A study on dual-tip scanning tunneling microscopy and nanoscale surface material science

本工作的目的是为纳米级功能表面材料的研究奠定基础。为此，我们研究了(1)用于研究纳米级表面材料输运和动力学性质的双尖端扫描隧道显微镜的基本工作原理；(2)经过电荷密度波相变的新型表面材料。对于双针尖扫描隧道显微镜，我们首先研究了超高真空高分辨率扫描隧道显微镜的热漂移特性，并开发了一套扫描隧道光谱的快速测量系统。为了建立两针尖位置接近的双针尖扫描隧道显微镜的稳定运行，我们研究了几种稳定两针尖距离的操作算法。利用扫描隧道显微镜、角分辨光电子能谱和低能电子衍射等手段研究了Cu（001）上铟单层膜的原子和电子结构。我们发现在该系统中观察到的两个可逆相变本质上是由于由in诱导表面共振带构成的费米表面嵌套而引起的电荷密度波转变。预计在相变过程中，表面电子导电性会发生较大的变化。我们还研究了几个相关体系的结构，发现Bi原子在Ag（001）上形成一维排列的之字形链，这将成为准一维导体的一个新例子。

The aim of this work was to establish a basis for the study of the nanoscale functional surface materials. To this end, we have studied (1) the basic operation principle of dual-tip scanning tunneling microscopy for the study of transportand dynamical properties of nanoscale surface materials, and (2) the novel surface materials which undergo charge-density-wave phase transitions.As to the dual-tip scanning tunneling microscopy, we first studied the thermal-drift characteristics of an ultrahigh vacuum high-resolution scanning tunneling microscopy and developped a system for the fast measurement of the scanning tunneling spectroscopy. In order to establish the stable operation of the dual-tip scanning tunneling microscopy with two tips positioned in close proximity, we have studied several operation algorisms for the stabilization of distance between two tips.The atomic and electronic structure of In monolayers on Cu(001) was studied by means of scanning tunneling microscopy, angle-resolved photoelectron spectroscopy, and low-energy electron diffraction. We have found that two reversible phase transitions observed in this system are essentially the charge-density-wave transitions due to the nesting of the Fermi surface constituted by the In-induced surface resonance bands. It is expected that the surface electronic conductivity exhibits a strong change Hpon the phase transition. We also studied the structure of several related systems and found that Bi atoms form one-dimensionally-alligned zigzag chains on Ag(001), which would serve a new example of quasi-one-dimensional conductor.