Electron field emission from surface treated tetrahedral amorphous carbon films

Abstract

The electron field emission properties of tetrahedral amorphous carbon thin films deposited using a filtered cathodic vacuum arc system have improved as a result of surface treatment with H, O, and Ar ions. The limiting factor of the emission process does not appear to be only the front surface of the films. The improvement in the emission after ion beam treatment appears to be independent of the ions used. The surface which has been analyzed using ultraviolet photospectroscopy, reflected electron energy loss spectroscopy, and scanning tunneling microscopy shows evidence of the creation of segregated sp 2 and sp 3 rich regions of less than 20 nm in dimension. An extension to the space charge-induced band bending model including a multistep emission process that occurs in this mixed phase material is proposed.

Influence of sp2 clusters on the field emission properties of amorphous carbon thin films

“…[4] The reduction of the threshold field with N content [4], the dependence of the threshold field with film thickness [5], and the non-uniformity of emission across a film surface have also been reported. [6,7] The relative proportion of the different hybridised C states influences the electronic structure with the optical properties being largely controlled by the size of sp 2 clusters. [8,9].…”

Modeling of the electron field emission process in polycrystalline diamond and diamond-like carbon thin films

“…The DLC in the diamond grain boundaries effectively acts as a stepping stone for the emission of electrons by providing a two ͑or multi͒ stage process for the gaining of energy. 24 Although it is possible for the electrons to be directly emitted to the vacuum from the DLC ͑grain boundaries͒ if it were to gain sufficient energy, it would have to overcome a significantly larger surface barrier in comparison to if it were to use the two or multistage process. Therefore, it is more probable that the emission will be via the diamond surface rather than the grain boundaries.…”

“…Due to the amorphous nature of the grain boundaries it is quite possible that instead of two barriers there could be multiple barrier components associated in a mixed sp 3 /sp 2 phase material. 24 Assuming a typical value for the DLC grain boundary thickness of 10-20 nm, 21 and an active nitrogen dopant concentration of say 5ϫ10 18 cm Ϫ3 (ϳ3ϫ10 20 cm Ϫ3 was measured as the N content 7 ͒ in the n-doped diamond films discussed here, values between 1 and 5 V are calculated for the potential drop in the space charge induced fully depleted DLC layer purely based on the solution to Poisson's equation. In this calculation, an electron affinity and mobility gap of 2.5 and 2.0 eV have been assumed for the DLC in the grain boundaries.…”

Polycrystalline InN thin films prepared by ion-beam-assisted filtered cathodic vacuum arc technique

“…Many progresses have been achieved in improving the crystal quality of InN. However, in comparison with the conventional semiconductor growth techniques, filtered cathodic vacuum arc (FCVA) technique offers several advantages as a versatile, large area and low processing temperature, and thus it has been proven useful in many areas [7,8]. This technique has a great potential in developing group-III nitrides semiconductor, especially InN films.…”