Electron and hole capture processes in Cu-doped glass exhibiting radiophotoluminescence

Abstract

Radiophotoluminescence (RPL) is a radiation effect, and materials exhibiting RPL can be used in dosimeters. In this study, we observed remarkable RPL in Cu-doped aluminoborosilicate and silica glasses upon their exposure to 60Co γ-rays. The RPL intensity increased proportionally with the irradiation dose up to several hundreds of grays and then saturated beyond a certain dose level. An equation was derived theoretically to express the relationship between the RPL intensity and irradiation dose based on the RPL mechanism, in which copper ions, Cu2+ and Cu+, capture electrons and holes, generated by the irradiation, respectively, resulting in a change in the valence. The equation fitted well with the experimental results, providing two parameters for the equation. These parameters are associated with the saturation dose level and sensitivity, which are important for the application of materials to dosimeters. These parameters were discussed based on electron and hole capture processes in the RPL mechanism.

Research Progress of Radio-photoluminescence Materials and Their Applications

“…事实上，有关 Cu 离子掺杂材料的辐射发光现 象早已被广泛研究，不过多集中在 TSL、OSL 和闪 烁发光，基于 RPL 特性的研究有限 [42] 。大多数 Cu 离子掺杂体系的 RPL 材料能够显示良好的化学耐 久性，但由于较低的辐射探测灵敏度，并不适用于 个人剂量监测，但在大剂量监测方面具有较大的应 用潜力。 Hashikawa 等 [42] (a) Schematic diagram of RPL/OSL/TSL general luminescence mechanism [13] ; (b) Excitation and emission spectra of Ag-PG [7] ; (c) Emission spectrum of Ag-PG under different doses of X-ray irradiation [52] ; (d) Excitation spectrum (pink dotted line) and emission spectrum of Ag-Rb glass before and after X-ray (10 Gy) irradiation [54] ; (e) Emission spectra of Ag-Nd co-doped phosphate glass at different radiation doses (310 nm excitation) [55] ; (f) Excitation spectrum (dashed line) and emission spectrum (solid line) of Ag-doped CsCl before and after X-ray irradiation [59] ; (g) Excitation and emission contour spectra of Al2O3:C,Mg irradiated by β-rays ( 90 Sr/ 90 Y) [63] ; (h) Excitation spectrum and emission spectrum of LiF after X-ray irradiation (126 Gy) [64] ; (i) RPL defect center in LiF, where F3 + is formed by three anionic vacancies capturing two electrons and F2 is formed by two anionic vacancies capturing two electrons [7] 随后， Hashikawa 等 [66] [68] 。Sm 离子是目前研究最多的镧系元 素， Sm 离子掺杂体系的 RPL 特性于 21 世纪初被发 现，但最初并没有用于辐射剂量学，而是用于高密 度的光学存储器 [7] 。直到 2011 年，Okada 等 [69][70] 才 将 Sm 离子掺杂材料用于 X 射线微束的剂量分布检 测。基于 Sm 离子掺杂的 RPL 材料体系有许多，主 要包括氟磷酸盐、氧化物、氟氧化物和卤化物等， 但实际只有少部分能够表现出 RPL 特性。特别需要 指出的是，Sm 离子掺杂材料具有极大的剂量范围 (mGy~kGy)，且大部分材料具有较好的辐射灵敏度 和可循环使用性等特点 [32,34,71] 。此外，Sm 离子掺 杂材料记录的 RPL 信号极其稳定，几乎不会衰退。 同时，辐照后产生的 RPL 信号具有极短的积聚时间， 因此适用于辐射剂量的实时监测。在 Sm 离子体系 的化合物中， Sm 离子在二价和三价下均具有稳定的 氧化态，但它们却拥有不同的电子架构。基态下的 [7,32,72]…”

“…3 RPL and its responses of Cu-doped materials (a) Photos of undoped, 0.005% and 0.01% Cu-doped (in mole) aluminoborosilicate glass under natural and ultraviolet light (254 nm). The brown part of the glass was exposed to X-ray [42] ; (b) Emission spectra of undoped and doped aluminoborosilicate glass at 240 nm excitation before and after X-ray irradiation [42] ; (c) The relationship between PL intensity and irradiation (or absorption) dose of 0.005% Cu-doped aluminum-borosilicate glass irradiated by γ-rays ( 60 Co) [42] ; (d) Effect of heat treatment on X-ray irradiated 0.005% Cu-doped aluminoborosilicate glass [42] ; (e) Emission spectra of Cu-doped silica glass before and after γ-ray irradiation at 240 nm excitation [66] ; (f) The emission spectrum of Cu-doped silica glass before irradiation and after irradiation with γ-rays (1519 Gy). The emission band after irradiation contains two bands of 2.5 eV and 2.1 eV (blue line) [66] ; (g) Fitting curve of the relationship between PL intensity and radiation dose of Cu-doped silica glass [66] ; (h) Emission spectra of the two Cu-doped aluminoborosilicate glasses before and after X-ray irradiation at 240 nm.…”