We have formed two type very thin whiskers on a diamond substrate using a RIE technique. We have found by observation of TEM that the whisker is a single crystal diamond. Diamond whiskers using O-2 = 100% gas have a size of<200 nm and the minimum size of approximately 2 nm. Diamond whiskers using CF4 /O-2 =1% gas have a size of 50 to 200 nm and the minimum top size of<5 nm. diamond whisker RIE TEM FE-SEM