Doped n-type a-Se alloys for use in x-ray image detectors: preparation, thermal and electrical properties

拟议的NSERC-CRD赠款是与蒙特利尔的Analogic Canada(ANRAD)公司合作的，其总体目标是合成和表征稳定的n型a-Se合金，其中稳定是通过将As含量从2%增加到10%来实现的。n型a-Se用于a-Se X射线图像探测器中靠近正偏置金属电极的关键层之一，以减少暗电流。然而，随着时间的推移，掺入n型掺杂的a-Se容易使结构晶化，而且比I-层更难制备。该CRD的目标是合成一系列As含量从0.3%到10%的Se(1-x)As(X)合金以及掺杂各种IA和IIA元素的合金，并对其结构、热学和电学性能进行表征。CRD项目包括以下研究：(A)合成基础Se(1-x)As(X)合金；(B)这些Se(1-x)Se(X)合金的n型掺杂；(C)通过差示扫描量热(DSC)和温度调制DSC对新的n型合金进行结构和热表征，以获得玻璃化转变、晶化和熔化温度、热容、松弛和晶化热焓、晶化动力学；(D)通过电荷传输测量(例如瞬变光电导型飞行时间测量)、暗电流测量和过量噪声实验的电学特性。对实验工作的补充将是建立新的有用的暗电流模型，以便可以根据具有新的n型a-Se层的x射线探测器的本征材料性质来预测暗电流作为时间和外加磁场的函数。拟议的CRD赠款建立在前一次CRD中获得的专门知识的基础上，因此从已经建立的专门知识开始，并建立在实力的基础上。预计结果将导致探测器性能的增强，使探测器中的n层更薄和更高的生产成品率。这项研究直接影响了目前用于乳房X光检查的a-se x射线探测器；因此也影响了妇女的医疗保健(乳腺癌筛查)。

The proposed NSERC-CRD grant is in collaboration with the Analogic Canada (Anrad) Corporation in Montreal, and has the overall goal of synthesizing and characterizing stabilized n-type a-Se alloys in which the stabilization is achieved by increasing the As content from 2% to 10%A. The n-type a-Se is used in one of the key-layers in the a-Se x-ray image detector next to the positively biased metal electrode to reduce the dark current. However, the doping of a-Se with n-type dopants tends to crystallize the structure over time, and it is more difficult to fabricate than the i-layer. The goal of this CRD is to synthesize a range of Se(1-x)As(x) alloys with As content varied from 0.3 to 10%, and the alloys doped with various IA and IIA elements, and characterize their structural, thermal and electrical properties. The CRD project involves the following research: (a) synthesis of the base Se(1-x)As(x) alloys; (b) n-type doping of these Se(1-x)Se(x) alloys; (c) structural and thermal characterization of the new n-type alloys through differential scanning calorimetry (DSC) and temperature-modulated DSC to obtain the glass transition, crystallization and melting temperature, the heat capacity, relaxation and crystallization enthalpies, crystallization kinetics; (d) electrical properties through charge transport measurements (such as transient photoconductivity type time-of-flight measurements), dark current measurements, and excess noise experiments. The experimental work will be supplemented by the formulation of new useful models for the dark current so that it can be predicted as a function of time and applied field from the intrinsic material properties for x-ray detectors that will have the new n-type a-Se layer. The proposed CRD grant builds on the expertise gained in the previous CRD and therefore starts from an already established know-how and builds on strength. The results are expected to lead to enhancements in detector performance in terms of having the n-layer in the detector thinner and higher production yield. The research directly impacts a-Se x-ray detectors currently used in mammography; and also therefore impacts the healthcare of women (breast cancer screening).