Fig. 2: Performance of the conventional LLO and GLLO methods.

a Schematic illustration of the lift-off process of the ultrathin PI film with ultraviolet (UV) laser irradiation. The process results were categorized into partial separation (pink, upper half-filled symbol), wrinkling (red, lower half-filled symbol), successful lift-off (green, right half-filled symbol), and rupturing (black, left half-filled symbol) (b, c) Lift-off results with respect to laser fluence and scanning pitch for (b) conventional LLO and (c) GLLO methods. The green areas represent process windows for successful lift-off. d Optical microscopy (OM) images of PI films after the lift-off process for each laser fluence with a fixed scanning pitch of 15 μm. The images in the first and second rows correspond to the conventional LLO and GLLO methods, respectively. Scale bars: 300 μm. e Surface roughness of the free-standing PI films separated with the conventional LLO and GLLO methods for each laser fluence. Inset images display the 3D surface topographies of the PI films (scale factor: 5). Error bars represent standard deviations obtained from samples (n ≥ 8). f The measured thickness of carbonaceous residues on the glass carriers, and (g) Raman spectra analyzed on the glass carriers after each process. The shaded region highlights the differences in Raman peaks between the graphene-integrated thin residue from the GLLO method and the thick residue from the conventional LLO method.