ИСТИНА

Field emission (FE) properties of various nanocarbon materials have been examined using a scanning anode field emission microscopy (SAFEM) technique. The scanning anode was made of a tungsten wire with micron sized tip. The anode had an ability to scan the area of 1x1mm2 and move in vertical direction in the range of 50 µm. The FE properties were examined with voltage applied between the nanocarbon sample and the anode. The FE current dependencies vs. applied voltage and other parameters of the FE obtained during scanning were analyzed and compared for different nanocarbons. The materials examined included films consisting of entangled single-wall carbon nanotubes (SWNTs) obtained by an aerosol method [1] (the samples for these investigations were supplied by Dr. A. Nasibulin from Aalto University) and nanographite films consisting of the few-layer graphene (FLG) flakes obtained by a CVD method [2]. The flakes have predominant orientation perpendicularly to the flat Si substrates. The FE properties of the films prepared with different parameters of the synthesis processes were examined. Obtained data revealed that there is clear correlation of the current density and emission cites distribution depending on the type and thickness of the film. The possible reasons for the observed differences are discussed. The FE degradation of individual emission cites at high emission currents has been investigated in other experiments where FE parameters, at which the destruction of individual emission sites occurred, were determined. Using obtained data the maximum average current for the multiemitter FE cathodes consisting of tip-like emitters was estimated to be in the range of 1-10 A/cm2. The FE properties of the planar CVD thin graphite films deposited on dielectric glass substrates were investigate using the SAFEM technique. A high density stable FE current was detected from the edge of the graphite film. The stability and maximal value of the FE currents were determined experimentally. The possible mechanisms of the emission from planar graphite emitters and prospects of their application in vacuum electronics are discussed. [1] A.G. Nasibulin, A. Moisala, D.P. Brown, H. Jiang, and E.I. Kauppinen, Chem. Phys. Lett. 402, 227 (2005). [2] A.N. Obraztsov, and V.I. Kleshch, J. Nanoelectronics and Optoelectronics 4, 207 (2009). [3] Obraztsov A.N., Obraztsova E.A., Tyurnina A.V., Zolotukhin A.A., Carbon 45, 2017 (2007).