M.A. Smithers

Characterization of titanium hydride film after long-term air interaction: SEM, ARXPS and AES depth profile studies

Thin titanium hydride (TiHy) films are compared with thin titanium films after analysis using a combination of scanning electron microscopy (SEM), Auger electron spectroscopy (AES) and angle-resolved x-ray photoelectron spectroscopy (ARXPS). The TiHy films were prepared under ultrahigh vacuum conditions by precisely controlled hydrogen sorption at 298 K on Ti films evaporated onto a glass substrate. Analysis was performed in separate systems after long-term exposure of the films to air. Scanning electron microscopy analysis revealed a grain structure of the TiHy film, with a smaller grain size than the Ti film. Both the surface and bulk regions have been analysed in terms of their chemical composition and elemental distribution. Titanium dioxide was found to be the main chemical compound forming a contamination layer on both the TiHy and Ti film surfaces. Also, significant concentrations of carbon monoxide and hydrocarbon as well as small amounts of nitrogen and titanium carbide were detected. The thickness of the contaminated titanium oxide layer on the TiHy and Ti films was found to be ~13 and~20 nm, respectively. Long-term air interaction with the TiHy film leads to bulk penetration of oxygen but not to complete TiHy decomposition.

High-temperature interaction of nitrogen with thin iron films: Thermal desorption kinetics studies combined with microstructure analysis of Fe–N films

The interaction of nitrogen with thin iron films at 673 K has been studied by means of thermal desorption mass spectrometry (TDMS) and a combination of scanning electron microscopy and transmission electron microscopy. TDMS spectra indicate the coexistence of atomic and molecular states of nitrogen adsorbed at 673 K and at a nitrogen pressure of 0.75 Pa. The origin of the molecular state is discussed as an intermediate state towards dissociative adsorption of nitrogen. Reconstruction of the polycrystalline iron film occurs as a result of both nitrogen interaction at 673 K and thermal desorption by heating the sample substrate to 950 K. The Fe grains become finer and the Fe film surface shows an increase in roughness upon interaction with nitrogen at 673 K. TDMS heating involves annealing of the Fe film and decomposition of the “surface nitrides.” The bulk structure of the Fe film is affected by the nitrogen-induced reconstruction of its topmost surface region.

TEM and SEM studies of microstructural transformations of thin iron films during annealing

High-temperature induced transformations of the bulk structure as well as the surface and bulk morphology of thin polycrystalline iron films have been investigated using a combination of scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The polycrystalline Fe films were evaporated onto a quartz substrate at 78 K under UHV conditions and then annealed in situ within a temperature range 330–1000 K. The morphology of both the surface and bulk Fe films have been observed ex situ after successive annealing steps of the Fe film using SEM and cross-sectional TEM analysis, respectively. An anisotropic polycrystalline bulk morphology accompanied by a fine-grained surface and the formation of microvoids was observed after heating the Fe film at 330 K. The iron films annealed at higher temperatures, exhibit large grain size surface morphology. Polycrystalline Fe film transformation occurred at an annealing temperature of 700–1000 K, resulting in the formation of a columnar microstructure of the bulk phase. The crystallites formed as a result of annealing at 1000 K revealed a monocrystalline structure characterised by low-index Fe bcc diffraction patterns.

Characterization of thin alumina films prepared by metal-organic chemical vapour deposition (MOCVD) by high resolution SEM, (AR)XPS and AES depth profiling

Thin alumina films deposited by metal-organic chemical vapour deposition (MOCVD) on AISI 304 substrate have been analyzed using the combination of Scanning Electron Microscopy (SEM), Auger Electron Spectroscopy (AES) and Angle Resolved X-ray Photoelectron Spectroscopy (ARXPS). Both the surface and the alumina/substrate interface region have been analyzed in terms of chemical composition and elemental distribution. Only OH-groups (bounded as AlO(OH):boehmite) have been found as an impurity in the surface region of the oxide film. No carbon was detected. Due to higher temperature deposition, the concentration of OH-groups decreased. After annealing, the oxide/substrate interface changes as a result of chromium penetration into the alumina matrix. Carbon impurities have been detected on both delaminated and annealed alumina film surfaces. Also small amounts of sulfate groups as well as Ca and C impurities have been found on delaminated alumina film after prolonged high-temperature annealing.

Ge2Pt hut clusters : A substrate for germanene

The formation and structure of Ge2Pt clusters was studied in order to understand their germanene termination layer. The Ge2Pt clusters are formed by depositing a few layers of Pt on a Ge(110) surface. Annealing at temperatures above 1043 K results in eutectic Ge-Pt droplets that etch grooves on the surface in the [1 1 ¯0] direction. Upon cooling down, they solidify and decompose into a Ge2Pt phase and a pure Ge phase. Electron diffraction reveals that the hut-shaped clusters have their (001) plane oriented parallel to the Ge(110) surface and their (100) plane facing in the Ge[1 1 ¯0] direction. The facets of the Ge2Pt hut clusters have been determined to be the {101} and {011} planes. The germanene layers which cover these facets are commensurate with the {101} and {011} facets of the Ge2Pt substrate.The formation and structure of Ge2Pt clusters was studied in order to understand their germanene termination layer. The Ge2Pt clusters are formed by depositing a few layers of Pt on a Ge(110) surface. Annealing at temperatures above 1043 K results in eutectic Ge-Pt droplets that etch grooves on the surface in the [1 1 ¯0] direction. Upon cooling down, they solidify and decompose into a Ge2Pt phase and a pure Ge phase. Electron diffraction reveals that the hut-shaped clusters have their (001) plane oriented parallel to the Ge(110) surface and their (100) plane facing in the Ge[1 1 ¯0] direction. The facets of the Ge2Pt hut clusters have been determined to be the {101} and {011} planes. The germanene layers which cover these facets are commensurate with the {101} and {011} facets of the Ge2Pt substrate.