Date of Award

1-1-2013

Document Type

Open Access Thesis

Department

Electrical Engineering

Sub-Department

Electrical Engineering

First Advisor

Krishna C. Mandal

Abstract

High resolution noninvasive tools of diagnosis has always derived and enabled scientific and medical research to probe and better understand subtleties of matter, intangible to the human eye. Radiation detection systems are highly dependent on advancements in materials and devices with front-end electronics. There are various discrete applications of these radiation detectors and each application imposes certain requirements so there is no single optimum radiation detector.

Flat panel x-ray imagers have gained high demand in the past decade because of exponential improvement in readout electronics. We have synthesized and investigated stabilized amorphous selenium (a-Se) alloys suitable for high resolution flat panel x-ray imagers for medical diagnostic applications, primarily in digital mammography and chest radiography systems. Also, in our pursuit to develop high energy physics radiation detectors, we present a novel method to detect neutrons by exploring alpha detection capabilities of isotopic boron doped a-Se alloys.

The synthesis of well-defined a-Se (As, Cl) alloys and boron doped a-Se alloys have been carried out using a specially designed alloying reactor. The alloy composition has been optimized to ensure good charge transport properties and opto-electronic device performance. The synthesis of a-Se (As, Cl) alloys has been carried out by thoroughly mixing zone-refined (ZR) Se (~7N) with previously synthesized Se-As and Se-Cl master alloys. These synthesized alloys were then used as precursor materials for synthesizing isotopically enriched boron doped alloys. To study and verify the desired physical, electrical, and opto-electronic properties of the synthesized alloys, they have been characterized by various characterization techniques such as scanning electron microscopy (SEM), x-ray diffraction (XRD), glow discharge mass spectroscopy (GDMS), differential scanning calorimetry (DSC), Raman spectroscopy, x-ray photoelectron spectroscopy (XPS), and current-voltage (I-V) characteristics. We have achieved our goal, and have successfully grown stable highly-resistive a-Se alloys and fabricated single layer planar detectors which can perform under high voltage bias with low electronic noise. Results of high energy alpha particle response with a specific signature of thermal neutron detection using boron doped a-Se alloy detector has been successfully investigated and demonstrated.

Rights

© 2013, Abhinav Mehta

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