Structural Inhomogeneities and Nonlinear Phenomena in Charge Transfer under Cold Field Emission in Individual Closed Carbon Nanotubes

The structure and phenomena arising from charge transfer in cold field emission mode in a single closed carbon nanotube (CNT) under cold field emission conditions are studied. Inhomogeneities of the structure of CNT in the form of two types of superlattices are found by studying microphotographs obtained by AFM, SEM, and TEM. The features of charge transfer in a quasi-one-dimensional carbon nanotube emitter with a small gap between the anode and cathode are studied under conditions of low-voltage field emission. It is established that the <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><mi mathvariant="normal">I</mi><mtext>-</mtext><mi mathvariant="normal">V</mi></mrow></semantics></math></inline-formula> characteristics reveal voltage thresholds and resonant peaks, which are associated with the opening of conduction channels in the region of van Hove singularities. In the region of peaks in the <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><mi mathvariant="normal">I</mi><mtext>-</mtext><mi mathvariant="normal">V</mi></mrow></semantics></math></inline-formula> characteristics, the emission current exceeds the one calculated using the Fowler–Nordheim (<inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><mi mathvariant="normal">F</mi><mtext>-</mtext><mi mathvariant="normal">N</mi></mrow></semantics></math></inline-formula>) function by one to three orders of magnitude. The <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><mi mathvariant="normal">I</mi><mtext>-</mtext><mi mathvariant="normal">V</mi></mrow></semantics></math></inline-formula> characteristic is not that the curve straightens in F-N coordinates. It is found that the peaks in the <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><mi mathvariant="normal">I</mi><mtext>-</mtext><mi mathvariant="normal">V</mi></mrow></semantics></math></inline-formula> characteristics have distinct regions of negative differential conductivity.