Atomic Behavior of Oxygen Adsorption and Its Effect on the Mitigation of Metallic Adhesion

用场离子显微镜(FIM)研究了氧在W针尖上的吸附行为，并扩展到氧吸附对W与Au的附着力的影响的研究。氧在中心(011)面上的吸附比在功函数较低的其他平面上的吸附要小。由于[110]的功函数最高，吸附发生在最后位置。场发射电流测量和俄歇电子能谱对氧在钨表面吸附的研究表明，在200朗缪尔(L)照射下，氧在钨表面的覆盖率是统一的。在超高真空条件下，用有无吸氧的W-针尖进行了粘接接触。结果表明，当氧暴露至60L时，粘附力随氧暴露时间的增加而降低，L氧暴露为16L时，粘附力达到中等水平。因此，附着力取决于氧气的覆盖度。用场蒸发技术研究了粘附型晶格缺陷的深度。当超过200 L时，未检测到粘附力，也未检测到W原子的变形。这项研究的结果可以推广到空间摩擦学所涉及的问题，特别是在氧气存在的500公里高度工作的机械元件的摩擦和磨损的缓解方面。

A field ion microscope (FIM) has been used to investigate the behavior of oxygen adsorption on W-tip, and extended to the study of the effect of oxygen adsorption on adhesion of W to Au. The adsorption of oxygen on the central (011) was found to be less than those on the other planes with lower work functions. Owing to the highest work function of the [110], the adsorption occurred as the last site. Field emission current measurement and Auger electron spectroscopy on the adsorption of oxygen on tungsten showed that the coverage is unity at an exposure of 200 Langmuirs (L). An adhesion contact in ultrahigh vacuum of the FIM was carried out using a W-tip either with or without oxygen adsorption. It was found that adhesion force decreased with increasing oxygen exposures up to 60 L. With an oxygen exposure of 16 L, an intermediate adhesion resulted. Adhesion is thus dependent upon the coverage of oxygen. The depth of adhesion-induced lattice defects was studied using the field evaporation technique. Over 200 L, adhesion force was not detectable, nor was distortion of W atoms. The results obtained in this study could be extended to the problems involved in space tribology, especially to the mitigation of friction and wear of machine elements which function at an altitude of 500 km where oxygen exists.