Quantitative non-destructive nanoscale characterisation of advanced materials

为了满足电子和光电子器件近期发展的性能要求，将需要开创性的材料生长，器件制造和表征技术的进步。基于石墨烯或氮化硼等较轻材料以及先进的硅和金刚石纳米结构的几个原子厚度的设备即将问世。这些设备对目前可用的生产和理解所产生的设备以及它们如何失效的技术提出了新的挑战。优化此类设备的性能需要详细了解扩展结构缺陷及其对技术相关材料性能的影响。这些缺陷包括螺纹位错和晶界，并且通常是电活性的，因此对纳米级器件的效率和寿命非常有害（单个行为不良的缺陷可能导致灾难性的器件故障）。这些缺陷对于硅太阳能电池、先进的紫外线发光二极管和先进的碳化硅和氮化镓基大功率器件（用于大电流的有效开关或高功率微波电信）等设备来说尤其成问题。对于石墨烯和类似的现代二维材料，晶界对其性能有重大影响，因为它们很容易跨越器件的整个尺寸。解决所有这些问题需要新的表征技术来成像扩展缺陷，同时快速使用，非破坏性和在纳米尺度上具有结构确定性。电子通道对比成像（ECCI）是一种有效的结构表征工具，它允许在扫描电子显微镜下快速非破坏性地可视化扩展晶体缺陷。然而，ECCI通常被用作研究纳米级材料的定性方法，它在可以解决的最小尺寸特征上有限制，并且在解释所得图像时存在困难。这限制了这项技术在这些先进材料中找出缺陷性质的能力。我们将利用能量分辨电子探测器的新发展，固体电子束建模的新进展，以及我们研究团队和合作伙伴的知识和经验，使ECCI技术的空间分辨率提高6倍。这种新的能量滤波方法进行ECCI测量，将从根本上提高通过该技术获得的信息质量。我们将把我们的新能力与其他先进的表征技术结合起来，以精确地测量和解释缺陷图像。这将使ECCI被采用为非破坏性的定量结构特征的选择技术，在广泛的重要材料中，并提供一种新的技术来分析扩展缺陷在电子设备故障中的作用。

To satisfy the performance requirements for near term developments in electronic and optoelectronic devices will require pioneering materials growth, device fabrication and advances in characterisation techniques. The imminent arrival of devices a few atoms thick that are based on lighter materials such as graphene or boron nitride and also advanced silicon and diamond nano-structures. These devices pose new challenges to the currently available techniques for producing and understanding the resulting devices and how they fail. Optimising the performance of such devices will require a detailed understanding of extended structural defects and their influence on the properties of technologically relevant materials. These defects include threading dislocations and grain boundaries, and are often electrically active and so are strongly detrimental to the efficiency and lifetimes of nano-scale devices (a single badly-behaved defect can cause catastrophic device failure). These defects are especially problematic for devices such as silicon solar cells, advanced ultraviolet light emitting diodes, and advanced silicon carbide and gallium nitride based high power devices (used for efficient switching of large electrical currents or for high power microwave telecoms). For graphene and similar modern 2D materials, grain boundaries have significant impact on their properties as they easily span the whole size of devices.Resolving all of these problems requires new characterisation techniques for imaging of extended defects which are simultaneously rapid to use, are non-destructive and are structurally definitive on the nanoscale. Electron channelling contrast imaging (ECCI) is an effective structural characterisation tool which allows rapid non-destructive visualisation of extended crystal defects in the scanning electron microscope. However ECCI is usually applied as a qualitative method of investigating nano-scale materials, has limitations on the smallest size features that it can resolve, and suffers from difficulties in interpreting the resulting images. This limits this technique's ability to work out the nature of defects in these advanced materials.We will make use of new developments in energy resolving electron detectors, new advances in the modelling of electron beams with solids and the knowledge and experience of our research team and partners, to obtain a 6 fold improvement in the spatial resolution of the ECCI technique. This new energy-filtered way of making ECCI measurements will radically improve the quality of the information that can be obtained with this technique. We will couple our new capabilities to accurately measure and interpret images of defects to other advanced characterisation techniques. This will enable ECCI to be adopted as the technique of choice for non-destructive quantitative structural characterisation of defects in a wide range of important materials and provide a new technique to analyse the role of extended defects in electronic device failure.