| dc.description.abstract | Nanotechnology has strong influence over many known technologies with plenty of
advantages, such as low-cost and larger surface-area-to-volume ratio compared with
their bulk counterpart. Among II-IV semiconductor materials zinc oxide (ZnO) is an ntype semiconductor with band gap energy of 3.37 eV and having large exciton binding
energy of ~ 60 meV. ZnO and its alloys have vast device applications mainly in
manufacturing of light emitting diodes (LEDs), solar cells, optical waveguides and
Ultraviolet (UV) photodetectors. Ultraviolet (UV) photodetectors are widely used in
various commercial and military applications, especially to secure space-to-space communications, pollution monitoring, water sterilization, flame sensing, and early
missile plume detection. In contrast to gallium nitride (GaN), ZnO has a highest
electron saturation velocity thus, photodetectors equipped with ZnO can perform at a
maximum operation speed. The objective of research is to deposit ZnO thin film and
ZnO nanorods by sol-gel method at selective area of microgap electrodes spacing and
characterization for ultraviolet (UV) sensing application. Therefore the Zerogap
structure of butterfly topology was designed by AutoCAD software, and to achieve the
better resolution during photo masking process the design was transferred to
commercial chrome glass photomask. All the area selective deposited ZnO based nanosensors
were further tested for ultraviolet (UV) sensing application. On exposure of
ultraviolet (UV) light the current gains, response/recovery times, repeatability,
sensitivity, reproductivity and responsivity of the fabricated ZnO based microgap
electrodes sensors displayed the promising application for UV light detection.
Moreover the signal detection at low operating voltage (1 V) revealed that fabricated
sensors can be used for miniaturized devices with low power consumption. The surface
morphologies structural, optical and electrical properties of the synthesized
nanostructures ZnO were characterized using SEM, XRD, and sourcemeter
respectively. To study the doping effect on ZnO nanostructures finally, tin (Sn) was
selected, and successfully synthesized on glass substrate by low temperature sol-gel
hydrothermal growth process. The as synthesized Sn-doped ZnO nanorods were post
annealed at three different temperatures and investigated the effect of post-annealing
temperatures on structural, optical, electrical and photoresponse properties by using Xray
diffraction, UV-Vis spectroscopy, I-V and i-t measurements. The crystallinity and
c-axis orientation of Sn-doped ZnO nanorods were increased with annealing
temperatures. As post-annealing temperature increased the Sn-doped ZnO nanorods
showed noticeable variations having agglomerated and spherical shape at surface
morphology than those at a lower post-annealing temperature; this result indicates that
the samples are highly crystalline in nature. The optical bandgap energy of Sn-doped
ZnO nanorods decreased as annealing temperature increases. Electrical characteristics
reveal the effect of annealing temperature on resistivity and photoresponse properties of
Sn-doped ZnO nanorods. Hence, the proposed Herve and Vandamme model and the
improved ultraviolet (UV) photoresponse of post-annealed samples are applicable in
optoelectronic device applications. | en_US |
