Parametric investigation on laser interaction with polyimide for graphene synthesis towards flexible devices

Abstract

Graphene, is one of the prominent materials in device fabrication due to its high conductive and high flexural strength for electrodes/device applications. The latest technique for graphene synthesis i.e. carbonization of polyimide by laser patterning has received much attention because of its capability to create various functional materials and flexible devices. The requirement of graphene demands larger volume production where laser-induced graphene (LIG) by consideration of pulse overlap could prove to be the solution if a recipe is prepared through appropriate optimization. The present study focused on the CO2 laser (λ = 10.6 µm) interaction with polyimide by generating raster pattern with varying pulse overlap in linear direction. The raster pattern is fabricated at different laser energies and pulse overlap with a constant 30% line overlap between two consecutive lines, in the lateral direction, for synthesizing LIG at relatively low laser power. Various combinations of laser fluences (46 J cm−2, 56 J cm−2, 66 J cm−2) and pulse spot overlap (60%, 70%, and 80%) were used for the polyimide carbonization. Both experimental and numerical simulation (using ComsolTM) results present an insight that optimal control of laser pulse overlap shows significant effect on crystallinity and electrical resistivity of synthesized graphene. The macroscopic quality of the raster pattern is investigated through the optical microscope. Detailed Raman spectro-microscopic analysis is carried out to study the defect to graphenization ratio and its impact on the properties of graphene synthesized. Through Raman analysis, the average in-plane crystallite length of graphene synthesis was observed from 27.732 ± 4-37.132 ± 6 nm. At last, a resistive type strain sensor was fabricated to check the stability of LIG and its reliability for repetitive loading conditions. The pulse overlap photo-thermal model, and its finite element analysis implementation presents better understanding towards optimizing the promising technique towards synthesizing LIG. © 2022 IOP Publishing Ltd.