Temperature dependent selective and sensitive terbium doped ZnO nanostructures

In the present work, influence of terbium doping on structural, morphological, optical and gas sensing properties of zinc oxide has been studied. A chemical route was adopted for synthesis of pure and terbium (Tb) doped zinc oxide. X-ray diffraction study confirmed the formation of hexagonal wurtzite structure for synthesized materials. Raman analysis revealed the shifting and broadening of peaks with increase in Tb concentration. The presence of terbium in ZnO and its oxidation states was confirmed using X-ray photoelectron spectroscopy. Photoluminescence emissions indicated increase in concentration of oxygen vacancies with introduction of dopant. Gas sensors were fabricated out of synthesized samples and it was observed that doped samples have significantly high sensing response, temperature dependent selectivity toward ethanol and acetone, and sensors were able to detect even low concentration (∼10 ppm) of these vapors. The temperature dependent selectivity of terbium doped ZnO depends on target gas which may be ascribed to interaction of target gas molecules and doped metal oxide surface at optimum operating temperature. It was found that 4% Tb doped ZnO sensor exhibited maximum sensor response toward ethanol and acetone. The enhanced sensing response has been attributed to increase in oxygen vacancies, reduction in particle size, large structural disorders and high surface basicity.