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 alpha to beta 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. (C) 2013 Elsevier B.V. All rights reserved.