X-ray studies of materials modified by high energy ion beams

当一个高能的重离子击中硅或玻璃等固体目标时，它会产生一个又长又窄的损伤圆柱体，即所谓的离子径迹。许多人相信，多年来，离子径迹会熔化，即使熔化的时间如此短暂(不到一纳秒)。然而，没有令人信服的证据存在，这是令人遗憾的，因为这些离子碰撞发生的频率比大多数人想象的要频繁(离子束处理、核废料储存、宇宙线干扰)。我正计划提供这样的证据，并将在我的提案中解释如何。 计划中的实验将在非晶硅中进行，我还计划发现这种重要材料的其他基本性质。例如，我们最近证明了a-Si是“超均匀”的，这是它与晶体(非非晶态)材料共享的一种性质，但与液体不同。我们计划研究它的近亲--无定形锗，因为我们预计它会更“超均匀”。在超均匀度测量过程中，我们在非晶硅的衍射图中发现了一个不应该存在的小但重要的峰，我在提案中描述了我们将如何找出导致它的原因。 无序材料的一个重要应用是将光转化为电。在这项提议中，我提出了两个项目来改进进行这种类型转换的设备：一个是旨在改善新型(高灵敏度)红外探测器的响应时间，另一个是旨在提高塑料太阳能电池的转换效率。

When an energetic, heavy ion hits a solid target such as silicon or glass, it creates a long and narrow cylinder of damage, the so-called ion track. It is believed by many, and since many years, that the ion track melts, if ever so briefly (for less than a nano-second). However, no convincing proof exist and that is a pity, because these ion impacts happen more often than most would think (ion beam processing, nuclear waste storage, cosmic ray interference). I am planning to provide exactly such evidence, and will explain how in my proposal. The planned experiment will take place in amorphous silicon, and I plan to discover other fundamental properties of this important material as well. For example, we have recently shown that a-Si is "hyperuniform", a property it shares with cristalline (non-amorphous) materials but not with liquids and we plan to study its close cousin, amorphous germanium, because we expect it to be even more "hyperuniform". In the course of the hyperuniformity measurements, we discovered a small but significant peak in the diffraction pattern of amorphous silicon that should not be there, and I describe in the proposal how we are going to find out what causes it. One important application of disordered materials is for the conversion of light to electricity. In this proposal, I present two projects to improve devices that do this type of conversion: one is aimed to improve the response time of a new type of (highly sensitive) infra-red detector and another aims to improve the conversion efficiency of plastic solar cells.