Improved temporal performance and optical quantum efficiency of avalanche amorphous selenium for low dose medical imaging.

Purpose: Active matrix flat panel imagers (AMFPIs) with thin-film transistor arrays experience image quality degradation by electronic noise in low-dose radiography and fluoroscopy. One potential solution is to overcome electronic noise using avalanche gain in an amorphous selenium (a-Se) (HARP) photoconductor in indirect AMFPI. In this work, we aim to improve temporal performance of HARP using a novel composite hole blocking layer (HBL) structure and increase optical quantum efficiency (OQE) to CsI:Tl scintillators by tellurium (Te) doping.

Effect of Substrate Temperature on the Structural, Optical and Electrical Properties of DC Magnetron Sputtered VO Thin Films.

This study focuses on the effect of the substrate temperature () on the quality of VO thin films prepared by DC magnetron sputtering. was varied from 350 to 600 °C and the effects on the surface morphology, microstructure, optical and electrical properties of the films were investigated. The results show that below 500 °C favors the growth of VO phase, whereas higher (≥500 °C) facilitates the formation of the VO phase.

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

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.

Erratum: Zhang, C. et al., The Effect of Substrate Biasing during DC Magnetron Sputtering on the Quality of VO Thin Films and Their Insulator-Metal Transition Behavior. 2019, , 2160.

The authors would like to correct a typographical error in their paper [...

Electronic structure investigation of wide band gap semiconductors-MgPNand ZnPN: experiment and theory.

The research on nitridophosphate materials has gained significant attention in recent years due to the abundance of elements like Mg, Zn, P, and N. We present a detailed study of band gap and electronic structure of MPN(M = Mg, Zn), using synchrotron-based soft x-ray spectroscopy measurements as well as density functional theory (DFT) calculations. The experimental N K-edge x-ray emission spectroscopy (XES) and x-ray absorption spectroscopy (XAS) spectra are used to estimate the band gaps, which are compared with our calculations along with the values available in literature.

The Effect of Substrate Biasing during DC Magnetron Sputtering on the Quality of VO Thin Films and Their Insulator-Metal Transition Behavior.

In this work, VO thin films were deposited on Si wafers (onto (100) surface) by DC magnetron sputtering under different cathode bias voltages. The effects of substrate biasing on the structural and optical properties were investigated. The results show that the metal-insulator transition (MIT) temperature of VO thin films can be increased up to 14 K by applying a cathode bias voltage, compared to deposition conditions without any bias.

Measured and calculated K-fluorescence effects on the MTF of an amorphous-selenium based CCD x-ray detector.

Purpose: Theoretical reasoning suggests that direct conversion digital x-ray detectors based upon photoconductive amorphous-selenium (a-Se) could attain very high values of the MTF (modulation transfer function) at spatial frequencies well beyond 20 cycles mm(-1). One of the fundamental factors affecting resolution loss, particularly at x-ray energies just above the K-edge of selenium (12.66 keV), is the K-fluorescence reabsorption mechanism, wherein energy can be deposited in the detector at locations laterally displaced from the initial x-ray interaction site.

Amorphous and polycrystalline photoconductors for direct conversion flat panel x-ray image sensors.

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 of the current amorphous and polycrystalline semiconductors fulfill these requirements. At present, only stabilized amorphous selenium (doped and alloyed a-Se) has been commercialized, and FPXIs based on a-Se are particularly suitable for mammography, operating at the ideal limit of high detective quantum efficiency (DQE).

Excitation diffusion in GeGaSe and GeGaS glasses heavily doped with Er3+.

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 self-quenching are determined by fitting experimental data to existing models.

The dependence of the modulation transfer function on the blocking layer thickness in amorphous selenium x-ray detectors.

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 evaluated was 25 microm and the blocking layer thicknesses varied from 1 to 51 microm.

Ghosting caused by bulk charge trapping in direct conversion flat-panel detectors using amorphous selenium.

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.

Strong Bragg gratings photoinduced by 633-nm illumination in evaporated As2Se3 thin films.

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.