Studying defects in the silicon lattice using CCDs
Studying defects in the silicon lattice using CCDs
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使用 CCD 研究硅晶格中的缺陷
DOI：
10.1088/1748-0221/9/12/c12004
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发表时间：
2014
影响因子：
1.3
通讯作者：
A. Holland
中科院分区：
文献类型：
--
作者：
D. Hall;N. Murray;J. Gow;D. Wood;A. Holland
从空间天文学到同步加速器研究，硅一直是许多应用中探测器的首选材料。当在太空中或在同步加速器或其他加速器内工作时，探测器可能会受到恶劣的辐射环境的影响。这些高能电子、质子和伽马的存在可导致检测器的硅晶格内的辐射诱导损伤，除了晶格固有的任何缺陷之外，还产生进一步的缺陷或"陷阱“。电荷耦合器件（CCD）已经被用于填充空间望远镜的焦平面多年，最近的例子从哈勃太空望远镜到最近发射的欧空局盖亚使命。这种任务中的辐射环境通常由高能质子主导，并导致陷阱，这些陷阱在信号电荷包通过设备转移时从信号电荷包中捕获电子。任何捕获的电子随后被释放，该时间由所讨论的陷阱物质的发射时间常数确定。当信号通过CCD传输时，信号的反复捕获和释放产生"拖尾“效应，导致成像物体形状的变化。这种形状上的变化不仅是不希望的，而且对未来的应用，例如欧空局的欧几里得使命，具有特别重要的意义，在该使命中，由于弱引力透镜而引起的细微形状变化将被测量。为了校正CCD中存在的任何辐射损伤，必须能够产生一个模型，该模型准确地表示通过包含此类陷阱的设备的电荷转移。虽然目前的模型通常是基于对观察到的数据的拟合，但现在非常希望能够通过更深入地了解晶格中存在的缺陷，在子像素，单陷阱水平上主动预测任何辐射对器件的影响。然而，目前我们对硅中缺陷的理解主要是基于分析许多陷阱的平均性质的技术，通常是几个陷阱物种。这里提出了一个选择的方法，实验和模拟，可以用来开始研究人口的晶格缺陷下降到个别缺陷本身。这些研究不仅使调查的缺陷密度和设备的平均陷阱参数，而且在设备中的个别晶格缺陷的属性，途中积极预测发射前的辐射环境的影响。
Silicon has long been the material of choice for detectors for many applications, from space astronomy to synchrotron research. When operating in space, or within a synchrotron or other accelerator, the detector can be subjected to a harsh radiation environment. The presence of these high energy electrons, protons and gammas can lead to radiation-induced damage within the silicon lattice of the detector, creating further defects or ``traps'' in addition to any defects intrinsic to the lattice. Charge-Coupled Devices (CCDs) have been used for many years to populate the focal planes of space telescopes, with recent examples ranging from the Hubble Space Telescope to the more recently launched ESA Gaia mission. The radiation environment in such missions is often dominated by high-energy protons, and leads to traps which act to capture electrons from signal charge packets as they are transferred through the device. Any captured electrons are then released later in time, with this time determined by the emission time constant of the trap species in question. The repeated capture and release of signal as it is transferred through the CCD produces a ``smearing'' effect, resulting in a change in shape of the objects imaged. This change in shape is not only undesirable, but has particular importance to future applications such as the ESA Euclid mission, in which the subtle shape changes due to weak gravitational lensing are to be measured. In order to correct for any radiation damage present in a CCD, one must be able to produce a model that accurately represents the transfer of charge through a device containing such traps. While current models are often based on fits to observed data, it is now highly desirable to be able to actively predict the effects of any radiation on the device through a deeper understanding of the defects present in the lattice, at a sub-pixel, single-trap level. However, currently our understanding of defects within silicon has been based largely on techniques which analyse the average properties of many traps, often over several trap species. Here is presented a selection of methods, both experimental and simulated, that can be used to begin to study populations of lattice defects down to individual defects themselves. These studies have enabled the investigation of not only the defect densities and the device-averaged trap parameters, but also the properties of individual lattice defects in the device, en route to actively predicting the impact of the radiation environment before launch.