Morphology and hydrogen sensing studies of the electrodeposited nanostructure palladium on porous silicon

We have investigated hydrogen sensing properties of electrodeposited Pd clusters on macroporous silicon substrates. Porous layer was prepared by electrochemical etching of p-type silicon (100) wafer in organic electrolyte DMF (dimethylformamide) diluted by HF (%95 Vol. %). The deposition of Pd was carried out by linear voltammetry (LV) technique. This technique was taken for reduction of palladium ions in the potential range from 0.4 V to -1 V vs. SCE, at the scan rate of 20 mV s -1 . Some samples were annealed at 300°C for an hour in air to study the effect of heat treatment on their gas sensitivity. Surface structural and chemical properties of the samples were characterised using Scanning Electron Microscopy (SEM) and Energy-Dispersive X-ray Spectroscopy (EDXS), respectively. The LV method results semi-continuous Pd layer contain dispersed clusters on the surface that can behave as catalyst for hydrogen molecules. Variation of sample's electrical current due to various hydrogen concentrations was measured and compared before and after annealing at 300°C. Our data show that annealing process reduces sample sensitivity and recovery times whereas increases the response time. At last a qualitative description has been introduced in the base of oxide formation on the surface of the Pd doped macroporous silicon after annealing process.