Novel optical hydrogen sensors based on 3C-SiC membrane and photovoltaic detector

This paper presents novel optical hydrogen sensors using metal catalysts on a transparent 3C-SiC membrane and demonstrates the photovoltaic effects. The 3C-SiC membrane was fabricated by anisotropic etching in a TMAH (tetramethyl ammonium hydroxide) solution. Gasochromic materials of Pd and Pd/WO3 were deposited by sputtering on a 3C-SiC membrane for the gas sensing area. Gasochromic materials become transparent when exposed to hydrogen. Light intensity variations, which pass through the 3C-SiC membrane, generate the photovoltaic response of the P–N junction between N-type 3C-SiC and P-type Si. With the ambient gas of nitrogen, Pd and Pd/WO3 do not show photovoltaic variations with any light intensity change. A single layer of Pd shows a higher photovoltaic response compared with the bilayer of Pd/WO3 with hydrogen. However, in a Pd single layer, the phase transition from α to β is experimentally determined at 6%. The Pd/WO3 structure shows a more linear response to hydrogen in the range of 2–10%. Also, Pd/WO3 shows almost two times the response speed and recovery characteristics of Pd. These fast performances are due to the Pd, which improves the chemical reaction between hydrogen and WO3.