Field emission enhancement of ZnO nanorod arrays with hafnium nitride coating

Abstract

Vertically well-aligned single crystal ZnO nanorod arrays were synthesized and enhanced field electron emission was achieved with hafnium nitride (HfN x ) coating under proper sputtering condition. HfN x films with various composition have been coated on ZnO nanorod arrays using a reactive direct current (DC) magnetron sputtering system. Morphology and crystal configuration of the ZnO nanorod arrays were investigated by scanning electron microscopy and X-ray diffraction. The field emission properties of the coated and uncoated ZnO nanorod arrays were characterized. The as-grown ZnO nanorod arrays showed a turn-on electric field of 6.60 V μm − 1 at a current density of 10 μA cm − 2 and an emission current density of 1 mA cm − 2 under the field of 9.32 V μm − 1 . While the turn-on electric field of the coated ZnO nanorod arrays sharply decreased to 2.42 V μm − 1 , an emission current density of 1 mA cm − 2 under the field of only 4.30 V μm − 1 can be obtained. A method to accurately measure the work function of the coated films was demonstrated.