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DEVELOPMENT OF SCANNING TUNNELING MICROSCOPE CAPABLE OF CHEMICAL ANALYSIS

具有化学分析功能的扫描隧道显微镜的研制

基本信息

批准号：
11555005
负责人：
MAEDA Koji
金额：
$ 8.83万
依托单位：
THE UNIVERSITY OF TOKYO
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (B)
财政年份：
1999
资助国家：
日本
起止时间：
1999 至 2001
项目状态：
已结题

项目摘要

In order to develop a scanning tunneling microscopic (STM) system that enables chemical analysis of light elements in the imaged regions, the following issues have been addressed.(1)Quantitative considerations on a newly devised photoluminescent X-ray excitation electron energy spectroscopy (PXEEES) revealed that element analysis based on the threshold energy of electrons for X-ray generation is possible if a sufficient amount of field emission current is obtained from very sharp STM tips.(2)To fabricate reproducibly sharp tips necessary for the PXEEES measurements, a novel method of tip fabrication, the ultra-fast current shut-off method, has been developed. The fabricated tips proved to be stable even at high bias voltages up to 500 V.(3)Preliminary experiments using graphite samples revealed that irradiations of electrons in energies as low as 100eV can cause evaporation of ionic carbons, which led us to conclude that the PXEEES measurements are not possible in some materials vulnerable to such low energy electron radiation damage.(4)As an alternative method, spatially-resolved photoabsorption spectroscopic measurements on a nanometer scale were found to be possible by using STM. Tests have been done successfully on GaAs samples.(5)Electric-field modulation spectroscopy coupled with STM revealed to be capable of measuring band structures of semiconductors (low-temperature grown GaAs used as test samples) on nanometer scales.(6)We have proposed a novel scheme of infrared absorption spectroscopy that utilizes infrared light generated by difference frequency generation due to the non-linear current-voltage relation and the tip-enhanced electromagnetic field in the STM tunneling junctions.

为了开发能够对成像区域中的轻元素进行化学分析的扫描隧道显微镜（STM）系统，解决了以下问题。（1）对新设计的光致发光X射线激发电子能谱（PXEEES）的定量考虑表明，如果从非常小的场发射电流中获得足够量的场发射电流，则基于X射线产生的电子阈值能量的元素分析是可能的。 (2)为了制造 PXEEES 测量所需的可重复的锋利尖端，开发了一种新颖的尖端制造方法，即超快电流关断方法。事实证明，即使在高达 500 V 的高偏压下，所制造的尖端也能保持稳定。(3)使用石墨样品进行的初步实验表明，能量低至 100eV 的电子辐照会导致离子碳蒸发，这使我们得出结论，在一些容易受到如此低能电子辐射损坏的材料中，无法进行 PXEEES 测量。(4)作为一种替代方法，人们发现，使用 STM 可以实现纳米尺度的空间分辨光吸收光谱测量。已在 GaAs 样品上成功完成测试。(5)电场调制光谱与 STM 相结合，能够测量纳米尺度的半导体（低温生长的 GaAs 用作测试样品）的能带结构。(6)我们提出了一种新的红外吸收光谱方案，该方案利用非线性差频产生的红外光。 STM 隧道结中的电流-电压关系和尖端增强电磁场。