Metal incorporation in sputter-deposited MoS_2 films studied by extended x-ray absorption fine structure
Metal incorporation in sputter-deposited MoS_2 films studied by extended x-ray absorption fine structure
复制标题
DOI：
10.1557/jmr.1995.2091
复制
发表时间：
1995-08
影响因子：
2.7
通讯作者：
J. R. Lince;M. R. Hilton;A. Bommannavar
中科院分区：
文献类型：
--
作者：
J. R. Lince;M. R. Hilton;A. Bommannavar
用MoS_2溅射金属和形成金属/MoS_2多层膜制备固体润滑膜，计划用于下一代航天器固体润滑装置，包括万向节和传感器轴承、执行器和滑动电触点。与未添加添加剂的薄膜相比，膜的密度和磨损寿命有所提高，但密度增强的机理尚不清楚。扩展x射线吸收精细结构（EXAFS）技术是理想的阐明这些不良结晶膜的结构。我们分析了Ni含量为0、2和10%的MoS_2薄膜，以及Ni/MoS_2和Au(Pd)/MoS_2多层薄膜。在Mo-K吸收边得到的结果表明，含金属薄膜主要由与未添加金属的类似薄膜相同的纳米晶相组成：纯MoS_2和MoS_2−x O_ x相。MoS_2−x O_ x与MoS_2是同构的，MoS_2晶格中O原子取代了S原子。在Ni- k吸收边获得的EXAFS数据表明，Ni没有与MoS_2 - x O_ x和MoS_2发生化学反应，而是形成了无序的NiO_ x相。然而，随着Ni含量的增加，Ni溅射膜在MoS_2−x O_ x相中Mo-Mo键长减小，这可能是由于Ni比MoS_2更优先氧化所致。这些Ni溅射膜的EXAFS结果显示，随着Ni含量的增加，薄膜在近程数量级上有较小的下降，而x射线衍射结果显示，薄膜在远程数量级上有较大的下降。结果表明，ni共溅射薄膜的致密化是由于在成核的MoS_2−x O_ x /MoS_2晶体边缘形成NiO_ x，限制了薄膜内可获得的晶粒尺寸。
Solid lubricant films produced by cosputtering metals with MoS_2 and by forming metal/MoS_2 multilayers are being planned for use in the next generation of solid lubricated devices on spacecraft, including gimbal and sensor bearings, actuators, and sliding electrical contacts. The films exhibit increased densities and wear lives compared to films without additives, but the mechanism of density enhancement is not well understood. The extended x-ray absorption fine structure (EXAFS) technique is ideal for elucidating the structure of these poorly crystalline films. We analyzed MoS_2 films cosputtered with 0, 2, and 10% Ni, as well as Ni/MoS_2 and Au(Pd)/MoS_2 multilayer films. The results obtained at the Mo-K absorption edge showed that the metal-containing films comprised predominantly the same nanocrystalline phases present in similar films without added metals: pure MoS_2 and a MoS_2− x O_ x phase. MoS_2− x O_ x is isostructural with MoS_2, with O atoms substituting for S atoms in the MoS_2 crystal lattice. For all Ni-containing films, EXAFS data obtained at the Ni-K absorption edge showed that the Ni had not chemically reacted with the MoS_2− x O_ x and MoS_2, but formed a disordered NiO_ x phase. However, Ni-cosputtered films showed decreasing Mo-Mo bond lengths in the MoS_2− x O_ x phase with increasing Ni content, probably due to preferential oxidation of Ni compared to MoS_2. EXAFS of these Ni-cosputtcred films showed only a small decrease in short-range order with Ni content, while x-ray diffraction showed a concurrent large decrease in long-range order. The results indicate that film densification in Ni-cosputtered films is caused by NiO_ x formation at the edges of nucleating MoS_2− x O_ x /MoS_2 crystallites, limiting the crystallite size attainable within the films.