Spectroscopic ellipsometric investigation of clean and oxygen covered copper single crystal surfaces

Spectroscopic ellipsometric measurements (400–820 nm) have been performed on clean and oxygen covered Cu(110) and Cu(111) surfaces in an AES-LEED UHV system. The complex dielectric functions of the clean surfaces were calculated from measurements between room temperature and 600 K. In contrast with Cu(111), for the Cu(110) surface the ellipsometric parameters Δ and Ψ depend on the azimuth of the plane of incidence of the light beam. Such an anisotropy was also found for the changes in Δ and Ψ measured upon adsorption of oxygen to coverages corresponding with approximately 1/2 and 1 monolayer. To explain the results, several models are discussed, in which changes with substrate optical properties are taken into account

Composition and thickness of surface layer on molybdenum tips for scanning tunnelling microscopy (STM) studied by SEM/AES/(AR)XPS

A combination of SEM, AES and angle-resolved XPS (ARXPS) has been applied to analyse the distribution of chemical compounds in the surface region of electrochemically etched molybdenum tips and to determine the contamination layer thickness. Carbon monoxide, graphite, molybdenum carbide and molybdenum oxide were found to be the main surface contaminants on molybdenum tips. Auger line profiling revealed a significant enrichment of carbon and oxygen upon the tip. The thickness of the oxygen-carbon contamination layer on the tip was estimated to be 13.5 ± 1.0 nm as measured by AES. The thickness of the contamination layer on a molybdenum sheet was found to be 8.0 ± 1.5 and 6.8 nm using AES and ARXPS respectively. Quantitative analysis of the surface concentrations of carbon, oxygen and molybdenum has been performed

Surface and bulk magnetic behaviour of sputtered CoCr films

The magnetic hysteresis curve at the surface of RF- and magnetron-sputtered CoCr (81/19 at.%), in the thickness range of 20-2500 nm, was measured with a rotating-analyser apparatus using the magneto-optic Kerr effect. The Kerr rotation of CoCr films (13-19 at.% Cr) decreases with increasing Cr content, and depends slightly on wavelength, showing a faint minimum between 550 and 600 nm. The surface hysteresis is compared with the bulk hysteresis as measured with a VSM. For RF films the maximum surface coercivity is higher than the bulk coercivity, being 120 and 95 kA m-1 respectively for 80 nm thick films but an abrupt decrease in only the surface coercivity was found at t=125 nm. The coercivity of magnetron-sputtered CoCr deviates from that of RF-sputtered films. Until a maximum coercivity is reached at approximately=1 mu m, the surface coercivity is about 20% higher, but at approximately=2 mu m both coercivities decrease strongly. The existence of reversed domains within the main domains of CoCr is proposed, and the reversal mechanism is thought to be one in which the reversed domains grow at the expense of the main domain

Decomposition of thin titanium deuteride films: thermal desorption kinetics studies combined with microstructure analysis

The thermal evolution of deuterium from thin titanium films, prepared under UHV conditions and deuterated in situ at room temperature, has been studied by means of thermal desorption mass spectrometry (TDMS) and a combination of scanning electron microscopy (SEM), transmission electron microscopy (TEM) and X-ray diffraction (XRD). The observed Ti film thickness dependent morphology was found to play a crucial role in the titanium deuteride (TiDy) film formation and its decomposition at elevated temperatures. TDMS heating induced decomposition of fine-grained thin Ti films, of 10–20 nm thickness, proceeds at low temperature (maximum peak temperature Tm about 500 K) and its kinetics is dominated by a low energy desorption (ED = 0.61 eV) of deuterium from surface and subsurface areas of the Ti film. The origin of this process is discussed as an intermediate decomposition state towards recombinative desorption of molecular deuterium. The TiDy bulk phase decomposition becomes dominant in the kinetics of deuterium evolution from thicker TiDy films. The dominant TDMS peak at approx. Tm = 670 K, attributed to this process, is characterized by ED = 1.49 eV

Structural and chemical characterisation of titanium deuteride films covered by nanoscale evaporated palladium layers

Thin titanium deuteride (TiDy) films, covered by an ultra-thin palladium layer, have been compared with the corresponding titanium and palladium films using a combination of scanning electron microscopy (SEM), transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS). The TiDy layers were prepared under ultra-high vacuum (UHV) conditions by precisely controlled deuterium sorption at 298 K on a Ti film evaporated onto a Si(100) substrate. Both Ti and TiDy films were then covered in situ by a nanoscale Pd layer. It was found that a 10- to 12-nm-thick Pd layer protects the TiDy films efficiently against extensive air interaction. The morphology of both the surface and bulk Pd/TiDy (Ti) films have been observed using SEM and cross-sectional TEM analysis, respectively. A polycrystalline bulk morphology in both Ti and TiDy films accompanied by a fine-grained Pd surface was observed. High-magnification cross-sectional TEM images reveal the TiDy film to be plastically deformed leading to an increase in the roughness of the top Pd layer. Complex structures, including Moiré patterns, have been identified within the Pd/TiDy interface. The chemical nature of this interface has been analysed after partial sputtering of the Pd top layer using XPS. Besides TiDy and Pd, TiO and PdO were found to be the main chemical species in the interface region of the Pd/TiHy film. The XPS valence-band spectra of the Pd/TiDy interface reveal electronic features characteristic of a Pd–Ti bimetallic structure

Some place in Cambodia

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