Research On Preparation And Properties Of NiTi/ZnO Intelligent Thin Films

In this thesis, based on the present status and future development of intelligent materials for MEMS applications, NiTi/ZnO multilayer films were prepared by RF magnetron sputtering process. The microstructure, composition, mechanical properties and damping characteristics of the multilayer films were invesitgated by XRD, SEM, EDS, DMA, Nano Hardness Tester and scratch test methods.At first, the influences of main processing parameters of magnetron sputtering, such as substrate temperature, input power and gas pressure, on the film thickness, microstructure, composition and mechanical properties of NiTi films were thoroughly investigated. The optimized deposition parameters of NiTi films were obtained, namely substrate temperature: 500℃, input power: 250W, gas pressure: 0.19Pa, Ar flowrate ratio: 10sccm, distance between target and substrate: 50cm, depositing time: 1h. The crystallized NiTi thin films can be prepared in situ anealing at 500℃. The value of elastic modulus and transmutation ratio of the NiTi films prepared with these parameters are 69.7GPa and 38.2%, respectively, obtained from the nanoindentation tests. The critical adhesion forces exist between the NiTi coatings and the Quartz substrates is 35.26N, based on the analysis of scratch tests.Secondly, by combining the composite multiplication principle of functional material theory and the optimized depositing parameters of NiTi films, a novel structure of Quartz/ZnO/NiTi and Quartz/NiTi/ZnO multilayer thin films were fabricated. The microstructure, interfaces, crystallization behaviors of the multilayer thin films were also investigated. The results show that the structure of Quartz/ZnO/NiTi represents better surface morphology. Furthermore, the critical adhesion forces between the multilayer thin films and Quartz substrates are 45.75N and 40.15N respectively, based on the analysis of scratch tests.Finally, the damping capability of Quartz/NiTi and Quartz/ZnO/NiTi were studied with the swing resonance methods, based on the analysis of DMA. The rule that the damping capability changes with the frequency and amplitude is investigated. These results show that the damping capability of Quartz/ZnO/NiTi differs greatly from Quartz/NiTi. The frequency response of Quartz/NiTi is within 7Hz, while the frequency response of Quartz/ZnO/NiTi is almost 20Hz. The damping amplitude of Quartz/ZnO/NiTi is 1.0V, while that of Quartz/NiTi is only 0.6V. These results demonstrate that the multilayered structure of Quartz/ZnO/NiTi deposited by RF magnetron reactive sputtering process shows better damping capability.