Amorphous diamond is diamond-like carbon (DLC) that contains no other impurities. It can be conveniently deposited by bombarding a substrate with a cathodic are. The arc contains a flux of ionized carbon atoms that are driven by a negative bias. In this research, this bias is set at 20 V. Various forms of amorphous diamond were deposited on silicon substrate of n-type (100) by varying the arc current set at 30, 50, 80, and 100 A. The sp(3)/(sp(3) + sp(2)) ratios of these deposited coatings were measured by electron spectroscopy for chemical analysis and Raman spectroscopy, and the asperity height these films were imaged by an atomic force microscope. It was found that the sp(3)/(sp(3) + sp(2)) ratio peaked at a value of about 50% when the current was set at 80 A. The average roughness increased linearly with the increasing current from similar to0.5 mn at 30 A to about 1.1 run at 100 A. The maximum asperity height was approximately 10 times that of the above average roughness figures in all cases. The minimum effective work function (Phi(e)) calculated by a Fowler-Nordheim plot was about 0.063 14 eV. By controlling the asperity height of amorphous diamond, high-emitting efficiencies could be achieved with good reproducibility.