Selenium Amorphous Film

INTRODUCTION This data sheet presents properties of amorphous, vacuum-deposited selenium film. 

Transmission Region, (External Transmittance 10% with 2. 0 mm. thickne s s)  

Caldwell, Special Report on Contract DA 36-039-SC-71131, Purdue University, (1958). 

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Bindu, K. Lakshmi, M. Bini, S. Sudha Kartha, C. Vijayakumar, K. P. Abe, T. Kashiwaba, Y. 2002. Amorphous selenium thin films prepared using chemical bath deposition Optimization of the deposition process and characterization. Semicond. Sci. Technol. 17 270-274. 

If blue light is used for the discharge process, then the absorption is very close to the charged surface, and one can assume that the discharge process involves the transport of photogenerated holes through the bulk. Trapping of these holes in the bulk then results in the observed first residual potential Vri. In the case of amorphous selenium photoreceptor films, it has been found that Ki is predicted by the Waiter expression [16]... 

Fig. 3.8 XRD patterns (CuKc( source) showing a rich in selenium (x > 0.6) CdSej Tei-jt electrodeposited film, which adopts the hexagonal CdSe wurtzite structure by annealing at 520 °C (b). The as-deposited (from a typical acidic solution) film is rather amorphous (a). Segregation of a Te phase is observed in the solid. (Reprinted from Bouroushian et al. [137], Copyright 2009, with permission from Elsevier)...

To conduct experiments of this kind it is very convenient to make use of disorder adsorbent provided by a film of amorphous selenium. During deposition under vacuum conditions, the pressure being no higher than lO Torr, the amorphous modification of selenium is being formed [38]. There are two forms of amorphous selenium which differ in coordination numbers and radii of coordination spheres. The first form is... 

The experiment with films of amorphous selenium with adsorbed ethyl radicals [39] showed that during heating of these films in vacuum... 

Black amorphous selenium, 22 74 Black-and-white instant films, 19 282 Black-and-white instant imaging processes, 19 279-282... 

Returning to the depletion discharge, it should be stressed that with thick films and a good blocking contact between a-Se and the preoxidized aluminum substrate, the depletion discharge process dominates. There are several reasons that amorphous selenium possesses good dark decay characteristics ... 

The first major commercial application of amorphous semiconductors was as the photoreceptor in xerographic copiers and subsequently in laser printers. The early photoreceptors were selenium films, but several other materials were subsequently developed, including ASgSCg and various organic films. Amorphous silicon is a good material for a xerographic photoreceptor (e.g. Shimizu (1985), Pai (1988)) and is used in some commercial copying machines. 

Thin film transistor (TFT) arrays are produced inexpensively and in large numbers for use in modern computer monitors and televisions. This readout system can be combined with amorphous hydrated silicon or amorphous selenium which is deposited over the large surface of the TFT array and acts as the X-ray conversion layer. Having established themselves firmly as an X-ray detector for medical imaging already, they have until now failed to make an impact on the field of crystallography, their high noise level being the main drawback. It can be surmised with some confidence that this type of detector will become standard equipment in the near future. 

In the last decade or so, amorphous selenium has been applied as a photoconductor in X-ray image detectors, particularly for biomedical imaging. For this application, flat-panel detectors with large sensing areas (> 30 cm x 30 cm) have been developed. The coating of amorphous Se is typically 500 pm thick, and is deposited over a silicon thin film transistor layer. After applying an electrical potential to the surface, the detector is exposed to an X-ray beam and the electrons released are used to transmit information that ultimately provides an image. 

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