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<p>Zinc aluminate (ZnAl<sub>2</sub>O<sub>4</sub>), a wide band gap semiconductor, is a promising material for blue-emitting optoelectronic applications. In this study, ZnAl<sub>2</sub>O<sub>4</sub> thin films were deposited on glass substrates by chemical spray pyrolysis at substrate temperatures between 350 and 450&#xa0;°C. The novelty of this work lies in establishing a systematic correlation between structural properties, defect-mediated emission, chromaticity behaviour, and time-resolved photoluminescence dynamics as a function of deposition temperature. X-ray diffraction confirmed the formation of a cubic spinel structure, with the film deposited at 400&#xa0;°C showing a dominant (311) orientation and improved crystallinity. Optical measurements revealed high transparency and band gaps ranging from 3.84 to 3.90&#xa0;eV, with the highest value observed at 400&#xa0;°C. The SEM images reveal stone-like and nearly spherical grains with noticeable variations in grain distribution and connectivity as a function of substrate temperature. Under 224&#xa0;nm excitation, all films exhibited dominant blue emission with chromaticity coordinates located in the blue–violet region. Time-resolved photoluminescence analysis showed that the 400&#xa0;°C film possesses the longest lifetime (1269&#xa0;ns) and highest quantum efficiency (49%), indicating reduced non-radiative recombination. These results demonstrate that substrate temperature effectively governs defect-related recombination processes, enabling optimization of blue emission in ZnAl<sub>2</sub>O<sub>4</sub> thin films.</p>

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Temperature-driven structural and optical modulation in spray-deposited ZnAl2O4 thin films for blue light LED and LASER applications

  • 期刊论文

  • 发表日期：

    2026年5月20日

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  • J. Merrila Nissi,
  • R. Shabu,
  • T. R. Beena,
  • J. T. Anandhi

摘要

Zinc aluminate (ZnAl2O4), a wide band gap semiconductor, is a promising material for blue-emitting optoelectronic applications. In this study, ZnAl2O4 thin films were deposited on glass substrates by chemical spray pyrolysis at substrate temperatures between 350 and 450 °C. The novelty of this work lies in establishing a systematic correlation between structural properties, defect-mediated emission, chromaticity behaviour, and time-resolved photoluminescence dynamics as a function of deposition temperature. X-ray diffraction confirmed the formation of a cubic spinel structure, with the film deposited at 400 °C showing a dominant (311) orientation and improved crystallinity. Optical measurements revealed high transparency and band gaps ranging from 3.84 to 3.90 eV, with the highest value observed at 400 °C. The SEM images reveal stone-like and nearly spherical grains with noticeable variations in grain distribution and connectivity as a function of substrate temperature. Under 224 nm excitation, all films exhibited dominant blue emission with chromaticity coordinates located in the blue–violet region. Time-resolved photoluminescence analysis showed that the 400 °C film possesses the longest lifetime (1269 ns) and highest quantum efficiency (49%), indicating reduced non-radiative recombination. These results demonstrate that substrate temperature effectively governs defect-related recombination processes, enabling optimization of blue emission in ZnAl2O4 thin films.