Semiconductor array detectors

As an alternative to using the blackening of a photographic film for radiation detection "instant imagers" based on semiconductor array detectors are commercially available. 

The application of ICP-AES has been pioneered since 1962 by the group of Albright and Wilson (e.g., Greenfield) and by Fassel (1978). The electronic equipment, the aerosol injection and the optical systems have been steadily improved to reduce sample amounts and to lower detection limits. The recently developed semiconductor array detectors in ICP technology, in combination with a powerful data processing system, offer the advantage of simultaneous detection and calibration of 30 or more elements. For details of the physics and equipment we refer to Atkins (1987) or Robinson (1996). 

Light detection can also be achieved by semiconductor photodiodes or by photodiode array detectors. Their sensitivity, so far, is lower than that of PMTs but they possess the great advantages of much smaller dimensions and lower demand on power supply. These features make them attractive, especially for the construction of portable chemiluminometers. The sensitivity of these detectors... 

Some spectrophotometric techniques work to enhance sensitivity or utility in other ways. The advent of semiconductor diode array detectors permits entire spectra to be acquired simultaneously instead of one wavelength band at a time. Also, automated spectrophotometric analyzers originally developed for clinical use have been adapted for use at sea when many samples... 

It is seen that the ultimate resolving power of the diode array detector will depend on the semiconductor manufacturer and on how narrow the individual photo cells can be commercially fabricated. 

Array detectors scintillators coupled to very large arrays of semiconductor detectors that have largely replaced film in medical diagnostics... 

Photodiode array detectors are an offshoot of semiconductor technology. In semiconductors, impurities have been added to pure silicon to create two classes of materials. The addition of arsenic, bismuth, phosphorous, or antimony creates a pentavalent material (n-type) that is able to function as a donor of electrons. The addition of trivalent elements such as aluminium, boron, gallium, indium, etc., to silicon gives rise to the p-lypc material, in which the trivalent material is able... 

The diffraction equipment used for the study of conducting polymers in no way differs fi-om that used for the study of conventional polymers. This short section does not cover the experimental methods in any technical detail, however, but merely presents some considerations about their applicability. Details can be found in the standard books on this topic [3-5]. Admittedly, these books are somewhat dated they do not, for instance, reflect the impact of computers on both automation of equipment and data evaluation. Another result of the ever-accelerating progress in microelectronics (still based on metals and inorganic semiconductors instead of polymers), is to be found in the field of x-ray detector systems linear photodiode array detectors, Charge-Coupled-Device area detectors and Image Plate detectors have all become available recently. 

The detector geometry used is a 3 layer design, with a semiconductor array top layer, and two lower layers which are scintillator/photodiode arrays. The semiconductor layer is made of CdTe 2mm thick and the scintillator arrays are 3cm of CsI(Tl). All the pixels are hexagonal with an across flats dimension of 11mm and a centre to centre spacing of 11.75mm. The detector is surrounded on all sides, and on the bottom by a 2cm thick BGO veto crystal. 

The first organic electronic products reached the market in 2005/2006. This included passive identification (ID) cards that could be mass printed on paper, which were used for ticketing or toys, became available in 2006. Similarly, flexible batteries, produced in a reel-to-reel process, have been used for smart cards and other mobile consumer products for some time. Printed strain sensors and the first printed semiconductor photo detector arrays for industrial, medical and security applications are also on the market. 

For infrared microspectroscopy, single-element detectors are used for point and mapping measurements. More recently, array detectors have been applied for spectroscopic imaging in the infrared. In infrared focal plane arrays, the monolithic silicon design used in CCDs is replaced by a hybrid construction. In a hybrid detector, photon detection occurs in a semiconductor layer (indium antimonide, mercury cadmium telluride, and doped-silicon are typical detector materials), while the readout and amplification stages are carried out in a silicon layer. The two layers are electrically connected at each pixel through indium bump-bonds . Other innovations such as microbolometer arrays also show promise for spectroscopic imaging applications. 

New types of detectors, such as OMA (optical multichannel analyser), SMA (spectrum multichannel analyser) and MCPD (multichannel photodiode array), are able to record the total emission spectrum by a single shot after flash excitation, so that acquisition of time-resolved emission spectra becomes much easier. One uses appropriate gating techniques, synchronized to the excitation flash, to control the time scale in the data acquisition. At the moment semiconductor based detectors are still less sensitive than photomultiplier (FMT) detectors. 

The largest item driving cost is the SNR requirement. Wide selections of detectors are available from a host of companies. There are literally thousands of photomultiplier mbe types, array detectors (line and 2-D array), and semiconductor light sensors and thermal infrared detectors covering a spectral range from 150 nm to more than 40 pm. The wavelength range often determines the choice of detector type. 

For the parallel recording of EEL spectra in STEM, linear arrays of semiconductor detectors are used. Such detectors convert the incident electrons mto photons, using additional fluorescent coatings or scintillators in the very same way as the TEM detectors described above. 

Since 1970 the subject of amoiphous semiconductors, in particular silicon, has progressed from obscurity to product commercialisation such as flat-panel hquid crystal displays, linear sensor arrays for facsimile machines, inexpensive solar panels, electrophotography, etc. Many other appHcations are at the developmental stage such as nuclear particle detectors, medical imaging, spatial light modulators for optical computing, and switches in neural networks (1,2). 

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