Real time High Resolution Electron Microscopy quantitative analysis of morphological transformations of Au particles supported on SiO were conducted to determine the relative probabilities of the different morphologies. The analysis indicates that the single crystal structure is the most preferred structure at all sizes. Among the multiply twinned structures (MTPs), the icosahedral MTPs occur most at smaller sizes and decrease with increase in size. The decahedral MTP population increases with size.

Ultra-fine gold particles supported on iron oxide have been synthesized by coprecipitation and subsequently heat treated in air at temperatures ranging from 200°C to 700°C. Structure analyses have revealed variations in the degree of crystallinity of the iron oxide support as well as gold particle size and size distribution with heat treatment temperature. In addition, lattice parameters of gold particles were observed to deviate up to ten percent from the bulk value. We discuss these observations in light of a total minimization of the energy of the system (support plus particles).

We have used atomic force microscopy (AFM) to study the in-plane structure in monolayer and multilayer Langmuir Blod-gett films containing disk-shaped molecules. The disks self-organize in columns parallel to the slide and aligned about the direction of deposition with a ∼ 35° distribution of orientations. Bilayer films exhibit unusual height modulations arising from the superposition of columnar features rotated with respect to one another. Preliminary results for star-shaped oligomeric species are also presented.

We resolve the atomic structure of the 1 monolayer incommensurate (IC) reconstruction of Pb on Si(111) using a tunneling microscope. The local structure of this surface consists of alternating domains of two types of Pb trimers together with quasi-lxl regions. A novel feature of this surface is its sensitivity of the domain morphology to surface stress inhomogeneities. We observe that the stress fields originating from nearby reconstructions transform the IC phase into a 1×1 structure. The transformation involves only small lateral displacements of Pb atoms from the T1 site.

An investigation of the properties of Si native point defects was undertaken using low temperature annealing of molecular beam epitaxially grown Sb and B doping superlattice structures. The superlattice structures, consisting of 10 nm B or Sb doping spikes separated by 100 nm, were annealed in NH3 at 810°C, 860°C, and 910°C. During thermal nitridation under these annealing conditions, we observed enhanced Sb diffusivity caused by the injection of vacancies, and retarded B diffusivity, resulting from the depletion of interstitials. Since the diffusivities of Sb and B are proportional to the vacancy and interstitial concentrations respectivity, spatially resolved diffusivity measurements permit effective point defect diffusivities to be inferred. From the spatial decay length of the Sb diffusion enhancement, lower limits for the effective vacancy diffusivity were obtained (limited by possible vacancy trapping). Evidence of vacancy assisted Sb clustering during NH3 anneals is also presented.

Co3O4 epitaxies grow readily on cobalt monoxide substrates under a wide range of oxidizing pretreatment conditions. The nucleation and growth of Co3O4 on CoO(lOO) have been investigated by XPS, HREELS and LEED. Both rocksalt CoO and spinel Co3O4 share the geometric characteristic of closest packed lattice O2+ with oxygen to oxygen distances that match to within 5%. We propose a mechanism whereby the Co2+ move from octahedral CoO(100) surface sites to bridging O2- -O2-, positions that correspond to tetrahedral Co2+ sites in the spinel. Oxygen added to the surface finds its way into the near-surface region both as lattice O2-, chemically indistinguishable in CoO and Co3O4, and as excess surface oxygen. The excess oxygen, which gives an XPS binding energy of 531.6 eV and a HREELS signature at 137 meV (1100 cm-1) identifies it as a superoxo species. This species can be added and removed reversibly from the surface by annealing under oxidizing/UHV reducing conditions.

A study has been made of metastable Au-Ni thin films codeposited by MBE on Au(001). The in-plane relaxation of the deposit was measured with RHEED during growth and the tetragonality of the whole Au-Ni layer was measured with non-symmetric X-ray scans and GDCD. Plan view and cross-sectional TEM show that the alloys relax via twinning on {111} planes. In addition, diffraction patterns show the presence of diffuse rings about points in the reciprocal lattice associated with the Lio structure. These are attributed to the presence of an antiphase structure which forms in response to the very high stresses in the Au-Ni layer. An Lio phase having a high degree of order has been grown by alternating single Au and Ni atomic layers.

Lathanum-aluminate (LaAlO3) is one of the optimum substrates for epitaxic growth of thin oxide films. In this paper, the structures of the {100} and {110} surfaces of annealed LaAlO3 are studied using reflection electron microscopy (REM). [010] and [001] steps have been observed on {100}, these are believed to be the lowest surface energy steps. The {100} surface is atomically flat, but the {110} surfaces exhibit high-density fine structures distributed on large surface terraces. These fine structures may correspond to the formation of small width (100) and (010) facets on the (110) surface. The 5×5 reconstruction is observed on {100}. No reconstruction is found on {110}.

Recent results about the atomic scale structure of pristine and metal covered, clean semiconductor surfaces using high resolution electron microscopy (HREM) and electron diffraction under ultrahigh vacuum (UHV) conditions are described.

The mechanism of nanofabrication with a scanning tunneling microscope (STM) is investigated. We report experiments both in ultra-high vacuum (UHV) and in air, using several kinds of materials to understand the mechanism systematically. Threshold bias voltages, which are defined as the voltages above which etching is possible under the STM tip, have a linear dependence on the binding energies of the materials. Therefore, the STM nanofabrication mechanism is attributed to the local sublimation of surface atoms induced by tunneling electrons (SITE: Sublimation Induced by Tunneling Electrons). It is also ascribed to the oxidation process by adsorbed water for nanofabrication in air (CRITE: Chemical Reaction Induced by Tunneling Electrons).

Epitaxial GaP films grown on silicon by chemical beam epitaxy contain planar defects that are related to three dimensional island formation of GaP nucleating on the silicon substrate. Attention in the surface preconditioning and to the surface chemistry during the initial stages of nucleation and growth allow the control from pronounced three-dimensional growth behavior toward almost two-dimensional growth. New results on defect structure and surface morphology obtained by a combination of atomic force microscope (AFM) and a new method p-polarized reflectance spectroscopy (PRS) are presented and related to growth conditions during the initial stages of heteroepitaxy.

Ge(001) surfaces misoriented towards the [011] direction have been investigated with a UHV STM. The vicinal Ge(001) surface consists of alternating straight SA steps and rough SB steps. The anisotropie surface stress tensor leads to interactions between the steps, which can be characterised by assigning a force monopole and a force dipole to each step. The monopole-monopole interaction describes the repulsion, the monopole-dipole interaction the attraction between adjacent steps. From STM images the distribution of the step-step separation was extracted. Using this distribution the value of the force monopole and the force dipole has been calculated. It was found that the short range monopole-dipole interaction attracts the SB step towards the lower lying SA step, which results in the formation of DB steps at a miscut angle of 5°.

Thin films of CeO2 deposited by rf magnetron sputtering on sapphire and silicon substrates have been characterized with variable angle spectroscopie ellipsometry, atomic force microscopy (AFM), transmission electron microscopy and x-ray diffraction. A novel multiple model was used successfully for determination of the optical properties and surface roughness of the CeO2films. AFM analysis showed that the CeO2 films have hillock-shaped facet morphology. It was found that the surface roughness of CeO2 increased with film thickness. For films on sapphire substrates, the surface morphology and the crystalline quality were improved by post-annealing, e.g. flat surfaces were obtained after annealing at 1100 °C.

In this study, a method is proposed for evaluating the crystalline perfection of semiconductor surfaces. This method takes advantage of the three-dimensional nature of the X-ray multiple diffraction (MD) phenomenon. The effects that crystalline imperfections have on the MD Bragg condition are theoretically investigated. This theory provides information regarding the dynamical (primary extinction) or the kinematical (secondary extinction) regime in which the energy transfer among the MD beams occurs. In dynamical regime when the surface consists of large perfect-crystal regions (low surface-defect density), the method permits analysis of misorientation of these regions in directions parallel and perpendicular to the crystal surface. The perfection of GaAs and Ge (001) surfaces has been investigated using this method after mechanical and/or chemical polishing.

The nature and properties of the surface layer of ice are important in many applications. This layer possesses peculiar optical, electric and mechanical properties. Various experimental techniques based on indirect measurements give different values of the thickness of this layer and different temperature domains for its existence. A new direct method for investigation of the surface layer of ice can be provided by scanning force microscopy (SFM). We studied the surface of ice using NanoScope III in the temperature range from -2 to -25°C. Images of the surface of ice and force calibration curves (FCC) were obtained in the open air and in hexane. The problem of surface melting at higher temperatures is analyzed. Stable images of the ice surface were obtained at lower temperatures. It was found that at temperatures corresponding to the transition of the surface layer to the quasi-liquid state the surface morphology and FCC change. When ice is brought in contact with hexane FCC indicate a formation of an unusually thick (∼ 1 μm) surface film.

Molecular dynamics simulations incorporating a many-body (glue) potential have been used to investigate the atomic structure and dynamics of the Pb(110) surface in the range from room temperature up to the bulk melting point. The Pb (110) surface starts to disorder approximately at 360 K via the generation of vacancies and the formation of an adlayer. At about 520 K we observe the onset of a quasiliquid region at the surface, which exhibits liquid-like energetic, structural and surface properties. The disordering is enhanced in the direction parallel to the close-packed rows. While losing long range order, the two outermost quasiliquid layers retain a considerable degree of short range order. The solid-liquid (S-1) interface exhibits fluctuating atomic-scale (111) facets. The thickness of the quasiliquid film grows logarithmically for T > 520 K in agreement with expectations from the Landau-Ginzburg theory, and in close correspondence with well-established experimental data.

Atomic steps are a common defect at surfaces. Observations made with low energy electron microscopy are presented which demonstrate the impact of steps in growth, phase transitions, magnetic and orientational properties of thin films and clusters at surfaces. Most of these observations can be explained if steps modify the overlayer strain or interface energy.

We discuss how the nanoscale structural and chemical properties of copper (Cu) single crystal surfaces immersed in acidic aqueous solutions affect local electrochemical function. In particular, perturbation of oxide adlayers with in-situ atomic force microscopy (AFM) is shown to locally enhance the electrochemical deposition of Cu on Cu electrode surfaces. The results are consistent with a heterogeneous nucleation and growth mechanism in which the tip-sample interaction creates surface defect sites in passivating oxide adlayers which are active towards the electrochemical adsorption of Cu species. This “protect-deprotect-react” scheme enables precise control of feature sizes and allows this technique to be used for fabrication and constructive modification of solid-liquid interfaces.

Scanning force microscopy of thin gelatin films on mica reveals two distinct film components with characteristic frictional, morphological and adsorptive signatures. A high-friction film 1–4 nm thick completely wets the mica surface, while a low-friction minority component is present primarily as porous islands on top of the high-friction layer. Additional domains of extremely high friction within the majority component are detected in frictional images obtained with a blunt, gelatin-covered tip; no corresponding topographic differences are imaged. A high-force scanning procedure remarkably transforms the majority component into the low-friction phase if a sufficient amount of water is present in or on the film. The nanostructure of both components is imaged using a nanometer-scale asperity of gelatin attached to the SFM tip. The anticipated network structure of gelatin is observed on the high-friction majority phase. The low-friction phase is interpreted as moieties of intramolecularly-folded gelatin, with thickness (1.5±0.2 nm) equal to the diameter of the collagen-fold triple helix, containing substantial structural water.

We have investigated the transitions that take place at high-temperature from the oxidized state to the 7×7 phase on the Si (111) surface using high-temperature (HT) scanning tunneling microscopy (STM). The oxidized surface was transformed at 580 °C after oxidation by exposing the surface to 45 L of oxygen at 480° C The structural modification was directly observed by HT-STM. The corner adatom was created at the initial stage of the reconstruction, and then the disordered, 5×5 and 7×7 phases successively appeared on the surface. By etching Si atoms, the island structure was formed on the surface because of the reduced Si density. Finally, the completed 7×7 terrace was created.