【作者】 郭欣；

【导师】 郑伟涛；

【作者基本信息】 吉林大学 ， 材料物理与化学， 2016， 硕士

【摘要】 TaN是一种有良好的力学性能、高热稳定性和好的抗氧化性的材料,而TaN又具有十分复杂的相结构,结构的多样性将导致了薄膜性能的多样性,有必要建立TaN中相结构与力学性能、热稳定性和抗氧化性的内在联系。因此为了研究TaN薄膜的各性能与结构的关系,我们采用磁控溅射的方法制备一系列具有不同结构的TaN薄膜。此外,AlN薄膜具有非常好的抗氧化性和结构稳定性（稳定结构为六方结构）,常作为调质层与过渡金属氮化物（TMN）构成多层膜,以提高硬度和抗氧化能力,其中当AlN与具有NaCl型结构的过渡金属氮化物（TMN）结合形成多层膜时,会形成亚稳态的立方结构,这种TMN/AlN多层膜结构已经有了很多的研究。非晶结构与结晶结构的材料形成多层膜,会发生先外延再恢复成非晶结构的现象。非晶结构的出现阻断了外延生长,破坏了薄膜的结晶完整性。目前大多数关于这种结构的研究都围绕着多层膜的硬度增强现象以及对致硬原理的分析。而我们则考虑研究非晶层对薄膜抗氧化性的影响,因此,我们制备具有不同AlN层厚度的TaN/AlN多层膜。我们应用到的分析表征手段包括:XRD、XRR、HRTEM、SEM、纳米压痕、摩擦磨损,真空退火和空气中退火等。实验的结果发现:利用氮气为反应气体,改变Ar-N₂流量比制备了11个不同结构的TaN薄膜。它们的相结构经历了TaN0.1-Ta2N-ε-TaN-c-TaN-Ta₃N₅以及中间出现的两相混合的情况。随着氮气流量的变化,TaN薄膜的硬度值先增大后减小,硬度的最大值出现在TaNx-5样品处,为34.043±1.931GPa,其结构为c-TaN和ε-TaN的混合结构。而且TaNx-2到TaNx-5的硬度都超过了30GPa。高硬度值得获得是相结构和内应力的共同作用的结果。对相结构为TaN0.1、Ta2N、c-TaN、Ta3N5的样品进行摩擦磨损测试,发现TaN0.1的摩擦磨损性能远远低于其他几个样品,平均摩擦系数为0.51926远高于相结构为Ta2N、c-TaN和Ta3N5样品的0.3876、0.3381及0.3374;只有TaN0.1截面能够观察到明显的凹痕,其他样品的截面曲线几乎没有凹痕;TaN0.1的磨痕宽度是其他样品的2倍。这是样品硬度、模量、抗氧化性等因素共同决定的,而且在这几个因素都相同的情况,样品的摩擦系数严重影响了其磨损率的大小。TaN薄膜的起始氧化温度由700℃增加到750℃、800℃、850℃,随着氮气流量的增加,薄膜的抗氧化性也提高了。在高温退火的后,部分薄膜出现了相转变的现象,这是由于氧化物的产生造成的晶格失配、体积膨胀和应力积聚造成的。（1）选取具有c-TaN结构的TaN薄膜的实验参数（Ar/N₂=60/20）,改变AlN层的厚度,制备的5个TaN/AlN多层膜,调制周期分别为4nm/0.4nm,4nm/0.8nm,4nm/1.6nm,4nm/3.2nm,4nm/4nm。多层膜在4nm/0.4nm时具有c-TaN（111）和（200）的混合织构,随AlN层厚度的增加,多层膜转变为c-TaN（111）结构。通过HRTEM图像观察到,4nm/0.4nm的薄膜完全共格,晶格结构贯穿整个薄膜,而4nm/1.6nm的薄膜则出现了明显的非晶层,薄膜的结晶完整性被破坏。经测量非晶层的厚度约为0.89nm,则非晶结构的AlN在TaN薄膜上的外延生长的临界厚度大约为0.89nm。多层膜的硬度都高于混合法则计算值,但随着AlN层的厚度的增加而减小,这是多层膜中的应力和非晶层的出现共同作用的结果。对TaN/AlN纳米多层膜进行真空退火后,发现薄膜在高温条件下会发生界面处的扩散现象,对于AlN层过薄的4nm/0.4nm的多层膜来说,它在700℃退火后即失去了调制结构,而其他4个多层膜则很好地保持了调制结构,并且多层膜的硬度在退火后都先增大后略微减小,多层膜具有比较好的高温稳定性。最后,我们对TaN/AlN多层膜的抗氧化性进行了一个初步的探索,多层膜的起始氧化温度随着AlN层厚度的增加而增加,而保温对于多层膜的抗氧化性有很大的影响,30min的保温,就导致多层膜的起始氧化温度大幅下降。更多还原

【Abstract】 TaN is a kind of material with good mechanical properties,high thermal stability and good oxidation resistance.However,TaN also has a lot of complicated structures,which will lead to the diversity of film performance.So in order to study the relationship between properties and structures of the films,we preparing a series of films with different structures by adopting the method of magnetron sputtering.Al N coating is also a very outstanding material that own well oxidation resistance and very stable structure（stable structure as hexagonal phase）.When the Al N combine with the Na Cl type transition metal nitrides（TMN） to form a multilayer film,will form a metastable cubic structure which was studied a lot.Alternately depositing the amorphous structure and crystalline structure as a thin solid film,will firstly epitaxial and then back into amorphous.The presence of the amorphous structure blocking the epitaxial growth,in consequence broken the crystallization integrity.Nowadays, most of the researches on this multilayer structure are about the hardness enhancement and the principle of this phenomenon. While we consider the influence of amorphous layer on film oxidation resistance, therefore, we prepared TaN/Al N multilayer films with different Al N layer thickness. We applied to the analysis of the characterization methods include: XRR, XRD, HRTEM, SEM, nano indentation, friction and wear,vacuum annealing and annealing in the air, etc.Display the results of the experiment below:（1） Prepared TaN thin film with 11 different structures by using nitrogen as the reaction gas and changing the ratio of Ar-N₂ flow. Their phase structures have undergone TaN0.1- Ta2N- ε-TaN-c-TaN-Ta3N5 and the mixture of two phases. TaN film hardness value increases at first then a little bit decreases with the changing of nitrogen flow.The maximum hardness is 34.043±1.931 GPa in TaNx- 5 sample, whose structure is c- TaN and ε-TaN mixture. Moreover, hardness of TaNx- 2 to TaNx- 5are also more than 30 GPa. High hardness is the result of the phase structure and the joint action of internal stress. The TaN0.1 friction and wear behavior is much lowerthan other samples, the average friction coefficient is 0.51926 is too much higher than other samples（0.3876,0.3381 and 0.3374）.Only TaN0.1 can be clearly observed the dent, other sample cross section curve almost no dent and grinding crack width of TaN0.1 is twice as many as other samples. This phenomenon is owing to the sample hardness, modulus, oxidation resistance combined action, and when these factors are the same, the friction coefficient of sample seriously affect the value of the wear rate.TaN film’s starting oxidation temperature is from 700 ℃ to 750 ℃, 800 ℃, 850 ℃,with the increase of nitrogen flow, oxidation resistance of films are improved. After annealing, part of the film appeared the phenomenon of phase transition, which is caused by the generation of oxide lattice mismatch, the volume expansion and stress accumulation.（2） Choosing the same experimental parameters of c- TaN（Ar/N₂ = 60/20） from TaN experiment with changing the Al N layer thickness to preparae five TaN/Al N multilayer films, that which modulation period is 4 nm / 0.4 nm, 4 nm / 0.8 nm, 4 nm/ 1.6 nm, 4 nm / 3.2 nm, 4 nm / 4 nm,respectively. Multilayer film in 4 nm / 0.4 nm has c- TaN（111） and（200） texture, then increasing the Al N layer thickness, the multilayer film change into c- TaN（111） structure. Observed from HRTEM images, 4nm / 0.4 nm film completely coherent, lattice structure throughout the entire film,while 4 nm /1.6 nm film appeared obvious amorphous layer, the crystallization of film integrity was damaged. The measured thickness of the amorphous layer is about0.89 nm, indicating that the amorphous Al N is epitaxial on TaN film as long as its thickness below the critical thickness（0.89 nm）. The multilayer film hardness is higher than that of mixed law calculated value, meanwhile decreasing accompany with increasing the Al N layer thickness,this is the influence of film stress and the combined action of the presence of the amorphous layer. After vacuum annealing,TaN/Al N multilayer film was founded that there is a diffusion phenomena at the film interface during high temperature conditions.A 4 nm / 0.4 nm multilayer film, will lost modulation structure after 700 ℃ annealing, while the other four multilayers well maintained the modulated structure.Hardness of multilayer show rapidly increasesthen slightly decreases after annealing, multilayer films perform good high temperature thermal stability. Finally, we conducted a preliminary exploration about the oxidation resistance of TaN/Al N multilayer, initial oxidation temperature of the multilayer films increasing with the increase of the Al N layer thickness.Oxidation resistance has a great relationship with the thermal insulation holding time, 30 min insulation, leads to the initial oxidation temperature fell sharply.更多还原