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Through Indium beam irradiation toward the substrate before growing, high density uniform InN nanocolumns were obtained on p-GaAs(0 0 1) substrate and their possible one dimensional (1D) growth mechanism was analyzed. Rocking curves of all samples showed that Indium beam irradiation method had improved the crystal quality largely, which might be an effective way to release the strain between hexagonal InN(0 0 0 1) and cubic GaAs(0 0 1) with large lattice mismatch. Through quantitative analysis of XPS spectra gotten by in situ measurement, it was found that the InN stoichiometric ratio of all three samples were close to 1:1, which revealed that there was no residual metal at the tip of our nanocolumns. No catalyst or residual metal left could keep its electronic and optical property intact. All three samples showed strong photoluminescence at room temperature. To effectively release the strain and get well surface and interface are important for heterojunction optoelectronic device based on InN. [ABSTRACT FROM AUTHOR]

Abstract: We report the growth of atomically smooth N-polar GaN on c-plane sapphire by metalorganic vapor phase epitaxy. A two-step growth technique was adopted; low-temperature growth of GaN buffer before high-temperature GaN growth. The complete two-dimensional N-polar GaN growth process was recorded by in situ reflectance. The phase composition of the low-temperature GaN was examined by X-ray diffraction pole figure measurements. The thickness of the low-temperature GaN buffer dramatically affected the crystalline and electronic properties of the N-polar GaN. A very small full width at half maximum for the (0002) X-ray rocking curve, 51arcs, was obtained for 700-nm-thick N-polarity GaN by optimizing the buffer thickness. [Copyright &y& Elsevier]

Abstract: It is well-known that there is a relatively small temperature window for the growth of epitaxial and c-axis oriented YBCO thin films by various methods. In this study, this window was more precisely examined for YBCO film growths by photo-assisted MOCVD. At specified total reactor pressure of 4.6torr, and specified respective partial pressures for the oxidizing agents, O2 and N2O at 1.7torr and 1.1torr, the film growths were tested at several substrate temperature (T s) points from 780°C to 864°C. The film growth time for each test was 3min. As to compositional purity, purity in c-axis orientation, and crystal structural quality of these tested films by using photo-assisted MOCVD technique, it was found that for the growth of purely c-axis oriented YBCO thin films with high crystalline quality, the appropriate growth temperature range (or “T s window”) was from about 800°C to 830°C, at relevant pressures as specified above. T c and J c of a typical YBCO film sample grown within this “T s window”, i.e., 810°C, were found as 90K and 1.32MA/cm2 (77K, 0Oe) respectively by magnetization measurements. It is noticeable that this film, and other purely c-axis oriented YBCO films are all single-crystal like and dense, with no SEM visible grain boundary or void. The causes of precipitates found on top surface of these c-axis oriented YBCO films are also discussed. [Copyright &y& Elsevier]

High-quality ZnO films were grown on epi-GaN predeposited on c-Al2O3 substrates using low-pressure metal-organic chemical vapor deposition (MOCVD). Detailed study of the X-ray diffraction spots and patterns by different diffractometers showed high structural perfection of the zinc oxide layer, which indicated that the growth of ZnO film was strongly c-oriented. The full-width at half-maximum (FWHM) of the ω-rocking curve was 0.39°. Surface morphology of the films studied by AFM showed that the growth of the ZnO film followed the regular hexagonal column structure with about 500 nm grain diameter. Zn and O elements in the deposited ZnO/GaN/Al2O3 films were investigated and compared by X-ray photoelectron spectroscopy (XPS), in which the dissociative O and Zn atom peak was hardly observed. The ratio of O/Zn atoms of the film was about 1 with O-rich. Photoluminescence spectra of the ZnO films grown on epi-GaN showed dominating exciton emission peak, and the deep-level emission which was obvious on ZnO/Al2O3 film had hardly been observed. [Copyright &y& Elsevier]

β gallium oxide (β-Ga 2 O 3) homoepitaxy films were grown on (2 ‾ 01) β-Ga 2 O 3 substrates by metal organic chemical vapor deposition (MOCVD). The effect of growth temperature on the crystalline quality was measured and systematically analyzed. The results showed the growth temperature played an important role in crystalline quality of β-Ga 2 O 3. The optimized single crystalline β-Ga 2 O 3 film was grown at 750 °C, and the full width at half maximum (FWHM) of X-ray diffraction (XRD) rocking curve was 21.6 arcsec, smaller than that of the β-Ga 2 O 3 substrate (26.3 arcsec). The film exhibited a greatly smooth surface and the root-mean-square (RMS) roughness was 0.68 nm. And the arrangement of atoms inside the film was in good accordance with lattice constants of β-Ga 2 O 3. In addition, the effect of the band structure on the luminescent properties of β-Ga 2 O 3 was discussed. • The crystalline quality of the optimized film was superior to that of the substrate. • Atomic arrangement inside the β-Ga 2 O 3 films was displayed. • The effect of band structure on the luminescent properties of β-Ga 2 O 3 was discussed. [ABSTRACT FROM AUTHOR]