High resolution patterning of pristine and doped polymeric films is required in a number of applications while this can be adequately achieved with state of the art pulsed and femtosecond lasers even in non-photosensitive materials. Laser ablation and processing have been lately demonstrated by low-cost diode laser-based systems in properly doped polymers, attracting significant interest towards rapid prototyping, however with significant limitations in the spatial patterning resolution. The important case of noble metal doped polymers patterning is considered here due to significant potential for sensing, energy, plasmonic and nanotechnology applications. The precise synthesis and characterization of silver nanoparticles and their efficient incorporation into a photodegradable poly(methyl methacrylate) (PMMA) matrix for direct laser ablation are presented. Direct Laser Writing (DLW) system setup equipped with a suitable high-magnification microscope objective and utilizing a near UV 405 nm diode laser enabled the fabrication even of sub-diffraction structures with exceptional precision. Laser ablated structures including repeatable wave-like microchannels and hole-like patterns, were obtained, by properly varying the laser intensity, focus precision, and nanoparticle concentration parameters, and thus achieving highly controlled spatial manipulation and high-resolution patterning. The findings suggest that suitable preparation protocols of silver nanoparticles for incorporation into the PMMA matrix are of critical importance for achieving precise fabrication of micro and nanostructures, showcasing the potential of this approach in overcoming optical diffraction limitations in various nanopatterning applications with the highly cost-efficient usage of diode lasers.
Heterostructures are key components in photonic devices consisting of two-dimensional (2D) materials. Therefore, understanding the impact of their fabrication process parameters on their performances is of utmost importance. We fabricated MoS 2 /hBN heterostructures and investigated the effect of the adhesion temperature on their light emission. Raman analysis reveals that adhesion temperatures above ~ 100 ° C induce atomic modifications, manifested by redshifts of the E 2g and A 1g vibrational modes. Light-emission analysis revealed a lower emission intensity in the heterostructure than in bare MoS 2 , with a further reduction in intensity as the adhesion temperature increased. Additionally, photoluminescence (PL) analysis revealed that the A-excitons and trions dominate the light emission (jointly composing above 99% of the emission spectral weight), while the B-excitons contribution was negligible. Importantly, the adhesion temperature did not alter the charge-carrier concentration. Atomistic molecular dynamics simulation reveals that these changes result from thermal buckling induced by the thermal-expansion mismatch between the MoS 2 and hBN layers. Therefore, these insights identify the fabrication parameters that influence the light-emission characteristics of heterostructures and enable modulation of their excitonic emission, paving the way for the future development of optically engineered emitting devices.
Heterostructures are key components in photonic devices consisting of two-dimensional (2D) materials. Therefore, understanding the impact of their fabrication process parameters on their performances is of utmost importance. We fabricated MoS2/hBN heterostructures and investigated the effect of the adhesion temperature on their light emission. Raman analysis reveals that adhesion temperatures above ~100°C induce atomic modifications, manifested by redshifts of the E2g and A1g vibrational modes. Light-emission analysis revealed a lower emission intensity in the heterostructure than in bare MoS2, with a further reduction in intensity as the adhesion temperature increased. Additionally, photoluminescence (PL) analysis revealed that the A-excitons and trions dominate the light emission (jointly composing above 99% of the emission spectral weight), while the B-excitons contribution was negligible. Importantly, the adhesion temperature did not alter the charge-carrier concentration. Atomistic molecular dynamics simulation reveals that these changes result from thermal buckling induced by the thermal-expansion mismatch between the MoS2 and hBN layers. Therefore, these insights identify the fabrication parameters that influence the light-emission characteristics of heterostructures and enable modulation of their excitonic emission, paving the way for the future development of optically engineered emitting devices.
Large-wafer-scale metalenses offer strong potential for next-generation imaging and sensing, but centimeter-scale implementation requires coordinated control of fabrication deviation, electromagnetic assessment, layout generation, and optical validation. Here we present a process-aware, electron-beam-lithography (EBL)-enabled workflow for rapid maskless prototyping and process-rule validation of large-wafer-scale metalenses. Post-fabrication scanning electron microscopy measurements show that optimization of the Bosch deep reactive ion etching process reduces RIE-lag-induced etch-depth deviation at a 6μm target depth from 30% to 15%. For the simulated reference metalens, process-aware optical modeling further shows that a 10μm focal-length compensation under the residual 15% depth-deviation condition improves the predicted focusing performance. A rotational-symmetry-based simulation strategy enables efficient full-aperture assessment by rotationally stitching reduced-domain near-field responses, while a distributed vectorized layout pipeline generates a 100-mm-diameter pattern in less than 5 min using 10 compute nodes. Using this workflow, we fabricate a 100-mm-diameter silicon metalens with NA = 0.25 on an 8-inch wafer for operation at λ=10μm in the long-wave infrared, demonstrating focal-length consistency and thermal image formation under system-level validation. This work establishes an integrated platform for rapid prototyping and process-rule validation of large-wafer-scale metalenses.
Some substrate materials used in biodegradable and transient electronic systems require semiconductor fabrication routes that avoid high thermal budgets and liquid chemistries. Amorphous indium–gallium–zinc oxide (IGZO) is attractive for such platforms because it can be deposited by sputtering near room temperature. However, conventional patterning of IGZO commonly relies on photolithography and wet etching, which are incompatible with such substrate materials. In this work, we introduce stencil lithography as a dry, resist-free route for patterning IGZO films. Using a SiNₓ-membrane micro-stencil, both direct RF sputtering and stencil-assisted ion-beam etching (IBE) produced 5 μm IGZO features, while IBE achieved 1 μm resolution and steeper sidewalls. Two laser-cut stainless-steel stencils were then used to fabricate Van der Pauw test structures. Four-probe and Hall measurements of these test structures showed linear V-I and VH–B curves, an electron density of 3.5 × 1019 cm−3, and a mobility of 21 cm2V−1 s−1 for a representative patterned film. Increasing the oxygen flow during deposition reduced the carrier density while maintaining the mobility within the range reported for sputtered IGZO. XPS depth profiling showed similar metal-cation compositions across independently prepared films, together with a depth-dependent O 1s bonding gradient across the SiOₓ/IGZO transition. These results indicate that stencil patterning is a practical dry route for IGZO, with potential for transferring the entire process to fragile substrates.
