Effect of functionalization on the conductivity and noise characteristics of arrays of multiwall carbon nanotubes

The electrophysical and noise characteristics of arrays of multiwall carbon nanotubes (MWCNTs) functionalized in various ways were studied. It is demonstrated that the as-prepared and annealed MWCNT arrays have semiconductor-type resistivities and temperature dependences of resistivity, while the arrays of annealed MWCNTs functionalized with acids have metallic properties. Low-frequency $1/f$ noise in the 0.2–20 kHz range was observed for all MWCNT arrays. Simple thermal annealing raised the noise level severalfold and annealing with acid treatment resulted in noise reduction and a change in the index of power in its current dependence. The normal amplitude distribution of noise spikes transformed to a lognormal one as the density of as-prepared MWCNT arrays increased. The duration distribution of these spikes became narrower at higher densities.