Micro-spectroscopic soft X-ray studies of low-cost epitaxial graphene and adsorbates

石墨烯是一种了不起的二维材料，其发现者获得了诺贝尔奖，它可能会给电子行业带来革命性的变化。这取决于控制材料的电子性能，以及以低成本制造这种材料。在像硅这样的普通三维材料中，控制是通过在材料中引入杂质(“掺杂”)实现的。在不破坏石墨烯的一些电子性质的情况下，以传统的方式掺杂石墨烯是不可能的，这些性质首先使石墨烯变得如此有吸引力。另一种选择是“转移掺杂”，即我们将某些分子放置在石墨烯薄片的顶部，它们添加或移除电子，而不会损害石墨烯薄片的卓越电学性能。我们还需要研究石墨烯薄片所在衬底的影响。在这个项目中，我们将研究石墨烯在不同衬底上和其上有不同分子的电子结构。这将使用一种名为“角度分辨光电子能谱”(ARPES)的技术来完成，在该技术中，我们使用软X射线光子将电子从石墨烯中剔除，并计算它们的动量和能量，以建立电子结构的完整图景。然而，我们将在法国、意大利和其他地方的主要X射线设施中使用先进的ARPES系统，这些系统能够在微小的长度尺度上进行这些测量-不到一微米。这将使我们能够利用电子工业可能采用的相同技术，在我们的实验室中以非常廉价和简单的方式计算出石墨烯的电子结构的变化。与昂贵的晶体衬底不同，我们的样品是在廉价的金属箔上制成的，而且不均匀，因此我们在ARPES测量中需要空间分辨率。我们项目的一个关键部分是与理论物理学家建立合作，他们将能够帮助我们理解和预测我们廉价的、具有工业意义的石墨烯的电子性质的变化。这种预测能力将是石墨烯在信息技术、先进探测器和能源效率等领域的现实应用方面向前迈出的一大步。

Graphene - the remarkable two-dimensional material whose discoverers were awarded a Nobel prize - may revolutionise the electronics industry. This depends on controlling the electronic properties of the material AND on making such material cheaply. In ordinary three-dimensional materials like silicon, control is achieved by introducing impurities into the material ("doping"). It is not possible to dope graphene conventionally without destroying some of the electronic properties that make it so attractive in the first place. An alternative is "transfer doping" where we place certain molecules on top of the graphene sheet and they add or remove electrons without damaging the sheet's superb electrical properties. We will also need to examine the effects of the substrate that the graphene sheet lies on.In this project we will investigate the electronic structure of graphene on different substrates and with different molecules on top of it. This will be done using a technique called "angle resolved photoemission spectroscopy", or ARPES, in which we knock electrons out of the graphene using soft X-ray photons and calculate their momentum and energy to build up a complete picture of the electronic structure. However, we will be using advanced ARPES systems at major X-ray facilties in France, Italy and elsewhere which are capable of making these measurements on tiny length scales - less than one micrometre. This will enable us to work out changes in the electronic structure of graphene made in a very cheap and simple way in our lab using the same techniques likely to be employed by the electronics industry. Unlike expensive crystalline substrates, our samples are made on cheap metal foils and are not uniform so we need spatial resolution in the ARPES measurement.A key part of our project is building up collaborations with theoretical physicists who will be able to help us understand and predict the changes of electronic properties of our cheap, industrially relevant graphene. Such a predictive ability will be a big step forward in bringing graphene to real-world applications in areas such as information technology, advanced detectors and energy efficiency.