Role of annealing temperature on structural and optical properties of zinc oxy-nitride films synthesized by powder vapor transport technique

Zinc oxy-nitride (ZnON) is an emerging semiconductor having tunable energy bandgap (Eg) and refractive index (n). Herein, the effect of annealing temperature on ZnON films synthesized on glass substrates at different (50, 100 and 150 sccm) nitrogen gas flow rates (NGFR) by simple powder vapor transport (PVT) technique is studied. All the synthesized ZnON films are annealed at 300 degrees C for 60 min. The unannealed and annealed ZnON (Un-&-An-ZnON) films are characterized by XRD, SEM, Raman and UV spectroscopies. XRD analysis confirms the formation of polycrystalline ZnN films and no diffraction plane related to oxide phase. The crystallinity of -films is increased after annealing, however, it is maximum for 100 sccm NGFR. Raman analysis indicates the presence of vibrational modes related to ZnN and ZnO phases, thereby confirming the formation of ZnON films. After annealing, the surface morphologies of Un-ZnON films is transformed from nano-sheets/nano-blocks to rounded nanoparticles. The change in structural and morphological features of ZnON films, associated with annealing temperature causes to create stresses and defects and hence Eg and n. The values of n (1.85-1.87) and Eg (2.6-2.7 eV) of Un-ZnON films are increased to (1.98-2.62) and (3.16-3.25 eV), after annealing, respectively. These inexpensive but high quality ZnON films can be used for semiconducting and optoelectronic devices.

Automated summary

This study investigates the effect of annealing temperature on ZnON films synthesized using a powder vapor transport technique. The results show that annealing affects the crystallinity, surface morphology, energy bandgap, and refractive index of the ZnON films.