Investigation On Microstructure, Hardness And Tribological Properties Of TaN And Ti_1-xAl_xN Thin Films

Deposition of thin films by sputtering is a complex process, sensitive todeposition parameters. Due to reactivity and bombardment of particles with highenergy, phase transition, preferred orientation and compositional variation will takeplace during film growth, and many thin films’ properties (such as hardness, adhesiveforce, tribological behaviors, optical, electrical, magnetic properties etc.) depend onphase structure, preferred orientation. Although lots of different thin films can bedeposited by sputtering, it is still a challenging topic to control films’ growth tocontrol phase structure, preferred orientation, microstructure by changing theexperimental parameters. To investigate the deposition parameters’ effects on filmsphase structure, preferred orientation, microstructure and mechanical properties, wetuned the N2flow rate, bias voltage and deposited many TaN, Ti1-xAlxN thin films byDC reactive magnetron sputtering. The main results are summarized as following:(1) The N2flow rate has significant influence on deposition rate, microstructure,morphology and mechanical properties, and we can gain TaN0.1phase, γ-Ta2N phase,coexistence of γ-Ta2N and-TaN phase,-TaN phase; however, the deposition ratedecreases dramatically because of the serious nitridation on target surface;；thecompressive stress in films with hexagonal structure γ-Ta2N phase contributes for hehardness increase; the tribological behaviors of films deposited at different N2flowrate depend on the compressive stress, phase structure distribution and H3/E2of films.The factors above interact with each other, leading the wear tracks of TaN0.1film at N22sccm and Ta2N film at N25sccm to be intensive and distinct but the wear tracks ofcubic TaN films at N230sccm,45sccm,60sccm broad and dispersive.In the following experiments to investigate the bias voltage’s influence on films,the roughness on film surface and wear resistance decrease, the (111) preferredorientation appears, hardness and compressive stress increases with bias voltage rising.Through thermodynamic calculation, the preferred orientation (111) tends to appear to release strain energy, so does preferred orientation (200) to decrease interface energy,and the competence between strain energy and interface energy determine thepreferred orientation in films; it is more likely for particles with high energy tomigrate on the films surface with increase of bias voltage and this contributes to thedensification of films and roughness decrease on surface; the preferred orientation(111) and residual compressive stress in films better hardness, however the high infilms worsen the films’ wear resistance.(2) TiAl and Ti3Al targets have been used to deposit a variety of TiAlN andTi3AlN films by DC magnetron sputtering In Ti1-xAlxN films, the Al atoms replacethe Ti atoms in TiN crystal structure to form Ti-Al-N solid solution. According toXRD results, the grain in TiAlN and Ti13AlN films all have FCC crystal structure. TheTi content decreases but Al content increases in Ti1-xAlxN films when N2flow raterises. And the films grow denser when bias voltage is applied to the substrate whichcauses the particles reaches substrate with higher energy. The grain growthmechanism, strain energy and interface energy codetermine crystal orientation infilms. Preferred orientation, intensification of texture and compressive stress in filmsall better films’ hardness.。...