Search results for "surface structure"

Optical Properties of Composite Films Based on Copper Chloride in PMMA Matrix

2014

The composite lms based on PMMA, CuCl2 and photoinitiator were prepared.Transmission spectra of the lms with and without photoinitiator were measured. The holo-graphic gratings were recorded, the sensitivity of the lms and surface structure of gratingswere studied. Microanalysis of the lms was performed in di erent part of structure elementsof grating.

Surface passivation of gallium selenide by nitrogen implantation

2002

In this paper we report on the characterization of nitrogen-implanted single-crystal GaSe samples. Nitrogen atoms were implanted at 80 keV, with doses ranging from 4 × 10 13 to 10 15 N + ions cm -2 . Next, samples were aged in open air and characterized by small-area XPS, together with an unimplanted clean surface, in order to quantify the effects of the nitrogen implantation. In general, we found that the oxidation was fully prevented in N + -implanted samples.

Structural characterization of a-plane Zn1−xCdxO (0 < x <0.085) thin films grown by metal-organic vapor phase epitaxy.

2006

Zn1−xCdxO(11math0) films have been grown on (01math2) sapphire (r–plane) substrates by metal-organic vapor phase epitaxy. A 800-nm-thick ZnO buffer, deposited prior to the alloy growth, helps to prevent the formation of pure CdO. A maximum uniform Cd incorporation of 8.5 at. % has been determined by Rutherford backscattering spectrometry. Higher Cd contents lead to the coexistence of Zn1−xCdxO alloys of different compositions within the same film. The near band-edge photoluminescence emission shifts gradually to lower energies as Cd is incorporated and reaches 2.93 eV for the highest Cd concentration (8.5 at. %). The lattice deformation, due to Cd incorporation, has been described using a n…

Structural Characterization of Monolayers at the air-water interface

1991

Scanning tunneling microscopy and spectroscopy of Mo clusters grown on TiO2(110).

2007

Molybdenum was deposited in two steps (3 eq. ML and 1 eq. ML) on the light blue rutile TiO2 10) (1 x 1) surface at room temperature, each Mo deposition cycle being followed by an annealing up to 950-1000 K. This procedure was found to lead to formation of separated clusters having a size in very wide range (1-20 nm). Scanning tunneling microscopy showed a dependence of the cluster morphology as a function of the size. The scanning tunneling spectra of Mo clusters was studied as a function of cluster dimensions and discussed in comparison with photoelectron spectroscopy results previously obtained for homogeneous Mo films. The dI/d V curves do not display the valence band structure of deposi…

Field-induced tip–sample oxygen transfer in scanning tunneling microscopy on TiO2(110) (1 1).

2008

International audience; A study on the field-induced tip–surface oxygen transfer at room temperature and its influence on the tunneling conditions for stable STM imaging of the TiO2(110) (1 1) surface is reported. A simple model of field-induced transfer is applied to tungsten and platinum–iridium tips. The oxygen transition rates from the sample to the tip or from the tip to the sample depend on the oxygen desorption barriers formed at tunneling distance. For stable imaging the applied bias voltage has to balance the oxygen transfer probabilities in both directions. In the case of Pt/Ir tips, the tunneling conditions for images with clear evidence of bridging oxygen point defects have been…

Comments on surface structure analysis by water and nitrogen adsorption

2004

Specific surface area and pore size distribution are determined usually from adsorption isotherms at low temperatures using nitrogen or noble gases. These are not absolute parameters and the measuring methods are fraught with serious difficulties. General problems of sorption measurements and recent developments are discussed. To obtain information for practical purposes these measurements need to be supplemented by investigations of the sorbate/sorbent system used in practice. Results of the measurement of nitrogen and water vapour adsorption on different materials are compared.

Modeling of surface structure formation after laser irradiation

2011

The Stefan problem in a semi-infinite media under laser irradiation is considered. It is related to the melting and solidification processes, resulting in certain surface structure after the solidification. A simple model, as well as a more sophisticated one is proposed to describe this process. The latter model allows us to calculate the surface profile by solving a system of two nonlinear differential equations, if the shape of the solid-liquid interface is known. It has to be found as a solution of two-phases Stefan problem. The results of example calculations by the fourth-order Runge-Kutta method are presented, assuming that the solid-liquid interface has a parabolic shape. The calcula…

Ab initiomodeling of surface structure forSrTiO3perovskite crystals

2001

We present and discuss the results of calculations of ${\mathrm{SrTiO}}_{3}$ (100) surface relaxation and rumpling with two different terminations (SrO and ${\mathrm{TiO}}_{2}).$ These are based on ab initio Hartree-Fock method with electron correlation corrections and density functional theory calculations with different exchange-correlation functionals, including hybrid exchange techniques. Both approaches use the localized Gaussian-type basis set. All methods agree well on surface energies and on atomic displacements, as well as on considerable increase of covalency effects nearby the surface. More detailed experiments on surface rumpling and relaxation are necessary for further testing …

AB INITIO CALCULATIONS OF SrTiO3, BaTiO3, PbTiO3, CaTiO3 AND BaZrO3 (001) AND (011) SURFACES

2009

I present results of calculations of surface relaxations and rumplings for the (001) and (011) surfaces of BaZrO3 and ATiO3 perovskites (A = Sr, Ba, Pb and Ca) using a hybrid B3PW description of exchange and correlation. The (001) surface energies of AO, TiO2 and ZrO2 terminations are found to be comparable with each other for all five materials. The surface energies for BaZrO3, SrTiO3, BaTiO3, PbTiO3 and CaTiO3 (011) surfaces for all terminations are considerably larger than for (001) surfaces. We predict a considerable increase in the Ti-O (Zr-O) chemical bond covalency near the (011) surface as compared both to the bulk and to the (001) surface.