Proof-of-principle proposal: Developing epitaxial graphene for nanoelectronics

在这个项目中，我们将证明以一种可用于制造纳米级电子产品和制造一些简单设备的形式制造石墨烯的原理。石墨烯是21世纪发现的碳的一种形式：它是一种以六边形铁丝网排列的单一二维原子片。它完成了一套碳材料，已经有零维（巴基球）、一维（纳米管）和三维（石墨）成员，这些成员都是通过滚动或堆叠石墨烯片形成的。它最简单的形式是任何人都可以制作的，铅笔的痕迹由数百万片碳片组成，而在数百万片碳片中，只有一层原子厚。对这些薄片的实验表明，它们具有非凡的性能，特别是用于电子元件。这种材料的二维性质，加上晶格的对称性，意味着石墨烯薄片中的电子与相对论粒子（如中微子）具有相同的动力学：它们现在通常被称为无质量狄拉克费米子，具有新的量子数，手性，而不是自由电子所拥有的。这已经被证明会导致奇异的新物理学，比如没有载流子的有限电导率和新版本的量子霍尔效应。尽管基于这种新物理的新型纳米电子设备提供了令人兴奋的可能性，但使用石墨烯也可以显著改进现有技术。这是因为它具有比任何其他半导体更高的关键材料特性：迁移率。一个简单的场效应类似cmos的晶体管，使用石墨烯薄片形成沟道，其性能超过硅的十倍以上。实现这一目标的一个主要障碍是，利用当今的平面制造技术，用随机放置、形状和大小的薄片构建复杂电路是不可能的，而再现性是关键。我们所需要的是一层均匀的石墨烯涂层，覆盖在整个晶圆上，可以用常规的方式进行图案和加工。目前最有希望的方法似乎是在高功率电子产品中使用商业化的SiC晶圆。在超高真空条件下，适当的表面处理会优先去除硅原子，而保留下来的碳原子会自我重建，形成石墨烯。晶圆级器件级材料的前景不仅提供了用石墨烯制造晶体管通道的可能性，还提供了用单片石墨烯雕刻整个电路的可能性。在利兹，我们已经在外延石墨烯的生产上工作了大约一年。我们已经设置并测试了各种表面科学仪器，这些仪器将需要证明石墨烯确实在我们的SiC晶圆表面形成。我们最近的努力集中在实现超高压硅片的高温，这是生产表面石墨烯的关键步骤，经过一系列改进，我们现在接近达到所需的温度。一旦我们有了石墨烯，我们将优化其生产，并开始用它制造电子设备。在这个原理验证项目中，我们有两个主要目标：开发一种可靠的协议，用于在SiC晶圆上形成石墨烯，这种形式有助于扩大生产规模；并建立一些简单的演示设备，以证明这种材料可以在纳米级设备中加工，包括可以控制开关动作的门。我们还将开始一些将磁电极连接到石墨烯器件的试点实验，以期为石墨烯中涉及自旋电子学的未来项目奠定基础/使用电子自旋和电荷来存储和处理信息/这可能是一个非常丰富的领域，因为量子自旋态在石墨烯中非常长，即使在室温下也是如此。

In this project we will prove the principles of fabricating graphene in a form useful for manufacturing nanoscale electronics and fabricate some simple devices. Graphene is a form of carbon discovered in the 21st century: a single two dimensional sheet of atoms in a hexagonal chickenwire array. It completes the set of carbon materials, which already had zero-dimensional (buckyballs), one-dimensional (nanotubes), and three-dimensional (graphite) members that are all formed by rolling or stacking up graphene sheets. In its simplest form it can be made by anyone / a pencil trace consists of millions of carbon flakes, and amongst the millions a few will be just one atomic sheet thick. Experiments on these flakes have shown that they have really remarkable properties, particularly for electronic components. The two-dimensional nature of the material, along with the symmetry of the lattice, means that the electrons in the graphene sheet have the same dynamics as relativistic particles such neutrinos: they are now commonly referred to as massless Dirac fermions, with a new quantum number, chirality, not possessed by free electrons. This has been shown to lead to bizarre new physics such as finite electrical conductivity without charge carriers and new versions of the quantum Hall effect. Although new nanoelectronic devices based on this novel physics offer exciting possibilities, using graphene can also make marked improvements to present day technologies. This is because it possesses the higher value of a key materials property than any other semiconductor: the mobility. A simple field effect CMOS-like transistor, using a graphene flake to form the channel, outperformed Si by more than a factor of ten. A major obstacle to achieving this is that building complex circuits from randomly placed, shaped, and sized flakes is not possible using today's planar fabrication technologies where reproducibility is key. What is needed a uniform layer of graphene coating an entire wafer that can be patterned and processed in the usual way. The most promising way to do this currently seems to be to use SiC wafers used commercially in high power electronics. A proper surface treatment in ultrahigh vacuum preferentially removes silicon atoms, and the carbon atoms that remain reconstruct themselves to form graphene. The promise of wafer-scale device-grade material offers the possibility of not just forming transistor channels out of graphene, but carving entire circuits from a single graphene sheet. At Leeds we have been working on epitaxial graphene production now for roughly a year. We have set up and tested the various surface science instruments that will be needed to show that graphene has indeed formed on the surface of our SiC wafer. Our recent efforts have concentrated on achieving the very high temperatures for the wafer in UHV that are the key step of producing the surface graphene, and after a series of improvements we are now close to reaching those needed. Once we have graphene, we shall optimize its production and start to make electronic devices from it. In this proof-of-principle project we have two main aims: to develop a reliable protocol for forming graphene on SiC wafers in a form useful for scaling up to manufacturing; and to build some simple demonstrator devices to show that this material can be processed in nanoscale devices including gates that can control a switching action. We will also begin some pilot experiments on connecting magnetic electrodes to graphene devices, with a view to preparing the ground for future projects involving spintronics in graphene/using the electron spin as well as charge to store and process information/which is potentially a very fertile area, as quantum spin states are very long lived in graphene, even at room temperature.