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Notes: We find two different surface structures, (1×2) and (1×1), for H2S-treated InP(001). They depend upon exposure of H2S at about 350 °C. The coverage of sulfur is estimated to be about a half monolayer and one full monolayer for the (1×2) and (1×1) structures, respectively. The (1×1) structure is reconstructed to the (1×2) structure upon annealing at about 550 °C. It is suggested that sulfur is bonded to only In atoms and substitutes some of the phosphorus atoms below the first layer. Inverse photoemission spectra show strong reduction in intensity of 1.2 eV peak above the Fermi level for a clean InP(001)-(4×2) surface upon adsorption of H2S. This reduction implies a decrease in unoccupied surface states due to dangling bonds of indium dimers on the clean surface. The result of adsorption of oxygen on the (1×2) and (1×1) surfaces indicates significant passivation to oxidation of the surfaces. © 1996 American Institute of Physics.

Notes: Clean and H2S-adsorbed GaP(001) surfaces have been studied by inverse and ultraviolet photoemission spectroscopy (IPES) and (UPS) and by high-resolution electron energy loss spectroscopy. H2S is found to be dissociated on the surface, leaving only sulfur on it, which is consistent with UPS results. IPES spectra show strong reduction in intensity at 1.5 and 4.5 eV above the Fermi level upon sulfur adsorption. The reduction in the former indicates tremendous decrease of unoccupied states, which correspond to dangling bonds of surface gallium atoms, in the band gap by H2S passivation.

Notes: The crystallinity of a phosphorus-doped n-type diamond thin film as grown on a C(001) substrate by gas source molecular beam epitaxy has been examined by x-ray photoelectron diffraction (XPD) and atomic force microscopy (AFM). AFM showed that the growth mode of the n-type film is not an island-growth type that hinders the application of XPD. C 1s XPD patterns for the n-type film and the substrate showed almost perfect similarity. This proves that, like the substrate, the phosphorus-doped n-type thin film is in a good diamond structure. © 1999 American Institute of Physics.

Notes: We have built a simple and high performance inverse photoemission spectrometer using a BaF2 window and a Cu–BeO electron multiplier with KBr as the photocathode for low- and high-pass filters, respectively. It is found that using the BaF2 low-pass filter improves the resolution by 0.2 eV to compare with SrF2. The intensity was reduced to a quarter of that with SrF2, although it is enough to obtain good inverse photoemission spectra.

Notes: It has been an earnest desire of protein crystallographers to collect fast, accurate, high resolution diffraction data from protein crystals, preferably with exposure time as short as possible. In order to meet this challenge, a new type of Weissenberg camera has been developed for the recording of diffraction intensity from protein crystals using synchrotron radiation. The BL6A2 line has a plane-bending mirror designed by Y. Sato. The optical bench with triangular tilt-cut Si crystal monochromator was designed by N. Kamiya and was installed in the BL6A2 hutch. The Weissenberg camera was set on the 2θ arm of the optical bench. This camera can be used with Fuji Imaging Plate (IP) as an x-ray detector, and the reading out of the image from the IP is carried out by using BA100. The characterization of this system was carried out using the native crystal of chicken gizzard G-actin DNase I complex and its Yb3+, PCMB, indium, and FMA derivatives. Since these crystals are very sensitive for x rays, the resolution limit of the diffraction was 5 A(ring) with a 4-circle diffractometer on a rotating anode x-ray generator (N. Sakabe et al., J. Biochem. 95, 887. This complex was crystallized in space group P2,2,2, with a=42.0, b=225.3, and c=77.4 A(ring). The data were collected with this system with the 430-mm radius cassette when Photon Factory was operated at 2.5 GeV and 270 mA and the wavelength λ=1.004 A(ring) was chosen. In order to avoid overlapping of diffraction spots, oscillation angle range and coupling constant (degree/mm) were settled on the basis of simulation patterns of diffraction spots up to the maximum resolution to be measured considering the direction of the crystal axes, wavelength, radius of the camera, and mosaicness of the crystal. When the oscillation axis was a axis, the oscillation angle range was selected at either 10° (1°/mm) or 5° (0.5°/mm) depending on the density of reciprocal lattice points along the incident beam, and typical exposure time in each IP was 50 and 25 s, respectively. The exposure was stopped after 10 times oscillation. The total range of 117.5° was recorded on 16 sheets of IP with an overlapping range 0.5°.The data processing was carried out using program weis coded by T. Higashi. Two complete data sets along the a and c axes were collected using two crystals, independently, and the merge R(F2) for native crystal was 0.068. In order to know the feasibility of the data (F+−F−), Patterson maps were calculated with data of each derivative, and heavy atom vectors clearly appeared as prominent peaks in the Harker sections of the Patterson maps of both Yb3+ and PCMB derivatives. The heavy atom positions were obtained from the combinations of different Patterson and different Fourier maps, and were refined by using least-squares techniques. The final figure of merit up to 2.5 A(ring) resolution was 0.61 with 22 700 reflections. The assignment of DNase I part on the electron density maps is progressing using the Nicholson molecular model referring to its structure reported by C. Oefner and D. Suck [J. Mol. Biol. 192, 605 (1986)]. In addition to promising results of ω-aminoacid pyruvate aminotransferase [N. Watanabe et al., Book of abstracts of second Japan-China Bilateral Symposium on Biophysics, p. 83 (1988)], these results support that this data collection system consisting of a new type of Weissenberg camera using SR, Fuji Imaging Plate, BA100, and program weis is one of the fastest and most accurate systems for protein crystallography in use today. We thank the Education Ministry and the Foundations of Yamada, Naito and Toray for the financial support of this project. We are grateful to Dr. K. Namba of ERATO for our use of BA100.

Notes: Reconstruction of an InP(001) surface structure upon H2S adsorption has been studied by low-energy electron diffraction (LEED), scanning tunneling microscopy (STM), high-resolution electron energy loss (HREELS), and x-ray photoelectron spectroscopies (XPS). The HREELS result indicates that H2S is dissociated on the surface even at RT, leading to evolution of hydrogen from the surface. LEED patterns show (2×4) and (2×1) structures for the surface with sulfur coverages, 0 and 0.5–1 ML, respectively. A complex pattern appears at 0.25 ML. We find in STM images that the (2×1) structure starts to form even at 0.1 ML sulfur coverage at 350 °C. The (2×1) structure is almost established at 0.5 ML although the protrusions of about two atoms in size exist on the surface. The new (2×1) structure begins to grow from protrusions above 0.5 ML on the (2×1) surface found at 0.5 ML and it is established at about 1 ML where the c(2×2) structure with small domain is found. XPS result shows one chemical state of sulfur at 0.55 ML with the binding energy (BE) at 161.8 eV. Above 0.55 ML, S 2p spectra contain two components with the BE at 161.8 and 162.2 eV. Based on the angle dependence of the spectrum and the result of the STM images, these can be ascribed to sulfur on and under the surface, respectively. Sulfur is found not to be bonded to phosphorus atoms at 350 °C. © 1998 American Institute of Physics.

Notes: We report the synthesis and electroluminescent properties of the organometallic complex diphenyltin bis-hydroxyquinoline (Sph2q2). The complex was prepared by the reaction of diphenyltin dichloride with 8-hydroxyquinoline and shows an absorption cutoff wavelength of 460 nm and bright photoluminescence with a peak wavelength at 508 nm. The ionization potential of Sph2q2 was determined to be ∼6.0 eV by photoemission apparatus, and the electron affinity is estimated to be 3.3 eV. Sph2q2 was used as an emitting and electron injection layer in bilayer devices. The electroluminescence (EL) properties and charge injection properties of Sph2q2 are characterized. Sph2q2 is easily soluble in common organic solvents and further modification of its properties is possible. The results indicate that tetravalent tin complexes are potential emitting and charge injection materials for EL applications. © 2000 American Institute of Physics.

Notes: Clean GaP(001)-(4×2) and H2S-treated (1×2) surfaces are studied by scanning tunneling microscopy (STM). We have observed a (4×2)/c(8×2) STM image for the cation-stabilized GaP(001) surface. The result suggests that the unit cell of the (4×2) structure consists of two Ga dimers with two missing Ga dimers. For the (1×2)S surface, the previous model that sulfur atoms are adsorbed on the Ga dimer and that a missing row of sulfur is formed along the [11¯0] direction is supported by the STM result. © 1995 American Institute of Physics.