Development and characterization of a near-infrared cathodoluminescence detector
LE3 .A278 2011
2011
Robertson, Michael Williams, Peter
Acadia University
Bachelor of Science
Honours
Physics
As an alternative to purchasing commercially available optical detectors for the detection of cathodoluminescence signals, two cost effective and high performance detectors were developed and investigated. The first was a near-infrared (IR) luminescence detector based on avalanche photodiode (APD) technology, and the second was based on a 3000 pixel linear CCD array for the parallel acquisition of spectra and full colour imaging. The primary motivation for this work was that the existing optical detectors presently available on the CL system do not operate efficiently in the near IR wavelength regime and the time required to record a CL spectra serially can be prohibitively long for specimens that are easily damaged when interacting with an electron beam. All aspects of the design: mechanical, electrical, optical, and programming, are discussed, including justification for the methods and approaches used during development. Signal-to-noise considerations will be investigated and how the implementation of avalanche photodiode cooling improved the signal-to-noise ratio (SNR) considerably. The optical characterization of the detector is discussed, including experimentally measured optical system response curves showing the wavelength response of the APD detector in comparison to the existing detectors. The performance of the APD detector was studied using two phosphorescent powders displaying a wide range of luminescent intensity. CL examination of the weakly luminescent red phosphorescent powder highlighted the lower SNR of the APD, as compared to the PMT, when operated in the linear mode. In order to improve the low-light performance of the APD, it is recommended that the Geiger mode of operation be the focus of future study. . The development of a parallel acquisition system for CL spectroscopy was successful. However, the wavelength range of the CL signal that could be measured was limited to 325 nm using the 600 lines/mm diffraction grating. A grating with a ruling of 150-300 lines/mm would be viii required to cover the entire visible-to-near IR wavelength range. In addition, recommendations are made on the use of the parallel spectrometer for the collection of colour images.
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https://scholar.acadiau.ca/islandora/object/theses:825