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|Title:||Diamond Radiation Detectors|
|Authors:||Muller, Erik M.|
Department of Materials Science and Engineering.
|Abstract:||Synchrotron X-ray facilities have a tremendous impact in many fields of scientific research. Modern synchrotrons aim to provide collimated high brightness coherent X-ray beams. But due to its high power, no reliable detection technique is currently available which can operate under high radiation dose with a reasonable response and life time. Recent progress in single crystal electronic grade diamond synthesis promotes diamond’s application in radiation detectors, as diamond has a magic combination of excellent electronic properties and great mechanical properties. The crystalline quality of diamonds are characterized by X-ray topography and Birefringence Microscopy. Defects such as slip bands, “V” shape dislocation bundles, inclusions and single dislocations are observed; and their impact on the performance of diamond photodiodes is tested. A standard sample selection criteria is used to eliminate device failure originating from crystalline defects. The electrical structure of a diamond double-side Schottky diode is described in detail; and a model based on the minor nitrogen dopant and Near Edge X-ray Absorption Fine Structure (NEXAFS) data on one platinum coated diamond detector is put forward to explain some common device failures, such as radiation induced photoconductive gain. In addition to diamond detectors with simple lithography patterns, our efforts on the design and fabrication a state-of-the-art diamond imaging detector is summarized. This device has some prominent features over other imaging systems such as Si-based CCDs. It can visualize the position, shape and flux of the high power X-ray beam in transmission mode in real-time with a scanning rate of 32 Hz. The novel readout scheme and device was tested in various beamlines and the integration with a vacuum flange is in process now to have the diamond imaging device work as a vacuum-air interface window at the X-ray Footprinting Beamline at NSLS-II. In order to expand diamond’s application in soft X-ray monitoring, a new recipe for diamond deep reactive ion etching is developed to fabricate ultra-thin diamond membrane (3∼10 μm) detectors. Gas mixture, pressure, temperature and RF power is investigated in detail to achieve different etching chemistry. Multiple thin diamond membrane detectors have been fabricated and tested at the Soft Matter Interaction Beamline at NSLS-II, and they provide a significant advance in real-time soft X-ray beamline diagnostics. Future work including developing diamond detectors for Medical Dosimetry using gamma rays or ion beams, electrode passivation layer development to prevent radiation induced photoconductive gain and other contacting material such as ultrananocrystalline diamond are proposed in the last two chapters.|
|Appears in Collections:||Stony Brook Theses and Dissertations Collection|
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