Analysis of low-temperature CVD growth process of diamond films in C-H-F atmosphere
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摘要: 基于第一性原理的密度泛函理论对C-H-F氛围下低温CVD金刚石薄膜的生长过程进行仿真分析,计算H、F原子在氢终止金刚石表面发生萃取反应的吸附能、反应热与反应能垒,并分析CF3、CF2、CF 3种生长基团在带有活性位点基底上的吸附。结果表明:与H原子相比,F原子更容易在氢终止金刚石表面萃出H,并以HF形式脱附,且在C-H-F氛围下有利于在低温时产生更多的活性位点;CF3、CF2、CF基团在吸附后的结构和吸附能绝对值都更有利于金刚石相的生成,适当提高CF3、CF2、CF基团的浓度有助于实现金刚石相的更高速率生长。Abstract: To better understand the growth mechanism of diamond films via low-temperature chemical vapor deposition in a C-H-F atmosphere, this paper employed density functional theory based on first principle. It calculated the adsorption energy, reaction heat, and reaction energy barrier of H and F atoms undergoing extraction reactions on the hydrogen-terminated diamond surface. Additionally, the analysis included the adsorption of CF3, CF2, and CF growth groups on the active site substrate. The results show that compared with H atoms, F atoms are more likely to extract H from the surface of hydrogen terminated diamond and desorb it in the form of HF. This process is advantageous for generating more active sites at low temperatures in a C-H-F atmosphere. Both the structure and the absolute value of the adsorption energy of CF3, CF2, and CF groups are more favorable for the generation of the diamond phase after adsorption. Increasing the concentration of CF3, CF2, and CF growth groups appropriately can facilitate the growth of diamond phase at a higher rate.
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Key words:
- CVD diamond film /
- fluorine /
- deposition mechanism /
- first-principles /
- adsorption /
- surface chemical reaction
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表 1 H、F原子在金刚石基底表面的吸附能
Table 1. Adsorption energy of H and F atoms on the diamond substrate surface
原子 Eads / eV H −0.170 8 F −2.092 8 表 2 CF3、CF2、CF基团吸附后的键长、键角值
Table 2. Bond length and bond angle values after adsorption of CF3, CF2, and CF groups
参数 取值 CF3 CF2 CF HC-CCFx吸附后键长 L2 / nm 0.162 2 0.161 9 0.161 0 HCC-CFx吸附后键长 L1 / nm 0.158 4 0.150 5 0.148 8 Fx-1C-F键长 L3 / nm 0.136 4 0.135 7 0.135 4 HCC键角 α / (°) 113.950 111.357 111.395 CCC键角 β / (°) 118.012 109.059 110.553 表 3 CF3、CF2、CF、CH3基团在生长基底的吸附能
Table 3. Adsorption energies of CF3, CF2, CF and CH3 groups on growth substrate
基团 吸附能 Eads / eV CF3 −3.7251 CF2 −3.4282 CF −3.5366 CH3 −3.3260 -
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