|Student Name:||Michael G. Lee, MAJ, US Army|
|Thesis:||Depth-Resolved Cathodoluminescence of Thorium Oxide|
|Location:||ENP Conference Room|
|Date & Time:||02/11/2013 at 1000|
|Abstract:|| Single crystal Thorium Dioxide (ThO2) samples were hydrothermally grown and were studied using depth-resolved cathodoluminescence (CL) to radiatively characterize the quality of the material. X-Ray diffraction (XRD) measurements were taken to confirm that these hydrothermally grown crystals were actually ThO2; fluorite structure. The depth-resolved CL was conducted utilizing an EMG-12 electron gun that has an energy range of 1-20keV and a current range of 1-65 microAmps. The CL system runs on ThO2 were conducted in an evacuated chamber with pressures varying from 5x10-7 to 1.2x10-9 Torr. Temperature was varied from 24K – 297K (room temperature). Two samples were examined: an as-grown sample and a cleaved sample. The samples were impinged with beam energies of 1.5keV, 5keV, 7keV, 10keV, and 12keV and beam currents of 30-60 microAmps. CASINO depth-penetration simulations provided the expected electron interaction locations within the depths of the ThO2 crystals. A broad UV-band was observed at around 3,200Å, which shifted to lower energies. The ThO2 depth-resolved CL indicated that the crystal is highly dependent on temperature variations.