[论文解读] Morphology and Structure of Carbon Films Deposited at Varying Chamber Pressures

Mubarak Ali, Mustafa Ürgen|arXiv (Cornell University)|Jan 29, 2018

Diamond and Carbon-based Materials Research参考文献 36被引用 5

一句话总结

本研究探讨了在甲烷源热丝CVD反应器中，腔室压力（3.3–14 kPa）对碳膜形貌与结构的影响。结果表明，当压力增至8.6 kPa时，由于气体活化与原子氢刻蚀的优化，金刚石相形成与薄膜生长速率均得到增强；而当压力超过11.3 kPa时，石墨相形成占主导，且生长速率下降，揭示了通过压力调控实现碳相选择与薄膜质量控制的依赖关系。

ABSTRACT

Depositing thin and thick films through different deposition technology systems has been a topic of great interest. In the hot-filaments reactor, a carbon film is deposited at some value of the chamber pressure, where the photon energy is also found in addition to gases and heat energy. Having dissociated from methane, gaseous carbon atoms convert into graphite and diamond states. Increase in chamber pressure from 3.3 kPa to 14 kPa alters the morphology and structure of carbon films. Increasing the chamber pressure upto 8.6 kPa increases the growth rate of carbon film along with discernible features of its tiny grains, grains and particles. The conversion rate of gaseous carbon atoms into the diamond state also increases. At high set chamber pressures, i.e., 11.3 kPa and 14 kPa, gaseous carbon atoms converted into the graphite state at high rate. However, the films with low growth rates had deposited. The gas activation process and the gas collision vary largely at different chamber pressures. Hence, the morphology and structure of carbon films got deposited with different nucleation and growth rates. The dissociation rate of molecular hydrogen becomes different at each chamber pressure. Consequently, the amount of formation of typical energy varies. On dissociation, atomic hydrogen is used to etch the photon energy into typical energy of different shapes. A suitable typical energy involves in the conversion of gaseous carbon atoms to graphite and diamond states. Graphite atoms get bound by the same involved energy. A different shaped typical energy involves in the process of binding diamond atoms. Clearly, this study sets a new foundation in depositing carbon films and other carbon-based materials.

研究动机与目标

• 理解腔室压力对热丝CVD法制备碳膜形貌与相结构的影响。
• 确定最大化金刚石相形成与薄膜生长速率的压力范围。
• 分析气体活化、原子氢及能量传递在碳膜沉积过程中相选择中的作用。
• 为通过调节沉积系统中的压力来控制碳膜结构奠定基础。

提出的方法

• 在不同腔室压力（3.3–14 kPa）下，使用热丝反应器以甲烷为碳源沉积碳膜。
• 监测不同压力条件下气态碳原子的解离及其向石墨与金刚石相的转化。
• 基于压力依赖的气体活化与碰撞动力学，分析碳膜的成核与生长速率。
• 评估原子氢在刻蚀与能量传递中的作用，及其对相特异性结合能的影响。
• 利用光子能量与典型能量形式，解释石墨与金刚石结构中相特异性结合机制。
• 关联压力引起的气体解离与活化变化与最终薄膜形貌及相组成之间的关系。

实验结果

研究问题

• RQ1 从3.3 kPa增至14 kPa时，腔室压力的增加如何影响碳膜的生长速率与形貌？
• RQ2 在不同压力下，原子氢与气体活化在决定沉积碳膜相结构（金刚石与石墨）中的作用是什么？
• RQ3 气态碳原子向金刚石相的转化速率在何种压力下达到最大？
• RQ4 腔室压力的变化如何改变石墨与金刚石原子结合过程中涉及的能量传递过程？
• RQ5 为何在高压力（11.3 kPa与14 kPa）下，尽管石墨形成量增加，薄膜生长速率反而下降？

主要发现

• 薄膜生长速率随腔室压力增加至8.6 kPa而上升，在更高压力下开始下降。
• 气态碳原子向金刚石相的转化速率在8.6 kPa前显著提升，表明此为金刚石形成的最佳条件。
• 在11.3 kPa与14 kPa时，气态碳原子向石墨相的转化占主导，同时薄膜生长速率降低。
• 分子氢的解离速率随腔室压力变化，从而改变可用于刻蚀与能量传递的原子氢可用性。
• 不同形状的典型能量形式参与石墨与金刚石原子的结合，解释了相特异性结构结果。
• 碳膜的形貌与结构强烈受压力依赖的成核与生长动力学影响，8.6 kPa时表现出显著特征。