Time-resolved cathodoluminescence scanning electron microscope

该提案旨在为英国带来一种令人惊叹的显微镜，这将为了解发光材料和器件的特性提供新的强大能力。这些材料是许多技术的关键，不仅是直接利用材料发光的技术（例如基于发光二极管的节能灯泡），而且是利用同一系列材料的一系列其他设备，例如太阳能电池和用于功率转换的电子设备。其中一些技术目前正在使用，但可以通过更好地了解相关材料来提高其效率和性能。其他目标技术离市场更远，但可能代表着我们未来安全和繁荣的基石。例如，新的显微镜将提供有关光源的信息，这些光源根据需要发射一个且只有一个基本光粒子（光子）。这种“量子光源”是量子计算机和量子密码学方案的潜在基石，量子密码学方案代表了最终的安全数据传输。新的显微镜将如何让我们推动所有这些技术的发展？它是基于扫描电子显微镜，利用电子束入射到样品表面，以实现分辨率几乎三个数量级优于可以实现使用标准光学显微镜。因此，它进入了纳米尺度，这对解决现代电子设备至关重要。标准的电子显微镜检查表面的形貌，但是入射的电子束也会激发被检查材料中的一些电子进入更高能量的状态。当这些电子弛豫回到它们通常的低能态时，光可能会发出，而光的颜色和强度是关于被测材料性质的令人难以置信的信息。这种光发射可以在~10纳米的尺度上进行映射，以便可以解决从缺陷到故意设计的量子物体的纳米级结构。这种技术被称为阴极射线发光，已经使用了很多年。我们提出的系统的新功能是，它不仅可以映射光发射的颜色和强度，还可以让我们测量电子弛豫回到低能态的时间尺度。我们用“in the blink of an eye”这个短语来形容发生得非常快的事情。一次真实的眨眼至少需要100毫秒，而电子返回到低能状态的相关时间尺度可能比这快近100亿倍！新的显微镜将能够测量在这个时间尺度上发生的过程，通过解决电子脉冲激发材料后多久发出光子。它甚至能够区分在不同时间尺度上发射的不同波长（或颜色）的光子。至关重要的是，将这种时间分辨能力与改变温度的能力结合起来，我们不仅能够推断出电子弛豫到发射光子的低能位点的时间尺度，而且还能够推断出电子通过其他非发光途径降低能量的时间尺度。例如，这些非发光过程限制了发光二极管的效率。总的来说，在广泛的材料中，我们将建立对电子如何与纳米结构相互作用的理解，以定义材料的电学和光学特性，从而了解哪些因素限制或提高器件的性能。拟议中的系统将是世界上最先进的，并将使英国研究人员在这些非常重要的光子和电子技术方面在开发新材料，设备和最终产品方面具有全球优势。

This proposal aims to bring to the UK an amazing microscope which will provide new and powerful capability in understanding the properties of light emitting materials and devices. These materials are key to many technologies, not only technologies that utilise the light emission from materials directly (such as energy efficient light bulbs based on light emitting diodes) but also a range of other devices which utilise the same family of materials such as solar cells and electronic devices for power conversion. Some of these technologies are in current use, but their efficiency and performance can be enhanced by achieving a better understanding of the relevant materials. Other target technologies are further from the market, but may represent the building blocks of our future security and prosperity. For example, the new microscope will provide information about light sources which emit one and only one fundamental particle of light (photon) on demand. Such "quantum light sources" are a potential building block for quantum computers and for quantum cryptography schemes which represent the ultimate in secure data transfer.How will the new microscope allow us to advance the development of all these technologies? It is based on a scanning electron microscope, which utilises an electron beam incident on a sample surface to achieve resolutions almost three orders of magnitude better than can be achieved using a standard light microscope. It thus accesses the nanometre scale, which is vital to addressing modern day electronic devices. Standard electron microscopy accesses the topography of a surface, but the incoming electron beam also excites some of the electrons within the material under examination into states with a higher energy. When these electrons relax back down to their usual low energy state, light may be given out, and the colour and intensity of that light is incredibly informative about the properties of the material under examination. This light emission can be mapped on a scale of ~10 nanometres so that nanoscale structures ranging from defects to deliberately engineered quantum objects can be addressed. This technique is known as cathodoluminescence, and has been in use for many years.The new capability of our proposed system is that it will map not only the colour and intensity of the light emission, but also allow us to measure the timescales on which an electron relaxes back down to its low energy state. We use the phrase "in the blink of an eye" to describe something that happens extraordinarily quickly. A real eye blink takes at least 100 milliseconds, whereas the relevant timescales for the electron to return to its low energy state could be almost 10 billion times quicker than this! The new microscope will be able to measure processes occurring on this time scale, by addressing how long after an electron pulse excites the material a photon is emitted. It will even be able to distinguish between photons with different wavelengths (or colours) being emitted on different time scales. Crucially, coupling this time-resolved capability with the ability to vary the temperature, we will be able to infer not only the time scales on which electrons relax to low energy sites emitting a photon, but also the time scales by which electrons reduce their energy by other, non-light-emitting routes. These non-light-emitting processes are what limit the efficiency of light emitting diodes, for example. Overall, across a broad range of materials, we will build up an understanding of how electrons interact with nanoscale structure to define a material's electrical and optical properties and hence what factors limit or improve the performance of devices. The proposed system will be the most advanced in the world, and will give UK researchers working on these hugely important photonic and electronic technologies a global advantage in developing new materials, devices and ultimately products.