二氧化碳对同质外延生长单晶金刚石内应力的影响

本文研究了在反应气体中引入不同浓度的CO₂对微波等离子体化学气相沉积(MPCVD)法同质外延生长单晶金刚石内应力的影响,并对其作用机理进行了分析。研究发现,随着CO₂浓度增加,单晶金刚石内应力逐渐减小,这是由于添加的CO₂提供了含氧基团,可以有效刻蚀金刚石生长过程中的非金刚石碳,并能够降低金刚石中杂质的含量,从而避免晶格畸变,减少生长缺陷,并最终表现为单晶金刚石内应力的减小,其中金刚石内应力以压应力的形式呈现。此外反应气体中加入CO₂可以降低单晶金刚石的生长速率和沉积温度,且在合适的碳氢氧原子比(5∶112∶4)下能够得到杂质少、结晶度高的单晶金刚石。     

金刚石高成核选择比图形化技术

报道了一种新的金刚石薄膜选择生长图形化技术。首先用直流偏压增强的微波等离子体化学气相沉积（ＭＰＣＶＤ）对图形区域（Ｓｉ）高密度金刚石成核，接着对掩模区域（ＳｉＯ２）进行一次化学浅腐蚀，然后正常生长金刚石薄膜，得到表面光滑、侧壁陡直的金刚石精细图形。用该技术制作了金刚石微马达结构，其厚度为２μｍ，转子直径１５０μｍ。图形间隙可控制至１－２μｍ。     

Relationship between the spatial position of the seed and growth mode for single-crystal diamond grown with an enclosed-type holder

The relationship between the spatial position of the diamond seed and growth mode is investigated with an enclosed-type holder for single-crystal diamond growth using the microwave plasma chemical vapor deposition epitaxial method. The results demonstrate that there are three main regions by varying the spatial position of the seed. Due to the plasma concentration occurring at the seed edge, a larger depth is beneficial to transfer the plasma to the holder surface and suppress the polycrystalline diamond rim around the seed edge. However, the plasma density at the edge decreases drastically when the depth is too large, resulting in the growth of a vicinal grain plane and the reduction of surface area. By adopting an appropriate spatial location, the size of single-crystal diamond can be increased from 7 mm × 7 mm × 0.35 mm to 8.6 mm × 8.6 mm × 2.8 mm without the polycrystalline diamond rim.     

金刚石聚晶碳膜场发射的场增强特征研究

利用微波等离子体化学气相沉积法(MPCVD),在镀金属钛的纯平陶瓷衬底上制备出一层微米量级的类球状金刚石聚晶颗粒碳膜。通过拉曼光谱仪、X射线衍射仪分析了碳膜的成分,通过扫描电子显微镜观察了碳膜的外部形貌。最后利用场发射的二级结构装置测试了碳膜的场发射性能。讨论了金刚石聚晶碳膜的场发射机理,得出碳膜场发射性能优异的原因是金刚石聚晶碳膜表面存在强大的场增强现象。     

MPCVD金刚石膜装置中 Ar的光谱特性分析

在MPCVD装置中,通过调节微波功率、气体流量及反应压强,使用高分辨率的多道光学分析仪采集得到Ar的400～440 nm光谱,利用玻耳兹曼"斜率法"得到Ar激发温度Texc. 结果显示:随气体流量增加Texc降低;随着微波功率的增加Texc升高;谱线强度随着功率的增加而上升,在550 W及700 W处开始降低继而又上升,此点是制备金刚石膜的功率关键点.     

[100]定向织构生长金刚石薄膜的红外光学性能研究

采用微波等离子增强化学气相沉积法在(100)镜面抛光的硅片衬底上实现了金刚石薄片[100]定向织构生长.并用扫描电子显微镜、拉曼散射和傅立叶红外光谱仪分析测试了不同工艺得到的金刚石薄片的表面形貌、组成结构和红外性能.结果表明:负偏压辅助定向成核和氢的等离子刻蚀不仅促进了金刚石薄膜的定向织构生长,而且还能刻蚀成核期的非金刚石成分.从而提高了金刚石薄片的红外光透过特性.     

Synthesis and characterization of C3N4 hard films

C3N4 films have been synthesized on both Si and Pt substrates by microwave plasma chemical vapor deposition (MPCVD) method. X-ray spectra were calculated for single phase α-C3N4 and β-C3N4 respectively. The experimental X-ray spectra of films deposited on both Si and Pt substrates showed all the strong peaks of α-C3N4 and β-C3N4, so the films are mixtures of α-C3N4 and β-C3N4. The N/C atomic ratio is in the range of 1.0-2.0. X-ray photoelectron spectroscopy (XPS) analysis indicated that the binding energy of C 1s and N 1s are 286.2 eV and 399.5 eV respectively, corresponding to polarized C-N bond. Fourier transform infrared absorption (FT-IR) and Raman spectra support the existence of C-N covalent bond in the films. Nano-indentation hardness tests showed that the bulk modulus of a film deposited on Pt is up to 349 GPa.     

The effect of oxygen on the epitaxial growth of diamond

We studied the effect of oxygen on the growth quality of diamond epitaxial layers. After oxygen is added during the growth of the diamond epitaxial layer, as the thickness of the epitaxial layer increases, the full width at half maximum of the rocking curve of the (004) plane of diamond epitaxial layer increases continuously, and, in addition, the intensities of both the Raman peaks and the free exciton emission peaks of the diamond epitaxial layer decrease continuously. These experimental results demonstrate that as the thickness of the diamond epitaxial layer increases, the quality of the diamond epitaxial layer degrades. The strong etching effect of the OH radical groups in the plasma on the diamond epilayers leads to the degradation of their crystallinity.     

Significant suppression of residual nitrogen incorporation in diamond film with a novel susceptor geometry employed in MPCVD

This work proposed to change the structure of the sample susceptor of the microwave plasma chemical vapor deposition (MPCVD) reaction chamber, that is, to introduce a small hole in the center of the susceptor to study its suppression effect on the incorporation of residual nitrogen in the MPCVD diamond film. By using COMSOL multiphysics software simulation, the plasma characteristics and the concentration of chemical reactants in the cylindrical cavity of MPCVD system were studied, including electric field intensity, electron number density, electron temperature, the concentrations of atomic hydrogen, methyl, and nitrogenous substances, etc. After introducing a small hole in the center of the molybdenum support susceptor, we found that no significant changes were found in the center area of the plasma, but the electron state in the plasma changed greatly on the surface above the susceptor. The electron number density was reduced by about 40%, while the electron temperature was reduced by about 0.02 eV, and the concentration of atomic nitrogen was decreased by about an order of magnitude. Moreover, we found that if a specific lower microwave input power is used, and a susceptor structure without the small hole is introduced, the change results similar to those in the surface area of the susceptor will be obtained, but the spatial distribution of electromagnetic field and reactant concentration will be changed.     

微波等离子体化学气相沉积制备SiCN结晶膜及SiCN微米棒阵列

本文采用微波等离子体化学气相沉积(MPCVD)系统,以CH4, H2, N2作为源气体,以Si棒作为Si源,在Si衬底上制备出了SiCN结晶及SiCN微米棒阵列.样品的形貌由场发射扫描电子显微镜(SEM)表征分析.用X射线光电子谱(XPS)、Raman散射谱及X射线衍射(XRD)对样品的键合状态及结构进行表征,结果表明,所得到的SiCN薄膜是一具有新的六方结构的三元化合物.