具有NE8色心规则分布的单晶CVD金刚石的制备研究

Along with an understanding of fundamentals of quantum information science, there is an urgent need and hot study for solid-state quantum information processing platform, such as diamond containing room-temperature photostable color centres, which can maintain and exploit non-trivial quantum coherence. NE8 color centre, a kind of Ni-related defects in diamond, is promising single photon source for quantum key distribution due to its near-infrared emission with narrow line-width and few weak sideband peaks. So far, however, none of fabrication techniques can supply NE8 capable of quantum manipulating. Neither ion implantation nor high pressure high temperature can do. The reason is that NE8 consists of one Nickel atom surrounded by four Nitrogen atoms. It is difficult to simultaneously implant one Nickel atom with four Nitrogen atoms in the diamond, while, for high pressure high temperature technique, other Ni-N complexes always co-exist with NE8 in the matrix of diamond under the condition of rich Ni catalyst. It is CVD technique that shows the possibility to fabricate only NE8 color centre with high density and proper distribution in the matrix of diamond. Nevertheless, this technique still requires overcoming several remaining problems at present state, such as unsatisfactory density, random distribution and multi-level emission. In this proposal, therefore, a research plan is suggested to solve the problem of fabrication of NE8 color centre in order to meet the requirements of quantum manipulation. In detail, NE8 will be fabricated by plasma enhanced CVD technique during single crystalline CVD diamond growth so that the fabricated color centres are installed in the single crystalline matrix instead of polycrystalline film. This idea will take advantage of diamond as low spin lattice and ensure the decoherence time long enough. As the amount and the distribution of the fabricated color centres are concerned, nano-/micro-processing technique will be employed to pattern the substrate before the fabrication of NE8 and the growth of single crystalline CVD diamond. By this way, the density of NE8 is expected to be increased with regular distribution. The principal idea in this proposal has not been reported to install NE8 in single crystalline CVD diamond by CVD technique. In the plan, the scientific issue is the crystal growth dynamics of single crystalline CVD diamond under the condition of doping large volume atom and/or multi-atom complexes. Understanding of this issue will benefit for N-type doping of diamond which is one of important tasks to fabricate diamond-based electronic device. Therefore, through performance of the research plan, it is fervently expected that the quantum grade single crystalline diamond can be fabricated to meet the requirement of quantum manipulating. The further knowledge, such as energetic density, thermal spread, correctability, is also expected to dig out of this material system.

随着对量子信息科学的深入理解，人们对能够保持和承载量子信息处理的固态材料平台- - 具有室温稳定色心的金刚石的研究越来越热烈，需求也更加迫切。金刚石中的NE8色心由于其近红外、窄线宽、边带峰少且强度低的光发射特点，成为量子密钥分配应用中优异的候选单光子源。但是，NE8色心的制备问题严重阻碍着光量子比特的操控以及光纤光量子器件的实现进程。本项目提出采用等离子体增强化学气相沉积技术，制备具有NE8色心的单晶CVD金刚石，并借助微纳加工技术，实现色心在单晶中的规则分布生长的研究计划,以应对NE8色心难以制备的问题以及由此而伴生的色心随机分布、光子三态发射的缺陷。通过本项目的实施希望揭示在大体积原子掺杂和多原子组态掺杂条件下的单晶CVD金刚石的生长动力学规律，发现量子级金刚石在制备和加工中的新现象，巩固我国在NE8色心研究中的国际领先地位,为金刚石量子信息处理平台的建立奠定关键的、原创性的工作基础。

按着《任务书》和《申请书》的内容要求，开展了以制备NE8色心规则排列的单晶金刚石为目标的研究。. 根据流体力学、电磁学、等离子体物理学、等离子体化学等理论，借助comsol计算软件，分析了射频激发等离子体增强化学气相沉积金刚石的环境特征，探索了等离子体发生区域和沉积区域的温度场、速度场、质量场，数值模拟分析的结果表明：传统的单频率模式激发等离子体具有空心化、热效率低、不适于高气压沉积的弱点。同时，采用光发射谱实验技术，诊断了等离子体的组分和空间分布，质量场的实验结果与数值模拟结果具有相符合的特点。. 基于数值模拟和光发射谱实验结果，设计了双射频等离子体激发系统，使等离子体中的电子温度达到2.6eV，密度达到6.5*10^21m^(-3)。利用该系统，通过调整制备参数，在0.8~10%的CH4和H2比的条件下，分别制备了纳米、微米和单晶金刚石，其中单晶的尺寸达到5*5mm^2。开展了含Ni-N组态掺杂的射频等离子体沉积实验，首先筛选了含Ni、N的有机前驱体（二茂镍），研究了该有机前驱体在射频等离子体环境下的沉积行为，发现了发光波长在320-360nm的Ni原子；其次，将二茂镍通过载气输运的办法引入到金刚石沉积环境中，获得了含有Ni-N组态的多晶金刚石，XPS结果显示Ni-N价健健能为855eV；最后，利用微纳光刻技术，实现了具有规则排列的Ni-N组态掺杂的金刚石单晶颗粒（即，每一个颗粒为单晶），单晶颗粒之间的间距为100微米。. 为了能够评价微纳加工制备的金属掩膜的质量，提出了采用超声检测方法评价金属膜与金刚石基底的膜基结合强度，该方法可以检测粗糙度Ra<10^2nm以下的膜基结合强度，具有对膜基界面灵敏、操作简便、工序兼容性好的优点。. 总之，在基金的资助下，发明了“双射频等离子体喷射制备金刚石的方法”和“射频等离子体进行镍氮掺杂金刚石的制备方法”，提出了适于金刚石器件制备技术的“膜基结合强度超声检测法”。. 发表9篇学术论文，其中SCI4篇，EI5篇，申请2项专利，其中授权1项。培养了7名研究生，其中1人博士毕业，2人硕士毕业，培养了1名博士后（已经出站）。