Ellipsometric study of the two dimensional phase of physisorbed rare gases.

物理吸附稀有气体二维相的椭圆测量研究。

• 批准号: 61460075
• 负责人: TAKEUCHI Kyoko
• 金额: $ 4.1万
• 依托单位: Gakushuin University
• 依托单位国家: 日本
• 项目类别: Grant-in-Aid for General Scientific Research (B)
• 财政年份: 1986
• 资助国家: 日本
• 起止时间: 1986 至 1987
• 项目状态: 已结题
• 来源: https://kaken.nii.ac.jp/en/grant/KAKENHI-PROJECT-61460075/
• 关键词: ellipsometry; physical adsorption; rare gas; two dimensional molecular system; 2次元相転移; 希ガス二次元相; 相転移; 偏光解析法

Quasi-two dimensional behavior is observed in the system of rare gases physisorbed on the atomically flat surface. Statistical thermodynamics of this system has been investigated experimentally by various methods: (1) absorption isotherms (2) LEED, X-ray and neutron diffraction, (3) calorimetry, (4) NMR, etc. But it has been impossible to compare, for example, the results on the single crystal surface measured by LEED with the well-extablished phase diagram on the exfoliated graphite by the adsorption isotherm measurement. This is mainly because of experimental restriction.The purpose of this project is to establish a new experimental method in this field, that is, to adapt ellipsometric techniques to the study of physical adsorption. Ellipsometry is believed to give a new aspect in this field because of the following merit: (1) a small amount of adsorbed species, as thin as 1/100 atomic layer, on a single crystal surface can be detected, (2) non-destructive to weak bonds of a physisorption system,(3) no limitation on the operating gas pressure (from 1 atm to ultrahigh vacuum).The experimental apparatus which was constructed in the project has the following features.(1) The vacuum chamber was made of an aluminum alloy and its final pressure is lower than 10^7 Pa. (2) Sample temperature can be controlled between 20 K and 150 K with the stability of 0.01 K. (3) Sample surface is cleaned by ion bombardment in Xe glow discharge followed by annealing. We chose Xe/Ag(111) system as the first sample. Preliminary experiment on multilayer adsorption of Xe showed step-like dependence of <delta> on Xe pressure in gas phase. Each step corresponds to the formation of 1st, 2nd, and 3rd atomic layer. The parameter <delta> measured by null-ellipsometry is reproducible within <plus-minus> 0.2 ゜ , which value corresponds to the sensitivity of 1/10 atomic layer.

在物理吸附在原子平坦表面上的稀有气体系统中观察到准二维行为。该系统的统计热力学已经通过各种方法进行了实验研究：（1）吸收等温线（2）LEED、X射线和中子衍射、（3）量热法、（4）NMR等。但是，例如，无法将LEED测量的单晶表面结果与通过吸附等温线测量得到的膨胀石墨相图进行比较。这主要是因为实验的限制。本项目的目的是在该领域建立一种新的实验方法，即将椭偏技术应用于物理吸附的研究。椭圆光度法被认为在该领域带来了一个新的方面，因为它具有以下优点：（1）可以检测单晶表面上薄至1/100原子层的少量吸附物质，（2）对物理吸附系统的弱键无损，（3）对操作气压没有限制（从1个大气压到超高真空）。该项目构建的实验装置具有以下特点： 特点：（1）真空室采用铝合金制成，最终压力低于10^7 Pa。（2）样品温度可控制在20 K至150 K之间，稳定度为0.01 K。（3）通过Xe辉光放电离子轰击清洁样品表面，然后退火。我们选择Xe/Ag(111)系统作为第一个样品。 Xe多层吸附的初步实验表明，<δ>对气相中Xe压力的阶梯依赖性。每个步骤对应于第一、第二和第三原子层的形成。通过零椭偏仪测量的参数<delta>可在<plus-minus>0.2゜内再现，该值对应于1/10原子层的灵敏度。