Various 2D materials with unique properties can be assembled layer by layer into designer van der Waals heterostructures, which can inherit individual properties from their parents or even create new functionality. The van der Waals heterostructures can be created by mechanically dry transfer techniques with the assistant of polymer stamps, such PMMA/PDMS, PPC/PDMS, or PC/PDMS.

In reality, the assembly is not as simple as we expect. During the transfer, bubbles can form due to the trap of either air or hydrocarbon residues. The main task during transfer process is to avoid the formation of bubbles, which is the prerequisite of high-quality devices. The title image shows an optical image of such large-area bubble-free stacks consisting of few-layer graphene encapsulated by h-BN.

References:

[1]. A.K. Geim, et. al.,"Van der Waals heterostructures",Nature, 499, 419-425, (2013).

[2]. K. S. Novoselov, et. al., "2D materials and van der Waals heterostructures",Science, 353(6298), aac9439, (2016).

[3]. R. Frisenda, et. al.,"Recent progress in the assembly of nanodevices and van der Waals heterostructures by determinstic placement of 2D materials",ChemicalSociety Reviews, 47, 53-68, (2018).