Investigating stimulated luminescence within complex silicates to explore charge mobility and trap distribution

Fitzgerald, Scott K. (2024) Investigating stimulated luminescence within complex silicates to explore charge mobility and trap distribution. MSc(R) thesis, University of Glasgow.

Abstract

The mechanisms behind charge storage and transport within feldspars are of key research interest to explain and model the observed behaviours of irradiated feldspars following stimulation. There is no general consensus on whether infra-red stimulated luminescence (IRSL) in feldspars is due to a single fundamental trap or multiple traps, or whether relaxation mechanisms are tunnelling derived or charge movement through band-tail states and conduction band.

Four separate investigations, using 22 feldspar samples which were previously used in several studies of feldspar luminescence, from four feldspar families (K-Feldspar, Albite, Plagioclase and Microcline samples as well as the F1 IAEA standard material), have been conducted to examine how post-IRSL phenomena can be used to model charge storage and transportation within the material lattice of feldspars. The investigations included the measurement of both post-IR poststimulation phosphorescence (PSP) and post-IR photo-transferred thermoluminescence (PTTL) at different temperatures and following different stimulation wavelengths to characterise variability in relaxation times on the order of microseconds to minutes.

This work highlights the intrinsic complexities of the lattices of feldspars, noting that most changes made appeared to have a measurable effect on either the decay lifetimes or the PTTL peak activation energies or lifetimes. This implies that a distribution of trapping systems must exist within the lattice to allow the observed variability in behaviour. The decay lifetimes of the post-IR PSP decay corresponded to the lifetimes of the PTTL peaks, suggesting a relationship between the two phenomena. This was then exploited by first modelling the potential activation energies of PTTL peak lifetimes that were approximately equal to the computed PSP decay component lifetimes at room temperature. A cryogenic investigation then confirmed that these predicted PTTL peaks were observed, for the first time, in feldspars.

These results demonstrate that, within feldspars, post-IR PTTL and PSP are representative of charge storage in multiple trap systems and transport of charge can be described by band-tail state movement post-stimulation, with no evidence of significant tunnelling.

• Item Type: Thesis (MSc(R))
• Qualification Level: Masters
• Subjects: Q Science > QD Chemistry; Q Science > QE Geology
• Colleges/Schools: College of Science and Engineering > Scottish Universities Environmental Research Centre
• Supervisor's Name: Sanderson, Professor David, Cresswell, Dr. Alan and Martin, Dr. Loic
• Date of Award: 2024
• Depositing User: Theses Team
• Unique ID: glathesis:2024-84101
• Copyright: Copyright of this thesis is held by the author.
• Date Deposited: 22 Feb 2024 12:07
• Last Modified: 22 Feb 2024 12:54
• Thesis DOI: 10.5525/gla.thesis.84101
• URI: https://theses.gla.ac.uk/id/eprint/84101