visualization of Fermi level pinning sites at metal semiconductor interfaces

我们已经在我们的超高真空扫描隧道显微镜上安装了弹道电子发射显微镜(BEEM)功能，现在正在检查它的性能。我们建立了一个由BEEM所需的电极、电馈线和传送杆组成的单元，将其连接到超高真空室上，并检查它们是否正常工作。我们还开发了控制信号的电子学，并适当调整了计算机辅助测量系统，以获取BEEM成像和测量I-V谱。由于对于这个项目来说，制备具有低界面态密度的金属半导体界面非常重要，我们建立了一个手套箱，用于对氧、水和颗粒浓度/密度极小的样品进行化学处理。我们开发了一种在硅样品上制作具有理想界面的样品的方法，但对于我们计划在本研究中使用的碳化硅，我们找不到适合于无钉扎界面样品的化学加工条件。我们还开发了一种提高原子力显微镜(AFM)空间分辨率的方法，用于钉扎点的观察。为了提高原子力显微镜的力灵敏度，我们致力于降低电子噪声和控制探针尖端的形状，成功地检测到了单一的共价化学键，并拍摄了高分辨率的硅表面图像。我们还尝试了表面电势分布成像的测量，证实了电势成像是以高灵敏度和高空间分辨率进行的。我们还研究了用于制作金属半导体界面的硅表面的基态结构。利用低温扫描隧道显微镜(STM)对样品位置进行了精确的温度测量，成功地确定了结构。

We have installed a function of ballistic electron emission microscopy (BEEM) on our ultrahigh vacuum scanning tunneling microscopy and are now checking its performance. We set up a unit composed of electrodes, electrical feedthough, and a transfer rod which are necessary for BEEM, attached it to the ultrahigh vacuum chamber, and checked they work properly. We also developed electronics for controlling the signal and adjusted computer-aided measurement system appropriately for taking the BEEM imaging and measuring I-V spectra.Since for this project it is very important to prepare metal semiconductor interfaces with a low density of interface states, we set up a glove box for the chemical processing of the samples in which concentration/density of oxygen, water and particle is extremely small. We developed a method to make samples with the ideal interface on silicon samples but for silicon carbide, which we planned to use for this study, we could not find an appropriate condition of the chemical processing for the pinning-less interface samples. We still need to work for that.We also developed a method of improving spatial resolution of atomic force microscopy (AFM) for the pinning site observation. With an intention of improving force sensitivity of AFM, we worked for reducing electrical noise and controlling the shape of the probe tip, successfully detected a single covalent chemical bonding, and took highly resolved images of silicon surfaces. We also tried for a measurement of surface potential profile imaging and confirmed that the potential imaging is taken with high sensitivity and high spatial resolutions.We also investigated the ground state structure of silicon surface, which is used to make metal semiconductor interfaces as a substrate. Using low temperature scanning tunneling microscopy (STM) with an accurate temperature measurement at the sample site, we successfully determined the structure.