Field-emission properties of Al:ZnO whisker emitters with various crystallite lengths and densities

The field-emission properties of Al:ZnO whisker emitters were investigated by varying the crystallite density and length. The crystallite density could be varied by adjusting the reactant concentration or the substrate temperature under which whiskers were formed. When the crystallite density was decreased from 18 x 10(4) to 3 x 10(4)/mm(2) and the crystallite length was increased from 12 to 19 mu m, the electric field necessary to obtain a current density of 100 mu A/cm(2) decreased from 7.0 to the range of 3.6 to 4.9 V/mu m. After the field emission, the crystallite density of some samples decreased. The electric field necessary to obtain a cathode current density of 100 mu A/cm(2) decreased with increasing geometric electric field enhancement factor beta.