Localized DLC etching by a non-thermal atmospheric-pressure helium plasma jet in ambient air

Abstract

Using a versatile atmospheric-pressure helium plasma jet, diamond-like carbon (DLC) films were etched in ambient air. We observed that the DLC films are etched at a nominal rate of around 60nm/min in the treated area (230μm in diameter) during a 20-min exposure. The etching rate increased after the initial 10-min exposure. During this period, the flat DLC surface was structurally modified to produce carbon nanostructures with a density of ~2.4×1011cm−2. With this increase in surface area, the etching rate increased. After 20min, the DLC film had a circular pattern etched into it down to the substrate where silicon nanostructures were observed with sizes varying from 10nm to 1μm. The initial carbon nanostructure formation is believed to involve selective removal of the sp2-bonded carbon domains. The carbon etching results from the formation of reactive oxygen species in the plasma.