Effects and thermal stability of hydrogen microwave plasma treatment on tetrahedral amorphous carbon films by in situ ultraviolet photoelectron spectroscopy.

This paper reports a comprehensive experimental study on the effects of hydrogen microwave plasma treatment on nonhydrogenated high sp³ content tetrahedral amorphous carbon (ta-C) film. In this study, a surface C–H dipole layer was first observed by high resolution electron energy loss spectroscopy, showing the presence of C–H bonding states. This resulted in the enhancement of electron field emission of the plasma treated films by largely lowering the turn-on field. Thermal stability tests using in situ ultraviolet photoelectron spectroscopy confirm that the C–H dipole layer not only reduces the work function of the films, it is extremely stable in both ambient and vacuum conditions and can sustain up to 600 °C annealing in vacuum. Atomic force microscopy studies also show minimal modifications to the surface morphology, leading to the conclusion that the C–H dipole layer is responsible for lowering the work function. This has improved the electron emission properties which can lead to potential applications such as electron emission displays. [ABSTRACT FROM AUTHOR]