Thesis (Ph.D.)--Boston University / Lutetium oxide doped with europium oxide (Lu20 3:Eu3+) has been established to be a bright, dense scintillator materi al with vast potential in both medical and high resolution X-ray imaging applications. Unfortunately its commercial viability has been restricted due to the manufacturing and post treatment costs associated with device fabrication. This research was aimed at the development of two vapor deposition techniques; chemical and physical vapor deposition (CVD and PVD), to produce coatings of Lu203:Eu3+ for various X-ray imaging applications. A customized CVD process to codeposit Lu20 3 and Eu20 3 was developed using lutetium and europium chloride (LuCb and EuCI3) precursors and reacting with carbon dioxide (C02) and hydrogen (H2) . An in depth study was performed by systematically varying the process parameters to explore the deposition kinetics and identify the rate limiting steps and their effects on the growth morphology using both cold and hot wall CVD reactors. The activation energy for the kinetically limited deposition of Lu20 3 from the LuCI3 - Ar - C02 - H2 system was identified to be approximately 170 kJ/mol , which is significantly lower than expected. The predominant growth orientations were identified to be { 111} and { 100} , depending on the deposition conditions. As the temperature is increased, the growth orientation preference decreases to produce a randomly oriented growth at 1150°C. The scintillation and X-ray imaging characteristics of a co-deposited Lu203:Eu3+ thin film with a {100} orientation were measured, confirming the feasibility and applicability of the CVD system to produce thick scintillator x-ray imaging devices. A fundamental study of the PVD process was performed by sputtering of Lu203:Eu3+ using a single target magnetron sputtering gun. Systematic vatiations of the deposition parameters were used to understand the effect of the ejected flux kinetic energies and deposition rate on the deposit density, stress, optical and scintillation properties. The deposition system was subsequently optimized for rapid, dense growth of a 10 um thick Lu203:Eu3+ coating at elevated temperatures. The X-ray imaging properties were measured and the results
yielded an X-ray imaging resolution slightly better than 1 um with the potential for 0.5 um with further optimization, a level never before attained.
| Identifer | oai:union.ndltd.org:bu.edu/oai:open.bu.edu:2144/32066 |
| Date | January 2012 |
| Creators | Topping, Stephen G. |
| Publisher | Boston University |
| Source Sets | Boston University |
| Language | en_US |
| Detected Language | English |
| Type | Thesis/Dissertation |
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