Adhesion of ferroelectric CuInP₂S₆ on various substrates measured by a blister test

Van der Waals (vdW) ferroelectrics, characterized by the weak interlayer interaction and switchable polarization, effectively bypass the challenge of dangling bonds that are typically found on the surfaces of conventional perovskite ferroelectric. As a result, these materials are well-compatible for the integration into microelectronic devices for a range of substrates. Nonetheless, the adhesion energy between the vdW ferroelectric and various substrates determines the interfacial mechanical properties and operational stability. Consequently, accurately quantifying the adhesion energy of vdW ferroelectrics on various substrates is a crucial step in achieving reliable two-dimensional electronic devices. Herein, we utilized the blister test to evaluate the adhesion energy of a cutting edge vdW ferroelectric CuInP₂S₆ (CIPS) on Au, Ti, Cr, and SiO₂ substrates, which were found to be 139 mJ/m², 126 mJ/m², 54 mJ/m², and 71 mJ/m², respectively. Additionally, loading/unloading cycle test under a strain of 0.6 % has been performed on CIPS/Metal/PET devices, the result suggests higher adhesion energy gives rise to more stable device performance in the presence of bending deformation.