Preparation And Field Emission Properties Of ZnO Arrays

Zinc oxide(ZnO)has been considered as an excellent field emission cathode material,because of its unique structure,wide direct band gap,negative electron affinity,good physical and chemical properties.One-dimensional ZnO nanostructures have many advantages,such as a simple synthesis process,low cost and easy device manufacture.However,one-dimensional ZnO nanostructures have some problems such as small surface area and poor stability.Multi-dimensional ZnO nanostructures were attracted by many researchers because of large surface area and stable performance.In this paper,patterned ZnO films were fabricated directly by inkjet printing method,and then ZnO arrays were prepared by electrochemical deposition method.This strategy controlled the growth of ZnO arrays in a certain area through inkjet printing,which reduced distribution density and field screen effect.Moreover,the local electric field was remarkably enhanced by sharp tips on the dendritic ZnO arrays prepared by electrodeposition.Each ZnO branch on the trunks would be regarded as an independent emitting site,and thus the field emission properties had been improved.ZnO nanostructures were fabricated by electrochemical deposition method.The effects of deposition time,deposition current on the surface morphologies and field emission properties of ZnO nanostructures were investigated.The results showed that ZnO structures were grown from nanorods to nanodendrites with increasing the deposition time from 30 min to 120 min.The deposition current also played a great role in the morphology of ZnO.At a deposition current of 2 mA,the prepared nano-ZnO was nanorod,while it turned to dendritic morphology at a deposition current higher than 3mA.The dendritic ZnO nanostructures prepared at a deposition time of 90 min and a deposition current of 3 mA exhibited the lowest turn-on field of 1.54V/?m.Secondly,the patterned ZnO films worked as seed layer for the growth of ZnO nanostructures.ZnO aqueous solution ink,ZnO anhydrous 2-methoxyethanol(EGME)solution ink and ZnO ethanol solution ink were prepared by using zinc acetate as solute,mono-ethanol-amine(MEA)as surfactant,pure water,EGME and ethanol as solvents,respectively.The printability of ZnO aqueous solution ink was poor,because printing films could not be uniform after heating.So the effects of zinc acetate concentration and MEA concentration on ZnO ink(ZnO EGME solution ink and ZnO ethanol solution ink)performances were studied.Viscosity was the key factor to obtain stable drop in inkjet printing.The ZnO EGME solution and ZnO ethanol solution ink prepared at a zinc acetate concentration of 0.5 M and a MEA concentration of 1 M was the most stable and suitable for inkjet printing.ZnO nano-dendritic arrays were fabricated by inkjet printing and electrochemical deposition methods.The ZnO nano-dendritic arrays had better field emission property than ZnO array prepared by inkjet printing and hydrothermal method due to many field emission tips,which showed a low turn-on field of 1.14 V/?m.In additional,the effects of ink formulation on ZnO arrays prepared by inkjet printing and electrodeposition were studied.The results showed that the ZnO arrays fabricated by ZnO ethanol solution ink exhibited a better field emission property.