Development of long lifetime cathode materials for microplasma application

Abstract

In this paper we present the growth of three kinds of diamond films including ultrananocrystalline diamond (UNCD), nitrogen doped UNCD and hybrid granular structured diamond (HiD) films on Au coated silicon for applying as a cathode in a parallel-plate type microplasma device. The phase constituents and microstructures of these diamond films were investigated in order to understand the role of the intrinsic properties of these cathode materials on manipulation of the plasma characteristics of the corresponding devices. We observed that, while the diamond materials with a high fraction of sp²-bonded carbons exhibited superior electron field emission (EFE) properties and hence better plasma illumination (PI) behavior, the cathode materials with a suitable microstructure are required to ensure longer lifetime for practical applications of the microplasma devices. Based on these observations, we have developed hybrid granular structured diamond films, in which the sp²-bonded carbons were hidden in the boundaries between the sp³-bonded diamond grains, such that the films exhibited not only excellent EFE properties and PI behavior but also good PI behavior with long lifetime.