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

• Local DLC etching was demonstrated using an atmospheric pressure plasma jet in air.
• Reactive oxygen species created interactions between the plasma jet and ambient air.
• The etching proceeded non-linearly due to developing of surface nano-structures.

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 60 nm/min in the treated area (230 μm 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 × 1011 cm− 2. With this increase in surface area, the etching rate increased. After 20 min, the DLC film had a circular pattern etched into it down to the substrate where silicon nanostructures were observed with sizes varying from 10 nm to 1 μm. 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.