Developement of In-situ Modulation Spectroscopy for Atomically Localized Electronic States

我们发展了一种利用调制光谱观测外延薄膜原子局域电子态的新技术。本文重点研究了光子和电子调制的反射信号，并对这方面的研究工作进行了总结。(1)为了发展一种分析方法，我们从理论上研究了半导体表面的电调制介电函数。(2)我们开发了一个新的系统来观察在半导体表面的原位电子态。探测光照射样品表面，并通过第二次光照射检测调制信号。研究发现，探测光的入射角对观察表面电子态是很重要的。观察到的各向异性字符的p和s波的探测光，这反映了介电函数的各向异性。这实现了一种新的灵敏检测的电子状态定位在表面上。利用这种技术，我们可以观察到突变表面和吸附原子对电子态的影响。(3)发展了一种新的电子束调制技术。调制条件，如电子束密度和加速能量，是观察局域电子态的重要参数。该技术为原位调制光谱技术的实际应用提供了保证。

We developed a new observation technique of atomically localized electronic states in epitaxial films by using the modulation spectroscopy. We focus our attention on reflectance signal modulated by photon and electron. The summary of this research are follwed. (1) In order to develope an analysis method, we theoretically investigated electro-modulated dielectric functions at semiconductor surfaces. (2) We developed a new system to observe in-situelectronic states at the semiconductor surface. A probe light irradiate the sample surface, and the modulated signal by a second light irradiation was detected. It was found that the incident angle of the probe light is important to observe the surface electronic states. An anisotropic character was observed for the p and s waves of the probe light, which reflect the anisotropy of the dielectric function. This realizes a new sensitive detection of electronic states localized at the surface. By using this technique, we can observe the electronic states changed by the abrupt surface and adsorped atoms. (3) A new electron-beam-modulation technique was developed. The modulation conditions, such as electron-beam density and accelerated energy, are important parameters in order to observe the localized electronic states. This technique promises a practical use of the in-situ modulation spectroscopy.