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Study of Ultrasensitive Nanoscale Spectroscopy using Electric Field Enhancement

利用电场增强的超灵敏纳米光谱研究

基本信息

批准号：
14550022
负责人：
MERA Yutaka
金额：
$ 2.62万
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 (C)
财政年份：
2002
资助国家：
日本
起止时间：
2002 至 2003
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-14550022/
关键词：
Field Enhancement Surface Plasmon Nanospectroscopy STM Probe tip TEM Self-diffusion GaN GaN

项目摘要

(1)In-situ transmission electron microscopy (TEM) experiments revealed that dimples formed in hexagonal thin crystals by irradiation of a focused TEM electron beam recovers to flatten the surface under a subsequent electron irradiation with a moderately defocused beam. The electron-stimulated recovery can be attributed neither to knock-on damage nor beam heating effects but to electronically enhanced self-diffusion in the GaN crystals.(2A)when the sample tip gap of STM was irradiated by chopped light, the light generates modulated tunneling current which is proportional to the second order differential of Voltage-Current curve and the square of light electric field. A modulated bias voltage of frequency fv applied to tip sample gap generates modulated tunneling current of frequency 2fv which is proportional to the second order differential of Vaoltage-Current curve. By comparing these two modulated signals, we can estimate quantitatively the light electric field beneath the STM tip including enhancement effects. We have successfully measured the magnitude of light enhancement on HOPG surface in situ.(3B)Drastic light enhancements over two orders were observed even with W tips and Pt tips, although expected magnitudes of enhancement for these materials estimated from surface plasmon mechanism were less than fifty. It was revealed that ordinally STM tips have a large amount of enhancement effects.

（1）原位透射电子显微镜（TEM）实验表明，通过聚焦TEM电子束照射在六方晶体中形成的凹坑在随后的适度散焦电子束照射下恢复以使表面变平。电子刺激的恢复既不能归因于撞击损伤，也不束加热效应，但电子增强的自扩散的GaN晶体。（2A）当STM样品针尖间隙被斩波光照射时，产生调制的隧穿电流，该电流正比于电压-电流曲线的二阶微分和光电场的平方。施加到尖端样品间隙的频率为fv的调制偏置电压产生频率为2fv的调制隧穿电流，其与电压-电流曲线的二阶微分成比例。通过比较这两个调制信号，我们可以定量地估计STM针尖下方的光电场，包括增强效应。我们成功地测量了HOPG表面的光增强的幅度。（3B）即使使用W尖端和Pt尖端也观察到超过两个数量级的剧烈光增强，尽管从表面等离子体机制估计的这些材料的预期增强幅度小于50。结果表明，普通STM针尖有很大的增强效应。