手性可控的石墨烯纳米带制备与逻辑器件探索

Graphene nanoribbon (GNR) has attracted enormous interest from people all over the world because of its outstanding material properties that depend sensitively on its exact structure. This structure–function relationship can be fully exploited only with access to structurally pure GNRs, but producing just one GNR type remains a considerable challenge. In addition, how to grow graphene nanoribbons on dielectrics directly without degrading its carrier mobility is also an open issue. In this project, we plan to directly grow high quality GNRs with controllable chirality on hexagonal boron nitride (h-BN) substrates, and try to control the GNRs lattice structure for tailor the GNR’s electronic structure. With the help of simplified density functional theory and reaction kinetics, the mechanisms for graphene nucleation and ribbon growth will be studied. The mechanisms may provide useful guidance for GNR growth in atomic precision. By optimizing the growth conditions, the morphology of nanoribbon (like thickness, width, length, stacking order and chirality) will become controlled. Finally, the photoluminescence spectra, optical absorption spectra and Raman spectra will be measured on the GNRs to determine their lattice structure and fundamental properties. Quantum confinement and quantum interference will be examined in GNRs based electrical field effect. All the measurements will give the information of electronic structure of GNRs. All factors which affect the bandgap of GNRs will be studied. Scalability strategy during fabrication of GNR-based logic electronics will also be studied. The research will benefit the development of graphene based logic electronics in future.

石墨烯纳米带以其独特的电学特性已成为当前科学界的研究热点，并有望成为未来电子器件的重要基础材料。然而, 石墨烯纳米带的性质完全由其晶体结构决定,制备手性均一可控的石墨烯纳米带仍然是亟需攻克的研究重点。本项目拟采用化学气相沉积法，在经过刻蚀预处理的六角氮化硼基底上直接制备出手性均一可控的石墨烯纳米带，并进行能带调控。开展六角氮化硼表面纳米台阶刻蚀和石墨烯纳米带外延研究。利用热力学和动力学双重调控，探索石墨烯纳米带厚度、长度、堆垛和手性(包括:宽度、取向和边界结构)等形貌控制条件及内在机理，从而获得手性可控的石墨烯纳米带。通过包括原子精度元素分辨的精细表征在内的多种手段系统地研究石墨烯纳米带晶格结构与其物性之间的内在关系，并研究其能带调控机理。以此为基础，探索石墨烯纳米带场效应器件工艺和新原理逻辑器件，分析其载流子迁移率的影响机制。该项目将为未来石墨烯逻辑器件的研发提供关键技术及实验基础。

本项目基于申请人在六角氮化硼表面石墨烯纳米带(GNR)制备与器件研究方面的长期积累，制备了亚5nm宽的具有原子级平整边缘结构且嵌入h-BN晶格的锯齿型和扶手椅型GNR，并通过微纳器件工艺成功制备室温开关比大于10E5，且迁移率达到1500cm2/Vs，载流子平均自由程超过60nm。输运测量表明亚7 nm的锯齿型GNR的带隙大小与其宽度成反比，而较窄的扶手椅型GNR的带隙-宽度关系表现出波动性。在8-10 nm宽的锯齿型GNR的传输曲线中观察到明显的电导峰，但是在大多数扶手椅型GNR中却没有出现。同时磁输运研究表明锯齿型GNR展现出较小的磁电导，但是扶手椅型GNR具有较高的磁电导。h-BN表面嵌入式手性可控GNR的成功制备为具有超薄特征尺寸的纳米级集成电路开发提供了新的途径。项目执行期间共发表了19篇论文，包括Nature Mater., Nature Comm., Sci. Adv.等高水平论文，授权国际国内发明专利4件，完成了项目的预期目标，形成一定的国际影响力。主要成果如下：1. 通过改进h-BN上的模板制备石墨烯纳米带（GNR）方案，成功制备了嵌入h-BN中的亚5 nm宽锯齿型和扶手椅型GNR，并制备出高开关比和迁移率性能的场效应晶体管。2. 我们提出通过在h-BN表面制备的单层多晶石墨烯薄膜表面生长石墨烯单晶畴的方法，实现了h-BN表面具有不同扭转角度的双层石墨烯制备。发现扭转双层石墨烯在~5°以下均存在晶格重构。3. 对多层h-BN的晶格结构进行了研究, 增加了对h-BN微观结构的理解并为其取向判断提供了依据。4.通过气液固相法成功制备超过一英寸且厚度约为46nm的h-BN薄膜晶体, 制备大面积高质量多层h-BN晶圆制备为未来发展新型功能材料器件、集成电路和其规模化集成提供衬底。