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In the last ten to fifteen years there has been much research in using amorphous and polycrystalline semiconductors as x-ray photoconductors in various x-ray image sensor applications, most notably in flat panel x-ray imagers (FPXIs). We first outline the essential requirements for an ideal large area photoconductor for use in a FPXI, and discuss how some(More)
Direct flat-panel detectors using amorphous selenium (a-Se) x-ray photoconductors are gaining wide-spread clinical use. The goal of our investigation is to understand the physical mechanisms responsible for ghosting, i.e., x-ray induced change in sensitivity that results in image persistence, so that the knowledge can be used to consistently minimize(More)
Photodarkening of amorphous As2Se3 thin films was generated by a 633-nm HeNe laser. The refractive index and absorption coefficient of the chalcogenide glass was determined, both before and after exposure, by analyzing the material's transmission spectrum. In order to accurately determine the optical constants, the thin film's non-uniform thickness was(More)
Bragg gratings are used in several photonic devices to reflect, and thus to isolate, specific wavelengths of light. Gratings can be photoinduced in chalcogenide glasses by illumination of bandgap light in an interference pattern. We used holographic interferometry to create Bragg gratings in amorphous As2Se3 thin films with a period of 0.56 microm by(More)
Using the photoluminescence from GeGaSe:Er to pump GeGaS:Er, we examine the efficiency of light trapping. By measuring the photoluminescence decay time in powdered materials with varying particle size, we are able to exclude the influence of light trapping and to pinpoint the effect of self-quenching. The critical concentrations of Er for efficient(More)
PURPOSE A numerical model and the experimental methods to study the x-ray exposure dependent change in the modulation transfer function (MTF) of amorphous selenium (a-Se) based active matrix flat panel imagers (AMFPIs) are described. The physical mechanisms responsible for the x-ray exposure dependent change in MTF are also investigated. METHODS A(More)
Blocking layers are used to reduce leakage current in amorphous selenium detectors. The effect of the thickness of the blocking layer on the presampling modulation transfer function (MTF) and on dark current was experimentally determined in prototype single-line CCD-based amorphous selenium (a-Se) x-ray detectors. The sampling pitch of the detectors(More)
It is known that deviation from the Drude law for free carriers is dramatic in most electronically conductive nanomaterials. We review recent studies of the conductivity of nanoscale materials at terahertz (THz) frequencies. We suggest that among a variety of theoretical formalisms, a model of series sequence of transport involving grains and grain(More)
Behind the effect of radiation trapping, also known as radiation diffusion, is a series the sequential emissions and absorptions of radiation by participating atoms or ions. This effect is widely observed in glasses doped with Er<sup>3+</sup> ions where there is a significant spectral overlap of <sup>4</sup>I<sub>15/2</sub> -<sup>4</sup>I<sub>13/2</sub>(More)
“One day in the year of 1820, walking to his lecture at the University of Copenhagen, Oersted got an idea. If static electricity did not affect magnets in any way, maybe things would be different if one tried electricity moving through the wire connecting the two poles of the Volta pile. Arriving at the classroom filled with a crowd of young students,(More)