Ali, Abdullah Taha
(2022)
Investigating Random Laser From Aluminium-doped Zinc Oxide Nanorods.
PhD thesis, Universiti Sains Malaysia.
Abstract
In this research, random lasing (RL) properties are investigated from
Aluminium-doped Zinc oxide (AZO) nanorods (NRs) prepared by chemical bath
deposition (CBD) method, then capped with silicon dioxide (SiO2) layer by radio
frequency sputtering technique. The integration of the two approaches aims to improve
ultraviolet RL emission from AZO NRs whilst enabling lasing tunability by adjusting
doping parameters. Therefore, this work is divided into three parts. The first part is to
determine the optimal growth conditions for AZO NRs. The second part is to identify
RL emission properties from AZO NRs. The third part focuses on investigating the
effect of having SiO2 capping layer on ZnO NRs and AZO NRs by varying SiO2
thicknesses. The structural, morphological, optical and electrical properties of the
samples were also investigated for clarity. Increasing Al concentration during the CBD
process led to a decrease in the growth rate and showed an increase in the size of
NRs. This becomes a problem in identifying the RL properties that is due to doping
since there is significant changes in morphology or structure. A different attempt in
increasing the Al doping percentage was done by varying the CBD temperature at a
fixed concentration of 5mM, this concentration, which was determined to be the
maximum concentration that preserves the morphology of AZO NRs, demonstrated to
solve this problem. The sample with the highest doping (1.72 at.%) exhibited the
lowest lasing threshold of 0.192 mW with spectral width less than 0.08 nm.
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