The microstructural development in a Type 309 stainless steel weldment associated with a post-weld heat treatment of 30 h at 580°C has been studied using analytical electron microscopy (AEM). The purpose of post-weld thermal treatments is generally to relieve stresses within the weld, thereby improving performance. Microstructural stability during these thermal treatments is important for the weld; i.e., no deleterious phases should form. in this example, detailed microstructural analyses of a weldment in the as-welded and postweld heat-treated condition have been performed. Microstructural analyses were performed using Philips CM 12 and CM300-FEG analytical electron microscopes equipped with Oxford Instruments ISIS analyzers and LZ5 energy dispersive x-ray spectrometers, and a CM200-FEG analytical electron microscope equipped with a Gatan Image Filter (GIF).

As-Welded Condition:The microstructure of the weld was characterized by the presence of dislocated austenite (γ) and a network of delta (δ) ferrite.

The high temperature application of iron-based ferritic alloys is limited by their rapid decrease of yield strength at temperatures approaching 1000°C. It has been shown that mechanical-alloying (MA) to produce oxide dispersion-strengthened (ODS) ferritic alloys improves their high temperature mechanical properties. Prior characterization of such materials has shown that in certain as-processed alloys the original yttria oxide particles are replaced by nanoscale (2-5 nm diameter) clusters containing Ti, Y and O. As a result of the high density of these fine clusters, dislocation pinning produced a ∼10-fold increase in dislocation density relative to similar ODS materials not exhibiting the nanoscale clustering. The improved creep resistance of the clustered material was attributed both to the higher dislocation density, additional dislocation pinning and resistance to recovery during creep. The current work examines clustering in a related alloy, as well as the effects of high temperature creep on the stability of such clusters.

The microscopy effort within the Saint-Gobain R&D labs involves working with a wide variety of ceramic materials. Samples vary from routine QC type work, to manufacturing plant emergencies, to failure analysis, to marketing support. A typical sample will require a variety of techniques to provide a solution within a few working days. Working in such an environment it is essential that people are aware of the different analytical tools that can be utilized in a given situation. For the microscopists in our lab this means a working knowledge of the techniques that are close to our core competencies centered around optical microscopy and SEM; these include AFM, XRD, Auger, SIMS, and FTIR, which are all used in a complimentary fashion. The examples shown here are illustrative of the kinds of problems worked on and the interactive nature of the solutions.

XRD of a siliconized silicon carbide material showed that it contained a higher fraction of the beta phase than was expected.

Electron diffraction can be a very useful technique in solving real world structure-related problems. However, electron diffraction is much less widely used in industry compared to x-ray diffraction for several reasons. So far, application of electron diffraction has been limited to large-sized companies either to characterize newly synthesized materials in a research division or to directly support business activities in an analytical laboratory. New materials produced on a commercial scale are more and more complex with micro-, even nano-meter sized structures. Development of these materials on a commercial scale, for example, high temperature superconducting compounds, fullerenes, and giant magneoresistance devices [1-7], has increased demand for electron diffraction techniques considerably. Here, I would like to review how electron microscopists in industry solve their real world problems using electron diffraction techniques [8].

Unit cell determination. Unit cell parameters and atom coordinates of a crystal can be routinely determined by single crystal x-ray technique if the crystal is large enough (about 0.1 mm in size).

CdTe is a promising photovoltaic material due to its near optimum band gap and high absorption coefficient. Polycrystalline, thin-film CdTe/CdS solar cells have demonstrated an efficiency of 15.8%. High density of extended defects is often found in polycrystalline CdTe films grown by close-spaced sublimation (CSS). So far, most investigations of defects in CdTe have focused on epitaxially grown films, and the reported extended defects are mainly lamellar twins. However, epitaxially grown films generally have a different microstructure compared to CSS grown polycrystalline CdTe thin films. in this paper, we report our study of extended defects in CSSgrown polycrystalline CdTe thin films by high-resolution transmission electron microscopy (HRTEM). We found that the extended defects are mostly lamellar twins and stacking faults. The stacking faults always propagate across the grains, without ending at a partial dislocation inside the grains.

Polycrystalline CdTe is a promising candidate for solar cells due to its nearly ideal band-gap, high absorption coefficient, and ease of film fabrication. Small-area CdTe/CdS cells with efficiencies of 16.0% have been demonstrated. The structure of a typical CdTe/CdS solar cell (Figure 1) consists of a glass superstrate, on which a thin layer of SnO2 is deposited (front contact), n-type CdS, p-type CdTe, and a back contact. Prior to applying the back contact to the CdTe, etching of the CdTe surface using a mixture of nitric and phosphoric (NP) acids is normally needed. It is known that the etching depletes a crystalline CdTe surface of Cd and creates a Te-rich layer. Two effects of the Te-rich layer has been proposed, namely, forming a Te-CdTe low-series-resistance contact and improving CdTe device stability by the gettering of Cu. Thus, the NP etching is an important process in the CdTe device fabrication. in this paper, we report on transmission electron microscopy (TEM) study of the microstructure of the surface of NP etched CdTe thin films.

A technique for very thin silicon oxide measurements using energy filtered TEM (EFTEM) is presented and applied for BiCMOS technology optimization.

In advanced VLSI circuits, thin silicon oxide layers are used as critical part of active devices such as MOS or bipolar transistors (BiCMOS). Today the 2 nm thick gate oxides of the 0.12 urn generation MOS transistors can be controlled using high resolution TEM (HRTEM). However, for the next generations these measurements will become difficult or will necessitate Cs corrected microscopes'. For the NPN bipolar transistor very thin oxides (less than 0.5 nm) are used at the base-emitter interface to control the forward base (hole) current and improve the transistor current gain. This interface presents generally some roughness and the oxide control is impossible using HRTEM. in this communication we demonstrate a new technique for very thin oxide measurement using low loss energy filtered TEM (EFTEM).

Silicon-on-insulator (SOI) is becoming a key technology for low power electronics due to substantially reduced power consumption of electronic components, and a capability of compact circuit design which are not readily achievable in bulk silicon technology [1]. Separation by IMplantation of OXygen (SIMOX) is the most promising technology for fabricating SOI material. The basic SIMOX process consists of implantation of oxygen into the single crystalline silicon wafer and the subsequent high temperature annealing. Oxygen implantation at low doses does not form a continuous buried oxide (BOX) layer but leads to an inhomogeneous distribution of the oxygen precipitates during implantation process. The formation and growth of oxygen precipitates in low-dose SIMOX depend strongly on the implantation conditions such as oxygen dose, implantation temperature, annealing temperature and ramping rate [2,3]. During the subsequent annealing, Ostwald ripening of the precipitates takes place and the larger precipitates grow at the expanse of small ones until they coalesce to the buried oxide layer.

The spontaneous formation of so-called self-assembled quantum dots (SAQDs) during heteroepitaxial growth has attracted much recent interest because of potential device applications. Much attention has been directed towards the Ge/Si(001) system, in particular to characterize the island shape and size distributions as a function of growth conditions, i.e., Ge coverage and substrate temperature. Due to the lattice mismatch, a layer-to-island transition occurs at coverages greater than about 3 monolayers, and thereafter small, coherent hut clusters and larger coherent and incoherent dome clusters are observed. Interdiffusion of Si into the Ge islands as a strain-relief mechanism also occurs. Strategies for achieving better control of island size, shape, composition and separation continue to be sought. in this paper, we report a preliminary investigation of island growth in the alternative Ge/Si(l12) system.

The Ge/Si(112) samples were grown by molecular beam epitaxy using a Riber 2300 system equipped with a Ge Knudsen effusion cell.

This study involved the application of the Scanning Electron Microscope (SEM) for the characterization of a GaN-based Light Emitting Diode (LED) by the Electron Beam Induced Current (EBIC) method. The diffusion length of the minority carriers in both the p and n-type regions of a GaN-based LED structure was determined with the EBIC technique in the line scan configuration. The diffusion length is a critical physical parameter that directly affects the electrical and optical properties of these devices. This value is generally understood to be a material property of the layers within a device. However, the measured values of the diffusion length are sensitive to the sample design, experimental conditions, measurement technique, and data analysis model and method utilized.

The EBIC measurements were performed at room temperature in a Hitachi S-3200N SEM using a GW Electronics Type 31 Specimen Current Amplifier.

Many different techniques have been used in attempts to minimize defects in single crystal semiconductors. This study examines semiconductors grown in the presence of a rotating magnetic field (RMF). The RMF method is commonly used in metallurgy to stir an electrically conducting liquid during the casting process which can reduce the effects of buoyancy driven convection and enhance the mass transfer process. The variation of heat and mass transfer processes by RMF can be controlled by selecting a specific frequency and strength of the magnetic field. Both numerical modeling and space-based crystal growth experiments using RMF indicate that the application of RMF to solidification of semiconductors will dramatically minimize defects and inclusions.

A ground based program in the Microgravity Research Division at NASA's Marshall Space Flight Center has been studying the effects of RMF on various semiconductor compounds grown by the traveling heater method (THM).

The ternary II-VT alloy Hg1-xCdxTe has become the material of choice for many infrared detector applications. Current state of the art Hg1-xCdxTe infrared focal plane arrays (IRFPAs) are constructed as hybrid structures consisting of an epitaxial sensing layer of Hg1-xCdxTe on either a CdTe or Cd1-xZnxTe substrate, hybridized to a silicon readout circuit chip. For backside illuminated structures, like the typical infrared Hg1-xCdxTe detector array, multilayer antireflective coatings (AR) are required on the backside of the detector chip. The next generation of higher performance IRFPAs will be based on high densities of smaller detector pixels fabricated on large area monolithic heteroepitaxial substrate materials. Since the ultimate performance of photovoltaic diodes of this type is determined by the signal to noise ratio of the device, reducing the size of the pixels while lowering the undesirable noise currents in the devices also reduces the amount of signal generated by the diode.

Two-dimensional dopant profiling continues to be a topic of great interest and importance to the semiconductor industry. Off-axis electron holography provides access to the phase of the electron wavefront that has traversed a sample, and it thus enables voltage contrast to be visualized. The technique was used by McCartney et al. (1994) to observe the potential distribution across Si/Si p-n junctions [1], and it was later also used by Rau et al. (1999) to map the two-dimensional electrostatic potential in deep-submicron transistor structures [2]. in this paper, we have used electron holography and a known test structure to demonstrate that accurate voltage profiles can be extracted under carefully controlled sample preparation conditions. Carrier information can be obtained using a simulation program. Experimental factors that affect quantitative measurement are also discussed.

The sample studied was a test structure fabricated at IBM for comparison of various profiling methods [3]. Both p-n junctions and p-p+ regions were available for study.

Even though all real objects are three dimensional, imaging and metrology performed by using electron-beam tools such as scanning electron microscopes is inherently two dimensional. Any information about the third dimension must therefore be obtained by inference, or by time consuming special methods such as stereo-photogrammetry. If, however, the structures of interest are thin enough to be electron transparent then quantitative three dimensional metrology can be performed directly by using off-axis transmission electron holography. Here we demonstrate the application to a SCALPEL lithography mask which consists of chromium lines on a silicon support film. The off-axis holography was performed in a field emission transmission electron microscope, a Hitachi HF2000 operated at 200keV. The sample is positioned so that half the beam passes through the specimen while the rest travels only through the vacuum. An electrostatic biprism then recombines these two components to form the hologram which is recorded onto a CCD camera.

The mechanism of action of the tumor promoter, phorbol 12-myristate 13-acetate (PMA), depends on its ability to substitute for an endogenous second messenger, diacylglycerol, and thereby activate certain members of an enzyme family known as protein kinase C. Previous work from this laboratory showed that the quantitative shape phenotype of cells treated with PMA resembled the phenotype of bona fidecancer cells. The effect of PMA on this phenotype was transient, and was restricted to a period of two- to five-hours after exposure to PMA. When the shape phenotype was dissected into components by relating different variable's values to shape features, several of the altered values appeared to rely upon a declining number of sharp features, such as filopodia and microspikes, at the cell edge.

Filopodia and microspikes are in turn regulated by a GTPase of the Rho family, Cdc42, which modulates actin architecture.

The extracellular matrix (ECM) plays a critical role in directing cell behaviour and morphogenesis by regulating gene expression and nuclear organization. Using non-malignant (S1) human mammary epithelial cells (HMECs), it was previously shown that ECM-induced morphogenesis is accompanied by the redistribution of nuclear mitotic apparatus (NuMA) protein from a diffuse pattern in proliferating cells, to a multi-focal pattern as HMECs growth arrested and completed morphogenesis . A process taking 10 to 14 days.

To further investigate the link between NuMA distribution and the growth stage of HMECs, we have investigated the distribution of NuMA in non-malignant S1 cells and their malignant, T4, counter-part using a novel model-based image analysis technique. This technique, based on a multi-scale Gaussian blur analysis (Figure 1), quantifies the size of punctate features in an image. Cells were cultured in the presence and absence of a reconstituted basement membrane (rBM) and imaged in 3D using confocal microscopy, for fluorescently labeled monoclonal antibodies to NuMA (fαNuMA) and fluorescently labeled total DNA.

Using human peritoneal explants, we have previously demonstrated that endometrial stromal cells (ESCs) and endometrial epithelial cells (EECs) attach to intact mesothelium. Attachment occurs within one hour and mesothelial invasion occurs within 18 hours (Figure 1). We have also demonstrated that, in vivo, the mesothelium overlies a continuous layer of collagen IV (Col IV).

More recently we have used CLSM, to study the mechanism and time course of ESC and EEC attachment and invasion through mesothelial monolayers. in these studies, CellTracker® dyes were used to label cells. Mesothelial cells were labeled with chloromethylbenzoylaminotetramethylrhodamine (CellTracker Orange). Mesothelial cells were then plated on human collagen IV coated, laser etched coverslips. Mesothelial cells were cultured to subconfluence. ESCs and EECs, labeled with chloromethylfluorscein diacetate (CellTracker Green) were plated on the mesothelial monolayers. Cultures were examined at 1, 6, 12 and 24 hours with simultaneous differential interference contrast and CLSM.

The centrosome is the major microtubule organizing center in most mammalian cells, and as such it determines the number, polarity, and spatial distribution of microtubules (MTs). Interphase MTs, together with actin and intermediate filaments, constitute the cell's cytoskeleton, which dynamically maintains cell polarity and tissue architecture. Interphase cells begin Gl of the cell cycle with one centrosome. During S phase, the centrosome duplicates concomitantly with DNA replication. Duplicated centrosomes usually remain in close proximity to one another until late G2, at which time they separate and then move during prophase to become the poles that organize the bipolar mitotic spindle. During the G2/M transition, interphase MTs depolymerize and a new population of highly dynamic mitotic MTs are nucleated at the spindle poles. The bipolar mitotic spindle apparatus constitutes the machinery that partitions and separates sister chromatids equally between two daughter cells.

Specific lipid self-associations in the fluid bilayer, particularly involving sphingolipids and cholesterol, are believed to result in the formation of membrane microdomains or “rafts” that mediate recycling of proteins between the cell surface and intracellular compartments or function as platforms for signal transduction events. Such membrane microdomains may be recovered in a low-density fraction that is insoluble in Triton X-100 at 4°C and referred to as detergent-insoluble, glycolipid-enriched complexes (DIGs). Membrane microdomains that constitute cell surface invaginations called caveolae can also be recovered in the form of DIGs. Caveolae are typically associated with a protein called caveolin, which coats their cytoplasmic surface.

Various glycosyl-phosphatidylinositol (GPI)-anchored proteins such as the folate receptor (FR) are believed to be associated with membrane rafts and to constitutively internalize and recycle to the cell surface although FR is the only known GPI-anchored protein with a transport function, i.e.,

Co-administration of Vitamin C (VC) and Vitamin K3 (VK3) combination (in a VC/VK3 ratio of 100:1) to several human carcinoma cell lines resulted in equivalent antineoplastic activity at concentrations that were 10-50 times lower than when either vitamin was administered alone. Peroxides generated by VC resulted in membrane lipid alteration. VC and VK3 combination resulted in cytoskeletal alterations, DNAses and RNase activation. This report documents LM and SEM morphological changes of ovarian carcinoma cells which accompany vitamin treatment and lead to autoschizic cell death.

MDAH cells were cultivated in titer dishes and on coverslips coated with polylysine. After exposure to either VC, VK3, or the VC/VK3 combination for 1 hour, cells on coverslips were fixed and processed for SEM. Cells in dishes (105 cells) were harvested, centrifuged (<500 r/min), fixed and embedded in PolyBed. Sections, oneurn thick, were stained by Toluidine blue prior to LM and TEM studies.