Unveiling the Mica-Interlayer-Mediated Exfoliation of β-Ga2O3 Thin Films

Abstract

Mechanically exfoliable oxide membranes on mica are promising for flexible optoelectronics, but the actual fracture pathway during oxide/mica delamination remains unclear. Here, β-Ga₂O₃ thin films were epitaxially grown on mica by pulsed laser deposition, and their tape-assisted exfoliation behavior was investigated. Although the films could be transferred onto adhesive supports, mica-related residues were repeatedly detected on the backside of the exfoliated β-Ga₂O₃ films. Combined XRD, SEM/EDS line-scan, XPS, and rocking-curve results show that exfoliation does not occur through clean separation at the β-Ga₂O₃/mica interface, but instead involves cleavage within the mica substrate. First-principles calculations show that the β-Ga₂O₃/mica adhesion energy reaches 40.6 meV Å^–2, approximately 40% higher than the mica interlayer cleavage energy of 28.9 meV Å^–2, supporting the preferential mica-interlayer fracture pathway. Energy decomposition further reveals that the DFT-D3 dispersion term accounts for 46.5% of the calculated β-Ga₂O₃/mica work of separation, challenging the simplified assumption of a purely vdW-bonded oxide/mica interface. This work identifies a mica-interlayer-mediated exfoliation mechanism and provides guidance for controlled transfer and interfacial cleanliness of flexible β-Ga₂O₃ membranes.