Electronic structures of homogeneous bulk samples of Zn0.9Co0.1O which do not exhibit diluted ferromagnetic semiconducting (DMS) behavior have been investigated using photoemission spectroscopy and x-ray absorption spectroscopy. We have found that the Co ions in Zn1−xCoxO are in the divalent Co2+(d7) states under the tetrahedral symmetry. Our finding indicates that the DMS properties will not be produced when Co ions are properly substituted for Zn sites, implying that the DMS properties observed in Zn1−xCoxO thin films are likely to be extrinsic.

The electronic structure of La0.7Ce0.3MnO3 (LCeMO) thin film has been investigated using photoemission spectroscopy (PES) and x-ray absorption spectroscopy (XAS). The Ce 3d core-level PES and XAS spectra of LCeMO are very similar to those of CeO2, indicating that Ce ions are far from being trivalent. A very weak 4f resonance is observed around the Ce 4d → 4f absorption edge, suggesting that the localized Ce 4f states are almost empty in the ground state. The Mn 2p XAS spectrum reveals the existence of the Mn 2+ multiplet feature, confirming the Mn 2+ -Mn 3+ mixedvalent states of Mn ions in LCeMO. The measured Mn 3d PES/XAS spectra for LCeMO agrees reasonably well with the calculated Mn 3d PDOS using the LSDA+U method. The LSDA+U calculation predicts a half-metallic ground state for LCeMO.

Yttrium‐doped barium zirconate (BZY) thin films were deposited on MgO and sapphire substrates using a pulsed‐laser deposition (PLD) method with varying deposition rates. The films deposited with a low deposition rate exhibited highly oriented microstructures with little grain boundaries. The electrical conductivities of these films were higher than those of the films, deposited with high deposition rates, which showed little‐oriented polycrystalline microstructure. While the films deposited on the MgO substrates had a stoichiometric composition, those deposited on the sapphire substrates had a high barium deficiency, which was possibly due to the differences in the crystal structure and large lattice mismatch between the sapphire substrate and the BZY film. The electrical conductivity of the highly oriented BZY film, grown on MgO substrate with a low deposition rate, showed little barium deficiency and the highest conductivity value that is higher than the typical conductivity of sintered pellets.

We grow Fe film on (4 × 2)-GaAs(100) at low temperature, (∼ 130 K) and study their chemical structure by photoelectron spectroscopy using synchrotron radiation. We observe the effective suppression of As segregation and remarkable reduction of alloy formation near the interface between Fe and substrate. Hence, this should be a way to grow virtually pristine Fe film on GaAs(100).Further, the Fe film is found stable against As segregation even after warmed up to room temperature. There only forms very thin, ∼ 8Å thick interface alloy. It is speculated that the interface alloy forms via surface diffusion mediated by interface defects formed during the low temperature growth of the Fe film. Further out-diffusion of both Ga and As are suppressed because it should then proceed via inefficient bulk diffusion.1 Fe film on GaAs(100) has been extensively studied as a representative system for ferromagnetic metal-semiconductor heterostructure.[1] Due to the small lattice mismatch (∼ 1.3%) between the double of the lattice constant of Fe and that of GaAs, epitaxial growth of Fe film on GaAs(100) is achieved. However, alloy formation near the interface and serious outdiffusion of both Ga and As from the bulk have been notorious problems.[2, 3, 4] There have been various attempts to solve those problems such as S-passivation of GaAs surface[5] and insertion of Er layer between Fe and GaAs [6]. For both cases, the interfacial reaction is reduced to some extent, but the segregated As is still observed. Chye et al. [7] grow Fe film on GaAs (100) at 120 K and also insert Al interlayer. They find improved squareness in magnetic hysteresis and reduced interface states in photo-luminescence spectra. However, no direct investigation on atomic and chemical structure of the Fe film is made.In the present work, we grow Fe film on GaAs(100) around 130 K, and examine the possibility of kinetic stabilization of the Fe film by photoelectron spectroscopy. Here, we report direct evidence for the effective suppression of the outdiffusion of both Ga and As and the minimal formation of the interface alloy during the growth of the Fe film. When the film is warmed up to room temperature, there forms very thin alloy limited near to the interface. Further outdiffusion of both Ga and As is, however, still suppressed.All the experiments are performed at 2B1 beam line of Pohang light source in Korea. It is equipped with an electron energy analyzer and low energy electron diffraction (LEED) optics. The base pressure of the chamber is below 5 × 10 −10 Torr. For the substrate, we use Si-doped, n-type GaAs(100). Repeated sputtering and annealing produce clean and wellordered GaAs substrate; sputtering is made by Ar ion beam of 0.5 K eV, with its incidence angle 45 o from surface normal to minimize surface damage. Annealing is made at 840 K for 30 minutes. As-prepared surface shows well-defined 4 × 2 LEED pattern.We use an e-beam evaporator to deposit Fe film whose thickness is determined by a quartz microbalance that is calibrated by in situ surfac...

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