Film-thickness effect of Ag lubricant layer in the nano-region
Film-thickness effect of Ag lubricant layer in the nano-region
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DOI：
10.1016/s0043-1648(03)00530-1
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发表时间：
2004-06
期刊：
影响因子：
5
通讯作者：
M. Goto;F. Honda
中科院分区：
文献类型：
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作者：
M. Goto;F. Honda
在超高真空（UHV）条件下，用销板式摩擦磨损试验机研究了Si（111）-7 7表面上不同厚度Ag膜的摩擦学性能。反射高能电子衍射（RHEED）结果表明，室温下沉积在Si（111）-7 7表面的Ag膜形成二维纤维晶体结构，并随着膜厚的增加逐渐生长为单晶Ag膜。170 nm的Ag膜的摩擦系数为0.06-0.08，当厚度减小到8.4-1.5nm时，摩擦系数减小到0.01-0.03。在厚度从1.5 nm减小到0 nm时，摩擦系数随着厚度的减小而增大。清洁的Si（111）表面显示出0.8的摩擦系数。在1.5nm Ag膜和170 nm Ag膜上的磨损痕迹宽度是相当的。俄歇电子能谱（AES）测量表明，磨损后的轨道的Ag MNN强度比非滑动表面为0.9-0.6。将0.4和1.5nm薄膜在500°C下退火，薄膜的形貌发生了显著变化，一个原子层的Ag形成了3 × 3Ag表面（3Ag），残留的Ag形成了细小的晶体。随着薄膜厚度的增加，晶体的数量增加。几乎所有的0.4nm退火的Ag膜区域都是3Ag表面，并且该膜显示出0.1的摩擦系数。3Ag被细小的Ag晶体覆盖，具有1.5nm的退火膜，其表现出小于0.01的摩擦系数。在纳米厚度区域的Ag膜的高润滑性机制进行了讨论，在其机械性能，如取决于膜厚度的Ag的剪切强度。
The tribological properties of Ag films with a wide range of thicknesses on an Si(111)-7×7 surface have been studied using a pin-on-plate type tribometer under ultrahigh-vacuum (UHV) conditions. Reflection high-energy electron diffraction (RHEED) patterns show that the Ag film deposited on an Si(111)-7×7 surface at room temperature (RT) forms a two-dimensional fiber crystal structure and gradually grows into a single-crystal Ag film as the film thickness increases. The coefficient of friction of 170nm as-deposited Ag film was 0.06–0.08, and that coefficient decreased to 0.01–0.03 when the thickness decreased to 8.4–1.5nm. In the thickness decreased from 1.5 to 0nm, the coefficient of friction increase as the thickness decreased. The clean Si(111) surface showed a coefficient of friction of 0.8. The worn track widths on both the 1.5nm Ag film and 170nm Ag films were comparable. Auger electron spectroscopy (AES) measurements showed that the Ag MNN intensity ratio of the worn track to non-slide surfaces was 0.9–0.6 after frictional experiments. By annealing the 0.4 and 1.5nm films at 500°C, the morphology of the film changed significantly; one atomic layer of Ag formed a 3 × 3 Ag surface (3 Ag), and the residual Ag formed fine crystals. The population of the crystals increased as the film thickness increased. Virtually all of the 0.4nm annealed Ag film area was 3 Ag surface, and the film showed a coefficient of friction of 0.1. The 3 Ag was covered by fine Ag crystals with the 1.5nm annealed film, which showed a coefficient of friction less than 0.01. The high-lubricity mechanism of the Ag film in the nanometer-thickness region is discussed in terms of its mechanical properties such as the shear strength of Ag depending on the film thickness.