Deng Bing, Hou Yuan, Liu Ying, Khodkov Tymofiy, Goossens Stijin, Tang Jilin, Wang Yani, Yan Rui, Du Yin, Koppens Frank H L, Wei Xiaoding, Zhang Zhong, Liu Zhongfan, Peng Hailin
Center for Nanochemistry (CNC), Beijing Science and Engineering Center for Nanocarbons, Beijing National Laboratory for Molecular Sciences (BNLMS), College of Chemistry and Molecular Engineering, Peking University, Beijing 100871, China.
CAS Key Laboratory of Nanosystem and Hierarchical Fabrication, CAS Center for Excellence in Nanoscience, National Center for Nanoscience and Technology, Beijing 100190, China.
Nano Lett. 2020 Sep 9;20(9):6798-6806. doi: 10.1021/acs.nanolett.0c02785. Epub 2020 Aug 4.
Graphene grown on Cu by chemical vapor deposition is rough due to the surface roughening of Cu for releasing interfacial thermal stress and/or graphene bending energy. The roughness degrades the electrical conductance and mechanical strength of graphene. Here, by using vicinal Cu(111) and flat Cu(111) as model substrates, we investigated the critical role of original surface topography on the surface deformation of Cu covered by graphene. We demonstrated that terrace steps on vicinal Cu(111) dominate the formation of step bunches (SBs). Atomically flat graphene with roughness down to 0.2 nm was grown on flat Cu(111) films. When SB-induced ripples were avoided, as-grown ultraflat graphene maintained its flat feature after transfer. The ultraflat graphene exhibited extraordinary mechanical properties with Young's modulus ≈ 940 GPa and strength ≈ 117 GPa, comparable to mechanical exfoliated ones. Molecular dynamics simulation revealed the mechanism of softened elastic response and weakened strength of graphene with rippled structures.
通过化学气相沉积法在铜上生长的石墨烯是粗糙的，这是由于铜的表面粗糙度增加以释放界面热应力和/或石墨烯弯曲能量。这种粗糙度会降低石墨烯的电导率和机械强度。在此，我们以斜角Cu(111)和平坦Cu(111)作为模型衬底，研究了原始表面形貌对石墨烯覆盖的铜表面变形的关键作用。我们证明了斜角Cu(111)上的台阶主导了台阶束（SBs）的形成。在平坦的Cu(111)薄膜上生长出了粗糙度低至0.2 nm的原子级平整石墨烯。当避免了SB诱导的波纹时，生长出的超平整石墨烯在转移后仍保持其平整特性。这种超平整石墨烯表现出非凡的力学性能，杨氏模量约为940 GPa，强度约为117 GPa，与机械剥离的石墨烯相当。分子动力学模拟揭示了具有波纹结构的石墨烯弹性响应软化和强度减弱的机制。
