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

在这个项目中，我们将证明以一种对制造纳米电子产品有用的形式制造石墨烯的原理，并制造一些简单的器件。石墨烯是21世纪发现的碳的一种形式：六角形鸡丝阵列中的单个二维原子片。它完善了一套碳材料，这些材料已经具有零维(巴克球)、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薄片形成的。在最简单的形式下，它可以由任何人制作/铅笔痕迹由数百万片碳片组成，而在数百万片碳片中，只有几片只有一个原子层厚。对这些薄片进行的实验表明，它们具有非常显著的性能，特别是在电子元件方面。这种材料的二维性，以及晶格的对称性，意味着石墨烯中的电子与中微子等相对论粒子具有相同的动力学：它们现在通常被称为无质量的狄拉克费米子，具有一个新的量子数手性，而不是自由电子所拥有的。这已经被证明导致了奇怪的新物理，例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当今的技术。这是因为它拥有比任何其他半导体更高的关键材料特性的价值：迁移率。一种使用石墨烯薄片形成沟道的简单的场效应型CMOS型晶体管，其性能比硅高出十倍以上。实现这一目标的一个主要障碍是，使用当今的平面制造技术不可能用随机放置、形状和大小的薄片来构建复杂的电路，因为在平面制造技术中，重复性是关键。所需要的是在整个晶片上均匀涂覆一层石墨烯，可以用通常的方式进行图案化和加工。目前最有希望做到这一点的方法似乎是使用商业上用于高功率电子产品的碳化硅晶片。在超高真空中进行适当的表面处理会优先去除硅原子，剩下的碳原子会自我重组形成石墨烯。晶片规模的器件级材料的前景不仅提供了用石墨烯形成晶体管通道的可能性，而且提供了用单一的石墨烯薄片雕刻整个电路的可能性。在利兹，我们从事外延石墨烯生产已有大约一年的时间。我们已经建立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已经在我们的碳化硅晶片表面形成。我们最近的努力集中在实现超高压晶圆的极高温度，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，我们就会优化它的生产，并开始用它来制造电子设备。在这个原则证明项目中，我们有两个主要目标：开发一种可靠的协议，以在碳化硅晶片上形成石墨烯，这种形式对扩大生产有用；以及建造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处理，包括可以控制开关动作的门。我们还将开始一些将磁性电极连接到石墨烯设备的试点实验，以期为未来涉及石墨烯自旋电子学的项目奠定基础/使用电子自旋以及电荷来存储和处理信息/这可能是一个非常肥沃的领域，因为量子自旋态在石墨烯中存在的时间非常长，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.