Characterization of Ion Implanted Materials for Photonic Applications: Radiation Damage in Tellurium Dioxide and Silicon LEDs
Date
2024-01-25
Authors
Journal Title
Journal ISSN
Volume Title
Publisher
ORCID
0000-0003-3539-8066
Type
Thesis
Degree Level
Doctoral
Abstract
Ion implantation is an important semiconductor modification tool. It can be used to introduce desired properties to a semiconductor material or it can be used to purposefully cause damage to a semiconductor material to see how it stands up to an environment in which there is an elevated level of radiation. In this work, the light emission properties of silicon LEDs fabricated using plasma immersion ion implantation were studied and radiation
damage was studied in tellurium dioxide which is an important material for space-based acousto-optic tunable filters. Prior to this work, radiation damage was applied to tellurium dioxide using a 10-keV ion beamline. These materials (silicon and tellurium dioxide) were then analyzed using a variety of spectroscopic techniques. These were X-ray diffraction, Raman spectroscopy, X-ray absorption spectroscopy, X-ray emission spectroscopy and X-ray excited optical luminescence. These spectroscopic techniques shed light on the structural
changes that occurred in these materials, allowing for the understanding of the luminescence mechanism in the case of silicon and of the radiation damage mechanism in the case of tellurium dioxide. In the silicon LEDs, it was observed that the fabrication process produced nanocrystallites beneath the surface of the silicon wafers that were used to fabricate the LEDs. These nanocrystallites were responsible for the light emission of the devices that were studied in this work. On conducting X-ray diffraction, it was observed that the greater the fluence of implanted hydrogen ions, the broader the silicon X-ray diffraction peak. This increased broadening corresponded to a decrease in the nanocrystallite size (as determined with a Scherrer analysis); as the silicon diffraction peak broadened with increased fluence, the crystallite sizes decreased. In addition, decreasing crystallite sizes corresponded to increasingly
blue shifted LED emission.
In the study of tellurium dioxide, broadening of the X-ray diffraction peaks of the implanted sample indicated radiation damage. Upon further examination with Raman spectroscopy,
it was determined that the radiation damage that occurred likely resulted in interstitial oxygen being introduced into the implanted tellurium dioxide sample. The interstitial oxygen was revealed by a fluorescence signal along with the Raman spectra that were recorded. This signal corresponded to the oxygen green line for atomic oxygen. It appeared
that there was evidence of this interstitial oxygen in the recorded X-ray excited optical luminescence spectrum. The bandgap of tellurium dioxide was also determined in this work which allowed the defect state that was observed in the X-ray excited optical luminescence spectrum to be contextualized.
Description
Keywords
Radiation damage, Ion implantation, X-ray diffraction, Raman spectroscopy, X-ray emission spectroscopy, X-ray absorption spectroscopy, X-ray excited optical luminescence, Beamline ion implantation, Plasma immersion ion implantation
Citation
Degree
Doctor of Philosophy (Ph.D.)
Department
Physics and Engineering Physics
Program
Physics