Gas sensing properties of single crystalline ZnO nanowires grown by thermal evaporation technique

The ZnO NWs were applied as effective material for the fabrication of ethanol (C₂H₅OH) and carbon monoxide (CO) gas sensor. The ZnO NWs were grown by thermal evaporation techniques on non-catalytic Si (100) substrates. The average width and length of ZnO NWs was 60 nm and 20 μm, respectively and they were single crystalline in nature. The maximum response was 51.64 at 300 C for 1000 ppm of CO gas, while 104.23 at 400 C for 250 ppm of ethanol gas. The response of ZnO NWs was very high for ethanol compared to the CO, whereas the recovery time for ethanol was very poor compare to CO gas. The response of ZnO NWs was about 25 times higher for ethanol compare to CO, at 400 C for 100 ppm of each gas. The high response for ethanol is related to electron donating effect of ethanol (10e^-) which was higher than the CO gas (2e^-). The high response of ZnO NWs was attributed to large contacting surface area for electrons, oxygen, target gas molecule, and abundant channels for gas diffusion.