Strain-Free Dry Transfer of 2D-CNT Heterostructures

First, WSe₂ (HQ graphene) flakes are prepared on 90-nm-thick SiO₂/Si substrates using mechanical exfoliation, and the layer number is determined by optical contrast. An anthracene single crystal is picked up with a glass-supported PDMS sheet to form an anthracene/PDMS stamp. Next, the WSe₂ flakes are picked up by pressing the anthracene/PDMS stamp against a substrate with the target WSe₂ flakes. The stamp is quickly separated ( > 10 mm/s) to ensure that the anthracene crystal remains attached to the PDMS sheet. The stamp is then applied to the receiving substrate with the desired chirality-identified CNT, whose position is determined by a prior measurement. Precise position alignment is accomplished with the aid of markers prepared on the substrate. By slowly peeling off the PDMS ( < 0.2 μm/s), the anthracene crystal with the WSe₂ flake is released on the receiving substrate. Sublimation of anthracene in air at 110 °C for 10 min removes the anthracene crystal, leaving behind a clean suspended CNT/WSe₂ heterostructure. This all-dry process eliminates contamination from solvents, and the solid single-crystal anthracene protects the 2D flakes and the CNT during the transfer, ensuring that the CNT/WSe₂ heterostructure experiences minimal strain^{17 (link),18 (link)}.