Position-controlled ZnO nanoflower arrays grown on glass substrates for electron emitter application.

The electron emission of position-controlled grown ZnO nanoflowers was investigated for application in cold cathode electron emission devices. ZnO nanoflower arrays, composed of several nanoneedles with sharp tips, were grown selectively on a conducting glass substrate using a chemical solution deposition method. The morphology and position of the ZnO nanoflowers were controlled by preparing polymethylmethacrylate submicron patterns using electron-beam lithography. Without the patterns, in contrast, vertical ZnO nanoneedles were randomly grown on the substrates with high density. Several samples prepared at the same conditions exhibited almost the same nanoflower morphology and field emission characteristics. Comparison of the field emission characteristics of the ZnO nanoflower arrays and ZnO nanoneedles showed that the arrays had excellent electron emission characteristics, with a low turn-on electric field of 0.13 V µm(-1) at 0.1 µA cm(-2) and a high emission current density of 0.8 mA cm(-2) in an applied electric field of 9.0 V µm(-1). Furthermore, light-emitting devices made using ZnO nanoflower arrays demonstrated strong light emission, and micropixels for display application were clearly displayed.