Adsorption sites of111In and111mCd on Pd(111) surfaces characterized by the electric field gradient

PAC measurements of the electric field gradient at the nucleus of isolated probe atoms on Pd(111) surfaces lead to the identification of five adsorption sites successively occupied by the parents¹¹¹In and^111mCd during annealing between 80K and 600K. The data are consistent with an estimated activation energy for Pd surface self diffusion of E_a=0.76(8)eV.     

Growth and thermal stability of Fe, Ni, Rh and Pd layers on the (111)W crystal face

LEED, AES and Δφ measurements were used to investigate the growth of Fe, Ni, Rh and Pd layers on the tungsten (111) surface. The thermal stabilities of the layers and of the substrate were also examined. Both were found to be thermally unstable at coverages above one monolayer. In addition, Rh and Pd were found to cause faceting of the substrate surface. In thick Fe layers, a non-wetting-wetting transition was observed.     

Diffusion of atoms incorporated in the surface layer of the fcc(111) face

The kinetics of the migration of the impurity atom due to the diffusion of vacancies on the fcc(111) face was investigated. The study focused on the dependence of the diffusion coefficient of the impurity on the degree of surface coverage with vacancies. It was shown by molecular dynamics that this dependence is linear in the limit of the vanishingly small concentration of vacancies 1; the results of modeling coincided with the predictions of our analytical theory. The diffusion coefficient increased nonlinearly with and its growth correlated with that of the size of the percolation clusters. After the percolation threshold was overcome, the diffusion coefficient of the impurity quickly tended toward its value for the surface without hindrances.     

Growth and characterization of semiorganic crystal: Thiosemicarbazide lead nitrate (TSLN)

Semiorganic material of TSLN (thiosemicarbazide lead nitrate) has been synthesized in the ratio of 1:1. Thiosemicarbazide lead nitrate single crystals were grown from aqueous solution by slow evaporation method at room temperature. The good quality optically transparent single crystals were harvested and it is characterized by Single crystal XRD study revealed that materials crystallized with triclinic crystal structure and its belongs to centrosymmetric space group Cc and powder X-ray diffraction(XRD) is to confirm the crystalline nature of the crystal, using FTIR spectrum studies confirm the functional groups present in the grown crystal and the presence lead in the compound and the composition of the grown crystal were analyzed by energy dispersive analysis of X-ray (EDAX).     

Si(111)衬底上GaN的MOCVD生长

利用LP-MOCVD在Si（111）衬底上,以高温AIN为缓冲层,分别用低温GaN（LT-GaN）和偏离化学计量比富Ga高温GaN（HT-GaN）为过渡层外延生长六方相GaN薄膜。采用高分辨率双晶X射线衍射（DCXRD）,扫描电子显微镜（SEM）,原子力显微镜（AFM）和室温光致荧光光谱（RT-PL）进行分析。结果表明,有偏离化学计量比富Ga HT-GaN为过渡层生长的GaN薄膜质量和光致荧光特性均明显优于以LT-GaN为过渡层生长的GaN薄膜,得到GaN（0002）和（1012）的DCXRD峰,其半峰全宽（FWHM）分别为698s和842s,室温下的光致荧光光谱在361nm处有一个很强的发光峰,其半峰全宽为44．3meV。     

Atomic layer growth on Al(111) by ion bombardment

We study equilibrium crystal shapes (ECS) near facet ridge end points (FRE) by means of a numerical study of a body-centered solid-on-solid model on a square lattice with an enhanced uniaxial interaction range. This tests the stability of the so-called stochastic FRE point where the model maps exactly onto one dimensional Kardar-Parisi-Zhang-type growth and where the local ECS is simple. We find that the generic shapes are more complex. They contain first-order faceted to rough boundaries terminating in Pokrovsky-Talapov-type end points, and first-order ridges inside the rounded part of the ECS where two rough surface orientations coexist.     

Electric field gradients at (111)In/(111)Cd probe atoms on A-sites in 211-MAX phases

The method of perturbed angular correlation (PAC) was applied to selected MAX phases with 211 stoichiometry. Radioactive (111)In ions were implanted in order to measure the electric field gradients (EFG) in the key compounds Ti(2)InC and Zr(2)InC to determine the strength and symmetry of the EFG at the In-site. Further PAC studies in the In-free MAX phases Ti(2)AlN, Nb(2)AlC, Nb(2)AsC and Cr(2)GeC were performed to confirm that the In probes occupy the A-site as well. The strength of the EFG, with a quadrupole coupling constant ν(Q) between 250 and 300 MHz in these phases, is quite similar to the ones found in Ti(2)InC with ν(Q) = 292(1) MHz and in Zr(2)InC with ν(Q) = 344(1) MHz, respectively. Different annealing behavior was observed whereas in all cases a linear decrease of ν(Q) with increasing measuring temperatures was found. The experimental results are also in excellent agreement with those predicted by ab initio calculations using the APW+lo method implemented in the WIEN2k code. This study shows in an exceptional manner that (111)In?→?(111)Cd atoms are suitable probes to investigate the local surrounding at the A-site in 211-MAX phases.     

Self-limited growth of a thin oxide layer on Rh(111)

The oxidation of the Rh(111) surface at oxygen pressures from 10(-10) mbar to 0.5 bar and temperatures between 300 and 900 K has been studied on the atomic scale using a multimethod approach of experimental and theoretical techniques. Oxidation starts at the steps, resulting in a trilayer O-Rh-O surface oxide which, although not thermodynamically stable, prevents further oxidation at intermediate pressures. A thick corundum like Rh2O3 bulk oxide is formed only at significantly higher pressures and temperatures.     

In situ spectroscopic ellipsometry: Application to Sb coverage measurement in the monolayer range on Si (111)

In this paper, we present an analysis of antinomy deposition on silicon in the range of 0.1 to 1 monolayer by in situ spectroscopic ellipsometry. After a careful choice of viewpoint material, ellipsometric measurements are found to be sensitive to small surface perturbations, especially with antimony. In fact, less than a 0.1 monolayer of antimony on silicon at room temperature is detectable. Moreover, a linear dependence of the ellipsometric signal on Sb coverage is observed in the monolayer range. Consequently, the signal versus time variation directly gives the Sb adsorption kinetics on silicon. The saturation to one monolayer of compact antimony on silicon surface is used in order to calibrate the spectra.     

TDPAC spectrum of111In in a single crystal of cadmium

TDPAC spectra of 111 In in a single crystal of Cd are measured as a function of its. orientation relative to the -direction. The results are compared with the theoretical calculation by Alder et. al.     

Local density of states of GaAs and InAs surfaces: Ideal (111), (001) and (110) surfaces and monoatomic steps on the (111) and the (001) surface

The ideal (111), (001) and (110) surfaces of GaAs and InAs are investigated by means of the LCAO Green function recursion method to obtain local density of states. Main emphasis is laid on the analysis of the nature and character of the inherent surface states. For this purpose, several imperfections on the (111) and the (001) surface (i.e. vacancies and steps with varying topology) are treated to demonstrate the local character of Shockley surface states and to confirm their chemical nature. The applicability of the results obtained to other A³B⁵ compounds is discussed. Comparison with experiment and other theoretical investigations is also made.     

Adsorption of CO on,and S poisoning of,a perfect Ni(111) single crystal and a Ni(111) crystal with small angle boundaries

A Ni(111) crystal with small angle boundaries was used to examine the adsorption of CO. The adsorption of CO on a perfect Ni(111) single crystal was used for reference. Auger spectra show that the boundary lines on the sample surface provide favorable sites for the adsorbed CO to dissociate at temperatures as low as 25°C. The post-dissociation carbon appears mostly in the form of a nickel carbide on the surface. After heating the crystal to 850°C, sulfur diffused to the surface and blocked the surface adsorption sites uniformly. The boundary-enhanced dissociation of absorbed CO is no longer observed after the diffusion of sulfur to the crystal surface. AES depth profiling of sulfur concentration at different positions on the crystal with respect to the boundary lines show no evidence that the boundary lines provide an enhanced path for sulfur diffusion.     

Carbon monoxide induced ordering of benzene on Pt(111) and Rh(111) crystal surfaces

Carbon monoxide induced ordering of an organic molecule, benzene, has been studied on the Pt(111) and Rh(111) crystal surfaces using low-energy electron diffraction, high-resolution electron energy loss spectroscopy, and thermal desorption spectroscopy. We propose detailed geometries for all the ordered structures of coadsorbed CO and benzene. Ordering in the adsorbed overlayer is proposed to result from the interactions between adsorbed CO molecules in the presence of benzene.