Chunjiu Tang, José Grácio, Neves A J, Hugo Calisto, Fernandes A J S, Lianshe Fu, Sérgio Pereira, Liping Gu, Gil Cabral, Carmo M C
Center for Mechanical Technology and Automation, and Department of Mechanical Engineering, University of Aveiro, 3810 Aveiro, Portugal.
J Nanosci Nanotechnol. 2010 Apr;10(4):2722-30. doi: 10.1166/jnn.2010.1450.
In this work, the coupled effect of nitrogen addition into CH4/H2 mixtures and surface temperature on diamond growth ranging from large grained polycrystalline to fine-grained nanocrystalline were investigated. Moreover a new growth parameter window for simultaneous growth of nanocrystalline diamond (NCD) and {100} textured large-grained diamond films was developed by using a high power high pressure 5 kW microwave plasma assisted chemical vapor deposition (MPCVD) reactor. Scanning electron microscope (SEM), Raman spectroscopy, and X-ray diffraction (XRD) are employed to characterize the morphology, crystalline quality and texture of the diamond samples. Our results can be grouped by two catalogs: First, deposition run without and with 0.24% N2 addition, while keeping all the other parameters constant, resulted in a high quality transparent large-grained polycrystalline diamond film and a NCD film, respectively. This result clearly evidences nitrogen induced nanocrystallinity. Then, two different substrate surface temperatures were obtained by overlapping a small silicon slice on the top centre of a large silicon wafer of 5.08 cm in diameter in only one deposition run using 0.24% N2 addition and the same set of parameters as the previous runs. From this growth run, a NCD film of growth rate around 2.3 microm/h was obtained at low temperature, while a {100} textured large-grained diamond film of much higher growth rate about 10.4 microm/h was grown at high temperature. These results not only confirm the reproducibility of NCD by N2 addition, but also indicate that distinct growth modes were involved at different substrate temperatures with 0.24% nitrogen addition, or coupled effect of nitrogen addition and temperature on the growth of CVD diamond films happened. Finite element method (FEM) analysis was employed to simulate the temperature gradient and distribution on these two samples, and based on this simulation and other simulation results in the literature, the growth mechanism is briefly discussed.
在本工作中，研究了向CH4/H2混合气体中添加氮气以及表面温度对从大晶粒多晶到细晶粒纳米晶金刚石生长的耦合效应。此外，通过使用高功率高压5千瓦微波等离子体辅助化学气相沉积（MPCVD）反应器，开发了一个用于同时生长纳米晶金刚石（NCD）和{100}织构大晶粒金刚石薄膜的新生长参数窗口。使用扫描电子显微镜（SEM）、拉曼光谱和X射线衍射（XRD）对金刚石样品的形貌、晶体质量和织构进行表征。我们的结果可分为两类：第一，在保持所有其他参数不变的情况下，不添加氮气和添加0.24%氮气的沉积过程分别得到了高质量的透明大晶粒多晶金刚石薄膜和NCD薄膜。这一结果清楚地证明了氮诱导的纳米晶化。然后，在仅一次使用0.24%氮气添加且与之前实验相同参数集的沉积过程中，通过在直径为5.08厘米的大硅片顶部中心重叠一个小硅片，获得了两种不同的衬底表面温度。从这次生长过程中，在低温下获得了生长速率约为2.3微米/小时的NCD薄膜，而在高温下生长出了生长速率更高约为10.4微米/小时的{100}织构大晶粒金刚石薄膜。这些结果不仅证实了通过添加氮气可重现NCD生长，还表明在添加0.24%氮气时，不同的衬底温度涉及不同的生长模式，或者说氮气添加和温度对CVD金刚石薄膜生长产生了耦合效应。采用有限元方法（FEM）分析来模拟这两个样品上的温度梯度和分布，并基于此模拟以及文献中的其他模拟结果，简要讨论了生长机制。
