Electron-bombarded Silicon Research Articles

Gamma detectors for tomographic flow imaging

The significance and limitations of gamma-ray flow imaging are discussed, with the conclusion that there is a need for compact detectors with fast response. Scintillation crystals are the only practical gamma-absorbers which provide sufficient stopping efficiency over the whole energy range of interest (60 keV to 1.2 MeV). Experimental data on two scintillation light read-out devices are presented. One is the new EDPMT (electron-bombarded silicon diode photomultiplier tube) which is capable of count rates close to 10 7 c.p.s. over a broad energy range when used with a GSO crystal. A proximity-focused EDPMT version can be made compact and allows tight stacking. The second device is a very compact and robust photodiode. This is a good alternative for low count-rate applications (<10 5 c.p.s) with gamma energies above approximately 600 keV. Both detectors are suitable for process tomography in general, not only flow imaging.

Position-sensitive detector performance and relevance to time-resolved electron energy loss spectroscopy

The use of position-sensitive detectors (PSDs) has become common in many spectroscopies. The increased signal provided by the parallel detection of many spectral elements affords increases in sensitivity and/or time resolution. Recently, the use of a PSD to increase the temporal resolution of an electron energy loss (EEL) spectrometer has been demonstrated in our laboratory. This article summarizes the present development of EEL spectrometers and then presents a detailed review of four classes of PSDs in the context of their potential application to EEL spectroscopy (EELS). The four classes considered are (a) discrete channel detectors, (b) coincidence array detectors, (c) charge division detectors, and (d) optical detectors imaging phosphor screens. All four designs, as typically implemented, utilize microchannel plates (MCPs) as spatially imaging electron multipliers. The performance of MCPs is reviewed and the constraints that MCP behavior at the high count rates achievable in EELS places on acceptable PSD performance are outlined. The inability of present MCPs to maintain saturation gain at count rates above 1 MHz mm−2 implies that the PSD must tolerate significant gain reduction in the electron multiplier. The possibility of eliminating the MCP and using an electron-bombarded silicon gain mechanism is proposed. Such a device could, in principle, support count rates in excess of 100 MHz/channel, providing an order of magnitude increase in performance over the best existing detectors.

Operation of CCD's with stationary and moving electron-beam input

For the detection of either stationary or moving objects in a LLLTV (low light level TV) environment with a charge coupled device (CCD), two techniques have been demonstrated which will result in improved detection. These are 1) use of an EBS (electron bombarded silicon) or EBIC Mode CCD which provides gain by accelerating photogenerated electrons and 2) use of a motion compensation mode where charge packets are shifted in unison with a (constant velocity) target.

Performance of the Intensified Electron-Bombarded Silicon Camera Tube in Low-Light-Level Television Systems

The combination of an image intensifier and a TV pickup tube incorporating the electron-bombarded silicon gain storage target is one of the more promising new sensors now available for low-light-level imaging. In this paper, the resolution vs irradiance characteristics of this sensor are predicted using the electrical parameters of the sensor and the observer requirements as derived from psychophysical experimentation. Analytically derived results, which include the obherver as an integral part of the sensory system, are shown to be in good agreement with experimentally measured results.

DETERMINATION OF INTERNAL ELECTRIC FIELDS IN SILICON DIOXIDE LAYERS BY OPTICAL PROBING

Existing nominal electric fields in unirradiated and electron-bombarded silicon dioxide layers of SOS-sandwich structures were determined by means of optical probing. The method of investigation is based on the quadratic electro-optical Kerr effect and employs a suitable optical arrangement in connection with a 0.6328-μ helium-neon laser.

Energy Levels in Electron-Bombarded Silicon

Electron bombardment of $n$- and $p$-type silicon reduces the lifetime of minority carriers and decreases the carrier concentration. This paper presents evidence that: (a) an electron trapping level is located 0.16 ev below the conduction band and a hole-trapping level 0.29 ev above the valence band, (b) the recombination centers responsible for the reduction of lifetime in $n$-type are located 0.31 ev from a band edge, and those in $p$-type approximately 0.24 ev from a band edge, (c) lattice imperfections are produced at a rate of 0.18 per electron-cm of bombardment at 700 kev.