[en] Oxidation of silver films of one- and two-monolayer thicknesses on the Ni(111) surface was investigated by low-energy electron microscopy at temperatures of 500 and 600 K. Additionally, intensity-voltage curves were measured in situ during oxidation to reveal the local film structure on a nanometer scale. At both temperatures, we find that exposure to molecular oxygen leads to the destabilization of the Ag film with subsequent relocation of the silver atoms to small few-layer-thick silver patches and concurrent evolution of NiO(111) regions. Subsequent exposure of the oxidized surface to ethylene initiates the transformation of bilayer islands back into monolayer islands, demonstrating at least partial reversibility of the silver relocation process at 600 K.

[en] The lattice location of Fe atoms in Fe-doped LiNbO₃ is determined experimentally employing X-ray standing waves. At a bulk concentration of 7.48x10¹⁸ cm^-3 Fe is found to occupy sites close to the ferroelectric Li position; shifted by 0.18 AA in the direction of the -c axis. Electronic structure calculations confirm this result insofar as computed spectroscopic data are more consistent with the respective experimental values for Fe located in the vicinity of the Li site than for Fe occupying the Nb lattice position. (author)

[en] Low-energy electron diffraction (LEED) is used to investigate the initial stages of rowth of silicon on Si(111) between 556 and 900 K. The partial coverages θ_h of the growing film are derived from the intensity variation during evaporation of the 00 and 7 x 7 spot. A preferred growth is observed in the second layer long before the first layer is completed. Surface defects caused by superstructure disorder on the grown islands act as nucleation centers for the diffusing adatoms, so at 633 K substrate temperature the grown islands show no ordered superstructure, although the film is epitaxial. The 7 x 7 spots show all the features of diffraction of a substrate with a non-scattering overlayer for coverages below two monolayers. The grown films show below 650 K an unordered superstructure, in an intermediate temperature range a mixture of 5 x 5 and 7 x 7 domains, and finally, above 870 K, perfect 7 x 7 superstructure. The average size of islands increases from 30 to 40 000 atoms. (author). 13 refs.; 6 figs

[en] Silicon nitride layers grown on Si (1 1 1) by atomic nitrogen exposure at elevated substrate temperatures have been investigated in situ by photoemission spectro-microsopy. From the X-ray photo emission spectra taken at various sample areas, the chemical composition of samples grown at 800 deg. C is found to be homogenous all over the surface, with a stoichiometry according to Si₃N₄. Due to attenuation of the photo electrons, the images also provide information about the morphology of the nitride films. For 800 deg. C, a smooth film is observed, whereas for growth temperatures exceeding 900 deg. C, an increased roughness is observed

No abstract available

[en] Grazing-incidence X-ray diffraction (GIXRD) has been used to study the structural properties of nanoscale In-GaN/GaN(0001) islands, and especially the influence of GaN low-temperature overgrowth of such structures on their strain state, chemical composition and defect structure. Prior to overgrowth, the presence of almost completely relaxed islands with a very high In content is deduced from the diffraction data. After cap layer growth, the In content is found to be significantly reduced and a broad distribution of composition and strain observed. In case of multiple InGaN island layers separated by GaN spacer layers, additional diffraction spots appear, allowing to identify the formation of cubic nitride material due to the low growth temperature (copyright 2009 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

No abstract available

[en] The dependence of the surface morphology on the growth temperature of InGaN/GaN(0001) samples grown by metal organic vapour phase epitaxy has been investigated using scanning probe microscopy. By lowering the growth temperature, the thermal diffusion of the InGaN is reduced which results in an increase of the island density. For 1.3 nm InGaN deposition at 650 C, large spiral disc-like InGaN islands with atomically flat top surfaces are observed which preferentially nucleate at GaN substrate defects. In contrast, InGaN growth at 600 C leads to a homogeneous nucleation of small islands with a granular appearance. (copyright 2006 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

[en] The heteroepitaxial growth of InGaN on GaN was studied by in-situ reflection high-energy electron diffraction, atomic force microscopy, scanning tunneling microscopy and transmission electron microscopy. The misfit strain between InGaN and GaN was relaxed by the deposition of a few-nm-thick wetting layer and the subsequent formation of nano-islands without misfit dislocations, which is the so-called Stranski-Krastanov growth mode. Thus, InGaN nano-islands with a very high density of around 10¹² cm^-2 and a very small aspect ratio of ∝2.1 (diameter/height) were achieved. In this paper, we also discuss the problems regarding GaN overgrowth of an InGaN nano-island layer. (copyright 2006 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

[en] A novel two-step growth method for creating InGaN quantum dots (QDs) was developed by using a combination of an In_xGa_1-xN nucleation layer with a platelet structure and an In_yGa_1-yN formation layer with an indium content lower than that of the In _xGa_1-xN nucleation layer. The realized QDs were investigated by micro-photoluminescence measurements. We observed sharp emission lines at 4 K with a spectral width down to the spectral resolution limit of the experimental setup of 0.17 meV. This growth concept is discussed in comparison with conventional growth methods. (copyright 2006 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)