Abstract
We demonstrate that diaphragms for sensor applications can be fabricated by laser ablation in a~variety of substrates such as ceramics, glass, sapphire or SiC. However, ablation can cause pinholes in membranes made of SiC, Si and metals. Our experiments indicate that pinhole defects in the ablated membranes are affected by ripple structures related to the polarization of the laser. From our simulation results on light propagation in Laser-Induced Periodic Surface Structures (LIPSS) we find out that they are acting as a slot waveguide in SiC material. The results further show that field intensity is enhanced inside LIPSS and spreads out at surface distortions promoting the formation of pinholes. The membrane corner area is most vulnerable for pinhole formation. Pinholes funnel laser radiation into the bulk material causing structural damage and stress in the membrane. We show that a~polarization flipping technique inhibits the formation of pin holes caused by LIPSS.
Highlights
Membranes are widely used as a structural unit for various sensor applications, MEMS, micro devices used in biology, medicine or life science [1] and [2]
We demonstrate that diaphragms for sensor applications can be fabricated by laser ablation in a variety of substrates such as ceramics, glass, sapphire or SiC
From our simulation results on light propagation in Laser-Induced Periodic Surface Structures (LIPSS) we find out that they are acting as a slot waveguide in SiC material
Summary
Membranes are widely used as a structural unit for various sensor applications, MEMS, micro devices used in biology, medicine or life science [1] and [2]. The materials we tested (including diamond) revealed Laser-Induced Periodic Surface Structures (LIPSS) similar as investigated in [8]. Comparing experimental and simulation results, we found that LIPSS are acting as slot waveguides in high refractive materials and can trigger the formation of pinholes. The generation and orientation of LIPSS in different materials during fs-laser ablation using linear polarized light were extensively studied in [8]. In materials we investigated, LIPSS were created perpendicular to the direction of the laser polarization. Such an angular orientated configuration is most suitable for a good perc 2017 ADVANCES IN ELECTRICAL AND ELECTRONIC ENGINEERING. The slot waveguide approach does not explain the formation of LIPSS and small pinholes some hundreds of nanometer in diameter. Offered a possibility to distinguish whether the scan pattern rotation or the polarization change is the dominant parameter for a proper surface quality of the obtained diaphragm
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