Structural, optical and field emission properties of ZnO nanowires grown by non-catalytic thermal evaporation process

Abstract

Well-crystallised vertically aligned ZnO nanowires have been synthesised on silicon substrate via simple thermal evaporation process without the use of metal catalysis or additives at 750°C by using metallic zinc powder and oxygen gas as source materials for zinc and oxygen, respectively. The X-ray diffraction (XRD) pattern of the grown nanowires reveals that the grown structures are well-crystalline and possessing a wurtzite hexagonal phase. The room-temperature PL spectrum exhibited a sharp and strong UV emission with a broad green emission confirming good optical properties for the as-grown ZnO nanowires. The field emission characterisation exhibited that a turn-on field for the vertically aligned ZnO nanowires was 3.7 V/μm and the emission current density reached to 0.014 mA/cm² at an applied electrical field of ∼5.5 V/μm and shows no saturation. Moreover, the ZnO nanowire based field emission device exhibited a uniform light emission.