A study of electron field emission as a function of film thickness from amorphous carbon films

Abstract

The electron field-emission properties of hydrogenated amorphous carbon and nitrogenated tetrahedral amorphous carbon thin films are examined by measuring the field-emission current as a function of the applied macroscopic electric field. The experimental results indicate the existence of an optimum film thickness for low-threshold electron field emission. The predictions of various emission models are compared to the experimental results.

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

“…[4,5] The low concentration of the more conductive sp 2 clusters is unable to screen the field at the front surface. In this way emission, from these low bias deposited films would be more correctly described as being determined by "the back contact" rather than the "front surface".…”

“…[3] An alternative mechanism in which the presence of a large internal electric field at the film/substrate interface resulting in hotelectron transport -the "back contact" model -has also been proposed. [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.…”

“…In a majority of the samples examined a large (> 40 V/µm) field was required to initiate emission on the first voltage cycle, this reduced after subsequent cycles and is evidence of conditioning of the film. [5] The threshold field (E th ) is defined as the macroscopic electric field which gives an emission current of 1 nA for a conditioned film. Room-temperature EPR measurements were made in a modified Bruker EPR spectrometer using 100 kHz field modulation and a microwave frequency of about 9.9 GHz.…”

Engineering the next generation of large-area displays: prospects and pitfalls

“…Firstly, what is the source of the electrons, secondly, how are the electrons transported through the film and finally, how are the electrons emitted into the vacuum. These questions have broadly led to the 'back contact' model of Amaratunga and Silva and later by Forrest and colleagues (Forrest et al, 1998) in which the rate controlling step is the barrier at the film/substrate interface as described above and to the 'front surface/internal enhancement' model, where the transport through the film and the physics of the film surface/vacuum interface are the most important factors (Carey et al, 2000). In order to investigate the transition from the back contact to the front surface a series of a-C:H films as a function of deposition self-bias were grown.…”

Carbon based electronic materials: applications in electron field emission

“…[17] In this model the a-C film acts as an interlayer with the true cathode being the underlying Si or metal substrate, with the crucial factor being the heterojunction that formed at the back contact. [18] In the case of DLC and ta-C films the density [16] of unpaired electron states near to the Fermi level is higher (10 20 cm -3 ).…”