Control of X-ray induced defects in chalcogenide glasses : Large area X-ray sensor for medical use

硫族化物玻璃中 X 射线引起的缺陷的控制：医用大面积 X 射线传感器

• 批准号: 14550297
• 负责人: SHIMAKAWA Koichi
• 金额: $ 2.56万
• 依托单位: Gifu University
• 依托单位国家: 日本
• 项目类别: Grant-in-Aid for Scientific Research (C)
• 财政年份: 2002
• 资助国家: 日本
• 起止时间: 2002 至 2003
• 项目状态: 已结题
• 来源: https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-14550297/
• 关键词: chalcogenide glasses; X-ray digital detector; carrier diffusion; X-ray induced defect; photo-induced defect; image degradation; flat panel; electronic space charge; X-ray digital detector for Medical use; X-ray detector; photoinduced defect; ph

To obtain X-ray images directly for medical use, a new system without using X-ray films has been proposed (direct conversion from X-ray into free electrons and holes using chalcogenide glasses). A large area and real-time observations should be required in the new system. The following big problems should be overcome : (1) A signal intensity (sensitivity) decreases with X-ray exposures, and (2) The real time observations are limited owing to a response time.In the present research project, the principal object is to understand the problem (1). It is well known that microscopic defects increase with visible light exposure in chalcogenide glasses. These light-induced defects lead to the decrease in sensitivity of optical devices. If the number of defect increases with X-ray exposure, sensitivity of X-ray images decreases, which is attributed to a decrease in collective efficiency of free electrons and holes induced by X-ray. Therefore, firstly, we should understand a correlation between defect creation arid sensitivity of X-ray images.The following results have been obtained in amorphous selenium which is one of chalcogenide glasses: (1) Carrier collective efficiency decreases with X-ray exposure time. Time dependence of the decreases in sensitivity is empirically described by a stretched exponential function. (2) The photoconductivity is unchanged by X-ray-exposure. (3) Photoluminescence (PL) intensity is unchanged by X-ray exposure. The above results suggest that new defects are not induced by X-ray exposure.Probably, trapping of electrons and holes induced by X-ray in deep localized states may affect carrier collection efficiency. These are also studied theoretically. Photo-structural changes have been also studied to understand these phenomena.

为了直接获得用于医疗用途的X射线图像，已经提出了一种不使用X射线胶片的新系统（使用硫属化物玻璃将X射线直接转换为自由电子和空穴）。新系统应要求大面积和实时观测。（1）信号强度（灵敏度）随着X射线照射而降低，（2）响应时间的存在使真实的观测受到限制。本研究课题的主要目的是解决（1）的问题。众所周知，硫族化物玻璃中的微观缺陷随着可见光暴露而增加。这些光致缺陷导致光学器件灵敏度的降低。如果缺陷的数量随着X射线曝光而增加，则X射线图像的灵敏度降低，这归因于由X射线引起的自由电子和空穴的收集效率的降低。因此，首先，我们应该了解缺陷产生与X射线图像灵敏度之间的关系，我们在硫系玻璃非晶硒中得到了以下结果：（1）载流子收集效率随X射线曝光时间的延长而降低。灵敏度下降的时间依赖性通过拉伸指数函数来经验描述。(2)光电导性不受X射线曝光的影响。(3)光致发光（PL）强度不受X射线曝光的影响。上述结果表明，X射线辐照并没有引起新的缺陷，可能是由于X射线引起的电子和空穴在深局域态中的俘获影响了载流子的收集效率。这些也从理论上进行了研究。光结构的变化也被研究，以了解这些现象。

项目成果

K.Shimakawa et al.: "Acceralation of photodarkening under d.c. electric field in amorphous As2Se3"J.Non-Cryst.Solids. (印刷中). (2004)

K. Shimakawa 等人：“非晶 As2Se3 中直流电场下的光暗化加速”J. Non-Cryst Solids（印刷中）。

Jai Smgh, Koichi Shimakawa: "Advances in Amorphous Semiconductors"Taylor & Francis (London and New York). 328 (2003)

Jai Smgh、Koichi Shimakawa：“非晶半导体的进展”泰勒

K.Shimakawa et al.: "Quantum efficiency of light-induced defect creation in hydrogenated amorphous silicon and amorphous As2Se3"Philosophical Magazine B. 84. 81-89 (2004)

K.Shimakawa 等人：“氢化非晶硅和非晶 As2Se3 中光致缺陷产生的量子效率”哲学杂志 B. 84. 81-89 (2004)

A.Ganjoo, K.Shimakawa: "Dynamics of photodarkening in amorphous chalcogenides"J. Optoelectronics and Advanced Materials. 4. 595-604 (2002)

A.Ganjoo，K.Shimakawa：“无定形硫属化物中的光暗化动力学”J。

K.Shimakawa: "Dynamics of Photo-induced Metastability in Amorphous Chalcogenides"Dynamics of Photo-induced Metastability in Amorphous Semiconductors (Book ed. by A.V.Kolobov) (Wiley-VCH). 58-68 (2003)

K.Shimakawa：“非晶硫属化物中光致亚稳态的动力学”非晶半导体中光致亚稳态的动力学（A.V.Kolobov 编着的书）（Wiley-VCH）。