Time dependent growth of ZnO nanoflowers with enhanced field emission properties

Herein, we report the facile growth of ZnO nanoflowers composed of nanorods on silicon substrate by non-catalytic thermal evaporation process. The grown nanoflowers were examined in terms of their morphological, structural, optical and field emission properties. The detailed characterizations revealed that the nanoflowers are grown in high density, possessing well-crystallinity and exhibiting wurtzite hexagonal phase. The Raman-scattering spectrum shows a sharp optical-phonon E-2 mode at 437 cm(-1) which confirmed the wurtzite hexagonal phase for the grown nanoflowers. The room-temperature PL spectrum depict a strong ultraviolet emission at 381 nm, revealed good optical properties for the ZnO nanoflowers. The field emission studies revealed that a turn-on field for the ZnO nanoflowers based field emission device was 4.3 V/mu m and the emission current density reached to 0.075 mA/cm(2) at an applied electric field of 7.2 V/mu m and exhibit no saturation. The field enhancement factor 'beta' for the fabricated device was estimated from the F-N plot and found to be similar to 2.75 x 10(3). Finally, systematic time-dependent experiments were performed to determine the growth process for the formation of ZnO nanoflowers composed of nanorods. (C) 2016 Elsevier Ltd and Techna Group S.r.l. All rights reserved.