Microscopic Tunneling Properties of Adsorbed Surfaces

研究项目“Si表面有机分子的电子态”：通过第一性原理计算，解释了5个苯环吸附在Si (001) 2×1表面的并五苯分子的STM图像。我们得出结论，在由尖端-真空-有机分子-衬底组成的系统中，电子从有机分子-衬底系统的本征态通过真空隧穿到尖端。研究项目“富勒烯衍生物的电子态”：我们考虑碳片上的1、2、3和6个杂质五边形。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。对于碳纳米管尖端的6个五边形模型，我们目前已经得到了初步的结果，并在继续进行计算。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。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。

Research item 'electronic states of organic molecule on Si surface' : By calculating from the first-principle, we explain STM images of pentacene molecules with five benzen rings adsorbed on Si (001) 2×1 surface. We conclude that in the system consisting of tip-vacuum-organic molecule-substrate, electrons tunnel from the eigen states of the organic molecule-substrate system to tip via the vacuum.Research item 'electronic states of fullerene derivatives' : we consider 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.For 6 pentagons which is the model of the tip of carbon nanotube (CNT), we have gotten primitive results at this stage and are continuing calculation. 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.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.