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Mesoscopic π electron control at the edges of nano-graphite

纳米石墨边缘的介观π电子控制

基本信息

批准号：
10309003
负责人：
OSHIMA Chuhei
金额：
$ 18.56万
依托单位：
Waseda University
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (A)
财政年份：
1998
资助国家：
日本
起止时间：
1998 至 2000
项目状态：
已结题

项目摘要

We have fabricates carbon nano-ribbons with 1.3 nm width on TiC(557) surface. The phonon spectra showed the quantized phonon modes, and edge phonon modes, of which the vibrational amplitude is localized at the armchair edges. The STM and STS studies indicates that the monolayer graphene/ h-BN/Ni (111) junction exhibiting the incommensurate system is the semiconductor with 2 eV energy gap. Structures, electronic and magnetic properties have been investigated using activated carbon fibers and heat treatment of nano-diamond particles. Activated carbon fibers is featured with a 3D random network of nano-graphite domain, while heat-treatment convert nano-diamond to nano-graphite. Around the insulator-metal transition around 1200 C, edge-state spins form spin glass state.Nanographite are nanometer-sized graphite fragments, which represent a new class of a mesoscopic system intermediate between aromatic molecules and extended graphite sheets. We investigated theoretically magnetic and transport properties of nanographites. We found that the existence of graphite edges and their shapes strongly affects various properties of nanographite. We have studied the electronic state of nanographite ribbons with a pair of zigzag edges by using the first-principle calculation based on the local density approximation. The edge state, which we predicted within the tight-binding approximation, was reproduced for single-layered and AB-staked zigzag ribbons. Ribbons without hydrogen termination keep the flat form throughout the process of atomic-structure optimization. The dangling-bond state of o-character makes no hybridization with the edge state of π characters.

我们在TiC(557)表面制备了宽度为1.3 nm的碳纳米带。声子谱显示了量子化声子模式和边缘声子模式，其中振动幅度位于扶手椅边缘。 STM和STS研究表明，表现出不通约体系的单层石墨烯/h-BN/Ni(111)结是具有2 eV能隙的半导体。使用活性碳纤维和纳米金刚石颗粒的热处理研究了结构、电子和磁性。活性炭纤维具有纳米石墨域的3D随机网络，而热处理将纳米金刚石转化为纳米石墨。在1200°C左右的绝缘体-金属转变周围，边缘态自旋形成自旋玻璃态。纳米石墨是纳米尺寸的石墨碎片，代表介于芳香分子和延伸石墨片之间的一类新的介观系统。我们从理论上研究了纳米石墨的磁性和传输特性。我们发现石墨边缘的存在及其形状强烈影响纳米石墨的各种性能。我们利用基于局域密度近似的第一原理计算研究了具有一对锯齿形边缘的纳米石墨带的电子态。我们在紧束缚近似中预测的边缘状态在单层和 AB 桩锯齿带中得到了重现。没有氢终止的带在整个原子结构优化过程中保持平坦的形状。 o字符的悬键态与π字符的边缘态不发生杂化。