New Materials for High Energy Colour X-ray Imaging

在过去的15年里，X射线数字成像的进步彻底改变了我们观察世界的方式。例如，医学图像的分辨率和清晰度正在提高；汽车和航空航天行业使用断层成像来发现敏感部件中的故障、裂缝和错位；机场用于行李监控的扫描仪已经变得更加复杂，并且经常使用物质识别技术；作为最后一个例子，X射线成像相机已经发射到太空，以便提供关于我们宇宙起源的更详细信息。无论这些发展如何令人印象深刻，3D成像技术都受到当前可用探测器阵列的严重限制。这种限制的起源可以在这些阵列中当前使用的材料中找到。我们希望开发一种由重元素制成的新的、新颖的半导体材料，非常适合制造使用高能X射线工作的阵列探测器。目前，不可能获得面积大于约1平方厘米的无缺陷材料，甚至不能保证这一点。我们将纠正这一问题，并为我们的应用提供高质量的半导体材料，此外，我们还将为许多其他英国应用提供材料，这些材料并不是我们联盟提议的具体部分。这些新材料将在整个科学领域立即得到应用。在这些情况下使用这种材料不仅是渐进的；它们将使我们能够审查全新的材料，并将向我们提供无与伦比的质量和信息内容的图像。我们将使用X射线源中存在的许多波长(颜色信息)来对材料进行指纹识别和成像。高能X射线具有深入材料的能力，允许检查致密物体，如钢的焊缝、含有石油或天然气的地质岩心部分，或用于重型工厂或机械内部的化学反应的内部观察。使用更高能量的X射线在医疗诊断中具有进一步的优势，能够以较低的辐射剂量提供更清晰的图像。目前，世界上还没有合适的材料来满足高能X射线成像的苛刻技术要求。我们将建立一个开发和生产高纯重型半导体材料的英国技术基地。这些材料是结合了高效率和良好的体电荷传输特性的很有前途的候选半导体。近年来，我们在发展合适的半导体生长方面取得了相当大的进展。我们将开发一种具有良好电荷传输的晶片生长工艺，该工艺有可能在项目后期扩大到更大的晶片直径。这种材料将根据电学和电荷传输特性进行表征，这些信息将被用于优化生长和掺杂制度。然后，我们将把材料加工成探测器设备；这将需要开发金属-半导体接触和钝化处理。这项工作将在CCLRC和萨里郡使用专门的清洁房间进行。然后，这些工作装置将被用于曼彻斯特、伦敦、利物浦达累斯伯里和钻石同步辐射光源的研究计划。这些高纯度晶片还将用于更广泛的研究应用，这将通过这个制造项目打开。我们合作的一个独特特点是我们有能力开发新材料，并将其用于完整的探测器系统。我们认为这是向不同的科学受众提供材料的关键一步，也是商业利用的一条途径。对后者来说，机遇是巨大的。

Advances in X-ray digital imaging over the last 15 years have revolutionised the way that we observe the world. For example, medical images are improving in resolution and clarity; the automotive and aerospace industries have used tomographic imaging to find faults, cracks and dislocations in sensitive components; the scanners used at airports for baggage surveillance have increased in sophistication and are often using substance recognition techniques and as a final example X-ray imaging cameras have been launched into space in order to provide more detailed information about the origins of our universe. However impressive these developments may be the technology of 3D imaging is severely limited by the currently available detector arrays. The origins of this limitation can be found in the materials that are currently used in these arrays. We wish to develop a new and novel range of semiconductor materials made from heavy elements ideally suited to making array detectors that will operate with high energy X-rays. At present it is not possible to obtain defect free material of area greater than about one square cm and even this cannot be guaranteed. We will rectify this problem and deliver high quality semiconductor material for our applications in addition to supplying material for many other UK applications that are not specifically part of our consortium's proposal.These new materials will have instant applications across the sciences. The use of such materials in these cases is not merely incremental; they will enable entirely new materials to be examined and will give us images of unparalleled quality and information content. We will use the many wavelengths (colour information) present in X-ray sources to fingerprint materials as well as image them. High energy X-rays have the ability to penetrate deeply into materials allowing the examination of dense objects such as welds in steel, geological core sections bearing oil or gas or for the internal observation of chemical reactions inside heavy plant or machinery. The use of higher energy X-rays has a further advantage in medical diagnosis delivering clearer images with lower radiation doses. At present no suitable materials exist anywhere in the world that will satisfy the demanding technical requirements of high energy X-ray imaging. We will establish a UK technology base for the development and production of high purity heavy semiconductor materials. These materials are promising candidate semiconductors that combine high efficiency with good bulk charge transport properties. Over recent years we have made considerable progress in developing the growth of suitable semiconductors. We will develop a process to grow wafers with excellent charge transport which has the potential for scale-up to larger wafer diameters in the later phase of the project. The material will be characterised in terms of electrical and charge transport properties, and this information will be used to optimise the growth and dopant regimes. We will then process the material into detector devices; this will require the development of metal-semiconductor contacts and passivation treatments. This will be carried out at CCLRC and Surrey using dedicated clean rooms. These working devices will then be utilised in the research programmes of Manchester, London, Liverpool Daresbury and the diamond synchrotron light source. These high purity wafers will also be made available for a much wider range of research applications that will be opened up by this manufacturing project.A unique feature of our collaboration is our ability to develop the new materials as well as utilise them with full detector systems. We see this as a vital step in delivering the materials to a diverse scientific audience as well as a route to commercial exploitation. The opportunities for the latter are significant.