Tseng Wei-Shiuan, Chen Yen-Chun, Hsu Chen-Chih, Lu Chen-Hsuan, Wu Chih-I, Yeh Nai-Chang
Department of Physics, California Institute of Technology, Pasadena, CA 91125, United States of America. College of Photonics, National Chiao-Tung University, Hsin-Chu 30013, Taiwan.
Nanotechnology. 2020 Aug 14;31(33):335602. doi: 10.1088/1361-6528/ab9045. Epub 2020 May 5.
Deposition of layers of graphene on silicon has the potential for a wide range of optoelectronic and mechanical applications. However, direct growth of graphene on silicon has been difficult due to the inert, oxidized silicon surfaces. Transferring graphene from metallic growth substrates to silicon is not a good solution either, because most transfer methods involve multiple steps that often lead to polymer residues or degradation of sample quality. Here we report a single-step method for large-area direct growth of continuous horizontal graphene sheets and vertical graphene nano-walls on silicon substrates by plasma-enhanced chemical vapor deposition (PECVD) without active heating. Comprehensive studies utilizing Raman spectroscopy, x-ray/ultraviolet photoelectron spectroscopy (XPS/UPS), atomic force microscopy (AFM), scanning electron microscopy (SEM) and optical transmission are carried out to characterize the quality and properties of these samples. Data gathered by the residual gas analyzer (RGA) during the growth process further provide information about the synthesis mechanism. Additionally, ultra-low friction (with a frictional coefficient ∼0.015) on multilayer graphene-covered silicon surface is achieved, which is approaching the superlubricity limit (for frictional coefficients <0.01). Our growth method therefore opens up a new pathway towards scalable and direct integration of graphene into silicon technology for potential applications ranging from structural superlubricity to nanoelectronics, optoelectronics, and even the next-generation lithium-ion batteries.
在硅上沉积多层石墨烯具有广泛的光电和机械应用潜力。然而，由于硅表面呈惰性且被氧化，在硅上直接生长石墨烯一直很困难。将石墨烯从金属生长衬底转移到硅上也不是一个好的解决方案，因为大多数转移方法涉及多个步骤，这往往会导致聚合物残留或样品质量下降。在此，我们报告了一种通过等离子体增强化学气相沉积（PECVD）在硅衬底上大面积直接生长连续水平石墨烯片和垂直石墨烯纳米壁的单步方法，且无需主动加热。利用拉曼光谱、X射线/紫外光电子能谱（XPS/UPS）、原子力显微镜（AFM）、扫描电子显微镜（SEM）和光透射进行了全面研究，以表征这些样品的质量和性能。生长过程中残余气体分析仪（RGA）收集的数据进一步提供了有关合成机制的信息。此外，在多层石墨烯覆盖的硅表面实现了超低摩擦（摩擦系数约为0.015），这已接近超润滑极限（摩擦系数<0.01）。因此，我们的生长方法为将石墨烯可扩展且直接集成到硅技术中开辟了一条新途径，可用于从结构超润滑到纳米电子学、光电子学乃至下一代锂离子电池等潜在应用领域。
