纳米金刚石复合薄膜结构及形成机理的第一性原理研究

发布时间：2018-08-06 13:11

【摘要】：课题组在研究Ti-Si-N薄膜结构的基础上提出了一种新颖的单晶式多晶体（SingleCrystal Like Poly Crystalline，SCLPC）纳米金刚石复合结构。本文采用了以密度泛函理论为基础的第一性原理计算方法考察了Diamond/Si纳米复合薄膜中的界面结构；为了确定界面中硅粒子的具体情况，在研究界面的基础上又研究了4C1Si岛构型的演变行为；在计算4C1Si岛演变过程中碳硅原子迁移激活能发现，碳原子从闭环桥位迁移到开环桥位非常困难，这种情况会造成薄膜生长不均匀。为了解决该问题，本文计算了在纳米金刚石薄膜中掺入不同粒子（B、P、N、C、Si、Cu、Ag）后碳原子的迁移激活能，以此来找出一种能够促进碳原子迁移的粒子。在实验方面运用微波等离子化学气相沉积方法制备了四组纳米金刚石薄膜，并且运用AFM、Raman设备检测了制备得到的金刚石薄膜表面的形态容貌和薄膜成分。主要得到如下结论：（1）单层硅界面能够稳定在金刚石（001）表面生长，然而在单层硅界面上进行金刚石薄膜的二次形核和生长时，界面结构遭到严重破坏，所以这种单层硅界面结构不能够稳定存在于该复合薄膜中。通过计算四种碳和硅原子比例为1:1的SiC界面结构可以发现，碳原子在二聚体闭环桥位和硅原子在二聚体开环桥位所形成的单层SiC界面与碳原子在二聚体开环桥位和硅原子在二聚体闭环桥位所形成的单层SiC界面是同一种界面结构，且该界面结构相对于其他界面结构稳定。同时该界面不仅能够稳定生长在金刚石（001）表面，且有利于薄膜生长过程中的二次形核。所以在Diamond/Si复合薄膜中沉积过程中可以形成这种单层SiC界面。（2）在金刚石（001）重构表面通过研究4C1Si岛构型的演变行为得到硅粒子不能稳定待在金刚石晶体内部，，而是迁移出来存在于金刚石晶粒的边缘处；而且金刚石晶粒中的碳原子相比于硅原子迁移特别困难，所以硅粒子更容易在金刚石表面迁移。（3）在金刚石（001）重构表面通过计算一个碳原子和一个掺杂原子（1C1M）组成的岛构型中碳原子和掺杂原子的迁移激活能可以得出：在2C岛中，碳原子迁移需要5.9154eV的激活能。加入铜粒子能够较明显的减小碳原子的迁移激活能为3.1126eV。然而相比于岛中的碳原子，岛中的铜原子更容易迁移为1.5775eV。这就会造成在加入铜粒子后碳原子不迁移而薄膜中的铜原子不停的迁移，起不到对碳原子迁移的促进作用；对于剩余掺杂粒子，碳原子的迁移激活能变化不明显，而且所需激活能量太大，不符合实验情况，因此本文所选的几种掺杂粒子不能够很好促进碳原子的迁移，需要进一步研究其它粒子对碳原子迁移的促进情况。（4）其它制备工艺参数一致，选取500℃、650℃、800℃、850℃四种温度制备了金刚石薄膜，通过拉曼图谱得出薄膜中主要成分为金刚石。通过比较薄膜的表面形态可以得出：随着温度增加，薄膜中晶粒聚集能力增强，薄膜表面的粗糙度减小。在850℃时，薄膜中(100)晶向的粒子趋于主导地位，晶粒呈现片状结构。而且，沉积温度为800℃时薄膜中金刚石成分含量最多。
[Abstract]:On the basis of the study of the structure of Ti-Si-N thin film, a new type of SingleCrystal Like Poly Crystalline (SCLPC) nanodiamond composite structure was proposed by the research group. The interface structure in the Diamond/Si nanocomposite film was investigated by the first principle calculation method based on the density functional theory. The specific situation of silicon particles in the interface is determined. On the basis of the research interface, the evolution behavior of 4C1Si Island configuration is also studied. In the calculation of the evolution of 4C1Si Island, the transfer activation of carbon and silicon atoms can be found that the migration of carbon atoms from the closed loop bridge position to the open loop bridge position is very difficult. This situation will cause the uneven growth of the film. In this paper, the transfer activation energy of carbon atoms in nano diamond films (B, P, N, C, Si, Cu, Ag) is calculated. In order to find a particle that can promote the migration of carbon atoms, four groups of nanoscale diamond films are prepared by microwave plasma chemical vapor deposition, and AFM and Raman equipment are used in the experiment. The morphology and film composition of the prepared diamond films were measured.
(1) the monolayer silicon interface can grow steadily on the surface of the diamond (001). However, when the diamond films are nucleated and grown on the monolayer silicon interface, the interface structure is seriously damaged, so the monolayer silicon interface structure is not stable in the composite film. The SiC boundary of 1:1 is calculated by the calculation of the ratio of four carbon and silicon atoms to 1:1. The surface structure can be found that the single-layer SiC interface formed by the carbon atom in the closed loop bridge position of the two polymer and the silicon atom in the two polymer open ring bridge position is the same interface structure with the carbon atom in the two polymer open ring bridge position and the silicon atom formed in the closed loop bridge position of the two polymer, and the boundary structure is stable to the other interface structures. The interface can not only grow steadily on the surface of the diamond (001), but also be beneficial to the two nucleation of the film during the growth process, so this monolayer SiC interface can be formed during the deposition of Diamond/Si composite film.
(2) on the reconstructed surface of diamond (001), by studying the evolution of the configuration of 4C1Si Island, it is found that silicon particles are not stable in the diamond crystal, but are migrated to the edge of the diamond grains, and the carbon atoms in the diamond grains are especially difficult to migrate to the silicon atoms, so the silicon particles are more likely to be in the diamond table. Surface migration.
(3) the transfer activation energy of carbon atoms and doped atoms in the island configuration of a diamond (001) reconstructed surface by calculating a carbon atom and a doped atom (1C1M) can be obtained: in the 2C Island, the transfer of carbon atoms requires the activation energy of 5.9154eV. The addition of copper particles can obviously reduce the activation energy of the carbon atoms to be 3.1126eV.. Compared with the carbon atom in the island, the copper atom in the island is more easily migrated to 1.5775eV., which causes the non-stop migration of copper atoms in the film after the addition of copper particles, which does not promote the migration of carbon atoms. For the remaining doped particles, the transfer activation energy of the carbon atoms is not obvious, and it needs to be excited. The active energy is too large and does not conform to the experimental conditions. Therefore, several doped particles selected in this paper can not promote the migration of carbon atoms well. It is necessary to further study the promotion of the transfer of carbon atoms by other particles.
(4) the other preparation process parameters are consistent, the diamond films are prepared at 500 degrees C, 650, 800, 850 temperature, and the main component of the film is diamond by the Raman spectrum. By comparing the surface morphology of the film, it can be concluded that the grain aggregation ability of the film increases with the increase of the temperature, and the roughness of the film surface decreases. In 85, the surface roughness of the film decreases. 85 At 0 C, the (100) orientation particles in the films tend to dominate, and the crystalline grains are flaky. Moreover, the content of diamond in the films is the highest at 800 C.
【学位授予单位】：内蒙古科技大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：O613.71;TB383.2

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