Fabrication of Homogeneous Nanoporous Structure on 4H‐/6H‐SiC Wafer Surface via Efficient and Eco‐Friendly Electrolytic Plasma‐Assisted Chemical Etching

Abstract

AbstractNanoporous single‐crystal silicon carbide (SiC) is widely used in various applications such as protein dialysis, as a catalyst support, and in photoanodes for photoelectrochemical water splitting. However, the fabrication of nano‐structured SiC is challenging owing to its extreme chemical and mechanical stability. This study demonstrates a highly‐efficient, open‐circuit electrolytic plasma‐assisted chemical etching (EPACE) method without aggressive fluorine‐containing reactants. The EPACE method enables the nano‐structuring of SiC via a plasma‐enveloped microtool traversing over the target material in an electrolyte bath. Through process design, EPACE readily produces a uniform nanoporous layer on a 4H‐SiC wafer in KOH aqueous solution, with adjustable pore diameters in the range 40–130 nm. Plasma diagnosis by optical emission spectrometry (OES) and surface microanalysis reveal that EPACE realizes a nanoporous structure by electrolytic plasma‐assisted oxidation and subsequent thermochemical reduction of an oxide. An increase in voltage or a decrease in etch gap intensifies the plasma and improves the etching efficiency. The maximum etch rate and depth reach 540 nm min−1 and 10 µm, respectively, demonstrating the significant potential of the approach as a time‐saving and sustainable nanofabrication method for industrial applications. Further, the effectiveness of the fabricated SiC nanoporous structure for application in photoelectrochemical water splitting is demonstrated.