Mesoscopic π electron control at the edges of nano-graphite

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的声子模和边缘声子模，其振动幅度集中在扶手椅边缘。STM和STS研究表明，呈现无公度体系的单层石墨烯/h-BN/Ni(111)结是具有2 eV能隙的半导体。利用活性碳纤维和纳米金刚石颗粒的热处理研究了纳米金刚石的结构、电学和磁学性质。活性碳纤维具有纳米石墨域的三维随机网络，而热处理将纳米金刚石转化为纳米石墨。在1200℃左右的绝缘体-金属转变附近，边缘态自旋形成自旋玻璃态。纳米石墨是纳米级的石墨碎片，代表了介于芳香分子和扩展石墨片之间的一种新的介观体系。我们从理论上研究了纳米石墨的磁性和输运性质。我们发现，石墨边的存在及其形状对纳米石墨的各种性质有很大的影响。用基于局域密度近似的第一性原理计算方法研究了具有一对锯齿形边的纳米晶带的电子态。我们在紧束缚近似下预测的边缘状态，在单层和AB-桩之字形带上被重现。在整个原子结构优化过程中，无氢端的薄带始终保持平坦的形状。O字的悬键状态与π字的边缘状态没有杂交性。

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.