Epitaxial thin films (4–1000 Å) of Ti contacts have been deposited via UHV electron beam evaporation at room temperature on monocrystalline, n-type, alpha (6H)-SiC(0001). The interfacial chemistry and microstructure, and the electrical properties, were investigated at room temperature and after annealing at 700 °C up to 60 min. High resolution TEM analyses revealed the formation during annealing of reaction zones consisting of Ti5Si3 and TiC. The corresponding electrical properties exhibited considerable stability except after an initial 20 min anneal. Current-voltage (I-V) measurements showed that the Ti contacts were rectifying with low ideality factors (n < 1.09) and typical leakage currents of 5 × 10−7 A/cm2 at −10 V. The Schottky barrier heights calculated from x-ray photoelectron spectroscopy and I-V and V-V measurements were between 0.79 and 0.88 eV for the as-deposited contacts and between 0.86 and 1.04 eV for the annealed contacts.

A theoretical explanation for L core-shell absorption edge of electron energy loss spectrum of Al, an analysis of the electronic populations and a comparison between different partial cross sections are given. The edge was first normalized to the same atomic ionization cross section (per atom per electronvolt). The contributions for the cross section come from three respects:the first one is the electronic transitions from the core-shell to valence-shell calculated by extended Hückel band model, the second one is the final ionization state obtained by electron gas model, the third comes from the elastic backscatting of outgoing waves by the atoms that neighbor the excited atom. The agreement between the calculation result and the experimental result is good.

The Al L near-edge fine structures of aluminum and its compounds with nitrogen and oxygen are studied using electron energy loss microspectroscopy in a transmission electron microscope. These edges are normalized to the same scattering cross section per Al atom per electronvolt. The cross section is calculated by using the Born approximation. The contributions to the cross section are from the valence shell crystal states obtained by using the extended Huckel band calculation and the ionization states obtained by using the electron gas model. The chemical effects in the ionization region are taken into account by including the contributions from the elastic backscattering of outgoing plane waves by the atoms that neighbor the excited atoms. The results by theoretical calculation agree semiquantitatively with experimental results.

AlL and OK near edge fine structures in sapphire are studied using electron energy loss microspectroscopy in a transmission electron microscope;an analysis of the electronic populations of atoms Al and O,and a comparison between different partial cross sections are given.We consider the ionization of an atom in a homogeneous solid to interpret the elemental effects in the ionization region near edges.The chemical effects in the region near edge onset are interpreted by using extended Hückel molecular orbital theory and Bloch's theorem including the effects of translation symmetry in crystals to calculate the electronic transitions from core-shell to unoccupied valence-shell.We also consider the additional chemical effects, which arise from the elastic backscattering of the atomic ionization waves by the atoms neighboring the exited atom,giving rise to the so-called extended fine structure in the ionization region.The agreement between the calculated results and the experimental energy loss spectra of sapphire from single-phase region is good.

Alternating bright/dark anomalous subunitcell contrast in HREM images along or near the close-packed direction of 6H-SiC, Ti5Si3, α-Ti, and 4H-SiC, all of which are hexagonal, was examined using computer-generated crystal models, HREM image simulations, and digital diffractograms from the corresponding experimental images. The primary variables were crystal tilt and thickness. Crystal model projections showed that the scattering potential was smeared anisotropically within the unit cells by small crystal tilts, which reproduced the experimentally observed anomalous subunit-cell contrast modulations in the corresponding simulations. The effect increased with thickness, but it did not occur in exact zone axis simulations for any crystal thickness. Structural considerations indicated that the contrast resulted from tilt-induced violations of Gjonnes-Moodie dynamical extinctions and excitation of kinematically forbidden reflections in the imaging zone. Digital diffractograms from experimental HREM images confirmed their presence in the imaging zone diffraction patterns. These effects were absent in HREM images from cubic crystals in this material system because the structurally induced requisite kinematically forbidden reflections do not occur in the imaging zone.

Aluminum oxide powders doped with MgO (300 to 500 nm) were sintered to almost theoretical density within just 10–15 min at 1150 °C using a plasma-activated sintering process based on charging the loosely filled powders with an electric discharge prior to densification by resistance heating. The microstructure of the consolidated disks was examined by high resolution transmission electron microscopy (HREM) and electron energy loss spectroscopy (EELS) and revealed excellent grain to grain contact with virtually no grain growth and structurally clean grain boundaries.

The spatial extent of chemical solute distributions that formed in interfaces between platinum or silicon nitride and silicon carbide or in silicon nitride grain boundaries during high temperature processing of these composites has been investigated by position resolved nanospectroscopy, Z-contrast imaging and energy selected imaging. The solute distributions resulted from intentional sintering aid additions or interfacial reaction. The distribution widths normal to the nominal interface/boundary planes, called chemical interface/boundary widths, were much larger than the corresponding structural widths of the same boundaries and interfaces, determined by HREM imaging. Qualitative agreement between the three methods used to determine chemical widths was excellent. Differences in count rate resulting from beam current differences among the methods resulted is some predictable quantitative disagreements in absolute chemical widths. Energy selected imaging proved to be a very fast, efficient method for examination of chemical distributions over large specimen areas.

The cross-sectional microstructure of a (Au, TiN) thin film deposited on a (100) Si substrate without further heat treatment was studied by CTEM, HRTEM, and AEM. HTREM was performed in a Topcon 002B microscope with interpretable resolution limit of 0.18 nm, and high spatial AEM was done in a Philips 400ST field emission gun microscope at 100 kV using a Gatan 666 parallel-detection electron energy loss spectrometer. Cross-section specimens of the interface were prepared by traditional polishing and ion milling. Temperatures used in the whole process of TEM specimen preparation were below 100°C and a liquid-nitrogen-cooled cold stage was used in ion milling to prevent interaction between Au and Si. Ti was co-deposited with Au by sputtering in a nitrogen atmosphere to increase the hardness of the thin Au contact film. Fig. 1a shows the microstructure of the (Au, Ti, N)/Si contact. The features of this microstructure are very similar to the those of pure gold thin films on Si substrates annealed below the Au-Si eutectic temperature (363°C). The thin, white layer was considered to be the original Au/Si interface by Chang et al.

Nanophase Ni particles (<10 nm in diameter) were produced by a blown arc method.A helium gas stream directed at the arc reduces the Ni vapor concentration and increases the quench rate.The helium gas velocity is the predominant factor influencing the size of the Ni particles.Gas velocities of 20 m/s and 56 m/s (at 26.6 kPa total helium pressure) resulted in Ni particle sizes of 13 nm and 7 nm, respectively.

Researches on interfacial structures by experimental HREM and computer simulation to the present have concentrated on solving one interface between two phases. Interfaces with a thin third phase interlayer between two major phases are of more recent interest. As the thickness of the interlayer phasedecreases, the strain fields of the bounding interfaces are no longer completely accommodated by the interlayer phase. The structures of both interfaces have to be considered simultaneously. This abstract describes some early work on establishment of a supercell including three phases and two interfaces for HREM simulation.The interface triad, Ti5Si3/TiC/6H-SiC, which was formed during annealing Ti/6H-SiC contacts, is an important example. The TiC thickness observed in the experimental HREM image, Fig. 1, is about 2.5 nm. The interlayer dimension normal to the interfaces is not large, and the size of the required supercell is small enough for computation on a moderately fast workstation.The simplest way to build a supercell including these three phases is to build each individual crystal constituent of the triad in the desired orientation and dimension and then assemble them with suitable translation vectors.

High spatial resolution chemical imaging results provided the first direct experimental evidence illustrating nanosegregation in thin films of sputtered Tb-Fe alloys. The observed chemical segregation appeared to result from the initial nucleation and growth of stable Fe-rich amorphous phase. The measured properties such as local fluctuation and magnetization reversal processes are explained on the basis of this chemical segregation effect.

Energy selected imaging with a Zeiss 912 ω-filter TEM was used to examine grain boundary solute distributions in an Si3N4/SiC(w) ceramic densified with Y2O3 + Al2O3 sintering aid. These results are compared to boundary region solute distributions in the same materials determined by field emission small probe electron energy loss spectroscopy and related methods. The intrinsic higher incident flux of the FEG small probe methods renders them the most useful for high spatial resolution local chemical width measurement. Energy selected imaging is fast and relatively simple for determining elemental distributions in boundaries at low magnifications. The methods are complementary.

Solid solution binary alloys are attractive for defect-free thin film semiconductor contacts because lattice matching can be obtained by composition adjustment, but chemical homogeneity is required. Highly composition sensitive energy-selected and hollow cone (HC) dark field imaging were evaluated for heterogeneity detection in Ti-Hf films using an Ω filter/Zeiss 912 TEM. Conventional HREM, which relatively insensitive to spatial composition variations in this case, was used to observe structural defects in the films near the interfaces.Thin films of pure Ti deposited via UHV electron beam evaporation at room temperature on n-type, vicinal (0001) 6H-SiC showed good epitaxy. This contact displayed rectifying characteristics. The interface was both structurally and chemically sharp. However, misfit dislocations at “stand off” positions were found, due to 4 % mismatch between the basal parameters of Ti and SiC. same column with Ti in the periodic table and has hexagonal crystal structure, but larger lattice parameter (aHf = 3.196 Å, and aTi = 2.950 Å). The Ti-Hf solid solution system obeys Vergard's law well, that is, the lattice parameters of this alloy change linearly with composition.

Magneto-optical (MO) recording offers a new dimension in erasable mass data stroage technology. Typical recording layers in presently used MO disks consist of rare earth-transition metal alloys enveloped by silicon nitride protective layers. Characteristic low media noise of amorphous TbFe-based alloys make them particularly attractive for use in MO disk recording layers. The synthesis/microstructure dependence for their performance is the subject of this research.

In our previous work on MBE grown low temperature (LT) InP, attempts had been made to understand the relationships between the structural and electrical properties of this material system. Electrical measurements had established an enhancement of the resistivity of the phosphorus-rich LT InP layers with annealing under a P2 flux, which was directly correlated with the presence of second-phase particles. Further investigations, however, have revealed the presence of two fundamentally different types of precipitates. The first type are the surface particles, essentially an artefact of argon ion milling and containing mostly pure indium. The second type and the one more important to the study are the dense precipitates in the bulk of the annealed layers. These are phosphorus-rich and are believed to contribute to the improvement in the resistivity of the material.The observation of metallic indium islands solely in the annealed LT layers warranted further study in order to better understand the exact reasons for their formation.

HRTEM has proven to be the best method to study the interface structure of heterogeneous materials at the atomic level. One of the critical steps in these experiments is preparation of sufficiently thin cross section TEM (XTEM) specimens with different materials on both sides of the interface in good condition for HRTEM, especially when metal/ceramic materials are of interest. For the material system of a thin metal film on 6H-SiC substrate, the conventional ion milling method did not produce satisfactory XTEM specimens, because of the large difference in ion milling rates between metals and SiC. Most of the metal was ion milled way before a thin area of SiC was obtained. Two very important parameters, the thickness of the metal thin film normal to the interface and the atomic bonding structure across the interface were usually lost. Fig.l shows an example. The original thickness of the metal was 100 nm, and most of that has been removed. An amorphous layer of 1 to 1.5 nm thickness apparently due to ion milling formed at the metal/SiC interface.

A prominent characteristic of high-resolution images of 6H-SiC viewed from [110] is a zigzag shape with a period of 6 layers as shown in Fig.1. Sometimes the contrast is same through the 6 layers of (0006) planes (Fig.1a), but in most cases it appears as in Fig.1b -- alternate bright/dark contrast among every three (0006) planes. Alternate bright/dark contrast is most common for the thicker specimens. The SAD patterns of these two types of image are almost same, and there is no indication that the difference results from compositional ordering. O’Keefe et al. concluded this type of alternate contrast was due to crystal tilt in thick parts of the specimen. However, no detailed explanation was given. Images of similar character from Ti3Al, which is also a hexagonal crystal, were reported by Howe et al. Howe attributed the bright/dark contrast among alternate (0002) Ti3Al planes to phase shifts produced by incident beam tilt.

High temperature applications of SiC semiconductor devices will be essentially limited by the metal/SiC interface interconnect properties. Pt/SiC was reported to have more stable and better electrical properties than other metal/6H-SiC after annealing above 700°C under UHV condition. Some work on the Pt/SiC interface has been conducted by AES and other low spatial resolution surface techniques, but there is no detailed direct image data reported. Here, we characterize the microstructure of the Pt/SiC interface after high temperature annealing in UHV at near atomic resolution and reported the first nanospectroscopic energy loss data for the system.As-deposited Pt film is polycrystalline with grain size of 10 ± 3 nm (Fig.l). The thin amorphous layer visible at the interface in Fig.l, gradually disappearing in the thick regions, was attributed to oxygen-induced ion-milling damage. Similar results were observed frequently in other metal/ceramic system. We consider the amorphous layer to be due to residual oxygen on the ceramic surface during synthesis, since trace oxygen was only detected at the as-deposited Pt/6H-SiC interface.