【作者】 孟庆南；

【导师】 郑伟涛；

【作者基本信息】 吉林大学 ， 材料物理与化学， 2013， 博士

【摘要】 氮化锆(ZrN)和碳化锆(ZrC)薄膜具有出色的物理和化学性能使其可以被应用于各种极端条件，如宇航用耐高温材料和核反应中燃料颗粒的涂覆材料。此外，由于其高硬度耐磨损的特点也可以用于切削工具的保护涂层。ZrN和ZrC薄膜的高电导率和优秀的化学稳定性也是其能够胜任滑动电接触器件，如电刷、微电器件，电路开关和机动车的启动器。ZrN和ZrC薄膜可通过多种方法制备，其中最普遍易行的方法是磁控溅射方法。本文中首先将采用反应磁控溅射的方法制备多晶ZrN薄膜，并探究了晶体择优取向、相结构和薄膜应力、硬度之间的关系：在第二章中，通过改变基底偏压增加粒子能量进而向ZrN薄膜中引入不同大小的应力。以应力对ZrN薄膜微观结构和相结构的影响作为着眼点，通过热力学计算探究并建立应力、择优取向演变和相转变之间的关系。热力学计算结果表明应变能是ZrN薄膜择优取向演变和相转变的驱动力，在高应力状态下薄膜总是优先选择低应变能的取向或相生长；由于在沉积薄膜的过程中，残余应力不可避免的会被引入，而残余应力对硬度测量中接触点附近样品的塑性形变行为势必产生影响。因此，在第三章中我们选择ZrN薄膜借助于原子力显微镜对应力与硬度的关系进行研究。通过对比有应力样品和应力释放后样品的最大载荷和接触面积来研究应力在硬度测量过程中的作用，并在此基础上探究应力对纳米压痕硬度测量的影响；在氮化物超硬薄膜的研究中多层膜体系通常表现出超常的硬度，因此在第四章中使用磁控溅射制备了ZrN/SiNx多层膜用以进一步提升ZrN薄膜的硬度，并探究了界面偶极现象对多层膜硬度增强的贡献。首先对ZrN/SiNx双层膜进行XPS深度剖析以表征界面电子状态，其结果表明ZrN/SiNx界面处出现电子极化现象，电子从ZrN层向SiNx层转移。此外，界面极化程度受SiNx层密度的影响。相应ZrN/SiNx多层膜的硬度测量表明多层膜的硬度增强和界面电子极化之间存在一定的内在联系；在实际生产应用中薄膜的耐摩擦性能直接决定了薄膜的使用寿命，ZrN薄膜的硬度优异但在耐磨擦性能上略显薄弱。与氮化物薄膜相比，碳化物薄膜的耐磨损性能更为优秀。因此，在后面的两章中通过磁控溅射制备了ZrC和ZrSiC薄膜，并研究了薄膜中微观结构、化学键态、应力、硬度、摩擦学性能和电学性能之间的关系：在第五章中通过改变溅射过程中CH4流量制备了具有不同碳含量的ZrC薄膜。在碳含量较低时薄膜表现为典型的nc-ZrC/a-C纳米复合结构，当碳含量高于86at.%时薄膜转变为非晶结构。薄膜的力学、摩擦学和电学性能明显依赖于纳米复合结构中a-C的含量。大量的a-C将导致电阻率快速增加且硬度下降，但其润滑作用会使得摩擦系数被大幅度改善。此外a-C相中碳原子的化学键态同样对性能有着一定的影响，较大的sp2/sp3将有助于释放薄膜的应力和改善电学性能。与其他典型的过渡金属碳化物纳米复合膜相比(如nc-MeC/a-C, Me=Ti, Nb)ZrC薄膜表现出更低的摩擦系数。尽管ZrC薄膜表现出优秀的耐磨擦性能，但其硬度与ZrN薄膜相比仍有所下降，而Si的加入将有可能在维持低摩擦系数的同时改善ZrC薄膜的硬度。因此在第六章中使用共溅射制备了ZrSiC非晶薄膜，系统的讨论了薄膜成分和化学键态的变化对薄膜结构和性能的影响，并与第五章中ZrC薄膜的结果进行对比。分析结果表明ZrSiC的电阻率表现出与ZrC类似的变化趋势，但硬度和摩擦系数的结果明显不同。在ZrSiC中硬度对a-C含量变化不敏感却强烈的依赖于Si-C键的含量。ZrSiC薄膜在摩擦过程中存在明显的摩擦化学反应，转移层中a-C的含量对摩擦性能的改善起着不可忽视的作用。但另一方面，剥层磨损的出现将抑制甚至恶化薄膜的摩擦学性能。转移层中a-C的含量以及剥层磨损的程度共同支配着ZrSiC的摩擦系数。更多还原

【Abstract】 Zirconium nitride and zirconium carbide have excellent physical and chemicalproperties suggesting a potential use in extreme environments, e.g. as-hightemperature aerospace material or as coating for fuel particles in high temperaturenuclear reactors. In addition, zirconium nitride and zirconium carbide can be used as aprotective film in cutting tools because of their high hardness and wear resistance.Furthermore, the high electrical conductivity combined with a good chemicalinertness suggest a potential use in sliding electrical contacts, such as brushes,microelectromechanical devices, circuit breakers and motor vehicle starters.Zirconium nitride and zirconium carbide films can be deposited by many techniquesand the most widely used techniques is sputter.Based on these issues, we start to deposite polycrystalline ZrN films, andinvestigate the relationship among preferred orientation, phase structure, stress andhardness.In Chapter2, the stress of zirconium nitride films is controlled by changing theenergy of sputtered atoms. The influence of stress on the evolution of microstructure,such as prefer orientation and phase transition, has been studied. Thethermodynamic calculations are used to understand the evolution of the preferredorientation. Also the mechanism of a phase transition from substoichiometric tooverstoichiometric films is revealed. According to the thermodynamic calculations,with increasing strain energy, induced by an increase in Vb, the preferred orientationchanges from ZrN(200) to ZrN(111). Being high enough, the strain energy becomes adriving force for a phase transition of the film.The residual stresses are often unintentionally introduced into films during thedeposition process. Therefore, the influence of the residual stress on deformationbehavior (pile-up) around the indent on the surface of zirconium nitride film has beeninvestigated in Chapter3. Atomic force microscopy (AFM) is performed to reveal thebehavior of deformation (e.g. pile-up) around the indent on the surface of the film. The pile-up occurs for the film under a compressive stress, and is enlarged withincreasing the compressive stress, which leads to that the actual contact area byindenter significantly deviates to the one calculated by Oliver–Pharr method. Aftercorrecting the contact area contributed by pile-up via AFM experiments, the residualstress does not affect the nanoindentation measured hardness and modulus.In Chapter4, the hardness enhancement mechanism for ZrN/SiNx multi-layershas been studied. First, ZrN/SiNx double-layers with different density of SiNx layers,which is controlled by applying different substrate bias for depositing SiNx layers, aresynthesized for investigating the interfacial electronic structure. Results indicated thatthe interfacial electrostatic polarization existed as the ZrN and SiNx bond with eachother to form a heterojunction, since the electrons donated from ZrN layer to SiNxlayer. Moreover, the degree of polarization is affected by the density of SiNx layer.The corresponding ZrN/SiNx multi-layers are deposited for studying the correlationbetween interfacial electronic structure and mechanical properties. The results ofhardness test imply that the interfacial electrostatic polarization would enhance thehardness to a certain extent.The working life of film on practical application is depanded on the tribologicalproperties. ZrN film has an excellent hardness, but does not have good tribologicalproperties. Comparing to ZrN, ZrC film shows an outstanding tribological properties.Therefore, in the following chapters we have deposited ZrC and ZrSiC films, andinvestigeted the relationship among microsturcture, chemical bonding state, stress,hardness, tribological properties and electrical properties.In Chapter5, Zirconium carbide films have been deposited on silicon (100)substrates using CH4as a carbon source. The films exhibit a typical nanocompositestructure consisting of nanocrystalline ZrCx(nc-ZrC) grains embedded in a matrix ofamorphous carbon (a-C) at low carbon content. Almost no crystalline phase can befound for carbon contents above86at.%. The mechanical, tribological and electricalproperties of the films showed a significant dependency on the amount of the a-C inthe nanocomposite structure. A larger amount of a-C gives rise to reduced hardnessand higher resistivity of the film. However, both friction coefficient and wear resistance are improved by increasing the content of the surplus a-C. The influence ofbinding state of excess a-C phase on the properties has also been investigated. Alarger sp2/sp3ratio was beneficial to relax the stress and improve the electricalproperties. The Zr-based films exhibited lower friction coefficients thannanocomposites films based on e.g. Ti suggesting a potential application for thismaterial in sliding contacts.In Chapter6, ZrSiC films with different Zr content and Si/C atomic radio havebeen deposited by magnetron co-sputtering. The relationship between composition,microstructure, chemical bond state, hardness, friction, and resistivity has beenstudied. Also, the results for ZrSiC films have been compared with those for ZrCfilms in Chapter5. The resistivity for ZrSiC films is similar to that for ZrC films. Themain difference is the influence of a-C content on hardness and friction. The affectionof a-C content on hardness for ZrSiC films is not obviously, because themicrostructure is XRD amorphous. The hardness of ZrSiC films depends on the Si-Cbond fraction in the films. The wear chemical reactive has been found during the weartest, and the a-C fraction in the transfer layer is also contributed to improve thefriction for ZrSiC films. However, the friction of some films with higher zirconiumcontent or silicon content shows an abnormal increase with the increase in a-C content,which is attributed to the existence of delamination. In summary, not only the a-Ccontent in transfer layer but also the level of delamination controls the friction ofZrSiC films.更多还原