Microscopic Tunneling Properties of Exotic Surfaces

研究项目“富勒烯衍生物的电子态”：通过第一性原理计算，我们解释了碳片中1、2、3和6杂质五边形的STM图像。计算1五边形系统再现STM图像。对于2个五边形，HOMOs与C60分子在Si(001)2×1表面的HOMOs非常相似。对于3个五边形，它们也类似于C60在Si(111)7×7表面的五边形。杂质6五边形是碳纳米管尖端的模型。虽然在世界范围内对碳纳米管的电子态进行了许多研究，但所有碳纳米管的尖端都是“开放的”。从利用碳纳米管作为STM尖端的角度出发，我们得到了“封闭”碳纳米管尖端的电子态。我们有两种碳纳米管：扶手椅（C60）和之字形（C80）。如果多之字形碳纳米管的五边形呈星形排列，则homo在6个五边形左右具有较高的电荷密度。因此，我们可以再现场发射显微镜（FEM）图像，这是最近在三重和早稻田大学获得的。研究项目“场发射基本理论”：通过上述第一性原理计算的完整集合，得到格林函数，数值求解李普曼-施温格积分方程，得到发射电子的波函数。我们将其应用于碳纳米管，并与FEM图像进行了比较。

Research item 'electronic states of fullerene derivatives': By calculating from the first-principle, we explain STM images of 1,2,3 and 6 impurity pentagons in carbon sheet. Calculation of 1 pentagon system reproduces STM images. For 2 pentagons, HOMOs quite resemble to those of C60 molecule on Si(001)2×1 surface. For 3 pentagons, they also resemble to those of C60 on Si(111)7×7 surface.Impurity 6 pentagons is the model of the tip of carbon nanotube (CNT). Although many researchs of electronic states of CNT have been done over the world, the tip ends of all of CNT are 'open'. From the view point to utilize CNT for STM tip, we obtain electronic states of tip apex of 'closed' CNT. We have two types of CNT : arm-chair (C60) and zig-zag (C80). if pentagons of multi zig-zag CNT are arranged stellately, HOMOs have high charge density around 6 pentagons. Thus, we can reproduce field emission microscope (FEM) images which are obtained quite recently at Mie and Waseda Universities.Research item 'basic theory of field emission': By the complete set of above mentioned first-principle calculation, we get Green function, solve numerically Lippmann-Schwinger integral equation, and get the wavefunction of emitted electron. We apply to CNT and compare with FEM images.