Articles written in Pramana – Journal of Physics
Volume 96 All articles Published: 20 April 2022 Article ID 0083 Research Article
A new model to estimate size distribution from the emission spectra of ZnO nanorods used for highly sensitive ammonia sensors
Ammonia gas sensors were fabricated using vertical ZnO nanorods (NR) on templated substrates using a new technique. The sensitivity was found to be 61% and with low response and recovery times of 6 and 13 s, respectively, for 10 ppm of NH$_3$. With an increase in growth duration, although the length and crystal sizes increased by 30% (600 to 800 nm) and 70%, i.e. 42 to 71 nm, respectively, the sensitivity dropped from 61 to 40%. With the increase in crystallinity, a decrease in strain was also found. The material showed weak quantum confinement,with a blueshift ranging from 20 to 120 meV for 5 mmol concentration, for an increase in growth duration from 3 to 7.5 h. Photoluminescence (PL) emissions showed broad convolution of multiple peaks corresponding to exciton transitions and defect-related transitions. A new model was developed to estimate NR size from the PL spectra. This model assumed a certain depth from the surface within which the recombinations occur due to redox reactionson exposure to gas. A change of radius from 15 to 23 nm was found when the PL intensity ratio changed from 0.042 to 1 for a depth of 10 nm, using this model.
Volume 97, 2023
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