Details are given of a systematic experimental study into the effect of interface structure on-the field emission properties of nanostructures using amorphous diamond (a-D) films. The field electron emission experiments indicates a better field emission characteristic after predepositing a metal (Al or Ti) interlayer. The effect of chemical etching of silicon. substrate on the field emission of a-D film/silicon has been studied systematically. In addition, surface features of the film considered to be responsible for low field emission are discovered. Based on this latter finding, a new mechanism named field-induced transform step enhanced emission mechanism, which is responsible for electron emission from a-D film, is presented. (C) 2003 American Vacuum Society.