Synthesis and characterisation of low- dimensional zinc oxide nanostructures by solution-immersion and mist-atomisation / Zuraida Khusaimi

Zinc oxide (ZnO) nanostructures on gold-seeded silicon
(Si) substrate were prepared using a low-temperature
solution-immersion method. Optimised ZnO structures
were then used as a template to grow a second layer
of ZnO nanostructures by mistatomisation method.
Low-dimensional, vertically-aligned ZnO nanorods
were successfully synthesised by the solution-immersion
method through optimisation of the reaction parameters,
such as concentration of precursor, ratio of stabiliser,
alignment of substrate in solution, heating medium,
gold-seeded substrates and its thickness, transition
metal-seeded substrates, immersion temperature and
time, pH of precursor solution, annealing temperature
and doping with Mg. SEM, FESEM, TGA, FTIR, XRD, EDX,
PL-Raman and I-V were the selected characterisation
tools to analyse the structural, morphological, bonding,
optical and electrical properties of the nanostructures.
TGA and FTIR analyses gave evidence that the prepared
ZnO nanostructures were pure with no traces of starting
material or contamination. The results give evidence that
6 nm thickness of gold-seeded on Si substrate immersed
for 4 hours at 70°C in precursor concentration of 0.005
– 0.05 M zinc nitrate hexahydrate (Zn(NO3)2.6H2O)
and hexamethylenetetramine (HMTA) at 1:1 ratio has
successfully formed (002) plane, c-axis, aligned ZnO
nanorods with diameter of approximately 60 ± 20 nm. The
nanorods prepared at low immersion temperatures were
found to be readily crystalline with no additional heat
treatment. Precursor solution of pH 6.8 and 5 produced
ZnO nanorods, while at pH 9 produced ZnO flower-like
structures. 1 atomic % of Mg-doped ZnO nanorods were
found to produce the highest electrical conductivity
relative to as-prepared ZnO, and higher doping content
of 3, 5, 7 and 9 atomic %. PL emission spectra of ZnO
nanorods consistently produced UV (362-388 nm) and
visible emissions (400-800 nm), confirming the formation of
a semi-conducting ZnO.