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The development of flexible electronics and biomedical sensors requires new materials that combine electrical conductivity, mechanical flexibility, and ease of fabrication. Among the most promising candidates are graphene and its chemical derivatives – graphene oxide (GO) and reduced graphene oxide (rGO). Graphene exhibits exceptionally high carrier mobility and mechanical strength; however, the absence of a bandgap severely limits its use in transistor and sensor structures where a high on/off current ratio is essential. The partially reduced graphene oxide, on the contrary, exhibits dielectric or semiconducting behaviour depending on the oxidation degree. One very popular approach to fabrication of the rGO films and structures is reduction of the preliminarily deposited GO film. The second approach that becomes increasingly popular with the recent development of affordable pulsed laser sources – local formation of graphene-like structures directly on carbon-based materials, such as polymers, paper etc [1]. The advantages of this approach are using no chemicals or deposition equipment, making laser-induced graphene (LIG) a cost-effective and sustainable approach.
Raman spectroscopy is one of the most versatile characterization tools for graphene material, because it can provide information on both the degree of oxidation, structural perfection, and number of monolayers. The key indicators are the D/G intensity ratio, which reflects the defect level, and the shape of the 2D band and its intensity ratio to the G band, indicating number of monolayers and lateral dimensions of graphene structure. The numerous Raman studies reported in the literature so far have demonstrated that the properties of LIG can be tuned in very broad range by using different laser sources and different regimes of their operation. At the same time, most of the studies used CO2 laser for LIG formation on polyimide, while other commercially available pulsed lasers were less studied. Especially attractive for the wide application of LIG technology are commercial laser scanning markers, which has not yet been systematically studied.
In this work, we analyse in detail the Raman spectra of LIG formed on the surface of polyimide (Kapton) formed by ns-pulsed 355 nm and CW 450 nm laser markers with different intensity, scanning speed, repetition rate and other parameters. We established correlations between the LIG structure and laser processing parameters, as well as analyse the properties of UV-induced LIG obtained in this work with the results of the literature, where other laser sources were used.
Establishing clear correlations between laser exposure regimes and rGO properties is an essential foundation for reproducible fabrication of sustainable materials for flexible electronics, biomedical sensors, and micro-energy systems.
The work was supported by the NRFU project 2023.05/0022 (Andriy Korchovyi, Volodymyr Dzhagan) and DAAD project “SOMMER!” (Vladyslav Dzhahan, Serhiy Kondratenko).
References
[1] V. Dzhagan, Y. Azhniuk, O. Dubikovskyi and D.R.T. Zahn. Advances in laser-based lithography and processing of semiconductors and insulators. J. Phys.: Condensed Matter 38 (25) 253001.
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