High-Efficiency and Low-Intensity Threshold Femtosecond Laser Direct Writing of Precise Metallic Micropatterns on Transparent Substrate

Laser direct writing (LDW) is a promising approach for fabricating metallic micropatterns on transparent substrates for transparent electronic circuits that satisfy both electronic and optical criteria. However, high efficiency and precision patterning remain a challenge for both photochemical and photothermal LDW. Here, a novel method is proposed with a femtosecond laser to achieve a highly-efficient photothermal process via single-photon absorption by photosensitive particles (SPA-FsLDW). The dispersive photosensitive particles act as numerous heating sources, enabling simultaneous multiple-location photothermal reactions and highly-efficient metallization due to heat-induced metal ion reduction. The new approach effectively exploits the excellent heat-input regulation with the ultrashort pulse of the femtosecond laser to achieve great temperature controllability and precision. It is shown that, with a deposition rate of ≈10⁷ µm³ s⁻¹ and electrical resistivity of ≈10⁻⁷ Ω m, SPA-FsLDW improves efficiency and electrical resistivity by at least one order of magnitude compared to previously reported FsLDW. A self-powered sensor is fabricated using SPA-FsLDW, demonstrating its practical applicability.