Plasma Etching Chemistry for Smoothening of Ultrananocrystalline Diamond Films

A new process to controllably smoothen ultrananocrystalline diamond films using H2/O2 plasma is presented. Diamond films were exposed to oxygen, hydrogen and hydrogen/oxygen mixture (19:1) plasmas. Evolution of morphology and thickness were monitored ex-situ using scanning electron microscopy (SEM) while roughness was measured using atomic force microscopy (AFM). Neither pure oxygen nor pure hydrogen plasmas were found suitable for smoothening the films. The H2/O2 mixture plasma exposure resulted in a constant roughness decrement of 0.043 nm/min with a slow etching rate (0.07 μm/h) allowing for the control of the final film roughness without sacrificing too much of the material thickness.