One-step transfer process via dual-function polyimide thermal pressing for wafer-scale graphene in flexible...

Conventional transfer methods for wafer-scale graphene rely on sacrificial polymer supports and multi-step handling, making them incompatible with thin polymer substrates. Here, we report a one-step thermal pressing approach for graphene transfer, in which spin-coated polyimide serves simultaneously as the transfer medium and the flexible substrate, eliminating the need for sacrificial polymer layers and intermediate handling steps. Under experimentally optimized conditions, the semi-cured PI conformally contacts the graphene and establishes sufficient interfacial adhesion to enable delamination from the copper growth substrate during wet etching. Following transfer, the PI can be mechanically peeled from the rigid carrier to release freestanding flexible devices. This process is compatible with conventional photolithography, as demonstrated by the fabrication of flexible Hall sensors on 3 × 3 cm² transferred graphene. The resulting devices exhibit an average current-normalized sensitivity of 130 ± 33 V A^-1 T^-1 and a carrier mobility up to 3640 cm² V^-1 s^-1, comparable to devices produced via conventional multi-step wet transfer using graphene from the same batch. This work establishes a scalable route for wafer-scale graphene transfer onto ultrathin flexible substrates without the complexity of sacrificial polymer processing.