Characteristics of field emission from silicon tips covered by thin diamond-like carbon films

Abstract

In this investigation we tried to combine the advantages of tips and diamond or diamond-like emitters as low work function jointly with surface asperities play dominant role in the enhancement of emission. The silicon tips with diamond-like carbon (DLC) film covers have been prepared and investigated. DLC films of different thickness and refractive index were grown by PECVD method from CH/sub 4/:H/sub 2/ mixture. In some cases the doping of DLC films by nitrogen has been made during deposition. The dependences of electron field emission efficiency (turn-on field, threshold field) on DLC film parameters have been studied. As a rule, current-voltage characteristics correspond to Fowler-Nordheim relation. However, in some cases of extremely high emission efficiency there is no fitting to the Fowler-Nordheim equation. For these emitters the electric field to indicative emission was very low (up to 10/sup 3/ V/cm). The estimation of effective work functions of the silicon tips with different DLC film covers have been performed. The experimental dependence of effective work function of DLC films on their refractive indexes and empirical curve connected sp3 bond content in DLC film with refractive index are presented. The model for explanation nonmonotonical dependence of effective work function on refractive index based on different relation sp3/sp2 bonds in films have been proposed.