  The dry release transfer of two-dimensional (2D) materials such as graphene,
h-BN, and TMDs is a versatile method for fabricating high-quality van der Waals
heterostructures. Up until now, polydimethylpolysiloxane (PDMS) sheets have
been widely used for the dry release transfer of TMD materials. However, this
method has been known to have limitations that make it difficult to transfer
few-layer-thick graphene and h-BN because of the difficulty to fabricate these
materials on PDMS. As an alternative method, we demonstrate the dry release
transfer of single- and bi-layer graphene and few-layer h-BN in this study by
utilizing poly(propylene) carbonate (PPC) films. Because of the strong adhesion
between PPC and 2D materials around room temperature, we demonstrate that
single- to few-layer graphene, as well as few-layer h-BN, can be fabricated on
a spin-coated PPC film/290-nm-thick SiO2/Si substrate via the mechanical
exfoliation method. In addition, we show that these few-layer crystals are
clearly distinguishable using an optical microscope with the help of optical
interference. Because of the thermoplastic properties of PPC film, the adhesion
force between the 2D materials and PPC significantly decreases at about 70
{\deg}C. Therefore, we demonstrate that single- to few-layer graphene, as well
as few-layer h-BN flakes, on PPC can be easily dry-transferred onto another
h-BN substrate. This method enables a multilayer van der Waals heterostructure
to be constructed with a minimum amount of polymer contamination. We
demonstrate the fabrication of encapsulated h-BN/graphene/h-BN devices and
graphene/few-layer h-BN/graphene vertical-tunnel-junction devices using this
method. Since devices fabricated by this method do not require an edge-contact
scheme, our finding provide a simples method for constructing high-quality
graphene and h-BN-based van der Waals heterostructures.
