【作者】 黑立富；

【导师】 李成明； 吕反修；

【作者基本信息】 北京科技大学 ， 材料科学与工程， 2015， 博士

【摘要】 论文研究了沉积工艺参数(输入功率、衬底温度、甲烷浓度、表面预处理)及氮掺杂等对气体循环旋转电弧DC Arc Plasma Jet CVD金刚石单晶外延生长的影响规律,研究结果表明衬底温度为1000℃C,甲烷浓度0.813%(体积百分比),功率密度285W/cm3左右生长的金刚石单晶表面相对平整,没有非外延生长,呈现典型的台阶生长模式,生长速率达到了17.4μm/h；在工艺优化的基础上首次采用气体循环旋转电弧DC Arc Plasma Jet制备出了7.5×7.5×1.4mm3的CVD金刚石单晶片(抛光后厚度1.03mm),并对CVD金刚石单晶片的结晶质量、PL谱、紫外、红外及可见光范围内的光学性能进行了表征和分析,结果表明DC Arc Plasma Jet CVD生长的金刚石单晶(400)峰X射线双晶摇摆曲线半高宽仅为0.013°,氮含量为76ppm。CVD金刚石单晶片在不经热处理的情况下其内氮杂质不仅有NV相关缺陷,而且还存在H3、H2和B聚体氮,表明通过CVD技术生长的金刚石单晶存在氮的聚合体。据我们所知,这属首次在未处理的CVD金刚石中发现氮的聚合体。通过CVD金刚石单晶生长模式和界面特征分析,表明金刚石单晶(100)面生长初期,生长基元优先嵌入表面等离子体刻蚀的蚀坑等位置呈现金字塔生长模式,随着生长时间的推移将向台阶生长模式转换,并在高温高压单晶晶种与CVD外延层之间呈现一层15微米左右的应力和荧光较强的过渡区；针对CVD金刚石单晶生长过程的失稳特点(生长一定时间后在单晶四周或偶尔在单晶表面出现非外延生长),分析单晶生长失稳的原因,研究了金刚石单晶稳态生长方法,通过off(100)生长及3D生长控制不仅有利于金刚石单晶的稳态生长(台阶生长),促进单晶生长面的平整化,同时有可能延缓或避免晶种四周非外延金刚石的形核和生长,最终有可能实现CVD金刚石单晶生长面的扩大;利用生长的CVD金刚石单晶制作了电流型金刚石辐射探测器,探测器全耗尽电压在420V左右(1V/μm),暗电流仅为0.56nA,击穿电压超过2500V。更多还原

【Abstract】 In the present investigation, the effects of the growth parameters (such as substrate temperature, CH4/H2ratio, substrate quality, substrate pretreatment, nitrogen addition, etc.) on the surface morphology, the growth rate and the quality of the synthesized single crystal diamond by high power DC Arc Plasma Jet with arc rotating and operated at gas recycling mode have been studied using optical microscopy, and Raman spectroscopy. The growth rate up to17.4μm/h has been obtained in the single crystal diamond sample deposited at1000℃with CH4/H2=0.813%(in volume fraction), exhibiting relatively smooth surface morphology with the typical feature of the step-flow growth, and no non-epitaxial diamond crystallites. Under the optimum synthesis conditions, large size (7.5mm×7.5mm) polished freestanding single crystal diamond plate up to1.03mm thickness has been successfully produced for the first time by DC Arc Plasma Jet with rotating arc and operated at gas recycling mode, and characterized by UV-Vis-IR absorption, photoluminescence and Raman spectroscopy, as well as high-resolution X-ray diffraction. The (400) peak of the CVD diamond is very sharp with a FWHM of0.013°only and7.6ppm incorporated nitrogen, indicating a rather good crystallinity. Besides the NV related defects, the presence of H3and H2centers as well as the513nm line indicated the existing of the aggregated nitrogen in the CVD single crystal diamond without heat treatment. To our knowledge, it may be the first report on the finding of the aggregated nitrogen in the as-grown CVD synthetic single crystal diamond.Based on the observations on the growth mode and the characterization of the nature of the interface between the epitaxial layer and the HPHT substrate, it showed that the first step of the epitaxial diamond growth might start from the preferential two dimensional nucleation and grow at the preexisting high density etch pits produced by the in situ H/Ar plasma pretreatment, and gradually change to a step-flow growth as the time running. That led to an interface transition layer about15μm thickness between the epitaxial diamond and the type Ib HPHT substrate, exhibiting a strong stress and fluorescence. Smooth surface growth was promoted by adopting a mixed growth mode of the off (100) axis growth and the3D mode growth, which means that it is possible to avoid the non-epitaxial diamond nucleation surrounding the HPHT seeds and ultimately achieve a single crystal CVD diamond larger than its HPHT seed. The synthesized single crystal diamonds were used to produce radiation detectors with MSM structure. The Ⅰ-Ⅴ characteristics of the detector showed that the full charge depletion electric field of the single crystal diamond was approximately1V/μm and the dark current was only0.56nA. and the electrical breakdown did not happen at2500V.更多还原