Testing the physical properties stability of Zinc (8-hydroxyquinoline) thin films toward stable photodetection performance: Effect of annealing

Abstract

In this study, the effect of thermal annealing on the structural and optical properties of thermally evaporated zinc (8-hydroxyquinoline) (ZnQ2) thin films is discussed in detail. Differential scanning calorimetry analysis revealed the thermal stability of the ZnQ2 powder up to 540 K. Fourier transform infrared spectrometer characterizations revealed the stability of the ZnQ2 molecular structure up to 423 K. The annealing effect on the surface morphology of the ZnQ2 films was tracked using the field emission scanning electron microscope (FE-SEM) technique, which revealed grain growth up to 423 K achieving the highest surface smoothness. Moreover, UV–Vis-NIR spectrophotometric measurements were used to examine how annealing affects the optical characteristics of the prepared films. The optical bandgap of ZnQ2 augmented when the annealing temperature increased to 373 K. The dispersion parameters were estimated from the analysis of the complex refractive index following the single oscillator model. The behavior of nonlinear optical susceptibility suggested the validity of utilizing ZnQ2 thin films in IR and UV optical switching applications and UV photodetection applications.