Growth and luminescence characteristics of zinc oxide thin films deposited by ALD technique

A striking correlation is observed between the characteristic defect-mediated deep level luminescence and deposition temperature of the zinc oxide (ZnO) thin films made by atomic layer deposition (ALD) technique. Near-ideal and virtually defect-free zinc oxide films are deposited at a temperature of 150 degrees C. However, distinct long-wavelength broadband luminescence features are identified for yellow (maxima at 570 nm) and green (maxima at 500 nm) at lower and higher temperature regimes of 150 degrees C, respectively. The decay time for yellow and green luminescence is different, having slower decay components for the yellow luminescence. The multi-step relaxation process governing the luminescence is discussed under the theory of efficient trapping of a photo-generated hole at a surface species in the first step, and radiative recombination at a deep-level acceptor type defect in the final step. Excess non-radiative surface recombination at the surface species is responsible for the shortening of the decay time of green emission line.

Automated summary

A strong correlation exists between the defect-mediated luminescence of zinc oxide thin films deposited using atomic layer deposition (ALD) technique and the deposition temperature. Films with minimal defects are obtained at 150 degrees C, while distinct long-wavelength luminescence features are observed for yellow and green at lower and higher temperature regimes, both at 150 degrees C. The decay time for yellow and green luminescence differs, with slower decay components for yellow luminescence.