An STM study has been initiated to investigate the various processes associated with electrodeposition of Cu-Ni multilayers on Cu (100). The substrates were prepared by electropolishing in phosphoric acid followed by immersion in 10 mmol/l HCl. A (√2×√) R°45 adlattice of oxidatively adsorbed chlorine is formed under these conditions. The adlayer stabilizes the surface steps in the 〈100〉 direction which corresponds to the close packed direction of the chloride adlattice. In dilute mmo1/1 solutions of cuprous ion, reduction occurs under mass transport control with the electrocrystallization reaction proceeding by step flow in the 〈100〉 direction. At more negative potentials chloride is reductively desorbed. Coincident with desorption the highly kinked metal steps become frizzy and move towards adopting the close packed 〈110〉 orientation of the metal lattice. Preliminary experiments on heteroepitaxial nickel deposition reveal regions where electrocrystallization on Cu(100) occurs via step flow in the 〈110〉 direction.

Recent progress with in-situ observations by electron microscopy is briefly surveyed by referring to developments in instrumentation for reflection and low energy electron imaging as well as for high resolution transmission imaging and spectroscopy. New opportunities have been opened up by environmental microscopy. With increased levels of illumination intensity, the ever present question of beam-induced effects is of mounting concern particularly in studies of non-metallic materials.

A specimen-heating holder which allows an observation of reactions of more than one materials, in a controlled manner, at such a high temperature as 1723K has been developed. Facet-unfacet transformation and reconstruction of Au-deposited Si surfaces have been observed at very high temperatures at near-atomic resolution.

A high-temperature straining stage was designed for the Halle HVEM. Electron bombardment is used to heat the specimen grips. At present the stage is operated at a maximum temperature of 1250 °C, but somewhat higher temperatures should also be possible. Details of the stage are described and results are presented on several materials. In yttria fully-stabilized (cubic) zirconia, the different slip behaviour on cube and octahedral planes is demonstrated at a specimen temperature of about 1150 °C. While the dislocations move very jerkily on the (primary) cube planes, their motion is more smooth on the octahedral planes suggesting the action of the Peierls mechanism. In t' zirconia, the switching of tetragonal domains was recorded during ferroelastic deformation. The same process was first observed for tetragonal precipitates in partially stabilized zirconia. In γ TiAl, at the temperature of the flow stress anomaly (about 650 °c), the so-called ordinary dislocations move in a viscous manner, in contrast to the room temperature behaviour, where glide seems to be controlled by localized obstacles. Over a wide temperature range in NiAl single crystals, moving dislocations show a discontinuous dependence of the curvature on the dislocation orientation, well agreeing with calculations of the line tension using anisotropic elasticity. Direct experimental proof of dislocation motion during plastic deformation of quasicrystals is first given for A1PdMn single quasicrystals. Dislocations smoothly move on planes orthogonal to threefold and fivefold directions.

Surface diffusion process of tungsten(W)-atoms on MgO (001) surfaces was studied by high-resolution electron microscopy (HREM) in the time resolution of 1/60 s. The W-atoms were prepared on single crystalline MgO (001) films at 300°C by vacuumdeposition of WO3 or W-metal. Analysis of the recorded images revealed individual jump-process of the W-atoms in the substrate temperature from R.T. to 400°C, and gave the barrier potential (Ed) and the pre-exponential factor (D0). The diffusion processes on terraces and along steps were also compared in viewpoint of the jump length.

A novel, in situ transmission electron microcopy technique for the direct observation of deformation and fracture in multilayered materials oriented in cross-section is reviewed. Cross-sectional tensile specimens were prepared from thick, free-standing, Cu/Zr and Al/Ti multilayered foils. These tensile specimens contain a micro-gauge section, thus predetermining the location at which dislocation activity and crack nucleation and growth can be observed at high magnifications in the transmission electron microscope. The results from these experiments are unique and cannot be realized by any other technique. These observations will aid us in our understanding of the micromechanisms of deformation and fracture in multilayered materials.

With a controlled environment electron microscope it is possible to remove the effect of another atmosphere, such air, to which the sample may have become exposed; to study in considerable detail the continuous development of a series of microstructures in a dynamic process, to identify important intermediate phases and defects in them which may only be metastable under specific reaction conditions of atmosphere and temperature, and to establish whether they are the origin, or merely the consequence, of the reaction. In this paper we report the extensive modification of a high resolution transmission electron microscope (Philips CM30T HRTEM) to add facilities for dynamic in-situ gas-solid reaction studies in a controlled atmosphere of gas or vapor at pressures of 0–50mbar which replaces the regular high vacuum TEM environment. The new environmental cell (ECELL) capability is combined with the original 0.23nm TEM resolution, STEM (BF/ADF) imaging and chemical and crystallographic analyses. Regular specimen holders are used; including hot stages capable of temperatures >1000°C. The full TEM resolution has been demonstrated at temperatures above 700°C and with limited (mbar) amounts of gas flowing through the integral 4-aperture differentially pumped ECELL (and with the additional pumps for the system operating). The ECELL system can be used to preserve, or if necessary to recreate, a continuous chain of evidence in a chemical reaction process.

We report, for the first time, direct studies of the dynamic VOHPO4·1/2H2O precursor to (VO)2P2O7 catalyst transformation using recently developed in-situ environmental-cell, high-resolution, electron microscopy (in-situ ECELL-HREM) under controlled environments. Our observations provide fundamental evidence concerning the nature of the topotactic transformation and associated temperature regimes critical to the formation of active catalysts. The direct ECELL-HREM studies show that the structural transformation begins at ˜ 400°C, and a mixture of the precursor and pyrophosphate phases exists at ˜ 425°C. At 450°C, most of the conversion to VPO has taken place. These atomic-scale studies reveal no amorphous phases during the transformation, and that the atomic periodicity is maintained throughout. No other phases have so far been identified in the transformation. The direct studies are important in the development of selective catalysts.

We describe a TEM specimen holder which has been designed and constructed in order to observe the process of electrochemical pore formation in silicon. The holder incorporates electrical feedthroughs and a sealed reservoir for the electrolyte and it accepts lithographically patterned silicon specimens. We present ex situ observations of progressive pore propagation and show dynamic, in situ observations of electrolyte movement within the pores.

Material synthesis by chemical vapor deposition (CVD) in a number of material systems has been investigated in real time using an environmental transmission electron microscope (ETEM) with 3.8 Å resolution. Here, we will focus on two metal / insulator systems. Al CVD onto SiO2 from trimethyl amine alane and Au CVD from ethyl (trimethylphosphine) gold (I), also onto SiO2. For Al deposition, dendritic growth was observed for all pressure / substrate temperature combinations investigated for growth on untreated SiO2. Subsequent to reaction of the substrate surface with TiC14, almost immediate continuous Al film growth was observed. Growth rates for the Al film could be measured in situ by monitoring the evolution of the growth front at the Al/vacuum interface. In this system, very little enhancement in the metal film growth rate was observed as a consequence of electron beam irradiation for continuous films grown after TiCl4 pretreatment.. This dramatically contrasts with the case of Au CVD investigated. In this instance, growth rate enhancements of up to 150 times were observed during electron beam irradiation as compared to purely pyrolytic decomposition of the precursor on the insulator surface. This growth rate enhancement decreased monotonically with substrate temperature. We surmise that this effect is related to the ratio of precursor surface residence time prior to ecomposition to the probability of collision from the impinging electron beam.

Individual vortices in superconductors were directly and even dynamically observed by using a “coherent” field emission electron beam. Magnetic lines of force of vortices were quantitatively observed in a holographic interference micrograph and their dynamics were observed by Lorentz microscopy. The interaction of vortices with both line- and point-defects was investigated by direct observation.

The evolution of domain structure with external stress in a free-standing PbTiO3 ferroelectric thin film of ˜100nm in thickness is observed by in-situ TEM technique. The thin film is composed of granular grains of ˜100nm in diameter, most of them appear to be single-domained whereas others are multi-domained showing domains of different sizes(5˜20nm). For some single-domained grains new domains appear during tension. For multi-domained grains, rearrangement of domain walls and coarsening of domains have been observed during tension. In many cases the domain walls disappear under high stress, i.e., a multi-domained grain changes into a single-domained grain. However, it is also observed that a large portion of single-domained grains appear not to respond to external stress. The dynamic behavior of domain walls in very thin ferroelectric thin films may help to understand the switching of these very thin films.

In this work a transmission electron microscopy (TEM) technique was used in obtaining local dielectric properties calculated from optical parameters for dynamic investigation of the effect of cubic to tetragonal phase transformation in barium titanate. In order to obtain in situ local dielectric during phase transformation, Kramers-Kronig relations were applied using the transmission electron energy loss (EELS) measurements. The optical excitations in the EELS spectra were consistent with the band structure results. The Re (1/ε) (real part of the dielectric function) obtained from the energy loss data indicated a change at the phase transformation. A broadening of the valence plasmon excitation suggested an order-disorder nature to the cubic to tetragonal transformation. In situ electron energy loss near edge structure (ELNES) studies from 500–700 eV energy range near the O-K edge exhibited a pre-edge feature that is associated with the Ti-L1, edge which further indicates an order-disorder nature to the phase transformation. The significance of the results is discussed.

Epitaxial growth is generally treated as a far-from-equilibrium process, dominated by kinetic restraints rather than thermodynamic driving forces. In this paper we show that homoepitaxial growth, at temperatures exceeding ∼500°C, is a process that can be approached very well from a thermodynamic equilibrium viewpoint, augmented with classical homogeneous nucleation theory.

We have used low-energy electron microscopy to investigate the real-time motion of (7×7) out-of-phase domain boundaries in the (7×7) reconstruction on vicinal Si(111), just below the phase transition temperature. As a function of time, the domain boundaries wander and coalesce in one-dimension, parallel to the step edges. We have established that the motion is consistent with the statistical problem of a random walk in the presence of absorbing barriers and have measured the diffusion coefficient for domain boundary wandering. The average distance between domain boundaries becomes large as they coarsen, consequently energetic interactions are not significant in determining their arrangement on this surface.

A new generation of ultrahigh resolution scanning electron microscope (UHRSEM) is designed to explore the potential for higher resolution imaging and chemical microanalysis from more representative bulk samples. A <0.5nm probe at 30kV and <2.5nm at 1kV have been integrated with high sensitivity energy dispersive x-ray spectrometry (EDX) [1] and a high vacuum (<3×10−8mbar) heating stage (to >1000°C). The sensitivity of surface imaging is generally enhanced at low beam energies. With low voltages and digitally integrated fast scan techniques, conductive coating of an electrically non-conducting sample, such as a ceramic substrate, is no longer a pre-requisite for SEM, and this opens up new possibilities for minimally invasive dynamic in-situ experiments. This paper focuses on metal particle migration and sintering on a ceramic substrate.

A study of surfactant-mediated epitaxy of Ge on Si(111) surfaces was carried out by in-situ transmission electron microscopy (TEM) and reflection electron microscopy (REM). Formation of 3D islands on the Si(111)-In surfaces was suppressed because of a change of critical nucleation size of the 3D islands. It was also found that formation of misfit dislocations at the interface between Si and Ge films was promoted by predeposition of In.

Annealing effects on InP (110) surfaces were observed in situ using a modified ultrahighvacuum transmission electron microscope equipped with a specimen heating holder. Reflection electron microscopy (REM) was used to record the dynamics of nucleation and growth of liquid In clusters at 650°C, following the desorption of P from the surface. These droplets showed no preference for nucleation at surface steps, and the steps appeared stationary throughout the annealing process. Two distinct types of In cluster growth rates and shape evolutions were detected. A model was developed to decouple height and length information in the REM images. Contact angle and volume above the InP(110) surface were calculated from the dynamic data. The change of contact angle with time provides evidence for sub-surface cluster etching.

Resonance scattering of high-energy electrons is responsible for the appearance of bright features observed in reflection high-energy electron diffraction (RHEED) patterns and has found numerous applications in reflection electron microscopy and in RHEED studies of dynamics of molecular beam epitaxial growth of semiconductor crystals. In this paper we report on recent developments in theoretical understanding of the processes leading to resonance reflection of high-energy electrons from a crystal surface.

In this paper, we discuss the sintering/fragmentation behavior of novel oganometallic rhenium compounds (candidates as catalyst materials) under high energy electron beam irradiation. The technique used was quantitative electron microscopy based on high angle annular dark field (HAADF) imaging in a scanning transmission electron microscope (STEM). Using this approach, we examine elastically-scattered electron intensity from graphite-supported rhenium clusters, and look for mass quantization. The emphasis in this article is not on the imaging technique, but on various sample preparation techniques, materials and synthesis issues of supports and of deposition of very small isolated clusters.