Department of Mechano-Informatics, Graduate School of Information Science and Technology, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656, Japan.
Nanotechnology. 2013 May 24;24(20):205302. doi: 10.1088/0957-4484/24/20/205302. Epub 2013 Apr 19.
We firstly introduce a facile method for the site-specific direct physical exfoliation of few-layer graphene sheets from cheap and easily enlargeable graphite grown on a Ni foil using an optimized polydimethylsiloxane (PDMS) stamp. By decreasing the PDMS cross-linking time, the PDMS elasticity is reduced to ∼52 kPa, similar to that of a typical gel. As a result of this process, the PDMS becomes more flexible yet remains in a handleable state as a stamp. Furthermore, the PDMS adhesion to a graphite/Ni surface, as measured by the peel strength, increases to ∼5.1 N m⁻¹, which is approximately 17 times greater than that of typical PDMS. These optimized properties allow the PDMS stamp to have improved contact with the graphite/Ni surface, including the graphite wrinkles. This process is verified, and changes in surface morphology are observed using a 3D laser scanning microscope. Under conformal contact, the optimized PDMS stamp demonstrates the site-specific direct physical exfoliation of few-layer graphene sheets including mono- and bi-layer graphene sheets from the graphite/Ni substrate without the use of special equipment, conditions or chemicals. The number of layers of the exfoliated graphene and its high quality are revealed by the measured Raman spectroscopy. The exfoliation method using tunable elasticity and adhesion of the PDMS stamp can be used not only for cost-effective mass production of defect-less few-layer graphene from the graphite substrate for micro/nano device arrays but also for nano-contact printing of various structures, devices and cells.
我们首先介绍了一种简便的方法，用于通过使用优化的聚二甲基硅氧烷 (PDMS) 印章从廉价且易于扩大的 Ni 箔上生长的石墨进行特定位置的直接物理剥离少层石墨烯片。通过降低 PDMS 的交联时间，PDMS 的弹性降低到约 52 kPa，类似于典型的凝胶。由于这个过程，PDMS 变得更加灵活，但仍然可以作为印章保持可处理的状态。此外，PDMS 对石墨/Ni 表面的附着力，如通过剥离强度测量，增加到约 5.1 N m⁻¹，大约是典型 PDMS 的 17 倍。这些优化的特性使 PDMS 印章能够更好地与石墨/Ni 表面接触，包括石墨褶皱。使用 3D 激光扫描显微镜验证了这一过程，并观察到表面形貌的变化。在共形接触下，优化后的 PDMS 印章可以在不使用特殊设备、条件或化学物质的情况下，从石墨/Ni 基底上进行特定位置的直接物理剥离，得到包括单层和双层石墨烯在内的少层石墨烯片。通过测量拉曼光谱揭示了剥离石墨烯的层数及其高质量。这种使用 PDMS 印章的可调节弹性和附着力的剥离方法不仅可以用于从石墨衬底高效地大规模生产无缺陷的少层石墨烯，用于微/纳器件阵列，还可以用于各种结构、器件和细胞的纳米接触印刷。
