Novel Diamond Cone Arrays: Single Crystalline and Nanocrystalline

We have developed a new method for fabricating uniform arrays of single crystal diamond and nanodiamond cones with a very high aspect ratio over large areas using a microwave plasma chemical vapor deposition system. The fabrication of diamond nanocones consists of: 1) deposition of diamond films which serve as base materials and 2) subsequent bias-assisted reactive ion etching in hydrogen plasma. In this two-step process [001].oriented diamond films are converted to very sharp diamond cones with an apical angle of 28 deg. and a tip radius as small as 5 nm. Each cone was identified by TEM as a single crystalline diamond with its [001] axis perpendicular to the substrate surface. Alternatively, when nanodiamond films are used as starting materials for reactive etching by hydrogen plasma, arrays of cones composed of nanodiamond are fabricated. The nanodiamond cones show exceptional electron field emission properties, particularly emission durability and stability compared to single crystalline cones.