Hydrothermally grown Pb2+ doped ZnOnanorods for hydrogen and acetylene gas sensing
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Date
2008
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Abstract
Randomly orientated ZnO nanorods were deposited hydrothermally on Si <100> wafers.
The precursor solutions used for ZnO nanorods deposition were zinc chloride + aqueous
ammonia and Zinc nitrate + HMT. ZnO nanorods were deposited on Si<100> wafers to
establish the optimal PH and concentration which yield the best substrate coverage for
each precursor solution. ZnO thin films were deposited on glass substrates using pulsed
laser deposition. These thin films were used for both gas sensing and as seed for
orientated ZnO nanorods deposition. Rutherford Backscattering was used to measure the
thickness and stochiometry of the deposited ZnO films. Orientated ZnO nanorods were
then deposited on glass slides with ZnO thin films using the optimal PH and
concentration for reagents established when Si<100> wafers were used as substrates. Pb
doped ZnO nanorods were prepared by adding Lead (II) Nitrate as the Lead source into
Zinc nitrate + HMT precursor solution. These Pb doped ZnO nanorods were then
deposited on glass substrates with a ZnO thin film. The crystal structure and preferred
plane orientation of all samples was studied using X-ray diffraction. Morphological and
elemental analysis of samples was investigated using Scanning Electron Microscopy
equipped with EDX. All samples showed good ZnO stochiometry with no foreign atoms
except the samples with Pd doped ZnO nanorods. Ag contacts were deposited on the
samples using EDWARDS vacuum coater. The gas sensing characteristics were
investigated on all samples using 20% hydrogen and acetylene as test gases while 80%
nitrogen was used as a carrier gas. ZnO thin films were found be at optimum for
hydrogen gas sensing in the range 300-350oC, the minimum temperature for acetylene
sensing was 400oC. Orientated ZnO nanorods also operated at their optimum in the 300-
350oC range like thin-films, however they exhibited better sensitivity in this range than
thin films. ZnO nanorods started sensing acetylene at 350oC, slightly lower than ZnO thin
films. Pb doped ZnO nanorods were able to sense hydrogen with 67% sensitivity at
250oC. These Pb doped ZnO nanorods were also found to be cable of sensing acetylene
in the whole temperature range.
Description
Dissertation presented in partial fulfilment of the requirements for the degree of Master of Science
to the DEPARTMENT OF PHYSICS
UNIVERSITY OF ZULULAND, 2008.
Keywords
Gas sensing