本文選題：微波等離子體 + 化學氣相沉積��； 參考：《武漢工程大學》2016年碩士論文

【摘要】：隨著氣相沉積技術的發(fā)展,CVD金剛石已經(jīng)具備與天然金剛石相差無幾的優(yōu)異特性,在諸多技術領域擁有非常好的實際應用前景。微波等離子體化學沉積方法具有無極放電、對沉積環(huán)境不產(chǎn)生污染的特點,是制備微米、納米及超納米金剛石膜最為理想的方法之一。目前,國內(nèi)外研究學者將主要目光集中在如何進行金剛石膜的可控性生長方面,通過添加惰性氣體、控制甲烷濃度等方式進行相關研究,其根本目的在于控制薄膜制備過程中的內(nèi)在反應機制。二次形核作為金剛石膜生長過程中重要階段之一,其速率的高低對金剛石膜的生長速率、表面形貌、晶粒尺寸及薄膜質(zhì)量方面有不同程度的影響。因此研究如何控制二次形核現(xiàn)象,探究二次形核率的高低對于薄膜生長的影響具有重要意義。本研究利用韓國Woosinent公司R2.0-MPCVD設備及實驗室自制的石英鐘罩式MPCVD設備,分別討論了在惰性氣體(Ar)添加及典型氣氛條件(CH4/H2混合氣體)下如何控制薄膜生長過程中的二次形核現(xiàn)象,并分析了二次形核率的高低對于金剛石膜晶粒尺寸、質(zhì)量及晶面取向的影響。主要研究工作如下:在利用CH4/H2/Ar為氣氛環(huán)境生長金剛石膜時,當氬氣流量低于一定閥值(92.5sccm),制備得到的樣品表面形貌成為微米結(jié)構(gòu)。在氬氣流量由80.0sccm向92.5sccm增加的過程中,微米級晶粒晶界處出現(xiàn)少量由二次形核現(xiàn)象產(chǎn)生二次晶核。惰性氣體Ar的添加對控制二次形核現(xiàn)象有一定影響:當Ar流量增加到95.0sccm以上時,二次形核現(xiàn)象得到促進,晶界處晶核增加,抑制了初始晶粒的長大,晶粒尺寸急劇下降。當Ar流量為95.0sccm時,薄膜表面逐漸呈現(xiàn)團聚體構(gòu)成的納米金剛石形貌;特別是當Ar流量增加至97.5sccm時,薄膜呈現(xiàn)出由二次形核長大的晶粒構(gòu)成的“針狀”的超納米級金剛石形貌。在高Ar流量條件下(95.0sccm)沉積金剛石膜,由于等離子體中H原子含量所占的比例較小,對沉積過程中的非金剛石相刻蝕效果變差,使得最終沉積的樣品中金剛石相相對含量降低,非晶碳和石墨含量增加。同時薄膜表面主要顯現(xiàn)(111)晶面。在利用CH4/H2典型氣氛環(huán)境條件生長金剛石膜時,在增加CH4濃度的過程中,金剛石結(jié)構(gòu)和特性出現(xiàn)明顯改變。當CH4濃度由1.0%增加到2.5%時,因CHx基團濃度增加而堆積的二次晶粒增多,促進了二次形核現(xiàn)象,從而引起金剛石膜晶粒尺寸急劇下降,同時膜層中非金剛石相含量隨之增加,薄膜質(zhì)量明顯變差。當CH4濃度≤1.5%時,金剛石晶面取向以(111)面和(220)面為主,其中(111)面強度遠遠高于(220)面;CH4濃度≥2.0%時,從XRD圖可以看到,金剛石膜晶面主要以(111)面為主,雖然部分金剛石顯露為(220)和(311)晶面,但薄膜整體呈現(xiàn)(111)取向,這說明CH4濃度的增加引起的二次形核對金剛石的晶面取向影響不大。
[Abstract]:With the development of vapor deposition technology CVD diamond has the same excellent characteristics as natural diamond and has a very good application prospect in many technical fields. Microwave plasma chemical deposition is one of the most ideal methods for the preparation of micron nanocrystalline and ultrananocrystalline diamond films due to the characteristics of electrodeless discharge and no pollution to the deposition environment. At present, researchers at home and abroad are focusing on how to control the growth of diamond films, by adding inert gas, controlling methane concentration and other ways. Its fundamental aim is to control the internal reaction mechanism in the preparation of thin films. Quadric nucleation is one of the most important stages in the growth of diamond films. The growth rate, surface morphology, grain size and film quality of diamond films are affected by the rate of growth. Therefore, it is of great significance to study how to control the phenomenon of quadratic nucleation and to explore the influence of the rate of quadratic nucleation on the growth of thin films. In this paper, using the R2.0-MPCVD equipment of Woosinent Company of Korea and the quartz bell type MPCVD equipment made by our laboratory, we discussed how to control the quadratic nucleation in the process of thin film growth under the conditions of (Ar) addition and typical atmosphere (CH4 / H2 mixed gas), respectively. The influence of the secondary nucleation rate on the grain size, quality and orientation of diamond films was analyzed. The main research work is as follows: when the diamond film is grown in the atmosphere of Ch _ 4 / H _ 2 / ar, the surface morphology of the sample becomes micron when the argon flow rate is lower than a certain threshold (92.5sccm). In the process of argon flow rate increasing from 80.0sccm to 92.5sccm, a small amount of secondary nucleation occurs at the grain boundary of micron grain. The addition of ar has a certain influence on the control of quadratic nucleation: when ar flow rate is higher than 95.0sccm, the secondary nucleation is promoted, the nucleation at grain boundary increases, the initial grain growth is restrained, and the grain size decreases sharply. When ar flow rate is 95.0sccm, the surface of the film gradually presents the morphology of nano-diamond composed of agglomerates, especially when ar flow rate is increased to 97.5sccm, the film presents a "needle-like" ultrananocrystalline diamond morphology composed of grains grown by secondary nucleation. Under the condition of high ar flow rate (95.0sccm), due to the small proportion of H atom in the plasma, the etching effect of the non-diamond phase in the deposition process is poor, which results in the decrease of the relative content of diamond phase in the final deposited sample. The content of amorphous carbon and graphite increased. At the same time, the surface of the film is mainly (111) crystal surface. When diamond films were grown under the typical atmosphere of Ch _ 4 / H _ 2, the structure and properties of diamond films changed obviously when the concentration of Ch _ 4 was increased. When the concentration of Ch _ 4 increased from 1.0% to 2.5%, the secondary grains accumulated with the increase of Ch _ x group concentration increased, which promoted the phenomenon of secondary nucleation, which led to the sharp decrease of grain size of diamond film and the increase of the content of non-diamond phase in the film layer. The quality of the film becomes worse obviously. When the concentration of Ch _ 4 鈮，

本文編號：2116502