In this paper, we summarize the results of high resolution transmission electron microscopy investigations of the structure of dislocations and interphase boundaries in Ti-Al alloys. Dislocations of the type 1/2<110] and 1/2<112] have been examined in 60° and 90° orientations, respectively, in single-phase Ti-52 at%Al. The former dislocation exhibits an extremely compact core configuration, suggesting a high complex stacking fault energy, while the latter is dissociated the scale of several nanometers in a coupled intrinsic/extrinsic stacking fault configuration. Two types of α2/γ interface structures have been observed in nearly fully-lamellar Ti-48 at%Al. The first is consistent with the common observation of structural ledges due to 1/6<112> dislocations in the interface plane. The second interface type consists of a quasi-periodic array of 1/2<110] dislocations which do not lie in the interface, and appear to be contained wholy within the γ phase. The possible implications of these observations with respect to the mechanical behavior of both single-phase γ and two-phase lamellar microstructures are discussed.

A 66° [110] asymmetric tilt grain boundary in Al prepared by cold rolling and annealing has been studied by high-resolution electron microscopy. Due to a 4.5° deviation from the perfect Σ3 misorientation, the boundary is heavily faceted with straight segments running parallel to (111) and (112) planes. All atomic sites across the (111) facets appear to be coincident with the (111) planes at an angle of 66°. The line defects which accommodate the deviation from the perfect twin orientation result in grain boundary stepping. The observed structural features can be described in terms of secondary grain boundary dislocations with Burgers vectors of the type ⅓<111>, and ⅙<112> as well as their interactions.

Conventional and high-resolution electron microscopy has been used to examine the interfacial structures in (α2 + γ) titanium aluminide alloys. Accommodation of misfit which arises because of differences in lattice parameters and crystal structure leads to dense structures of interfacial dislocations and coherency stresses. During deformation stress induced structural changes of misfitting interfaces occur. These are closely related to the generation of perfect and twinning partial dislocations. At elevated temperatures diffusion controlled structural changes take place at an atomic level and seem to limit the structural stability of the material.

TiB2 nano-lamellae, grown in-situ within a TiAl intermetallic melt, have been examined by high resolution electron microscopy. The use of the Stuttgart ARM enables Ti and B columns to be distinguished in the HREM images. Examination of the internal structure of the T1B2 platelets reveals extensive prismatic faulting on {1010}TiB2, {0110}TiB2 and {1100}TiB2 planes. Externally, the TiB2 platelets exhibit an orientational relationship {1010}TiB2 // {001}B2 and [0001]TiB2 // <010>B2 with interleaving platelets of B2-phase, with the predominating interface planes being {1010}TiB2 // {001}B2. The minor facets of the TiB2 platelets are [0001]TiB2 // <010>B2. {0110}TiB2 and {1100}TiB2, with the latter two facets showing no relationship with the interleaving B2-phase. No preferred orientation relationship of the TiB2 with the surrounding γ-TiAl and α2-Ti3Al phases is observed.

The step morphology of clean Si surfaces has been studied under conditions of thermal etching in the temperature range 950 – 1250°C. Kinetic-bunching of steps is caused by direct current in the step-down direction around 950°C. By comparing the rate of thermal decay of these structures with and without direct current, the electromigration force causing this step bunching is estimated to be due to an effective charge of less than or approximately 0.01 electron units. Around 1150°C, step-bunching is caused by direct current in the step-up direction. By analysis of the patterns of step structure, the effective charge of the driving force is found to be approximately -0.1 electron units. Oxygen-induced etching of Si(001) and Si(111) has been studied in the temperature range of 700 – 900 °C, and at a pressure of 5 × 10−7 torr, conditions under which the surface is etched by the desorption of SiO. On Si(001), the original narrow distribution of double-layer height steps is preserved during the oxygen-etching process. On Si(111), the original narrow distribution of mixed single- and triple-layer height steps changes dramatically during oxygen-etching, leaving wide terraces of flat (111) surface separated by regions of high step density. At low etching temperatures (700°C), the steps remain straight within the step bunches and retain their distinct character as single- and triple-height steps. However, following higher temperature etching, the steps begin to merge into facets in the vicinity of defect structures. Following etching at the highest temperatures studied (815 and 830°C), the pinning action of the defect structures becomes apparent, and the pinned step-bunches become identifiable as (113) facets.

The formation of the boron-induced reconstruction on Si(111) 7×7 surface has been studied with scanning tunneling microscope. By evaporating elemental B on Si elevated at high temperatures, reconstructed structures develop from the step edge to the adjacent lower terrace. They emerge at temperatures between 800°C and 900°C. It indicates that phase transition from 7×7 to 1×1 surface structure is necessary for forming the √3-B reconstructed structures. The phase boundary between 7×7 and regions is a straight line with termination of the faulted halves of 7×7 unit cell. It is also found that strip or triangle regions are formed, depending on the direction of the step propagation.

Photocurrent images of zinc-phthalocyanine (ZnPc) and coronene molecules adsorbed on Si(100)2×1 surface have been obtained by scanning tunneling microscopy. The ZnPc molecules are observed as bright images indicating large local density of state (LDOS) at the bias voltage. However, coronene molecules show wide variety of contrast in their images. This difference is the result of variations of LDOS on molecules which are attribute to the difference of energy gap between highest occupied and lowest unoccupied molecular orbitals

Height profiles spaced 0.008 μm apart across the fracture surface of TNT melt-cast in polycarbonate sleeves have been obtained with an atomic force microscope (AFM). Spatial power spectra (wavelengths of 0.016 μm to 4.0 μm) have been calculated using both a prolate spheroidal data window and a Kaiser window in the horizontal space domain prior to using a fast Fourier transform algorithm. Results based on topographical profiles across the surface include the following. The power spectral density of the individual fracture surface profiles is found to decrease with increasing spatial frequency over the dimensional region examined, ≈ 1.0 μm−1 to ≈ 10.0 μm−1. The spectral amplitudes are found to have a frequency dependence proportional to f s. The determined values of s in the dimensional region 1–10 μm−1 scatter in the range -1 < s < -4. Those values of s outside the range -3 < s < -2 indicate non-fractal fracture. There is significant structure in the spectra even for those with slopes within the range of a fractal dependence. Both observations are consistent with the appearance of numerous peaks in the spectra that indicate that a substantial amount of the fracture occurs at grain boundaries in the form of large clusters of TNT. Such a fracture process is deterministic.

The atomic structure and dynamic behavior of the solid-liquid interface of alumina were observed in a transmission electron microscope (TEM). The in-situ heating experiment of the alumina powder was performed using the newly developed heating holder. The surface of alumina was partially melted at about 2000K. Molten alumina on the surface migrated along the surface and formed liquid droplets. Such droplets existed stably on the surface during observation. The solid-liquid interface was observed by high resolution electron microscopy. The layer-by-layer growth of solid was observed on the solid-liquid interface. The nucleation of the monolayer island and the progress of the atomic step were observed directly. The velocity of the step progress at the solid-liquid interface was directly measured.

Interfacial reaction mechanisms were investigated in case of topotaxial formation of MgIn2O4 spinel on MgO crystals, which is an appropriate model system for thin film solid state reactions in ceramics. The reaction interface MgO/MgIn2O4(001), which is characterized by a large lattice misfit (+4.2%) between these cubic crystals, was investigated by transmission electron microscopy (TEM). Thin spinel films (thickness t< 0.5μm) consist of domains tilted off (≈3.5°) the exact cube-to-cube orientation into four directions, while thicker films (t> 1μm) show an accurate (001) orientation. High-resolution electron microscopy (HREM) showed that this time-dependent orientation behavior correlates with the atomic scale structure of the interface, especially with the different types of misfit dislocations. Based on these results, the misfit accommodation mechanism at the propagating reaction front in this spinel system is discussed including transitions between glide and climb processes.

The transient oxidation stage of single crystal (001)NiAl was investigated using scanning electron microscopy, transmission electron microscopy, electron diffraction, high resolution electron microscopy and electron energy loss spectroscopy (EELS). (001)NiAl was oxidized in air at 950°C in order to produce transient forms of alumina on the surface. After oxidation, an oxide scale with plate-like surface morphology formed. We found that the main transient alumina polymorph is γ-Al2O3. The platelets which formed on the surface of the oxide are most likely α-A12O3, not θ-Al2O3. Randomly-oriented α-Al2O3 grains were observed at the oxide/metal interface. The NiAl/γ-Al2O3 interfaces were examined with EELS. From the changes observed in the electron energy loss spectra, the interfacial terminating plane is determined. Lattice matching arguments are given to explain why these terminating planes are energetically favorable.

We demonstrate scanning tunneling microscopy studies of a Si(001)-c(4×4) structure which consists of a considerable number of dimer vacancies (missing dimers). Two different preparation methods are examined; one is hydrogen desorption and another is a special annealing and cooling process without hydrogen. The STM images reveal that atomic structure of the c(4×4) prepared without hydrogen is quite different from that prepared with hydrogen and is well described by the missing dimer model. A moiré-like pattern is observed on the c(4×4) surface prepared by hydrogen with an increase in the tip-sample distance, which suggests that the atoms lying in the subsurface should be considered for the precise description of the c(4×4) structure.

It is shown that the solid state equilibrium configuration of ZnO grain boundaries saturated with Bi-doping is a nanometer-thick amorphous film. Polycrystalline ZnO samples doped with Bi2O3 were studied using high resolution transmission electron microscopy (HRTEM) and dedicated scanning transmission electron microscopy (STEM). Samples were equilibrated below the eutectic temperature (Teutectic = 740°C) and at 1 atmosphere pressure, starting from three different initial states: one was cooled from above the eutectic temperature; a second was processed entirely below the eutectic temperature; and the third was de-segregated by applying high pressure (1 GPa) followed by annealing at 1 atmospheric pressure. In all instances, ZnO grain boundaries contain an amorphous film 1.0–1.3 ran in thickness, corresponding to a Bi excess equivalent to approximately one monolayer.

Thin films of {111} Au have been grown on {111} Ge substrates. The film grows epitaxially in two crystallographically equivalent orientations, (111) and (111). After annealing, the film is removed from the substrate and the resulting bicrystal appears as a maze of domains with faceted boundaries mainly of type {112}. The high density of edge-on interfaces in the films makes them well suited to electron microscopy. In the <111> orientation, the 1.44Å spacing of the {220} lattice planes tests the high resolution capabilities of the latest microscopes.

The nature of the Au {111} film contrasts with that of films grown using different materials or different substrates and was found to have a three-dimensional character with the occurrence of extensive twinning on (111) in the plane of the film. Areas were found to thin considerably in the high voltage electron microscope and interfaces in these regions were analyzed and rigid body translations across the facets measured. The existence of distinct rigid body translations across neighboring facets is of particular interest.

Very high angle (∼ 100mrad) annular dark-field (HAADF) images in a dedicated scanning transmission electron microscope (STEM) can be used to quantitatively measure the mass of a cluster on a support material. With knowledge of the annular dark field (ADF) detector efficiency, the absolute intensity of very HAADF images can be converted to elastic scattering cross-sections. By comparing the theoretical and experimental elastic scattering cross-sections, the number of atoms can be determined. Statistical measurement of absolute cross-sections from Re-6 clusters show good agreement with theoretical cross-sections. The experimental error corresponded to ±2 Re atoms. Our experiments demonstrate the exceptional stability of the Re-6 organometallic compound relative to Re-8 clusters. This technique is presently being applied to Pt clusters.

A new hard sp2-sp3 carbon stabilized by non-stoichiometric silica SiOx has been fabricated which combines a graphite-like layered structure with diamond-like mechanical properties, thermal stability and a very low density (≈ 1.6 g/cm3). This substance, which we refer to a quasi-amorphous material (QUASAM), has considerable potential applications as either thin films or bulk material since it can be grown as thick as 300 μm. Not only is the fine surface structure of crucial importance for thin films, but also the steadiness of a smooth growth front is a key factor for bulk material synthesis. Using atomic force microscopy (AFM) we have undertaken study of the surfaces/interfaces of such material over a wide range of thicknesses (5 nm < tf < 300 μm), including two free standing films.

We have examined the nucleation and growth of copper oxides formed by in-situ oxidation of copper thin films inside a modified transmission electron microscope (TEM). Based on this data, we have developed a semi-quantitative model of the initial oxidation stage where the dominant mechanism for transport, nucleation and growth of oxide islands is oxygen diffusion on the surface. The copper oxide can be desorbed by annealing and introducing methanol vapor into the chamber. The clean copper film can be oxidized by introducing oxygen gas. Both the desorption and oxidation processes were observed by planar TEM techniques. The copper film was oxidized in-situ at a partial pressure of 5×104 torr. Cu2O islands, which formed epitaxially to the copper film, nucleated and grew into the copper film.

In this paper we discuss the measurement of long range displacement fields associated with 90° domain boundaries in the ferroelectric ceramics BaTiO3 and PbTiO3. We have calculated displacement fields from high resolution lattice images by two techniques: firstly, measuring the positions of peaks in the images, and secondly, using a geometric phase analysis technique to magnify small lattice distortions. We describe the results and consider the complementary use of Fresnel contrast analysis to characterize local strain and electric fields near the boundaries.

Using EELS profiling, CaO planar faults of 1.36 nm spacing in CaTiO3 are resolved. Effective probe size was measured as 1.3 nm by quantitative analysis of EELS profiles, which is remarkably larger than 0.5 nm resolution for Z-contrast in similar conditions. Delocalization in EELS is the origin for this discrepancy, and strong elastic scattering near zone axis plays an important role in the quantification of profiles. Suitable spectrum subtraction successfully separates ELNES signal from the fault in one atomic distance with rock-salt structure. ELNES profiles for different local structures are also achieved. These examples demonstrate that EELS analysis can be performed reliably approaching atomic level, beyond the limit of probe size.

Recent work has demonstrated that high resolution electron microscopy in plan-view imaging mode is capable of directly imaging surfaces at a resolution of better than 2 Å. For the particular case of the Si (111) 7×7 surface, we have been able to image not only the adatoms visible in STM images, but all the atoms in the top three atomic layers including the dimers. The potential applications of this approach and its limitations will be discussed.