The effect of chemical etching of silicon substrates on the field-electron emission (FEE) from amorphous-diamond (a-D) films deposited on silicon has been studied systematically and thoroughly. It is found that the greater the roughness of the silicon substrate, the better the FEE performance of the a-D/silicon emitter. For a sodium hydroxide concentration between 20% and 40%, an etching, temperature in the range of 60-80 degreesC, and an etching time of 15-30 min, etching of the silicon substrate surface was found to be optimal for FEE from the a-D/silicon emitter. To explain the experimental results, qualitative analysis of the enhanced electric field caused by nanoprotrusions. was done. (C) 2003 American Vacuum Society.