Band gap engineering in graphene nanoribbons and their heterostructures

现在已经确定，如果以近一维条纹的形式合成，半导体中典型的电子带隙可以出现在无隙的二维材料石墨烯中。这种条纹，通常被称为石墨烯纳米带，或gnr，特别适合控制其电子带隙，使用其宽度，边缘结构和化学掺杂作为参数。本提案的目标是对gnr和基于gnr的半导体异质结进行基础科学研究，这些异质结是通过对众所周知的cgnr形成单体6,11-二溴-1,2,3,4-四苯基三苯进行系统结构修饰而衍生的分子家族中适当选择前体构建的。实现这一目标的一个目标是确定gnr的电子结构对系统的、原子精确的结构和化学修饰的依赖。第二个目标是通过连接两种已知形成具有明显不同带隙的gnr的前体分子（1型半导体结），或通过连接两种形成相似但交错间隙的gnr的前体分子（2型半导体结）来构建异质结。第三个目标是进行开创性的实验，寻求通过金属化连接gnr，特别是那些具有化学修饰边缘的gnr，形成二维金属-石墨杂化结构。这个基础科学项目的成果是一套基于选定前体分子家族的带隙工程GNR异质结的设计规则，这可能有助于实现一些新的和有趣的材料的应用，如碳基纳米电子器件和光学材料。

It is now well-established that an electronic band gap which is typical for a semiconductor can emerge in the gap-less 2D material graphene if it is synthesized in the form of nearly-one-dimensional stripes. Such stripes, commonly called graphene nanoribbons, or GNRs, are particularly amenable to controlled manipulation of their electronic band gap, using their width, edge structure and chemical doping as parameters. The goal of this proposal is to perform a basic scientific study of GNRs and GNR-based semiconductor heterojunctions, which are constructed by appropriate selection of precursors from a family of molecules that is derived by systematic structural modification of the well-known cGNR-forming monomer 6,11- dibromo-1,2,3,4-tetraphenyltriphenylene. One objective to achieve this goal is to determine the dependence of the electronic structure of the GNRs on systematic, atomically precise structural and chemical modification. A second objective is to construct heterojunctions by connecting two types of precursor molecules that are known to form GNRs of distinctly different band gap (type 1 semiconductor junction), or by connecting two types of precursor molecules that form GNRs of similar but staggered gap (type 2 semiconductor junction). A third objective is to perform pioneering experiments that seek to connect GNRs, especially those with chemically modified edges, via metalation to form two-dimensional metal-graphenic hybrid structures. The outcomes of this basic scientific project are a set of design rules for band gap engineered GNR heterojunctions based on the selected family of precursor molecules, which might help enable some new and interesting materials for applications, such as carbon-based nano-electronic devices, and optical materials.