这里，通过倒浮法（IFM）和真空下热处理两个步骤，制备得超洁净单层和双层化学气相沉积（CVD）石墨烯膜，其直径分别高达500 µm和750 µm。产量随着尺寸的增加而降低，该研究表明了选择优质石墨烯原料的重要性。所获得的不同直径的膜材料在热处理前后的动力学机械性能也被研究讨论。其质量因子范围从200到2000，且与尺寸没有明显的相关性。测试结果表明，共振频率与膜的直径成反比。 该工作还发现石墨烯中的有效固有应力减少，以及在测定中退火后应力的相对误差。这些测量表明生产可再生和优良机械性能的石墨烯膜是可能的。

Figure 1. CVD石墨烯转移过程。通过传统步骤制备悬浮CVD石墨烯，包括聚甲基丙烯酸甲酯（PMMA）旋涂，背面石墨烯蚀刻，铜箔蚀刻，冲洗，然后湿转移到多孔SiO2/Si基材上。                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                      
                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                  
 
Figure 2. 用IFM除去PMMA后的膜。（a）不同直径的双层石墨烯膜的SEM图，（b）直径为750μm的双层石墨烯膜光学图，（c）小晶粒尺寸（<20μm）的单层石墨烯膜的产量。
 

Figure 3.热处理前后对材料结构的影响。
 

Figure 4. 石墨烯膜的热机械噪声测量。通过执行非线性拟合具有背景的洛伦兹方程，获取了共振频率和质量因子。
 

Figure 5. 测量的共振频率。（a）单层石墨烯膜，插图为热处理前后的对比图，（b）双层石墨烯，紫色代表热处理前，橙色代表热处理后，共振频率与直径显示出很好的线性关系。
 
     该研究工作由伊朗伊斯法罕理工大学Shirin Afyouni Akbari课题组于2020年发表在Scientific Reports期刊上。原文：Large Suspended Monolayer and Bilayer Graphene Membranes with Diameter up to 750 µm。

摘自《石墨烯杂志》公众号