Sasaki, Takuo; Takahashi, Masamitsu; Suzuki, Hidetoshi*; Oshita, Yoshio*; Yamaguchi, Masafumi*
Journal of Crystal Growth, 425, p.13 - 15, 2015/09
Yokoyama, Yuta*; Uozumi, Yuki; Asaoka, Hidehito
Journal of Crystal Growth, 405, p.35 - 38, 2014/11
Si-Ge structures forming new shapes on a Si(110)-162 reconstructed surface were investigated via scanning tunneling microscopy. Pyramidal-shaped Si-Ge nanoislands lying along the 1 1 1 directions were formed on the striped structure at Ge coverage between 3 and 6 monolayers. However, when a single monolayer of Ge was deposited on the Si(110)-162 surface, single-domain of 162 striped structure disappeared, and a new double-domain striped structure was formed over the surface along directions that differed from the 1 1 2 directions. This structure represents a new Si-Ge striped structure that forms by the mixing of Ge and Si due to high temperature annealing. These results indicate that the surface structure changes specifically with trace amounts of Ge.
Asaoka, Hidehito; Yamazaki, Tatsuya; Yokoyama, Yuta; Yamaguchi, Kenji
Journal of Crystal Growth, 378, p.37 - 40, 2013/09
We have focused on stress measurements of the reconstructed Si(111) 77 and the H-terminated Si(111) 11 surfaces. In order to obtain information on both the surface stress and the surface structure simultaneously, we have combined the surface-curvature and the reflection-high-electron-energy-diffraction instrumentations in an identical ultrahigh vacuum system. At the beginning of Ge wetting layer growth on H-terminated Si(111), the stress gradient drastically changes accompanied by change in the surface structure resulting from the H desorption. Comparison of the surface stress behaviors between Ge wetting layer growth on the H-terminated Si(111) 11 and the Si(111) 77 surfaces reveals that the Si(111) 11 surface releases 1.6 N/m (=J/m), or (1.3 eV/(11 unit cell)), of the surface energy from the strong tensile Si(111) 77 reconstruction.
Yokoyama, Yuta; Yamazaki, Tatsuya; Asaoka, Hidehito
Journal of Crystal Growth, 378, p.230 - 232, 2013/09
The initial processes of Ge nano cluster formation on Si(110)-162 reconstructed structure were investigated via scanning tunneling microscopy. For a small amount of Ge deposited on Si(110)-162 single-domain structure at room temperature, the surface structure did not change significantly. After direct current heating at 973 K for 20 min, the striped structure almost broken and disordered-like structure was formed on the terrace. With increasing the annealing time, the surface structure changed from disordered-like structure to the 162 double-domain structure and pyramidal nano clusters were formed at the domain boundary. These results suggest that the surface stress was induced by Ge nano cluster formation and the double-domain structure was formed in order to relax the stress.
Takahashi, Masamitsu; Nakata, Yuka*; Suzuki, Hidetoshi*; Ikeda, Kazuma*; Kozu, Miwa; Hu, W.; Oshita, Yoshio*
Journal of Crystal Growth, 378, p.34 - 36, 2013/09
Journal of Crystal Growth, 401, p.372 - 375, 2013/09
Sasaki, Takuo*; Suzuki, Hidetoshi*; Sai, Akihisa*; Takahashi, Masamitsu; Fujikawa, Seiji; Kamiya, Itaru*; Oshita, Yoshio*; Yamaguchi, Masafumi*
Journal of Crystal Growth, 323(1), p.13 - 16, 2011/05
Growth temperature dependence of strain relaxation during InGaAs/GaAs(001) molecular beam epitaxy was studied by in situ X-ray reciprocal space mapping. Evolution of the residual strain and crystal quality for the InGaAs film was obtained as a function of film thickness at growth temperatures of 420, 445 and 477 C. In the early stages of strain relaxation, it was found that evolution of the residual strain and crystal quality was dependent on the growth temperature. In order to discuss this observation quantitatively, the strain relaxation model was proposed based on the Dodson-Tsao kinetic model, and its validity was demonstrated by good agreement with the experimental residual strain. Additionally, rate coefficients reflecting dislocation motions during strain relaxation were obtained as a function of growth temperature and strain relaxation was discussed in terms of the thermally active dislocation motion.
Takahashi, Masamitsu; Kaizu, Toshiyuki*
Journal of Crystal Growth, 311(7), p.1761 - 1763, 2009/03
The molecular beam epitaxial (MBE) growth of InAs/GaAs(001) quantum dots was investigated by grazing-incidence X-ray diffraction using a diffractometer integrated with an MBE apparatus. Use of synchrotron radiation and a two-dimensional X-ray detector enabled three-dimensional mapping of X-ray diffraction intensity at a rate of 10 s per frame. A series of X-ray diffraction images have revealed the evolution of the shape and internal strains of InAs quantum dots in the whole growth processes including the island formation and encapsulation with GaAs. The optical quality of InAs quantum dots was evaluated by photoluminescence spectra. It shows a clear correlation with structural properties measured by in situ X-ray diffraction.
Nakazato, Tomoharu*; Furukawa, Yusuke*; Tanaka, Momoko; Tatsumi, Toshihiro*; Nishikino, Masaharu; Yamatani, Hiroshi*; Nagashima, Keisuke; Kimura, Toyoaki*; Murakami, Hidetoshi*; Saito, Shigeki*; et al.
Journal of Crystal Growth, 311(3), p.875 - 877, 2009/01
The temperature dependence of scintillation properties of a hydrothermal-method-grown zinc oxide (ZnO) emission is investigated using a nickel-like silver laser emitting at 13.9 nm. A broad peak at 386 nm with a full-width at half-maximum (FWHM) of 15 nm at room temperature (298 K) is obtained. The peak position tends to be blue shifted while the FWHM becomes narrower when the crystal temperature is decreased to 25 K. Streak images fitted by a double exponential decay reveal that the measured emission decay at 105 K was = 0.88 ns and = 2.7 ns. This decay time of a few nanoseconds is suitable for lithographic applications and is sufficiently short for the characterization of laser plasma extreme ultraviolet (EUV) sources with nanosecond durations.
Kaizu, Toshiyuki*; Takahashi, Masamitsu; Yamaguchi, Koichi*; Mizuki, Junichiro
Journal of Crystal Growth, 310(15), p.3436 - 3439, 2008/07
An Sb-adsorbed GaAs(001) substrate that serves as a template for high-density InAs quantum dot (QD)growth was investigated using in situ X-ray diffraction. The Sb distribution in the top eight layers from the surface was determined by crystal truncation rod scattering analysis. It was found that Sb atoms penetrated to the eighth layer when GaAs(001) came in contact with an Sb environment. The amounts of Sb in the first and second layers were, however, saturated at 1/3 atomic layer (AL) and 2/3 AL, respectively. A comparison between the X-ray results and atomic force microscopy observations of the QD density showed that the formation of high-density QDs is correlated with the total amount of Sb in the surface and subsurface layers.
Saito, Hiroyuki; Utsumi, Wataru; Aoki, Katsutoshi
Journal of Crystal Growth, 310(7-9), p.2295 - 2297, 2008/04
Saito, Hiroyuki; Utsumi, Wataru; Aoki, Katsutoshi
Journal of Crystal Growth, 310(2), p.473 - 476, 2008/01
Takahashi, Masamitsu; Mizuki, Junichiro
Journal of Crystal Growth, 301-302, p.16 - 21, 2007/04
Recently, sophisticated surface analysis tools including scanning probes and diffraction techniques have been applied to GaAs surfaces towards the understanding of the atomistics of the MBE growth process. Under growth conditions, GaAs surfaces are exposed to the gas phase of source materials and thus exchanges atoms with the environment. This situation brings abouta variety of surface reconstructions whose stoichiometry is different from that of the bulk, depending on growth parameters. Determination of the surface reconstructions under growth conditions is a key to understand the elemental process of MBE. In this paper, we report on in situ X-ray analysis of the (24) structure under true growth conditions and its structural changes induced by As incorporation.
Kaizu, Toshiyuki; Takahashi, Masamitsu; Yamaguchi, Koichi*; Mizuki, Junichiro
Journal of Crystal Growth, 301-302, p.248 - 251, 2007/04
no abstracts in English
Saito, Hiroyuki; Utsumi, Wataru; Kaneko, Hiroshi; Aoki, Katsutoshi
Journal of Crystal Growth, 300(1), p.26 - 31, 2007/03
We have performed the synthesis study of group-III nitride crystals using a cubic-anvil-type large volume high pressure apparatus. Bulk crystals of the nitride compounds, which are key materials for developing optoelectronic and high-power/ frequency devices, can hardly be prepared by the conventional crystal growth technique such as the Bridgman method since they decompose on heating at ambient pressure before reaching the melting points. Appling pressure is expected to suppress decomposition reaction and consequently allow crystal growth from their melts. I will talk about the crystal growth of GaN and AlGaN under high pressure, and phase stability of InN under high pressure and temperature.
Fukazawa, Hiroshi; Hoshikawa, Akinori; Yamauchi, Hiroki; Yamaguchi, Yasuo*; Ishii, Yoshinobu
Journal of Crystal Growth, 282(1-2), p.251 - 259, 2005/08
We measured neutron diffraction profiles of powdered KOD-doped D2O ice to investigate the formation and growth of ice XI, a deuterium-ordered phase of ice, from ice Ih, a disordered phase. During the measurements, the ice was annealed at 57 K for about 17 h, and then warmed up and kept at 68 K for about 55 h, which are below the transition temperature Tc = 76 K. The diffraction profiles for the doped ice at 57 K did not change with time and were close to those for ice Ih with the deuterium-disordered arrangement. However, when the temperature increased from 57 K to 68 K, the diffraction profiles changed. We carried out the Rietveld analysis with the parameters for a two-phase model to obtain the structural evidence of the appearance and the growth of ice XI. The analysis provided evidence of ice XI as space group Cmc21 at 68 K. The temporal increase of the mass fraction of ice XI showed that nucleation of ice XI began just after warming up to 68 K. Then ice XI grew for several days in the doped ice. The study provides the first structural observation of the growth of ice XI.
Takahashi, Masamitsu; Yoneda, Yasuhiro; Inoue, Hirotane*; Yamamoto, Naomasa*; Mizuki, Junichiro
Journal of Crystal Growth, 251(1-4), p.51 - 55, 2003/04
The reflection high energy electron diffraction (RHEED) oscillation has been widely adopted for studies on growth kinetics and dynamics in molecular beam epitaxy (MBE). Recent development in brilliant X-ray source has enabled similar experiments with X-rays, which has great advantage in a straightforward interpretation of results and in a high angular resolution. In general, the diffracted intensity from surface is proportional to the surface structure factor associated with the surface reconstruction, F, multiplied by a damping factor associated with the surface roughness, m. We show that the two factors, F and m, can be obtained separately by measuring diffuse scattering around the two-dimensional Bragg peak during growth.
Abe, Hideki*; Ye, J.*; Imai, Motoharu*; Yoshii, Kenji; Matsushita, Akiyuki*; Kitazawa, Hideaki*
Journal of Crystal Growth, 241(3), p.347 - 351, 2002/06
no abstracts in English
Yamamoto, Shunya; Sumita, Taishi; Yamaki, Tetsuya; Miyashita, Atsumi; Naramoto, Hiroshi
Journal of Crystal Growth, 237-239(Part1), p.569 - 573, 2002/04
The epitaxial growth of TiO films has attracted much interest from the viewpoints of basic science and applications. In the present study, it is shown that TiO films with anatase or rutile structure can be grown by pulsed laser deposition(PLD) with an ArF excimer laser under the controlled O atmosphere. The TiO films were prepared on the LaAlO, LSAT SrTiO and -AlO single crystal substrates. The epitaxial films were analyzed by RBS and X-ray diffraction for investigating the crystallographic relationships with the substrates. The high quality anatase TiO(001) films have been successfully grown on the LaAlO (001), LSAT (001) and SrTiO (001) substrates at temperatures above 500C. Also the high quality rutile TiO(100) and (001) films were obtained on the -AlO (0001) and (10-10), respectively.The optical properties were characterized by optical absorption measurements. The optical band gaps for anatase and rutile TiO epitaxial films were evaluated to be 3.22 eV and 3.11 eV, respectively.
Yamaki, Tetsuya; Sumita, Taishi; Yamamoto, Shunya; Miyashita, Atsumi
Journal of Crystal Growth, 237-239(Part1), p.574 - 579, 2002/04
Pulsed laser deposition (PLD) with a KrF excimer laser was used to prepare epitaxial TiO films on a (0001) sapphire substrate. The crystalline structure and surface morphology of the films were then investigated as a function of the laser power density in the PLD. X-ray diffraction and Raman spectroscopy results showed that the films were composed of the (100) oriented rutile phase with a small amount of the (001) oriented anatase. The anatase-to-rutile ratio in such phase-mixed films was controlled by the laser power; the ratio increased as the power density decreased. From atomic force microscopy observations, the film deposited at the lowest power was found to have a rough surface consisting of coarse grains. This film exhibited the best photocatalytic performance during the decomposition of the organic dyes possibly due to the maximum relative content of anatase and the large surface area.