A wet/dry hybrid transfer method for deterministic and large area h-BN/graphene area

hong-xiang Zhang^1*, Wei-Yen Woon¹

¹Department of physics, National central university, Taoyuan, Taiwan

* Presenter:hong-xiang Zhang, email:yaoxo010909@gmail.com

Different stacked arrangements of 2D materials have been found to be useful for tuning the physical properties of 2D materials and have demonstrated interesting physics properties. There are two main ways to prepare such samples, one is to use CVD growth and the other is to stack one layer onto another. Because of the limitation of potential energy, CVD growth usually cannot render stacked 2D material at any twist angle. As for the layer stacking method, it can directly control the stacking conditions, including location and twist angle. In general, the difference between the wet transfer and dry transfer lies on the fact whether the 2D sample would contact with the solution and polymer. As a result, wet transferred 2D materials would inevitably contain residues from the supporting polymer or the transferred solution. On the other hand, dry transfer can result in cleaner surface, and the stacking condition of the stacked 2D materials can be determined through manipulation under optical microscopy during the transfer process. However, the CVD growth 2D material usually has a strong coupling with the growth substrate. In fact, CVD growth 2D materials are not easy to be transferred through dry transfer. In general, it has to be transferred by wet transfer. Here we develop a wet/dry hybrid transfer method to combine the benefits of the above methods and prepare high quality stacked 2D material heterostructure. The newly developed method prevents direct contact between the organic residue and the 2D materials using the h-BN as the protecting layer during wet transfer. Besides, by using the PVC/PDMS micro-dome, we can deterministically stack the 2D heterostructure (h-BN/CVD graphene/h-BN) at the desired location at the precision of 0.3 micro with arbitrary twist angle down to the precision of 0.05 degree. Raman spectroscopy, atomic force microscopy, and Hall measurement revealed high quality 2D materials with improved mobility, suggesting the hybrid wet/dry transfer method is helpful in preserving the intrinsic properties of the CVD graphene. Moreover, the stacked 2D heterostructure shows highly uniform coupling between the 2D materials with no blister between interfaces.

Keywords: Transfer technique, CVD growth graphene, 2D material heterostucture, Raman, mobility