A newly developed cold FE-GUN which enables to us to obtain large probe current and low emission noise, and conical strongly excited objective lens has been installed on the JSM-6700F Scanning Electron Microscope (SEM). In the range of accelerating voltages from 0.5 to 15kV, this instrument has got much better resolution as compared with in-lens type SEM (Ohyama et al 1986)(Fig. 1). We can obtain high-resolution secondary electron images with large samples (ex. 150mm ϕ×10mmH).

Our old type objective lens (Kazumori et al 1994) has the limitation of working distance (WD), but the new lens enables us to work at very short WD at accelerating voltage of 15kV. As a result the spherical (Cs) and chromatic (Cc) aberration constants are 1.9mm and 1.7mm respectively at a WD of 3mm.

In order to get large probe current, we increased emission current and got near the distance between the t ip of emi tter and the pr inciple plane of condenser lens.

Due to the very good combination of the most outstanding properties of ferrite and austenite, the microstructure of duplex stainless steels allows them to obtain high strength and toughness levels even at low temperatures . As a result of these combined effects, duplex stainless steels have become very popular for many applications . In practice, the prolonged use of these materials at temperatures below approximately 500°C may cause an embrittlement of the ferrite phase, which has been called 475°C embrittlement. Thus, the isothermal aging at 475°C can be exploited to produce a variety of strength values associated with the corresponding decreases in ductility and variations of the fractal dimension of the fracture surfaces. No experimental measurements of the fractal dimension - tensile properties relationships are available for many commercial metallic alloys, then, the present experiments on a duplex stainless steel were conducted to show that the fractal dimension, D, many be used as a characterization parameter in fracture morphology - mechanical properties studies.

There have been several attempts to find a relation between the fractal morphology of the fracture surfaces and the mechanical properties of engineering materials., although the current resuls are inconclusive. If there are correlations between the fractal dimension and such properties, this parameter could be very useful to predict them and to improve the resistance to fracture. The main part of the investigations concerned with the fractal geometry and fracture behavior concentrate on the relations between roughness and fracture toughness . In the present work, the effects of thermal aging at 850°C on the fracture topography developed during the rupture in tension at room temperature of a 304 type stainless steel and their relation with the strength and ductility, were studied using the fractal geometry approach.

The textile industry produces large quantities of waste and scrap materials. Most of this waste requires disposal. Both environmental and economic benefits could be derived by developing commercial products to use these materials. Environmentally acceptable textile products include those that utilize recycled materials, or materials that have not been chemically processed. Such products are often not economically profitable because of the added expense necessary for environmental protection. Development of such a cost-effective textile product requires use of low-cost materials, minimal cost production processes, and finishes that have already been developed and tested.

The objective of this research was to develop a semi-disposable, economical, light-weight, comfortable thermal blanket that would be both flame-resistant and antibacterial through a limited number of laundry cycles. Targeted uses would be in medical and health care facilities, disaster relief centers, short term and emergency housing needs, recreational areas such as camping, and in military maneuvers where environmental conditions could be harmful to long-term products.

The simple models for low energy secondary electron (SE) detection in the variable pressure or environmental scanning electron microscope (ESEM) describe a gas-amplified cascade from sample to detector when a conventional biased detector is used. Recent images obtained using a modified specimen current imaging approach however have suggested that at least a portion of the image is an induced field effect, in agreement with some of the early work. Our recent aim has been to investigate a range of detector designs and positions within the chamber in both the old ElectroScan E-3 model ESEM and the current generation FEI XL30 ESEM TMP. The results support the earlier observations of induced signal components being present, with even ‘negative’ or inverted images being obtained under some detector configurations due to the noise cancellation techniques used (figure 1). These results are being quantified using the DQE measurement approach to allow an objective comparison of different designs and positions. This data will be presented for the commercially available detectors and for the ‘Griffin’ grid detector under a range of operating conditions.

The environmental scanning electron microscope (ESEM) employs a series of pressure limiting apertures and a differential pumping system to allow for electron imaging at specimen chamber pressures of up to 50 torr. Images rich in secondary electron (SE) contrast can be obtained using the gaseous secondary electron detector (GSED) or ion current (Iion) signals. The GSED and Iion signals are amplified in a gas cascade. SEs emitted from a sample are accelerated through the gas in the specimen chamber by an electric field, EGSED, produced by a positively biased electrode located in the chamber, above the specimen. The accelerated SEs give rise to a cascade ionization process that can amplify the SE signal by up to three orders of magnitude. Electrons produced in the cascade are rapidly swept to the biased electrode and are efficiently removed from the gas. Positive ions produced in the cascade drift away from the electrode with a velocity that is at least three orders of magnitude lower than that of the electrons.

Electron detection in the environmental scanning electron microscope relies upon the presence of a small pressure of a gaseous phase inside the microscope chamber. The presence of this gas controls two important mechanisms by which the microscope functions. The conventional gaseous secondary electron detector (GSED) applies a variable positive bias (0 to +600 V) directly above the specimen. Electrons ejected from the specimen surface due to the incident scanning probe are accelerated by this field towards the positively biased detector. Whilst traversing the gap between specimen and detector the electrons undergo ionizing collisions with gas molecules. These result in an amplification of the incident electron signal through the production of ejected ‘daughter’ electrons and leave behind positively charged ions. After production these ions are repelled by the detector bias and drift back towards the microscope stage where they aid charge neutralization on the surface of the specimen.

The ability of Environmental Scanning Electron Microscopy (ESEM) to provide electron images of volatile and/or insulating samples without need for sample preparation allows imaging of liquid surface at resolutions substantially beyond those obtainable with optical microscopy.

The system chosen for study was a dispersion of di-iso-heptyl-phthalate (DHP) in water, stabilised with a mixed surfactant system comprising equal masses of Tween 20 (Polyoxyethylene sorbitan monolaurate) and Span 20 (Sorbitan monolaurate) at an effective HLB of 12.75. DHP was chosen for its unsaturated electronic structure, which improves secondary electron contrast in the ESEM, and for the similarity of its density (995 kgm-3) to water. Emulsions, containing between 25 and 80 vol% DHP and 0-3 wt% surfactant were produced in a Silverson mixer fitted with an emulsor screen. Samples were placed in a brass holder on a Peltier cooling stage and cooled to 2°C.

The ESEM uses a novel differential pumping system combined with a pressure-limiting aperture to achieve relatively high pressures of up to 10 torr in the specimen chamber. Using this system allows samples to be imaged in the presence of water vapour or other gases. Conveniently the saturated water pressure at 275K lies within this range, allowing the stabilisation of hydrated samples, condensation from water vapour and evaporation to be performed in situ within the microscope chamber.

Wetting of surfaces is of fundamental importance in many different areas of science, from textiles to petroleum engineering. The ESEM now provides an opening for high-resolution studies of these phenomena without the problematic depth-of-field limitations that optical methods present. The contact angle, θ, is defined as the angle between the tangent to the liquid-fluid interface and the tangent to the solid interface. It provides a ready indication to the wetting properties of a system.

The acid etching process is the primary stage for preparation of dental composite restorations. Dentin specimens from extracted teeth are usually prepared by fracturing etched pieces of dentin. Etching creates a demineralized layer on the dentin surface with the thickness of a few microns. The layer consists of wet collagen and dissolved proteins; its drying process is of special interest in dentistry since it affects the bonding of the resin adhesives to dentin. Observations of fractured surfaces can be performed in either a conventional or an environmental SEM.

Three wet dentin samples were observed (XL30 FEG ESEM, FEI/Philips) in wet mode at 5°C Peltier cooling stage temperature and 5.8 MPa water vapor pressure. Samples with excess water on their top surface were put in an ESEM. Thickness measurements of the demineralized zone were begun immediately after the evaporation of this water layer with subsequent measurements taken after 5, 10, 20, 40, 60 and 100 minutes of drying.

It has previously been shown that liquid microstructures can be observed, in their natural state, by use of Environmental SEM (ESEM). In order to take full advantage of the ability to observe the dynamics of complex fluids, efforts are now being directed at developing in situ experimental methodologies. For example, we have recently shown that the coalescence of oil droplets in emulsion systems can be observed in real time. The purpose of the present study is to tackle the challenge of making EM observations of complex fluids under electrical stress (and ultimately electrical & mechanical stress combined) by subjecting particle dispersions to an electric field.

The technique of attracting charged particles to one of two electrodes (electrophoresis) is commonly used as a means of determining the nature and density of charges on such particles. Another technique, using uncharged particle systems, involves applying an electric field across a sample as well as, for example, a shear strain (electro-rheology).

We have investigated the affect of accelerating voltage (E0), pressure (P), GSED bias (VGSED), field line geometry and specimen conductivity on the landing energy of the primary beam in an XL30 ESEM. The landing energy of the primary beam can be measured by using the Duane-Hunt cut-off energy, EDH, in EDS X-ray spectra. We present experimental evidence that the landing energy of the primary beam can be significantly altered when analyzing insulators in an ESEM. Shifts in EDH result from electric fields produced by the presence of positive ions in the ESEM chamber and electrons trapped in the bulk. No shift in EDH was observed with conductive specimens at all E0 and P. Changes in the landing energy of the primary beam can significantly effect the relative intensity of characteristic peaks in EDS spectra measured in the ESEM (Figure 1).

The magnitude and sign of the shift in EDH is determined by E0 and P for a specific insulator specimen and stage geometry.

It is of paramount importance to know the total elastic-scattering cross sections of the gases which are present in the specimen chamber of the variable pressure scanning electron microscope (VP-SEM) or in the environmental SEM (ESEM) since these values are needed to compute the width of the beam broadening skirt by the use of Monte Carlo simulations. However, these values are not well known for even the most common gases because the vibrational modes of the molecules add another contribution to the usual value of the elastic scattering cross-section. To overcome this difficulty a method has been proposed to measure total elastic cross-sections which is based on a measurement on the unscattered beam current as a function of the chamber pressure using a Faraday cup. The total elastic cross-sections are then deduced using the well-known exponential decay law.

Standard Reference Material (SRM) 482 of the National Institute of Standards and Technology is a set of 6 gold/copper wires, ranging in concentration from 0 to 100% Cu in 20% steps, intended for calibration studies of electron beam microanalyzers. This is an appropriate standard to test the accuracy of energy dispersive x-ray spectrometry (EDS) in the Environmental Scanning Electron Microscope (ESEM). While the presence of the gas in the sample chamber gives the ESEM its unique capabilities, it also is the source of complications to x-ray spectrometry. The gas can spread the primary electron beam into a wide skirt of electrons with the consequent production of x-rays many micrometers from the target location of the beam.

The six wires (∼ 500 jam in diameter) were embedded and polished in one epoxy mount. The mount was carbon coated in one set of experiments. The coating was removed and the sample retested.

Recently, a new correction procedure has been proposed in order to perform X-Ray microanalysis in the ESEM or in the VP-SEM1. This new correction procedure is based on this equation:

where I is the measured intensity at a given pressure P, Ip is the intensity that would be generated without any gas in the microscope (the corrected intensity) and Im is the intensity with complete scattering of the electron beam. Im is therefore the contribution of the skirt on I. In equation (1), fp is the fraction of the incident beam, which is not scattered by the gas above the specimen, and it can be obtained from Monte Carlo simulations or from an analytical equation.

In low vacuum scanning electron microscopes, the primary beam is partially scattered by the gas present in the specimen chamber. The development of these microscopes, in particular the so-called ‘Environmental’ SEM, was initiated when it was realized that this scattering does not necessarily compromise the imaging capabilities of the instrument. Indeed, some modern commercial instruments are capable of better than 2 nanometer resolution at gas pressures of several torr. The accepted explanation for this is as follows: The mean-free-path of the high energy primary electrons is several millimeters in one torr of water vapour (for example). Because the actual pathlength of electrons travelling through the gas is only a few millimeters, most of them do not scatter at all. Those that do scatter are supposedly distributed over a relatively large area. Thus, the probe features a high-intensity central region surrounded by a slowly decaying low-intensity skirt. High resolution imaging is possible because the signal-to-(skirt)background ratio is high.

With recent advances in computing power and application specific software it has become practical for smaller microcopy labs to either purchase or build a electron backscatter diffraction (EBSD) systems. This system can be used to probe the crystallography and microstructure of many different materials. One set of such materials is geological samples from deep within the earth's crust. In collaboration with the Geology and Geophysics department an EBSD system has been built to function with the Philips Electroscan E3 Environmental Scanning Electron Microscope (ESEM). Using an existing low light level SIT camera, the system was completed with the addition of a phosphor screen and appropriate software and acquisition cards.

One main advantage of the ESEM for EBSD is that since it is an environmental SEM samples can be imaged without coating. For insulating materials this is means that the sample can be imaged without coating.

In this work, phosphor imaging plate technology is applied to measure electron scattering directly in the environmental scanning electron microscope (ESEM) specimen chamber. The scattering of electrons from the primary electron beam, under relatively high-pressure conditions (266 Pa) in the ESEM sample chamber, degrades the analytical accuracy of elemental analysis. The degree of this degradation is poorly known. To date, attempts to measure experimentally the spatial distribution of the scattered electrons have been limited to observing secondary effects such as the intensity of x-rays produced from copper targets positioned at various distances from the primary electron beam interaction point. A more accurate distribution of the scattered electron intensity can be obtained from a direct measurement of both the scattered and unscattered electrons over a large area with single electron sensitivity. Improvements to the accuracy of Monte Carlo models of the scattering process will be made possible by the direct measurement data.

Multi-photon excitation has been used in microscopy for nearly a decade, providing a number of demonstrated advantages over other methods for fluorescence imaging. Because excitation is achieved using longer, less energetic light, photodamage and photobleaching of the sample are reduced. Furthermore, since excitation occurs only at the focal point, this approach allows the practical collection of three-dimensionally resolved fluorescence images of live cells. However, due to the small two-photon cross-section of most fluorophores, pulsed lasers are required to generate detectable signal levels. This is due to the quadratic dependence of twophoton absorption on the instantaneous power of the laser. Typically, these lasers are pulsed at very high repetition frequencies, on the order of 106 pulses per second with pulse durations of a few hundreds of femtoseconds. For example, a titanium:sapphire (Ti:S) laser mode-locked at 76 Mhz can provide up to 100,000 watts of instantaneous power and is ideal for exciting two-photon events.

The ability to observe the fluorescence arising from single molecules has revolutionized our ability to study the structure and dynamics of materials on a microscopic level and to probe the properties of individual members of a heterogeneous ensemble. A variety of near-field and far-field excitation techniques have been employed to study single molecules. Multiphoton excitation (MPE) techniques have a number of advantages that make them particularly attractive for singlemolecule detection. First, because the excitation and fluorescence wavelengths are significantly different from one another, Rayleigh and Raman scattering can easily be filtered out, leading to a low number of background counts. Second, because the probability for MPE depends on the excitation intensity to the second or higher power, the excitation is localized to the point in space where the excitation beam is most tightly focussed, thus providing three-dimensional resolution.