0000000001252373
AUTHOR
Davie Mtsuko
Nonlinear Transport in Hybrid Polypyrrole–Gold Nanostructures
We have studied charge transport in nanometer scale films of polypyrrole (PPy) that were grown electrochemically onto discontinuous ultrathin films of gold. The gold films consisted of 100 nm size islands, separated from each other by nanometer-size gaps. The thickness of PPy can be varied from 30 to 200 nm. The I-V characteristics of these hybrid PPy-Au nanostructures show strong non-linearity at low temperatures, and in particular for the more insulating samples. The hopping transport is further verified from the log / versus V-1/4 plots. Furthermore, the I-V data follow an empirical relation dlog//dV(1/4) similar to T-1/2.
Measurements of the transport gap in semiconducting multiwalled carbon nanotubes with varying diameter and length
Low temperature transport in multiwalled carbon nanotubes (MWNTs) has been studied at different diameters and lengths, within 2–10 nm, and 0.3–3.5μm, respectively. In a majority of the samples, semiconductivity showed up as a transport gap in the gate voltage controlled conduction, but metallic MWNTs are found in all diameters. The transport gap is seen to be quantitatively determined by a diameter dependent band gap, and length dependent localization of charge carriers. The band gap of semiconducting MWNTs is estimated to be smaller than that extrapolated from the conventional expression applicable to semiconducting single wall carbon nanotubes. The results constitute a systematical study …
Electronic transport in intermediate sized carbon nanotubes
We have studied systematically basic transport properties of multiwalled carbon nanotubes in a relatively unexplored diameter range, corresponding to tubes just slightly larger than single- or double-walled tubes to tubes up to 17 nm in diameter. We find in all the smaller tubes a gap in the transport data which increases with decreasing tube diameter. Within the gap region of several tubes, negative differential resistance was observed at small or moderate biases and at bias values that scaled inversely with the tube diameter. For this latter type of behavior of the conductance, we tentatively propose interlayer resonant tunneling as the cause.
Experimental study of electron transport in mesoscopic carbon based nanostructures
In this thesis we have studied experimentally electronic transport in mesoscopic hybrid polypyrrole-gold devices and single multiwalled carbon nanotube devices. A novel fabrication technique for mesoscopic conducting hybrid polymer-gold films has been developed. The hybrid polymer-gold films have been fabricated by electrochemical deposition of polypyrrole on a gold nanoisland layer. Temperature dependence of conductance show that the dominant transport mechanism in the polypyrrole-gold films is variable range hopping in the temperature range from 20 K to 300 K. At very low temperature strong nonlinearities in the field dependent conductance are observed. The field dependence follows a phen…