Resonant Tunnelling Behaviour in Multilayered Cold Cathodes Made of Nanoseeded Diamond and Nanocluster Carbon
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RESONANT TUNNELLING BEHAVIOUR IN MULTILAYERED COLD CATHODES MADE OF NANOSEEDED DIAMOND AND NANOCLUSTER CARBON B.S.Satyanarayana* and A.Hiraki. KUT Academic & Industrial Collaboration Centre, Kochi University of Technology, Miyanokuchi, Tosayamada, Kochi, 782-8502, Japan. * Also- Sistec Co Ltd, Nankoku-Shi, Kochi, 783 0014, Japan
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ABSTRACT Multilayered cold cathodes made of spin coated nanocrystalline diamond and cathodic arc process grown nanocluster carbon films, were studied. The nanocrystalline diamond was first coated on to the substrate. The nanocluster carbon films were then deposited on the seeded nanocrystalline diamond coated substrates using the cathodic arc process at room temperature. The resultant hetrostructured microcathodes were observed to exhibit electron emission currents of 1µA/cm2 at fields as low as 1.2 V/µm. Further some of the samples seem to exhibit I-V characteristics with a negative differential resistance region at room temperature conditions. This negative differential resistance or the resonant tunneling behaviour was observed to be dependent on the nanoseeded diamond size and concentration for a given nanocluster carbon film. INTRODUCTION There is an increasing interest in carbon based nanostructured materials like the nanodiamond, nanotubes and nanocluster or nanostructured carbon. The interest stems from the diverse fields of application envisaged for these materials which include, vacuum microelectronics, energy storage systems, MEMS, electronics, nanotechnology and sensors. Recently, these materials including nanocrystalline diamond,[1-3] nanotubes[4,5] and nanocluster carbon[6-10] have been more widely studied as low field electron emitters. In the case of electron emitters the need is for high emission currents at low fields accompanied by a high emission site density. In general the material and the growth process should be adaptable to varying application needs. Most of these nanocarbons have been grown using process such as hot filament CVD, microwave plasma CVD, Plasma assisted DC discharge and cathodic arc process for nanotube growth at high temperatures.[1-5,8] Only the coral like carbon films[6] and the nanocluster carbon films [7] grown using the cathodic arc process have been deposited at room temperature. In an effort to develop room temperature grown carbon based field emitters we have been studying nanocarbon based multilayered structures [10]. Presented in this paper is a study on field emission from these carbon based multilayered cold cathodes, consisting of a layer of nano-diamond and an over coat of nanocluster carbon fabricated at room temperature. These heterostructured microcathodes exhibit very low field electron emission (1µA/cm2 emission current at 1.5-2 V/µm applied field). The emission behaviour was observed to be dependent on the nanoseeded diamond size and concentration for a given optimised nanocluster carbon film composition. Under certain conditions the multilayered cathode consisting of nanodiamond with an overlayer of nanocluster Y8.42.1
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