It is just over one hundred years since Lord Rayleigh first showed the differences between coherent and incoherent imaging in the light microscope, pointing out the advantages of the latter for resolution and image interpretation. The annular detector in the high-resolution STEM provides the same advantages for electrons, allowing incoherent imaging at atomic resolution, with image contrast strongly dependent on atomic number (Z). Since incoherent imaging has no phase problem, these Z-contrast images may be directly inverted to give the (projected) atomic positions. A maximum entropy method avoids false detail associated with direct deconvolution, and gives atomic coordinates to an accuracy of ± 0.1 Å. Electron energy loss spectroscopy can provide valuable complementary information on light element bonding and the presence of impurities in specific atomic planes selected from the image. Together, these techniques have revealed some surprisingly complex interfacial structures. For surface studies, the 1.3 A probe of the VG Microscopes HB603U STEM provides sufficient penetration and contrast to image single Pt and Rh atoms on γ-alumina supports. Such images reveal preferred atomic configurations, and allow possible surface adsorption sites to be deduced.

The fine structure of a core-loss edge contains detailed information on the local atomic environment. It can be used as an extremely sensitive probe of the fluctuations in structure and bonding that can occur at internal interfaces. Interpretation of such fluctuations requires only a knowledge of the location of the electron probe when the spectrum is acquired and a means of interpreting the spectrum. The location of the probe can be controlled with atomic precision in the STEM by the use of the Z-contrast image, while the real space cluster methodology of multiple scattering analysis is ideally suited to the task of interpretation. This approach is used here to derive 3-dimensional models for tilt grain boundaries in TiO2 and SrTiO3.

A new technique for growth of exactly two monolayers of CaF2 on Si(111) substrates is demonstrated. This technique takes advantage of the tendency of CaF2 to form thick islands at Si step edges on vicinal substrates once a two-monolayer thick wetting layer is deposited. A comparison of I-V characteristics for epitaxial CaF2 layers grown on on-axis versus off-axis substrates demonstrates the advantages of this technique. In addition, preliminary results for electron tunneling through the CaF2 structure is shown using the ballistic electron emission microscopy (BEEM) technique.

Grain boundaries in [001]-oriented diamond films deposited on Si(001) by microwave-assisted chemical vapor deposition have been investigated in plan-view and cross-section samples using high-resolution electron microscopy. The poly-crystalline diamond films used in this study had large fractions of [001]-oriented grains with typical lateral dimensions of 2 μm at film thicknesses beyond 10 μm. Grains with growth orientations near (001) exhibit generally small-angle orientation deviations between their crystal lattices. Small-angle grain boundaries of symmetric and asymmetric geometry with misorientation angles below 15° are investigated in both [110]- and [001]-directions. It is found that the structures of such small-angle grain boundaries can be described by a dislocation model. These grain boundaries are on average parallel to the {110}-plane and contain in many cases micro-facets parallel to {lll}-planes. Large-angle grain boundaries with tilt angles up to 40° are also observed in interconnected films of smaller thickness. In all cases structural units with large open volumes and additional second phases are not found at the grain boundaries.

This paper reports on investigations of Ag-ZnO and Cu-ZnO interfaces, produced by internal oxidation. ZnO precipitates with the wurtzite structure were found showing mainly one orientation relationship (OR) with the matrix. However, closely related ORs were found, rotated by small angles from that orientation relation. The atomic structure of several interfaces surrounding these precipitates was studied and compared using high resolution transmission electron microscopy. This paper focuses on interfaces between low index facets of ZnO and vicinal planes of Ag. These interfaces clearly show relaxations. An interpretation of these relaxations in terms of dissociation of partial dislocations at the interface is put forward.

Internal oxidation of Ag-3at.%Mn resulted in Mn3O4 precipitates with a “parallel” topotaxy with the metal matrix and an octahedron shape due to {111} facets. Due to the tetragonali ty of Mn3O4, only a few planes and directions of Ag and Mn3O4 can be actual parallel. The precipitates exhibited a preference to align {111} planes parallel with the matrix for one pair of facets and then for another pair a tilt of 7.6° occurs which is relieved by ledges in Ag. The dislocation structure at these parallel and tilted {111} interfaces, originating from a 1-dimensional mismatch and including phenomena such as stand-off and dissociation of dislocations, was scrutinized.

A case study is presented in which HREM, Z-Contrast Imaging and EELS are used as complementary techniques for elucidating interface structure. The NiO-ZrO2(cubic) interface is investigated along two orthogonal directions by these electron imaging and spectroscopy techniques to reveal the three-dimensional interface structure. Based on findings from this study, a protocol is suggested for using all three experimental techniques to gain a thorough understanding of interface structures.

Interface microstractures of BaTiO3/LaAlO3 grown by metal-organic chemical vapor deposition (MOCVD) are studied using high-resolution transmission electron microscopy (HRTEM). Interface dislocations in BaTiO3/LaAlO3 have been shown to be directly linked with the 90° domain boundaries in BaTiO3. This association is a result of strain relief due to a phase transformation on cooling from the growth temperature. The {100} surfaces of BaTiO3 are terminated with the Ba-O layer.

We have applied high resolution chemical imaging in a transmission electron microscope to study compositional variations across InGaAs/InAIAs double quantum well structures. The structures of interest are grown on an InP substrate and consist of two 40 Å layers of InGaAs separated by 20 Å of InAlAs. For this (InGa)x(InAl)1-xAs system, we have been able to obtain compositional information with an accuracy of about 20 % and a maximum spatial resolution of 1/2 × 1/2 unit cell. The results clearly show irregularities on a monatomic scale.

Morphological studies of bulk porous-silicon (PS) are presented. Using the atomic force microscope, cleaved cross-sections of electrochemically processed porous-silicon were investigated. The porous-silicon/silicon interface was examined. Using a room temperature UV O3 generator, the porous silicon-samples were oxidized. Oxidation in air was also observed. The morphology of the oxidized porous-silicon is process dependent. AFM contrast was enhanced by selective wet chemical etching. Unusually fast oxide etching in BOE was observed. A possible oxide/PS model is proposed.

Hydrogenated amorphous silicon thin-film transistors (a-Si:H TFTs) are now widely used as elements for active matrix liquid crystal displays. The nanometer-scale multilayered structure of a-Si:H TFTs has been characterized by cross-sectional transmission electron microscopy (TEM). The discrete layer construction of a faulty TFTs and the generation of defects during manufacturing processes have been investigated. A combination of focused ion beam (FIB) etching and cross-sectional TEM leads to a successful failure analysis. A contamination layer with a thickness of 10–30 nm and microvoids inside multilayers are identified in faulty TFTs. An a-Si layer on silicon nitride (SiNx) is crystallized during TEM observation. Electron energy loss spectroscopy analysis indicates that the diffusion of nitrogen into a-Si layer causes the crystallization.

The space charge contribution to the electrostatic potential both inside and outside a dielectric slab containing a p-n junction is calculated using classical electrostatics, with particular reference to the use of phase contrast techniques in transmission electron microscopy for the characterisation of the carrier distributions present at such layers.

The nucleation and initial growth of titanium suicide on Si(111)7×7 surface has been studied using the scanning tunneling microscopy(STM) in ultrahigh vacuum. At room temperature Ti atoms react with Si atoms and preferentially adsorb on faulted half of the 7×7 surface. By annealing at 600°C, islandlike structures(amorphous titanium suicide) and striplike structures(crystalline titanium suicide) are formed. Annealing at 700°C drives the growth of striplike structures from islandlike structures. The striplike structures grow parallel to specific directions on the 7×7 surface.

We have studied the nucleation and growth of Au nanocrystallites with dimensions of tens of nanometers on strontium titanate surfaces using an atomic force microscope. Strontium titanate ablated from a pressed pellet target by a KrF laser was deposited on both planar and offcut strontium titanate substrates. In a separate step, submonolayer quantities of gold were deposited, also by pulsed laser deposition, on the strontium titanate. The surfaces were then scanned by an atomic-force microscope to determine the effects of surface defects (such as steps and kinks on offcut surfaces), substrate temperature, and gold ablation yield on the nucleation, growth and size distribution of the nanocrystallites. The competition between diffusion and nucleation on planar vs stepped surfaces was particularly apparent in the AFM images. These results suggest several ways in which lateral decoration of the strontium titanate by the gold nanocrystallites can be achieved, an important step toward designer nonlinear photonic materials.

Scanning tunneling microscopy (STM) is a powerful tool for nanoscale research since it can both create and probe the properties of nanostructures. We have used STM to create T-phase TaSe2 nanocrystals embedded in H-phase TaSe2 through a tip-induced solid-solid phase transition at liquid He temperature. Atomic-resolution images have been used to develop a structural model to understand this solid-solid phase transformation. Furthermore, STM studies of the charge density wave (CDW) state in the T-TaSe2 nanocrystals have been used to address CDW physics in finite dimensions.

Quantitative evaluation rather than visual inspection of HRTEM images provides objective, reproducible, and very accurate information on the atomistic structure of internal interfaces. This paper explains the method we have developed to analyze the structure of grain boundaries. To demonstrate the power of our approach we present an analysis of the Σ3 (111) grain boundary in SrTiO3. We have determined the coordinates of the atom columns at this interface with a precision of 0.015 nm. Thus, our experimental results provide a sensitive test for physical theories and model structures obtained by computer simulation. First results of computer modeling are presented in this paper. The calculated structure of minimum energy has the same characteristic features as the structure determined by experiment.

We investigate space-charge by analytic methods and Monte Carlo simulations as a possible source of blur in high-resolution TEM images. In doing so we believe to have identified a novel type of space charge effect, namely quantum space charge(QSC) effect. We predict the blur for typical HRTEM images and for electron holograms. Inclusion of this hitherto unrecognized effect in image simulations (and experimental design for HRTEM and related techniques, such as holography) should permit further progress in the critical field of quantitative HRTEM image matching as a means for atomic structure determination.

We examine the scattering distribution from thin C, Ge and thick Si specimens as a function of scattering angle and energy loss, in order to gain insight into the relative contributions to both low and high angle annular dark field images from elastically and inelastically scattered elections.

The Σ11 (113)/[110] symmetric tilt grain boundary has been characterized by high resolution transmission electron microscopy. The method by which the images are prepared for analysis is described. The statistics of the image data have been found to follow a normal distribution. The electron-optical imaging parameters used to acquire the image have been determined by non-linear least-square image simulation optimization within the perfect crystal region of the micrograph. A similar image simulation optimization procedure is used to determine the atom positions which provide the best match between the experimental image and the image simulation.

High-resolution transmission electron microscopy (HRTEM) observations are presented of a/3[111] grain-boundary dislocations in an aluminum Σ=3[011] bicrystal. These dislocations are present on both (111) (coherent twin) and (211) (incoherent twin) facets of the bicrystal boundary. The dislocations on the coherent twin facet migrate by a climb process that increases the thickness of the twinned material. These dislocations originate on a Σ=3 (211) incoherent twin boundary where they are closely spaced and dissociated in a wide core configuration. Atomistic calculations of the defect structure and interaction of multiple a/3[111] grain boundary dislocations are discussed.