本文選題：MPCVD + 甲烷濃度��； 參考：《吉林大學(xué)》2015年碩士論文

【摘要】：微波等離子體化學(xué)氣相沉積法（MPCVD）制備金剛石，是實(shí)現(xiàn)高速率高質(zhì)量金剛石單晶生長(zhǎng)的主要手段。甲烷濃度對(duì)金剛石單晶的生長(zhǎng)以及結(jié)晶質(zhì)量具有決定性作用。在高速生長(zhǎng)的基礎(chǔ)上，甲烷濃度的提高引起的變化主要包括： (1)改變等離子體中金剛石相前驅(qū)物、非金剛石相前驅(qū)物以及H原子的濃度比例。相較其他基團(tuán)，非金剛石相前驅(qū)物C2隨甲烷濃度的增加有較大幅度的增加，等離子體內(nèi)刻蝕作用呈先增大后減小的趨勢(shì)，使金剛石質(zhì)量先提高后下降。 (2)提高金剛石的成核率、生長(zhǎng)速率,生長(zhǎng)模式隨之發(fā)生改變，致使高甲烷濃度下金剛石的生長(zhǎng)速率較高，臺(tái)階密度增加，表面形貌變差。 (3)降低N的擴(kuò)散。單晶的生長(zhǎng)過程中，N是由擴(kuò)散作用進(jìn)入晶體內(nèi)。N2通入量不變的情況下，單晶沉積速率的增加使N得相對(duì)擴(kuò)散速率降低，外延層中N含量降低。 H2/O2等離子體可以刻蝕非金剛石相，同時(shí)對(duì)金剛石相也有一定影響。它對(duì)金剛石單晶表面拋光遺留缺陷有很好的祛除作用。本文初步研究H2/O2等離子體刻蝕對(duì)單晶表面形貌的影響。通過對(duì)四種不同單晶刻蝕情況進(jìn)行對(duì)比，得出： (1)等離子體刻蝕主要對(duì)非金剛石相和晶界進(jìn)行刻蝕，故在缺陷附近的刻蝕坑密度較高。 (2)由于本實(shí)驗(yàn)所用HTHP單晶金剛石結(jié)晶質(zhì)量較CVD單晶金剛石差，，相同條件下HTHP單晶表面刻蝕強(qiáng)度比CVD單晶刻蝕強(qiáng)度大。反之，可以通過比較表面刻蝕坑密度大小等來判斷金剛石單晶質(zhì)量的好壞。 (3)由于缺陷種類不同，HTHP單晶表面的刻蝕坑呈平臺(tái)狀，而CVD單晶的刻蝕坑形狀不規(guī)則，大致呈倒錐形狀。 (4)隨刻蝕時(shí)間的增加，由機(jī)械拋光引入缺陷產(chǎn)生的刻蝕坑逐漸消失，而晶體內(nèi)部缺陷引發(fā)的刻蝕坑則不會(huì)消失。
[Abstract]:The preparation of diamond by microwave plasma chemical vapor deposition (MPCVD) is the main method to achieve high rate and high quality diamond single crystal growth. Methane concentration plays a decisive role in the growth and quality of diamond single crystals. On the basis of high-speed growth, the changes caused by the increase of methane concentration mainly include: 1) changing the concentration ratio of diamond precursor, non-diamond precursor and H atom in plasma. Compared with other groups, the precursor C2 of non-diamond phase increases greatly with the increase of methane concentration, and the etching effect in plasma increases first and then decreases, which makes the quality of diamond increase first and then decrease. (2) increasing the nucleation rate, growth rate and growth mode of diamond, resulting in higher growth rate, higher step density and worse surface morphology under high methane concentration. 3) reducing the diffusion of N. In the process of single crystal growth, the N content in the epitaxial layer decreases and the relative diffusion rate decreases with the increase of the deposition rate of single crystal. The H2/O2 plasma can etch the non-diamond phase and has some influence on the diamond phase. It has a good effect on removing defects left over by polishing diamond single crystal surface. The effect of H2/O2 plasma etching on the surface morphology of single crystal was studied. By comparing the etching conditions of four different single crystals, it is concluded that: 1) Plasma etching is mainly used to etch non-diamond phase and grain boundary, so the densities of etched pits near defects are high. 2) because the quality of HTHP single crystal diamond is worse than that of CVD single crystal diamond, the etching intensity of HTHP single crystal surface is higher than that of CVD single crystal under the same condition. On the contrary, the quality of diamond single crystal can be judged by comparing the density of etched pits on the surface. (3) the etch pits on the surface of CVD crystals are flat because of the different defect types, while the etched pits of CVD single crystals are irregular in shape and generally in the shape of inverted cones. 4) with the increase of etching time, the etch pits induced by mechanical polishing defects gradually disappear, but the etching pits caused by internal defects do not disappear.
【學(xué)位授予單位】：吉林大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2015
【分類號(hào)】：TQ164.8;O78

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