UV-Assisted Alcohol Sensing Using SnO_(2) Functionalized GaN Nanowire Devices
Ritu Bajpai, Abhishek Motayed, Albert Davydov, Vladimir Oleshko, Geetha G. Aluri, Kristine A. Bertness, Mulpuri V. Rao, Mona E. Zaghloul
A chemiresistor type sensor for selective alcohol sensing has been realized from gallium nitride nanowires (NWs) functionalized with sputter-deposited tin dioxide nanoparticles. Two-terminal devices were fabricated using standard microfabrication techniques with the individual NWs air-bridged between the two metal contact pads. Combination of X-ray diffraction (XRD), electron-backscatter-diffraction (EBSD) and TEM/STEM confirmed the presence of rutile SnO2 nanocrystals on the GaN surface. Change in device current is observed when the device is exposed to alcohol vapors (methanol, ethanol, propanol and butanol) at room temperature under 215-400 nm UV illumination with 375 nW/cm2 intensity at 365 nm wavelength. The sensor reproducibly responded to a wide range of alcohol vapor concentrations, from 5000 parts per million (ppm) down to 1 ppm in air. Notably, devices show low sensitivity to acetone and hexane, which allows to selectively detect first few primary alcohol vapors mixed with these two common volatile organic compounds (VOCs). Also no response is observed towards the alcohols in absence of UV excitation. From the experimental results we found a relation between the chemical sensitivity and the length of carbon chain in the alcohol molecule: the chemiresistive response was decreasing with the increasing carbon chain from methanol to n-butanol. Also the isomeric branching in i-propanol and i-butanol caused reduced sensitivity as compared to n-propanol and n-butanol, respectively. We have qualitatively explained the sensor operation by employing a mechanism, which includes oxidation of analyte molecules on the SnO2 surface, leading to enhanced photoconductivity in GaN nanowire.
, Motayed, A.
, Davydov, A.
, Oleshko, V.
, Aluri, G.
, Bertness, K.
, Rao, M.
and Zaghloul, M.
UV-Assisted Alcohol Sensing Using SnO_(2) Functionalized GaN Nanowire Devices, Sensors and Actuators B-Chemical, [online], https://doi.org/10.1016/j.snb.2012.05.018
(Accessed November 30, 2023)