A radiofrequency gaseous detection device is proposed for use with instruments employing charged particle beams, such as electron microscopes and ion beam technologies, as well as for detection of ionizing radiations as in proportional counters. An alternating (oscillating) electromagnetic field in the radiofrequency range is applied in a gaseous environment of the instrument. Both the frequency and amplitude of oscillation are adjustable. The electron or ion beam interacts with a specimen and releases free electrons in the gas. Similarly, an ionizing radiation source releases free electrons in the gas. The free electrons are acted upon by the alternating electromagnetic field and undergo an oscillatory motion resulting in multiple collisions with the gas molecules, or atoms. At sufficiently low pressures, the oscillating electrons also collide with surrounding walls. These processes result in an amplified electron signal and an amplified photon signal in a controlled discharge. The amplified signals, which are proportional to the initial number of free electrons, are collected by suitable means for further processing and analysis.

The reverse flow pressure limiting aperture is a device that creates and sustains a substantial gas pressure difference between two chambers connected via an aperture. The aperture is surrounded by an annular orifice leading to a third chamber. The third chamber is maintained at a relatively high pressure that forces gas to flow through the annular aperture into the first of said two chambers. The ensuing gas flow develops into a supersonic annular gas jet, the core of which is coaxial with the central aperture. A pumping action is created at the core of the jet and any gas molecules leaking through the aperture from the second chamber are entrained and forced into the first chamber, thus creating a substantial pressure difference between the first and second chamber.

The development and makeup of a real-time full remote control system for the University of Michigan, Department of Materials Science and Engineering Teaching SEM is described. The instrument was initially controlled via the campus local area Ethernet network and cable TV network. The latest implementation employs Fast Ethernet, Asynchronous Transfer Mode (ATM) networks, and moving picture experts group (MPEG) video encoding to effect the remote control via the computer network alone. Remote control demonstrations from Washington, DC, Dearborn, MI, and Emerson School, Ann Arbor, MI are described.

A fiber-optic based spectral cathodoluminescence (CL) system has been successfully installed on a variable pressure “environmental” scanning electron microscope (ESEM). The fine size of the fiber (50 μm) has been found to require careful alignment. To provide this alignment, a simple X–Y translator has been used. The aligned fiber exhibits high efficiency and the system has recorded spectra at up to 3 million “counts” per sec on strongly cathodoluminescent doped yttrium aluminium garnet (YAG) samples, at 30 kV and ˜3 nA. A resolution of 3 nm [full width half maximum (FWHM)] at 621 nm has been measured from a red laser diode spectrum, on the ESEM column. A range of uncoated materials has been measured to characterize the CL system; these materials ranged from strongly luminescent YAG to weakly luminescent polymers. Wellcharacterized doped zircons have also been investigated. These data suggest that the previously reported intrinsic peak from zircon is a consequence of high-beam currents.

Charge contrast images (CCI) of synthetic gibbsite obtained on an environmental scanning electron microscope gives information on the crystallization process. Furthermore, X-ray mapping of the same grains shows that impurities are localized during the initial stages of growth and that the resulting composition images have features similar to these observed in CCI. This suggests a possible correlation between impurity distributions and the emission detected during CCI. X-ray line profiles, simulating the spatial distribution of impurities derived from the Monte Carlo program CASINO, have been compared with experimental line profiles and give an estimate of the localization. The model suggests that a main impurity, Ca, is depleted from the solution within approximately 3–4 μm of growth.

A new acoustic microscopy method was developed for providing near-surface elastic property mapping of a material. This method has a number of advantages over the traditional V(z) technique. First, it enables one to perform measurements in an automated mode that only requires user intervention in the setup phase. This automated mode makes it feasible to obtain quantitative microscopy images of the elastic property over an area on the material being tested. Also, it only requires a conventional ultrasonic system operating in pulsed mode for collecting the data, rather than a specialized tone-burst system, which is needed in the traditional quantitative scanning acoustic microscopy technique. Finally, unlike the traditional method, the new experimental process does not require calibration of the systems electronics or additional reference data taken under hard-to-duplicate identical conditions from a material that does not exhibit surface acoustic waves.

This article proposes a lossy three-dimensional (3-D) image compression method for 3-D secondary ion microscopy (SIMS) image sets that uses a separable nonuniform 3-D wavelet transform. A typical 3-D SIMS measurement produces relatively large amounts of data which has to be reduced for archivation purposes. Although it is possible to compress an image set slice by slice, more efficient compression can be achieved by exploring the correlation between slices. Compared to different two-dimensional (2-D) image compression methods, compression ratios of the 3-D wavelet method are about four times higher at a comparable peak signal-to-noise ratio (PSNR).