This work is focused on dust or debris produced by the wear of tire tread. Two problems are addressed, which are solved by analytical electron microscopy (AEM): characterization of tire debris and identification of tire debris particles in a heterogeneous specimen. The characteristic morphology, microstructure and elemental composition of tire debris can all be determined by AEM. The scanning electron microscope (SEM) shows that the surface of a tire debris particle has a typical, warped structure with pores. The characteristic elements of tire rubber are S and Zn, which are detected by energy dispersive X ray (EDX) spectroscopy. The identification of rubber particles in heterogeneous debris containing talc and produced by a laboratory abrader is possible by the analytical SEM. Transmission electron microscope images, EDX spectra and selected area electron diffraction patterns characterize tire debris at the sub–micron scale, where the material can no longer be treated as homogeneous.

We have developed a new electron microscopy technique called fluctuation microscopy which is sensitive to medium-range order in disordered materials. The technique relies on quantitative statistical analysis of low-resolution dark-field electron micrographs. Extracting useful information from such micrographs involves correcting for the effects of the imaging system, incoherent image contrast caused by large scale structure in the sample, and the effects of the foil thickness.

Abstract: For micro or nanophase identification, the ideal method is electron microscopy which combines experimental technique and theoretical analysis in order to solve the problem which is typical in non homogeneous materials. In this work, two heterogeneous materials have been investigated: a Fe- 22Cr - 5Ni -0.3Mo - 0.03C (wt%) duplex stainless steel and a 6H-SiC reinforced Al-Cu alloy fabricated by the Ospray technique followed by extrusion and aging. This aging often gives rise to the precipitation of intermetallic compounds some of which can be new phases. Using microdiffraction, EDS and HREM, it was possible to identify two new phases: the orhorhombic τ phase in the heat treated duplex steel and the tetragonal Al7Cu3Zr2 in the reinforced aluminium copper alloy

SiGe/Si p-channel heteroepitaxial MOSFET test structures have been fabricated using solid-source molecular beam epitaxy. High-resolution transmission electron microscopy and energy-loss filtered imaging have been used to quantitatively determine the nanoscale Ge distributions across the SiGe alloy channel. The Ge profile at the edges of the alloy channel were found to be asymmetrical due to the effect of Ge segregation, with an exponential-like distribution directed toward the surface. The results agree well with the predictions of segregation theory and indicate that the concentration of Ge in the extended distribution lay in the range 10%-1% over a distance of several nanometers from the body of the channel. Secondary ion mass spectrometry measurements upon the same samples were insensitive to this short range extended Ge distribution.

We report measurements of the distribution of Sb atoms in σ-doped Si, over a wide 2-D concentration range. Both annular dark-field imaging and electron energy loss spectroscopy proved sufficiently sensitive to locate Sb atoms at the atomic scale. Improvements in both detector sensitivities and specimen preparation were necessary to achieve these results, which offer a surprising explanation for the dramatic difference in electrical activity between 2-D and 3-D dopant distributions at the same effective volume concentrations. The prospects for the general identification of individual dopant atoms will be discussed.

In-situ TEM annealing experiments on the Pd (20 nm) / a-Ge (150 nm) / Pd (50 nm) GaAs ohmic contact system have permitted real time determination of the evolution of contact microstructure. As-deposited cross-sectional samples of equal thickness were prepared using a focused ion beam (FIB) method and then subjected to in-situ annealing at temperatures between 130-400 °C. Excluding Pd-GaAs interactions, four sequential solid state reactions were observed during annealing of the Pd:Ge thin films. First, interdiffusion of the Pd and Ge layers occurred, followed by formation of the hexagonal Pd2Ge phase. This hexagonal phase then transformed into orthorhombic PdGe, followed by solid state epitaxial growth of Ge at the contact / GaAs interface. The kinetics of the solid state reactions, which occur during ohmic contact formation, were determined by measuring the grain growth rates associated with each phase from the videotape observations. These data agreed with a previous study that measured the activation energies through a differential scanning calorimetry (DSC) method. We established that the Ge transport to the GaAs interface was dependent upon the grain size of the PdGe phase. The nucleation and growth of this phase was demonstrated to have a significant effect on the solid phase epitaxial growth of Ge on GaAs. These findings allowed us to engineer an improved two step annealing procedure that would control the shape and size of the PdGe grains. Based on these results, we have established the suitability of combining FIB sample preparation with in-situ cross-sectional transmission electron microscopy (TEM) annealing for studying thin film solid-state reactions.

The high-angle annular dark-field (HAADF) technique in a dedicated scanning transmission electron microscope (STEM) provides strong compositional sensitivity dependent on atomic number (Z-contrast image). Furthermore, a high spatial resolution image is comparable to that of conventional coherent imaging (HRTEM). However, it is difficult to obtain a clear atomic structure HAADF image using a hybrid TEM/STEM. In this work, HAADF images were obtained with a JEOL JEM-2010F (with a thermal-Schottky field-emission) gun in probe-forming mode at 200 kV. We performed experiments using Si and GaAs in the [110] orientation. The electron-optical conditions were optimized. As a result, the dumbbell structure was observed in an image of [110] Si. Intensity profiles for GaAs along [001] showed differences for the two atomic sites. The experimental images were analyzed and compared with the calculated atomic positions and intensities obtained from Bethe's eigen-value method, which was modified to simulate HAADF-STEM based on Allen and Rossouw's method for convergent-beam electron diffraction (CBED). The experimental results showed a good agreement with the simulation results.

The studied GaN layers are made of mosaYc grains rotated around the c-axis by angles in the range 0-25°. Using high-resolution electron microscopy, anisotropic elasticity calculations and image simulation, we have analyzed the atomic structure of the edge threading dislocations. Here, we present an analysis of the Σ = 7 boundary using circuit mapping in order to define the Burgers vectors of the primary and secondary dislocations. The atomic structure of the primary ones was found to exhibit 5/7 and 8 atom cycles.

Two CdTe/ZnTe/Si samples were grown on Si (211) and Si(111) substrates by molecular beam epitaxy for use as lattice-matched substrates for HgCdTe growth. An As precursor was used before growing ZnTe. In order to understand the interface structure, the Zn diffusion problem and any effect due to As passivation, high resolution bright-field images, dark-field images and energy-dispersive X-ray spectra were studied. Fourier-filtered images have revealed details of the atomic arrangements and the dislocation defects at the interface. Local lattice parameters such as (111) d-spacings at different distances from the interface were measured to determine the Zn concentration based on Vegard's law. The Zn concentration profiles were consistent with measurements from energy-dispersive X-ray spectroscopy. The As-passivated interface showed vacancy-type defects.

Cathodoluminescence images of individual pores have been obtained at nanometer resolution in europium-activated yttrium oxide (Y2O3:Eu) (001) thin films, epitaxially grown on LaA1O3 (001) substrates. Comparison with Z-contrast images, obtained simultaneously, directly show the “dead layer” to be about 5 nm thick. This “dead layer” is the origin of the reduced emission efficiency with increasing pore size. Pore sizes were varied by using different substrate temperatures and laser pulse repetition rates during film growth. These films are epitaxially aligned with the substrate, which is always Al terminated.

The Environmental Scanning Electron Microscope allows imaging of hydrated specimens, as well as fluid-containing or even fully fluid microstructures. This is possible so long as all of the phases can be thermodynamically stabilized. Experimental operating parameters include specimen temperature and chamber gas chemistry and pressure. However, it is also possible to alter the thermodynamic properties of phases by various chemical and physical means. These approaches have been used in ESEM studies on soft condensed matter such as emulsions, complex fluids and gels. By deliberately moving away from stabilizing conditions, it is also possible to perform dynamic experiments. A number of applications are illustrated.

Property characterization of nanomaterials is challenged by the small size of the structure because of the difficulties in manipulation. Here we demonstrate a novel approach that allows a direct measurement of the mechancial and electrical properties of individual nanotube-like structures by in-situ transmission electron microscopy (TEM). The technique is powerful in a way that it can directly correlate the atomic-scale microstructure of the carbon nanotube with its physical properties, providing an one-to-one correspondence in structure-property characterization. Applications of the technique will be demonstrated on mechanical properties, the electron field emission and the ballistic quantum conductance in individual nanotubes. A nanobalance technique is demonstrated that can be applied to measure the mass of a single tiny particle as light as 22 fg (1 f= 10−15).

We report on the imaging of single C60 molecules adsorbed on the surface of carbon nanotubes. In the course of the work, the efficacy of carbon nanotubes as substrates for the high signal-to-noise observation of molecules is examined. The stability of nanotubes as a function of temperature, chemical environment and irradiation environment is explored. Carbon nanotubes are found to have a threshold energy for ballistic irradiation damage of approximately 85 keV. Finally, the use of nanotubes as in-situ reaction chambers and for other in-situ experimentation is demonstrated.

We have applied Atomic Number Contrast Scanning Transmission Electron Microscopy (Z-Contrast STEM) towards the study of colloidal CdSe semiconductor nanocrystals embedded in MEH-PPV polymer films.

For typical nanocrystal thicknesses, the image intensity is a monotonic function of thickness. Hence an atomic column-resolved image provides information both on the lateral shape of the nanocrystal, as well as the relative thickness of the individual columns.

We show that the Z-Contrast image of a single CdSe nanocrystal is consistent with the predicted 3-D model derived from considering HRTEM images of several nanocrystals in different orientations. We further discuss the possibility of measuring absolute thicknesses of atomic columns if the crystal structure is known.

We have studied the effects of deposition conditions on the epitaxial orientation of Au or TiO2 (110) and on the atomic structure of Au/TiO2 interfaces by combined EBSD and HRTEM. Two experimental conditions were explored consisting of deposition of a 12 nim Au film at 300K followed by annealing at 770K and direct deposition of a 12 nm Au film at 770K. Deposition at 300K followed by annealing at 770K give rise to a (111)Au//(110)TiO2 epitaxial orientation relationship, while direct deposition at 700K temperature give rise to an epitaxial orientation relationship given by (112)Au//(110)TiO2. For both orientations, two epitaxial variants are observed which are twin related. The (112)Au//(110)TiO2 orientation has been found to minimize the interfacial lattice misfit while maximizing the number of Au-Ti bonds across the interface.

First-principles quantum-mechanical calculations on γ-alumina have revealed a fascinating “reactive sponge” phenomenon. γ-alumina can store and release water, but in a unique, “reactive” way. This “reactive sponge process” facilitates the creation of aluminum and oxygen vacancies in the alumina surface. Earlier atomic-resolution Z-contrast STEM images of ultradispersed Pt atoms on a γ-alumina support showed the individual atoms to form dimers and trimers with preferred spacings and orientations that are apparently dictated by the underlying support[1]. In turn, the reactive sponge property of γ-alumina is the key to understanding the Pt clusters. Our calculations demonstrate that if three Pt atoms fill three vacancies created during the reactive sponge process, the resulting geometry precisely matches that of the Pt trimers observed in the Z-STEM images. Understanding the initial nucleation of small clusters on the complex gamma alumina surface is an essential first step in determining the origins of catalytic activity.

Amorphous silicon formed by ion-implantation of crystalline silicon is investigated with the use of VC-TEM (variable-coherence transmission electron microscopy). This technique is sensitive to medium-range-order structures. The results from high-energy Si implanted samples showed a striking similarity to sputtered amorphous silicon. We found that both ion-implanted and sputtered samples have paracrystalline structures, rather than the expected continuous random network (CRN). We also observed the structural relaxation of the ion-implanted amorphous silicon after ex-situ thermal annealing towards the random network. The more disordered structures are favored and a large heat of relaxation is released as the temperature increases. Finally, we show some preliminary results on the structural variation with the sample depth.

HRTEM(High-Resolution Transmission Electron Microscope), HAADF-STEM (High Angle Annular Dark Field Scanning Transmission Electron Microscope) and EELS(Electron Energy Loss Spectroscopy) techniques were applied for the characterization of Au/TiO2 catalysts. HAADFSTEM provides precise size distributions for Au particles smaller than ∼2nm in diameter. It was observed that many small particles under 2nm were supported on anatase TiO2 having a large surface area. The HAADF-STEM method was examined as a way to measure the shape of Au particles. EELS measurements were also used to examine the interface between Au and TiO2 support to study electronic structure effects.

The use of a high-brightness field emission gun and novel secondary electron detection systems makes it possible to acquire nanometer-resolution surface images of bulk materials, even at low electron beam voltages. The advantages of low-voltage SEM include enhanced surface sensitivity, reduced sample charging on non-conducting materials, and significantly reduced electron range and interaction volume. High-resolution images formed by collecting the backscattered electron signal can give information about the size and spatial distribution of metal nanoparticles in supported catalysts. Low-voltage XEDS can provide compositional information of bulk samples with enhanced surface sensitivity and significantly improved spatial resolution. High-resolution SEM techniques enhance our ability to detect and, subsequently, analyze the composition of nanoparticles in supported metal catalysts. Applications of high-resolution SEM imaging and microanalysis techniques to the study of industrial supported catalysts are discussed.

Thermolysis of single-source molecular precursors has been used to prepare carbon-supported Pt1Sn1, Pt1Ru1, and Pt3Mo1 alloy nanoparticles. On-particle, high spatial resolution energy dispersive spectroscopy (HR-EDS) has been used to determine the extent of compositional variability between particles in the nanocomposite. The loss of volatile Ru and Mo oxides during the course of the HR-EDS analysis results in average compositions greatly enriched in Pt. Mathematical correction for loss of these volatile species results in average metal:metal ratios comparable to those measured by bulk elemental analysis.