Interface engineering for covalently bonded disordered thin films: boron nitride and diamond-like carbon

Abstract

Covalently bonded disordered thin films, boron nitride (BN) and diamond-like carbon (DLC), have been synthesized by two energetic deposition processes, ion beam-assisted deposition (IBAD) and filtered arc deposition (FAD), respectively. Interface engineering has been conducted for these two films to solve the adhesion and field electron emission problems. For the IBAD BN film, a TiN buffer layer has been built between the BN film and silicon substrate. Delimitation of BN films from substrates, which happens in conventional BN single layer thin films, does not occur with this approach. Structural investigation reveals that the BN layer is cubic phase dominated the small amount of hexagonal phase in the layer located at the interface region close to the underlying TiN layer. Evidence of TiB 2 formation at the interface between BN and TiN has been demonstrated. For the FAD DLC thin film, which is a very attractive cathode material for field electron emission, an intermediate layer of metal Ti has been added between the DLC film and silicon substrate. Then the field emission characteristics of the DLC/Ti films have been studied using a diode structure in comparison with the DLC films without the Ti interfacial layer. It is found that the Ti intermediate layer plays a significant role in improving field emission properties of the FAD DLC thin films. Exceptional field emission performance has been achieved by post-deposition annealing of the DLC thin films with a TiN transition layer. Formation of TiC at the interface, lowering the Schottley barrier for electron transportation from substrate to the DLC thin film, is believed to contribute to the improved field emission.