Influence of lithium on Cu-doped ZnO thin films fabricated via sol-gel spin coating technique for improved NO₂ gas sensing applications

We demonstrate the influence of lithium on copper-doped ZnO-based thin films for improved NO₂ gas sensing applications fabricated via the sol-gel spin coating technique. Structure studies confirmed hexagonal wurtzite structure and morphological analysis showed evenly dispersed, agglomerated spherical particles with an average grain size ranging from 25.94 to 30.79 nm. Lithium-doped Cu-ZnO with more surface oxygen vacancies and a higher carrier density demonstrated outstanding NO₂ gas sensitivity, excellent repeatability, excellent stability, and high selectivity at 210 °C. A possible gas-sensing mechanism is also discussed and correlated with structural, morphological, spectral, and electrical parameters.