Doped and Stabilized Amorphous Selenium Single and Multilayer Photoconductive Layers for<scp>X</scp>‐Ray Imaging Detector Applications

Kasap, S. O.

doi:10.1002/9781119579182.ch18

Cited by 6 publications

(8 citation statements)

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“…The dependence of the hole and electron ranges, r h and r e , on the As content has been studied by several authors as reviewed in [ 2 ]. In nearly all cases, the quoted As content is for the bulk, that is, the composition of the source material.…”

Section: Formulation Of the Modelmentioning

confidence: 99%

“…An average of 0.71 was used to obtain the average film content for the analysis of the dependence of the carrier ranges on the As content in the film. The carrier range determinations typically involve time-of-flight (TOF), interrupted field time-of-flight (IFTOF), and first xerographic residual voltage measurements which have uncertainties and errors in the range of 10–15% [ 2 ]. The composition measurements also have uncertainties (as apparent in Figure 2 ).…”

Section: Formulation Of the Modelmentioning

confidence: 99%

“…The latter observation is in line with the work in [ 8 ], where the hole response was shown to drop and flatten around 4%As. There is a large variation in the hole range in pure a-Se, which depends on the source of the material and batch [ 2 , 9 , 10 ]. An empirical equation r h = f ( C ) is needed to account for the experiments in Figure 4 so that this function can be used in the CE calculations.…”

Section: Formulation Of the Modelmentioning

confidence: 99%

“…With Equations (1) and (2), we can represent the variation in r h across the film thickness for both samples H and S, i.e., r h = r h ( x ). It is important to mention that the hole range r h depends on the substrate temperature during deposition [ 2 ]. It is assumed that the a-Se film that is to be used as a photoconductive layer has been deposited at a substrate temperature above the glass transition temperature of the source alloy.…”

Section: Formulation Of the Modelmentioning

confidence: 99%

“…Stabilized amorphous selenium (a-Se) is widely used in commercial mammographic imaging detectors as an X-ray photoconductor [ 1 ]. The properties of a-Se have recently been reviewed in [ 2 ] (see also references therein). The general fabrication process for a-Se detectors involves the vacuum deposition of the photoconductive film onto an imaging substrate held at a temperature usually above the glass transition temperature of the source alloy, but below the crystallization temperature.…”

Section: Introduction and Objectivesmentioning

confidence: 99%

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The Effect of Fractionation during the Vacuum Deposition of Stabilized Amorphous Selenium Alloy Photoconductors on the Overall Charge Collection Efficiency

Kasap

2022

Sensors

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The general fabrication process for stabilized amorphous selenium (a-Se) detectors is vacuum deposition. The evaporant alloy is typically selenium alloyed with 0.3–0.5% As to stabilize it against crystallization. During the evaporation, fractionation leads to the formation of a deposited film that is rich in As near the surface and rich in Se near the substrate. The As content is invariably not uniform across the film thickness. This paper examines the effect of non-uniform As content on the charge collection efficiency (CE). The model for the actual CE calculation is based on the generalized CE equation under small signals; it involves the integration of the reciprocal range-field product (the schubweg) and the photogeneration profile. The data for the model input were extracted from the literature on the dependence of charge carrier drift mobilities and lifetimes on the As content in a-Se1−xAsx alloys to generate the spatial variation of hole and electron ranges across the photoconductor film. This range variation is then used to calculate the actual CE in the integral equation as a function of the applied field. The carrier ranges corresponding to the average composition in the film are also used in the standard CE equation under uniform ranges to examine whether one can simply use the average As content to calculate the CE. The standard equation is also used with ranges from the spatial average and average inverse. Errors are then compared and quantified from the use of various averages. The particular choice for averaging depends on the polarity of the radiation-receiving electrode and the spatial variation of the carrier ranges.

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Section: Formulation Of the Modelmentioning

confidence: 99%

Section: Formulation Of the Modelmentioning

confidence: 99%