Water adsorption at ionic crystal surfaces

1.利用扫描力显微镜(SFM)的非接触监测模式，研究了水在常温和空气中碱金属卤化物表面的吸附行为。我们发现在LiF(001)表面上形成了水滴图案，然后形成了均匀的薄膜，这与在BaF_2(111)表面上观察到的情况类似。然而，在NaC(001)表面上似乎没有水滴图案。从NaF(001)表面的SFM图像显示了复杂的水滴图案特征，导致形成了不同厚度的薄膜。这些结果表明，在水-水相互作用强于水-基质相互作用的情况下，水滴容易在表面生长，但在相反的情况下，将形成具有单分子层或亚单分子膜的均匀薄膜。我们研究了水在电子辐照的NaF(001)表面的吸附。尽管水在非电子I-…上的吸附辐照程度较高的表面在几个小时内延续了水岛的复杂特征，水在电子辐照表面上的吸附在1h内从水岛图案快速形成为均匀的膜。这是因为被电子照射的表面有表面羟基中心。通过电子辐照技术，可以控制NaF(001)表面的润湿性。我们发现了随着载荷的增加而产生的逐级摩擦力以及摩擦力沿扫描方向的各向异性。这表明了尖端和表面之间的有效相互作用区域的离散性。这些实验结果也阐明了随着载荷的增加，表面变形和/或损伤对摩擦的影响。我们用扫描力显微镜(SFM)研究了在干燥空气中极低载荷下在KCl(001)表面上形成的C_&lt；60&gt；膜的纳米摩擦学行为。已经观察到，SFM针尖根据其扫描方向经历分子分辨的粘滑运动。0.024nN载荷下的摩擦力约为2nN载荷下的六分之一，这表明由于单分子针尖与样品的接触，C_&lt；60&gt；分子发生了滚动和/或平移。较少

1. We have investigated the behavior of water adsorption on alkali halide surfaces in air and at room temperature observed with the non-contact monitoring mode of a scanning force microscope (SFM). We have found a formation of water droplet pattern on LiF(001) surface and thereafter the formation of a uniform film, in the similarway as observed on the BaF2(111) surface. However, there appears to be no water droplet pattern on the NaC(001) surface. The SFM image from the NaF(001) surface has revealed complicated features with water droplet pattern resulting in films formed with different thickness. These results indicate that in those cases where a water-water interaction is stronger than a water-substrate interaction, water droplets would grow easily on the surfaces, but in the opposite case, the uniform film with a monolayer or submonolayer would be formed.2. We have researched water adsorption on an electron irradiated NaF(001) surface. Although water adsortion on the non- electron i … More rradiated surface continues a complicated feature with water islands over several hours, water adsorption on the electron irradiated surface has a fast formation in lh from a water island pattern to a uniform film. This is because the surface irradiated by electrons has surface OH-centers. It is possible, by the electron irradiation technique, to control the wettability of the NaF(001) surface.3. We have discovered the stepwise frictional forces with increasing load and the anisotropy of the frictional forces via a scanning direction. This indicates the discreteness of the effective interaction area between a tip and surface. These experimental results also clarify the influence on the friction due to a surface deformation and/or damage with increasing loads.4. We have studied the nanotribological behavior of C_<60> films formed on a KCl(001) surface at an extremely low load in dry air, using scanning force microscopy (SFM). it has been observed that the SFM tip undergoes molecularly resolved stick-slip motions depending on its scanning direction. The frictional force at 0.024nN load is about one-sixth that at 2nN load, which indicates rolling and/or translation of a C_<60> molecule due to a single-molecule tip-sample contact. Less