Growth, Characterization, and Properties of Epitaxial Metal/Nitride Superlattices

本研究的目的是研究外延单晶氮化物/金属超晶格的强化机制，这些层具有不同的滑移系统。材料体系有NbN/Mo、NbN/W、VN/Cr、AlN/Mo和AlN/W，提供了立方-B1/立方体心立方和六方纤锌矿/立方体心立方两种组合。同时使用(001)和(111)取向的氧化镁和钨衬底。当被立方(001)层包围时，将确定AlN是否可以在立方结构中生长。由于超晶格结构，这些材料应该表现出很大的强度和硬度提高。涂层特性、强度和硬度之间的相关性将为强化机制提供新的信息。层晶格失配的变化(在含有合金VN-NbN或Cr-Mo层的超晶格中)被用来产生既有共格界面又有非共格界面的超晶格。与以前研究的氮化物/氮化物超晶格不同，这些层是不相容的，因此结构在高温下是稳定的，并保持其理想的特性。研究了氮化物/氮化物超晶格的结构和性能随退火时间和温度的变化规律，并与氮化物/氮化物超晶格的结果进行了比较。%对氮化物/氮化物超晶格有很大的技术兴趣，早期的结果表明，在刀具中的氮化物涂层比传统的氮化物涂层有显著的改进。

The aim of this research is to investigate strengthening mechanisms in deposited epitaxial single-crystal nitride/metal superlattices where the layers have different slip systems. Materials systems are NbN/Mo, NbN/W, VN/Cr, AlN/Mo, and AlN/W, providing both cubic-B1/cubic-BCC and hexagonal-wurtzite/cubic-BCC combinations. Both (001) and (111) oriented MgO and W substrates are used. It will be determined if AlN can be grown in a cubic structure when surrounded with cubic (001) layers. These materials should exhibit large strength and hardness enhancements due to the superlattice structure. Correlations between layer characteristics, strength, and hardness will provide new information on strengthening mechanisms. Changes in the layer lattice mismatch (in superlattices containing alloy VN-NbN or Cr-Mo layers) are used to produce superlattices with both coherent and incoherent interfaces. Unlike previously-studied nitride/nitride superlattices, these layers are immiscible such that the structures are stable and retain their desirable characteristics at high temperatures. Structure a nd property studies versus annealing time and temperature are carried out, and the results compared with results from nitride/nitride superlattices. %%% There is technological interest in nitride/nitride superlattices where early results show dramatic improvements over conventional nitride coatings in cutting tools.