Phase transitions between 2-and 3-dimensions in rare gas thin films on a surface of a metal single crystal.

我们研制了一套可在超高真空和低温环境下进行物理吸附体系椭偏光谱研究的实验装置。在<-9>不使用实验元件的情况下，获得了低至10^ Pa的极高真空度，<-8>在实验条件下，真空度可达10^ Pa。本计画将物理吸附稀有气体的铂单晶安装在一台氦气流动式低温恒温器上。研制了一套采用PID控制器的自动调零椭偏仪系统，该系统对离子轰击和退火等表面清洗过程中的表面状态变化具有足够的跟踪能力。在10 ~ 10 μ Pa的压力范围内，获得了Pt/Pt（111）在Pt的三相点以上的吸附等温线<-7><-2>。我们的椭偏仪系统的上述性质使得观察Layr成为可能 ...更多信息 从亚单层到厚层的生长过程，其中平衡压力几乎等于体饱和蒸汽压。Pt与Pt+Rh热电偶连接到Pt晶体，因为其在退火过程中在高温下的耐久性。然而，热电偶在低温范围内的相对低的热电功率使得难以在吸附实验中测量精确的温度。我们准备用铂电阻温度计和热电偶相结合的方法，对Ne、Ar、Kr、Ar、CH_4等几种吸附剂-吸附质体系在Pt（111）、Ag（111）等表面上的相图进行测量。将所得吸附等温线与三相点或临界点的相对温度、与饱和蒸汽压的相对压力、晶格参数之间的比值等进行比较，从这些结果中，我们将推导出2d-3d和润湿转变、表面粗糙化和熔化等的经验规律。最后我们将讨论这些表面现象的理论模型。少

We have developed the new experimental equipment for ellipsometric studies of physisorption system, which can be operated under ultra-high vacuum and low temperature environment. Extremely high vacuum as low as 10^<-9> Pa is achieved without experimental components and the range of 10^<-8> Pa under experimental conditions. A platinum single crystal, on which rare gas is physisorbed, is mounted on a helium gas flow type cryostat that was designed and developed in this project. The ellipsometer system with automatic null method by PID controller was developed.We have found the enough traceability of the automatic null ellipsometer for the change of surface conditions during the cleaning process, ion bombardment and annealing, of the surface. The adsorption isotherm of Xe/Pt (111) at temperatures above the triple-point of Xe was obtained in the wide pressure range between 10^<-7> Pa and 10^<-2> Pa. The above-mentioned properties of our ellipsometer system makes it possible to observe layr … More growth from a submonolayr to thick layr where equilibrium pressure is nearly equal to the bulk saturation vapor pressure.The present experimental problem is temperature measurement. A Pt vs.Pt+Rh thermocouple is attached to the Pt crystal because of its durability at a high temperature during the annealing process. However, the relatively low thermoelectric power of the thermocouple in a low temperature range makes it difficult to measure a precise temperature in the adsorption experiment. We are preparing an alternative method : a combination of a Pt resistance thermometer and thermocouple.We are proceeding the measurement of a phase diagram of several adsorbent-adsorbate systems, Ne, Ar, Kr, Xe, and CH_4 on Pt (111), Ag (111), etc. for example. The obtained adsorption isotherms will be compared in the term of a relative temperature to the triple point or the critical point, a relative pressure to the saturation vapor pressure, a ratio between the lattice parameters, etc. From these results, we will deduce empirical laws of 2d-3d and wetting transition, surface roughening and melting, etc. On the basis of these observations, we will finally discuss the theoretical model of these surface phenomena. Less