Enhancement of sp3 hybridized C in amorphous carbon films by Ar ion bombardment and Si incorporation

Abstract

We report an effective method of increasing the sp3 hybridization fraction in sputtered amorphous carbon (a-C) film by the combination of Ar ion bombardment and Si incorporation. In the deposition of an a-C film, Ar ion bombardment by controlling the applied bias voltage plays a role in creating high stress in film and causes the local bonding configuration to change to a sp3 hybridized bond. Simultaneously, the incorporated Si in an a-C network breaks the sp2 hybridized bonded ring and promotes the formation of a sp3 hybridized bond. This enhancement of the sp3 hybridized bonding characteristic is maximized for an a-C film with 23 at. % of Si and 100–150 V of applied bias voltage. In this region, the increase of resistivity, optical band gap, and mechanical hardness of a-C is attributed to the reduction of the sp2 hybridized bonded ring and increased fraction of the sp3 hybridized bond. However, at a higher bias voltage above 150 V, the enhancement effect is reduced due to the resputtering and thermally activated reconversion of a sp3 to a sp2 hybridized bond.