Effect of reactive gas additives on surface morphology evolution of stainless steel substrate undergoing low energy Ar ion bombardment

•We investigate surface of stainless steel substrates after plasma ion sputtering.•Roughness (Ra) increases after ion sputtering from 2 nm to 38 nm with Ar gas plasma.•Addition of 1% dry air to the Ar reduces roughening from 38 nm to 4 nm.•AES profiling of the substrates shows significant difference for Ar and Ar/air cases.•Chemically active gases can be used for roughness control during ion sputtering.

In many cases surface ion bombardment results in roughening of metal's and alloy's surfaces. In the present study, a phenomenon of surface roughening inhibition during the ion bombardment is presented. The phenomenon occurred during the plasma extracted ion sputter etching at normal incidence with 400 eV positive ions, when 1% of dried air was added into the plasma forming Ar gas. Two 18%Cr–10%Ni mechanically polished to about 2 nm average roughness (Ra) stainless steel test pieces were sputter etched with and without the air additive. The roughening was inhibited to Ra ≈ 4 nm, which was about 9.5 times lower than that of the sputtered without air additive (Ra ≈ 38 nm). The phenomenon is discussed in terms of chemisorption of active plasma species introduced by the air additive and competing roughening/smoothening mechanisms.