ions are found to be trivalent for the whole range of x in BiFe(1-x)Mn(x)O(3)and a hybridization between the Fe 3d and O 2p states is decreased by increasing Mn concentration. Charge transfer multiplet (CTM) calculation is used to understand the experimental results of the Fe L-edge spectra. The experimental results plus the CTM calculation showsthe hybridization degree between the transition metal 3d and O 2p states areplay important role for the multiferroic properties of underlying systems.

The single phase (1−x)PbTiO3–xBi(Ni1/2Ti1/2)O3 thin films were synthesized on Pt/Ti/SiO2/Si substrate at 600°C by a chemical solution deposition route. The present films exhibit homogeneous and crackfree microstructure with low porosity. The surface roughness decreases from 5.56nm to 1.62nm with solubility. The remanent polarization monotonously decreases with the dopant Bi(Ni1/2Ti1/2)O3 increase. The leakage current desity increases when the solubility increases. O K-edge X-ray absorption spectroscopy and valence-band edge X-ray photoelectron spectroscopy were used to study the electronic structure. The results indicated that the change of ferroelectricity might be ascribed to the hybridizations between O 2p and Pb 6s and Ti 3d orbitals. The ferromagnetic behaviors were also observed in the thin films and saturated magnetization raises monotonously with the Ni solubility due to enhanced superexchange interaction. Magnetoelectic effects increases with dopant Bi(Ni1/2Ti1/2)O3 increase.

The in situ valence band photoemission spectrum (PES) and X-ray absorption spectrum (XAS) at V L-II-L-III edges of the VO2 thin film, which is prepared by pulsed laser deposition, are measured across the metal-insulator transition (MIT) temperature (T-MIT = 67 degrees C). The spectra show evidence for changes in the electronic structure depending on temperature. Across the T-MIT, pure V 3d characteristic d(parallel to) and O 2p-V 3d hybridization characteristic pi(pd), sigma(pd) bands vary in binding energy position and density of state distributions. The XAS reveals a temperature-dependent reversible energy shift at the V L-III-edge. The PES and XAS results imply a synergetic energy position shift of occupied valence bands and unoccupied conduction band states across the phase transition. A joint inspection of the PES and XAS results shows that the MIT is not a one-step process, instead it is a process in which a semiconductor phase appears as an intermediate state. The final metallic phase from insulating state is reached through insulator-semiconductor, semiconductor-metal processes, and vice versa. The conventional MIT at around the T-MIT = 67 degrees C is actually a semiconductor-insulator transformation point.

Polar and nonpolar ZnO thin films were deposited on MgO (001) substrates under different deposition parameters using oxygen plasma-assisted molecular beam epitaxy (MBE). The orientations of ZnO thin films were investigated by in situ reflection high-energy electron diffraction and ex situ X-ray diffraction (XRD). The film roughness measured by atomic force microscopy evolved as a function of substrate temperature and was correlated with the grain sizes determined by XRD. Synchrotron-based X-ray absorption spectroscopy (XAS) was performed to study the conduction band structures of the ZnO films. The fine structures of the XAS spectra, which were consistent with the results of density functional theory calculation, indicated that the polar and nonpolar ZnO films had different electronic structures. Our work suggests that it is possible to vary ZnO film structures from polar to nonpolar using the MBE growth technique and hence tailoring the electronic structures of the ZnO films.PACS: 81; 81.05.Dz; 81.15.Hi.

Multiferroic polycrystalline BiFe Mn O (0 ≤ ≤ 0.3) thin films have been prepared on the Pt(111)/Ti/SiO /Si(100) substrates by pulsed laser deposition method. The influence of Mn substitution on the electronic structure and magnetic properties has been studied. X-ray diffraction spectroscopy shows that Mn substitution slightly modulates crystal structure of the BiFe Mn O system within the same structural phase. According to Fe edge X ray absorption spectroscopy, Fe ions are found to be formally trivalent for doping amount in BiFe Mn O . The enhanced magnetization by increasing Mn content is attributed to an alternation degree of hybridization between Fe 3 -O 2 and Mn 3 -O 2 orbitals, basing on the carefully examined Fe and O edge X-ray absorption spectroscopy. The crystal structural and the electronic structural results show a causal relation between them by demonstrating intrinsic mutual dependence between respective variations.

Multiferroic polycrystalline BiFe1-xMnxO3(0≤x≤0.3) thin films have been prepared on the Pt(111)/Ti/SiO2/Si(100) substrates by pulsed laser deposition method. The influence of Mn substitution on the electronic structure and magnetic properties has been studied. X-ray diffraction spectroscopy shows that Mn substitution slightly modulates crystal structure of the BiFe1-xMnxO3system within the same structural phase. According to FeLedge X ray absorption spectroscopy, Fe ions are found to be formally trivalent for doping amountxin BiFe1-xMnxO3. The enhanced magnetization by increasing Mn content is attributed to an alternation degree of hybridization between Fe 3d-O 2pand Mn 3d-O 2porbitals, basing on the carefully examined FeLand OKedge X-ray absorption spectroscopy. The crystal structural and the electronic structural results show a causal relation between them by demonstrating intrinsic mutual dependence between respective variations.