Moiré patterns are so often observed in the HREM images and they could be mistaken as the direct image of the atomic structure of the sample under analysis. In this workwe presented some examples of these patterns and their computer graphic simulations.

Measurement of frequency dependent ionic conductivities is shown to be a simple and effective means for the detection and characterization of nanostructures in solid electrolytes. As an example, the conclusions drawn from the conductivity spectrum of a silveriodide/silver-borate glass are compared with scanning electron and scanning tunneling micrographs. The results consistently prove the existence of nanoscale heterogeneities about 25 nm in diameter.

The synthesis of two component clusters of Au/SiO2, Ag/SiO2 and Cu2O/SiO2 is described. These heteronuclear clusters are synthesized as metal/silicon clusters of controlled composition and controlled size using a novel gas aggregation source and by means of gas phase annealing are transformed into ‘structured’ particles. The final metal/oxide and oxide/oxide clusters are formed by air exposure. The structure of these nanostructured particles is determined by electron diffraction and transmission electron microscopy (TEM). The clusters exhibit two distinct structural forms: (1) clusters consisting of a metal rich core surrounded by a silicon rich skin and (2) clusters having a metal rich domain and a silicon rich domain separated by a sharp interface.

In a photoluminescence and surface photovoltage study of porous silicon films with crystallite dimensions assessed with the Atomic Force Microscope, we have found cases when the blue shifts of the luminescence spectrum and the optical absorption edge take place upon increasing crystallite dimensions, which is contrary to quantum size effects. Fourier transform infrared spectroscopy analysis of these samples shows significant differences in hydrogen and oxygen bonding, which imply that the origin of the luminescence is of chemical nature. Our results show that porous silicon luminescence is not a consequence of one mechanism, but rather results from several mechanisms with contributions depending on the chemistry and structure of porous silicon.

A new, simple and effective method was developed for preparing specimens of Fecarbide ultrafine particles (UFP), by suspending them in Formvar films. Various samples of Fe-carbide UFP's were obtained by a laser pyrolysis process by varying the process parameters. The UFP samples were mixed with different concentrations of Formvar in ethylene dichloride solution. The sample particles were embedded in ultra-thin Formvar films with thickness of 20 nm or more and mounted on the 200 mesh copper TEM grids. The influences of the concentration of the Formvar solution and the amount of sample powder on the UFP distribution in the micrographs were investigated to determine the optimal film-making parameters. The different sizes and same spherical morphology for the various UFP samples were revealed, indicating the main diameters to be between 5–20 nm. Compared with the size values obtained by using XRD, the UFP size measurements by the new process are in good agreement. The crystalline features and the surface of the UFP's are presented and confirmed by micro-diffraction studies.

Composition and strain depth profiles in heterostructures such as AlGaAs/GaAs, InGaAs/InP and SiGe/Si have been analyzed with a high resolution of 0.5 nm by using the thickness fringes in a transmission electron microscope image. This diagnostic method is found to successfully evaluate the compositional disordering caused by annealing multiple quantum well structures with abrupt interfaces, and determine the difference in strain distribution in the strained-layers with various lattice mismatches. Both the composition and strain depth-profiles are analyzed quantitatively by the image simulation based on the dynamical theory of electron diffraction. This method is also useful for sensitively detecting ion-implantation-induced defects.

Magnetic lines of force penetrating a superconducting thin foil have been investigated by means of electron holography. A field-emission TEM with a specially constructed cold stage was used to cool a Nb thin foil down to 4.5 K and apply magnetic fields up to 100 G. The specimen is tilted by 45° to both the electron beam and the magnetic field (applied horizontally) allowing the 2-D lattice of penetrating flux-lines to be discerned. The phase distribution of electrons transmitted through the specimen were quantitatively measured. Interference micrographs revealed tiny regions where the phase distribution rapidly changed. These regions coincided spatially with the spot-like contrast observed by Lorentz microscopy and were found to be quantized vortices containing a flux of h/2e. The experimental results were in good agreement with those predicted by theoretical simulations. Experiments exploring the vortex inner core structure at high resolution are presented.

Nanoindentation experiments on high quality Au films were performed in vacuum using an atomic force microscope. In these experiments, elastic behavior was observed until loading forces greater than ∼ 20 nN were applied. For loads larger than this, systematic changes in the jump-to-contact, loading/unloading and lift-off regions of the data occur. These observations are consistent with a transition from elastic to inelastic behavior during indentation.

A new method of electron interferometry/holography (CBED+EBI/H) has been realized which produces interference between convergent beam electron diffracted beams. An electron biprism placed between the diffracted beams compensates for their diffraction angle by an induced potential. When overlaid the diffracted beams interfere to produce an interferogram. Holography is possible due to coherency of the electron beam. Reconstruction of the hologram by standard methods enables the phase change around the defects to be measured. These methods are very easy to apply and examples are given for small defects and defect clusters in heavy-ion implanted Si.

Real space plan-view Transmission Electron Microscopy (TEM) of the interfacial structure at the amorphous-Ge / Si (111) interface is presented. Ge is deposited at between room temperature and 150°C on either a 5×5 or 7×7 reconstructed surface. Conventional Plan-view TEM analysis reveals microstructural details such as surface steps, reconstruction phase shift boundaries and the reconstruction itself buried under the amorphous film, features which have previously been seen only as clean surfaces in UHV. Also imaged are small regions where Ge grows epitaxially on the Si surface above room temperature. These are seen to appear preferentially at steps and phase shift boundaries.

We have demonstrated that thermal and vibrational investigations of sodium nitrate (NaNO3) physically confined in the porous silica hosts is an effective approach to mimic the solute clustering effects in aqueous solution. The results show that the structure of the NaNO3 confined in nanopores can be divided into three regions, i.e., the regular solid phase region, solution-like molecular aggregates region, and a new solid-like phase region. Depending upon the pore size of the porous host, the physical range of the three regions varies accordingly. For pore size d <2.5 nm, only the solution-like molecular aggregates phase remains.

Impurities at heterointerfaces can alter the interfacial structure resulting in changes in physical, electrical and optical properties. We present a study of the interfacial roughness of GaAs/A1xGa1-xAs superlattices which were grown using controlled addition of oxygen at the interface. The interfacial properties were characterized by x-ray diffraction. The morphology of the surface was determined by Atomic Force Microscopy (AFM). X-ray diffraction measurements, both θ-2θ and rocking curves, were used to analyze the correlated and uncorrelated component of the interfacial roughness. A strong difference in the interfacial roughness was observed depending on whether the intentional oxygen incorporation occurred at the GaAs-to-A1GaAs interface or at both interfaces. When oxygen is incorporated at both interfaces, the x- ray reflectivity of the superlattice is decreased considerably resulting from a much higher interfacial roughness. The substrate miscut has a significant effect on RMS roughness, correlated roughness and its correlation length when oxygen is incorporated at the GaAs-to-A1xGa1-xAs interface.

Direct observation of diffraction arcs by X-ray from nanoscale precipitates in steels has become possible for the first time by using a highly brilliant and focused synchrotron radiation beam at BL3A of Photon Factory, and also by using an “imaging plate”, a two dimensional X-ray detector which has a wide dynamic range and high sensitivity. For examples, most of the diffraction arcs from ε-Cu precipitates (∼200 Å in diameter and ∼1 at. % in concentration) in Cu-added steels were observed. The method can apply to nondestructive and in-situ observation of creation and growth processes of the precipitates which has close relationships to various physical properties of the matrix steels.

Application of 57Fe MÖssbauer spectroscopy to the determination of magnetic structural parameters relevant to nanostructural studies is discussed. Variable temperature and applied magnetic field strength investigations are considered in order to illustrate the power of the technique in rendering a microscopic picture of the internal spin structure and dynamical spin relaxation phenomena associated with nanoscale systems. Examples from biology and chemistry, where iron aggregates of nanometer dimensions are encountered, are presented.

We have studied ordered and disordered Cu-Au alloys via 63Cu NMR, probing local electronic structure in the bulk and near anti-phase boundaries in CuAuII. A line-shape model has provided good agreement for disordered and partially ordered alloys, and we thus have obtained a measure of local site symmetries, and Knight shifts and local densities of states within the alloys. We have combined Knight shift and relaxation measurements to obtain detailed local information. We report effects of the ordering process in Cu3Au, CuAu, and CuAu3 intermetallics. We find enhanced susceptibility at the CuAuII anti-phase boundary which is heavily anti-site populated. We compare these results to other measurements of these properties.

Electronic structure in small areas is obtainable by inspection of near edge fine structure of core excitations. We can accomplish this today with near atomic resolution, using EELS at high energy. At IBM, we have obtained results using a sub-0.2nm probe at 120KeV with enough current to allow 200meV resolution studies at the Si L2,3 edge. It is especially crucial for Si-based structures that this allows us to obtain Z-contrast dark field images of the Si lattice at an acceleration voltage that is low enough to minimize radiation damage, but with a high enough current to allow good quality spectra to be obtained. A review of instrumental requirements, spectral interpretation, and applications to Si-Ge alloys is presented.

Trace analysis of nanometer-scale objects can be performed with parallel-detection electron energy loss spectrometry in the analytical electron microscope. Spectra are collected in the second difference mode with the beam current chosen to maximize the spectral count rate. Numerous elements can be detected at trace levels below 100 parts per million atomic, including transition metal, alkali metal, alkaline earth, and rare earth elements, provided they have a “white line” resonance structure at the ionization edge. Trace nanoanalysis by AEM/PEELS permits direct examination of the microscopic distribution of trace constituents.

We have investigated the valence band structure of MoS2, a transition-metal dichalcogenide, using scannino tunneling microscopy (STM) and scanning tunneling spectroscopy (STS) for the first time. We have found characteristic peaks in the (dl/dV)/(I/V)-V characteristic at −1.0 and −1.4V below the fermi level, which correspond to the S Pz state and Mo dz2 state, respectively. Mo atoms are accessible only at the sampfe voltage of −1.4V in the range of −1.0 through − 1.5V, due to the strong localization of the Mo dz2 state with very small bandwidth.

In a 100 kV VG HB501 UX dedicated scanning transmission electron microscope, the 2.2 Å probe size allows the atomic structure to be observed with compositional sensitivity in the Z-contrast image. As this image requires only the high-angle scattering, it can be used to position the probe for simultaneous electron energy loss spectroscopy. Energy loss signals in the core loss region of the spectrum (>300 eV) are sufficiently localized that the spatial resolution is limited only by the probe. The electronic structure of the material at the interface can thus be determined on the same scale as the changes in composition, and atomic structure can be observed in the image, allowing the structure and chemical bonding at interfaces and boundaries to be characterized at the atomic level.

Dedicated scanning transmission electron microscopy and associated techniques were used to extract microstructural and compositional information about granular Ag-Fe magnetic films produced by sputtering. Nanometer-resolution compositional analysis by energy dispersive X-ray spectroscopy (EDS), showed that Ag-Fe granular films consist of two separate phases. It has been found that nanometer size Fe particles are separated by small as well as large Ag particles. Nanodiffraction patterns showed that a large proportion of small Ag particles have an icosahedral shape and that the Fe particles are highly disordered. The nanostructure of the Ag-Fe system and its relation to the giant magnetoresistance of granular films are discussed.