Characterization of thin carbon films capable of low-field electron emission

Abstract

Previous experiments have demonstrated that carbon nanoisland films (or disordered quantum-dot arrays) deposited on silicon wafers may possess the property of low-field electron emission. This paper presents our new work on comparative characterization of emitting and nonemitting thin carbon films. The experimental results acquired by Auger spectroscopy, electron energy loss spectroscopy, Anderson's technique for workfunction measurement, and secondary-emission techniques confirmed that the emitting films are discontinuous and consist of carbon in sp2-hybridization state, while their workfunction is relatively high (>4 eV). These experimental data clearly contradict the commonly accepted Fowler–Nordheim theory of field emission and suggest that the observed emission phenomenon has a different nature. A novel model is proposed as a development of the well-known hot-electron emission mechanism supplemented with nanoscale-related features of thermoelectric phenomena.

Corona with Streamers in Atmospheric Pressure Air in a Highly Inhomogeneous Electric Field

“…The emission of electrons from negative tips is more efficient than their emission from positive ones. Besides, nanoparticles [35] and dielectric films, including carbon [36] , lower the field emission threshold. Therefore, the start voltage of negative coronas is lower.…”

Low-Field Electron Emission Capability of Thin Films on Flat Silicon Substrates: Experiments with Mo and General Model for Refractory Metals and Carbon

“…An important difference between our previous experiments with thin carbon films [38][39][40] and the present work consists in different structures of as-fabricated films. The carbon films studied in [38][39][40] initially comprised nanoislands, whereas in this work (and in [63]), due to technological limitations, we deposited continuous films of metals. The process of agglomeration of flat thin films deposited on non-wettable substrates is known as solid-state dewetting [80,81].…”

“…However, as it has been noted in the Introduction, some of these mechanisms cannot be realized in films and structures of nm-scale thickness. In [39,62], we have proposed a special emission model for islet carbon films deposited on oxidized silicon wafers. The new data on LMF emission from metal thin films force us to revise this model.…”

“…In our previous works [38][39][40], we investigated low-macroscopic-field (LMF) electron emission from island carbon films on silicone substrates coated with a native oxide. Those smooth-surface structures had much in common with the structures discussed above, but in our experiments, no energizing current was passed either through or along the emitting structure.…”

“…To explain the observed LMF emission from such films, we proposed a model that combined elements of the known models of lateral potential variation ("patch field") [45,52,59,60] and hot-electron (or dual-barrier) emission [49,61], and it also accounts for specific nanoscale thermoelectric effects in the article [62]. Our further experiments were aimed at the verification of this model via testing of the LMF emissivity of metal films grown on identical substrates as the carbon films in [38][39][40]. Early results of these experiments were reported in [63].…”