高亮度金刚石硅-空位色心的杂质调制研究

SiV color centers in diamond have attracted much attention in the application of bio-imaging and optical sensors due to their excellent photoluminescence properties such as near-infrared emission with narrow line-width at room temperature. However, under the two popular fabrication methods based on ion-implantation and CVD growth through etching solid Si precursors, the photoluminescence properties of SiV in nano-diamonds severely deteriorate, which dramatically decreases the accuracy and efficiency of bio-marking process. . In this project, to solve this problem, Si-doped diamond films with controlled content are prepared under the flow of tetramethylsilane (Si (CH3)4) gas through microwave plasma CVD (MPCVD) technique. Based on the influence factors of SiV emission including the concentration of color centers and the optical absorption from crystalline defects, attention will be focused on the research of the defect evolution induced by Si doping, which decreases optical emission of SiV centers by the segregation of Si atoms and the optical absorption. At an atomic level, we will systematically investigate the distribution of Si atoms, the atomic structure and strain field of different defects by using high resolution scanning transmission electron microscopy (HR-STEM) and geometric phase analysis (GPA). The interplay between SiV optical properties and dopant content will be established based on the analysis of the transformation efficiency from Si dopant to SiV center and the absorption effect of crystalline defects. Finally, the approaches of fabricating nano-diamond film with high-brightness SiV centers will be provided through this project.. Our finding will be of significance in understanding the relationship between the microstructure and optical properties in doped diamond, also in designing nano-diamond materials with other color centers of high-brightness by means of optimizing deposition parameter and post-treatment.

金刚石中的硅-空位（SiV）色心由于其近红外，窄线宽等优异室温发光性能，在生物荧光标记和光学传感等领域具有非常高的潜在应用价值。但是，金刚石晶粒尺度降到纳米量级后SiV色心的荧光性能严重恶化，导致其在生物标记中的准确度和效率大幅下降。针对这一问题，本项目拟采用在微波等离子体化学气相沉积中通入四甲基硅烷气体的方法，制备掺杂可控的金刚石薄膜，利用高分辨Z衬度成像技术和几何相位分析方法解析掺杂原子对金刚石薄膜微结构演化的影响，包括位错和孪晶界等缺陷的原子结构和应力场，揭示影响SiV色心的转化效率和荧光性能的结构因素，并以此为基础开展提高SiV色心转化效率的后处理方法。通过本项研究，希望揭示纳米金刚石中SiV色心荧光性能与微结构的对应关系，获得含有高亮度SiV色心的纳米金刚石薄膜的掺杂生长工艺和后处理方法，为其在生物荧光标记领域的应用提供重要的理论指导和实验依据。

含有高亮度色心的纳米金刚石在生物荧光标记和光学传感等领域具有非常重要的应用价值。然而，色心的辐射荧光随着金刚石晶粒尺寸降低急剧恶化，产生荧光淬灭现象。针对如何提高纳米金刚石色心的辐射荧光问题，本项目主要利用微波等离子体化学气相沉积方法（MPCVD）调控工艺参数制备硅掺杂金刚石薄膜，深入系统地研究薄膜相结构、结晶质量、表面终端及硅原子分布对硅空位色心（SiV）辐射荧光的影响，解析纳米金刚石中硅空位色心荧光淬灭机理。在低温生长条件下发现增加TMS流量导致薄膜中出现碳化硅（SiC）相，形成金刚石/SiC复合薄膜，通过化学刻蚀方法去除SiC相或者提高薄膜沉积温度抑制其形成，SiV色心辐射荧光显著提高。基于不同表面改性方法调控纳米金刚石薄膜的表面终端和结晶质量，发现空气退火方法比混合酸（H2SO4/HNO3）氧化和臭氧等离子处理等方法可有效刻蚀薄膜中sp2碳和嫁接氧终端，确定sp3碳表面嫁接氧官能团是提高SiV色心的必要条件。进一步优化空气退火工艺参数使纳米金刚石中SiV色心大幅提高，最大增幅可达1400倍，并从电子能级角度给出氧终端增强SiV色心辐射荧光的机理：相比氢终端使金刚石表面能级向下弯曲，氧终端使金刚石及SiV色心表面能级向上弯曲，从而使SiV从非辐射复合状态向辐射状态转变，SiV色心辐射荧光大幅增强。基于硅掺杂[001]取向的微米/纳米金刚石复合薄膜的热氧化行为，发现纳米晶发生选择性刻蚀转变为富硅的非晶氧化物，其证实硅原子除一部分在金刚石晶格中形成SiV色心外，大部分在晶界产生偏聚；而微米晶保留下来形成含高亮度SiV色心的一维单晶金刚石纳米锥，可用于微区的温度或磁性测量等领域。.项目执行期间，在国际学术期刊发表SCI论文11篇，其中Carbon 4篇, Appl. Surf. Sci.3篇, Adv. Opt. Mater. 1篇, J. Mater. Sci. Technol. 1篇，J. Mater. Chem. C 1篇和Diam. Rel. Mater.1篇；获得已授权国家发明专利2项。