Rh Thin-Film Nanocatalysts as Chemical Sensors - The Flot Electron Effect

Ultra-thin-film 5 rot Rh/TiOx, and Rh/GaN catalytic metal-semiconductor Schottky nanodiodes were fabricated using dc magnetron reactive sputtering, rapid thermal annealing, and electron beam evaporation. 'file diode barrier heights were characterized in different gas mixtures using current-voltage measurements. Harrier heights were found to vary with the local gas composition for Rh/TO4 nanodiodes but did not vary with gas composition for Rh/GaN nanodiodes. The nanodiodes were also studied during the oxidation of CO by O-2 and during the oxidation of CO by NO using chemicurrent measurements and gas chromatography. The hot electron cheoticurrent was determined from the current in situ during reaction and the thermoelectric current measured in oxidizing conditions. Similar activation energies were measured from both the chemicurrent and gas chromatography, which indicates a correlation between hot electron chemicurrent and catalytic: activity.