Institute of Inorganic Methodologies and of Plasmas, IMIP-CNR, via Orabona 4, 70126 Bari, Italy.
Phys Chem Chem Phys. 2011 Dec 14;13(46):20836-43. doi: 10.1039/c1cp22347j. Epub 2011 Oct 17.
Understanding the chemical vapor deposition (CVD) kinetics of graphene growth is important for advancing graphene processing and achieving better control of graphene thickness and properties. In the perspective of improving large area graphene quality, we have investigated in real-time the CVD kinetics using CH(4)-H(2) precursors on both polycrystalline copper and nickel. We highlighted the role of hydrogen in differentiating the growth kinetics and thickness of graphene on copper and nickel. Specifically, the growth kinetics and mechanism is framed in the competitive dissociative chemisorption of H(2) and dehydrogenating chemisorption of CH(4), and in the competition of the in-diffusion of carbon and hydrogen, being hydrogen in-diffusion faster in copper than nickel, while carbon diffusion is faster in nickel than copper. It is shown that hydrogen acts as an inhibitor for the CH(4) dehydrogenation on copper, contributing to suppress deposition onto the copper substrate, and degrades quality of graphene. Additionally, the evidence of the role of hydrogen in forming C-H out of plane defects in CVD graphene on Cu is also provided. Conversely, resurfacing recombination of hydrogen aids CH(4) decomposition in the case of Ni. Understanding better and providing other elements to the kinetics of graphene growth is helpful to define the optimal CH(4)/H(2) ratio, which ultimately can contribute to improve graphene layer thickness uniformity even on polycrystalline substrates.
理解石墨烯生长的化学气相沉积（CVD）动力学对于推进石墨烯处理和更好地控制石墨烯的厚度和性质非常重要。从提高大面积石墨烯质量的角度出发，我们使用 CH(4)-H(2)前体在多晶铜和镍上实时研究了 CVD 动力学。我们强调了氢在区分铜和镍上石墨烯生长动力学和厚度方面的作用。具体而言，生长动力学和机制是在 H(2)的竞争解离化学吸附和 CH(4)的脱氢化学吸附以及碳和氢的内扩散竞争中确定的，其中氢在铜中的内扩散速度比镍快，而碳在镍中的扩散速度比铜快。结果表明，氢作为铜上 CH(4)脱氢的抑制剂，有助于抑制沉积在铜衬底上，降低石墨烯的质量。此外，还提供了在 CVD 石墨烯上铜形成 C-H 面外缺陷的氢作用的证据。相反，在镍的情况下，氢的重新表面复合有助于 CH(4)分解。更好地理解和为石墨烯生长动力学提供其他元素有助于确定最佳 CH(4)/H(2)比，这最终有助于提高即使在多晶衬底上的石墨烯层厚度均匀性。
