Ambient effects on the electrical conductivity of carbon nanotubes

Abstract

We show that the electrical conductivity of single walled carbon nanotubes (SWCNT) networks is affected by oxygen and air humidity under ambient conditions by more than a magnitude. Later, we intentionally modified the electrical conductivity by functionalization with iodine and investigated the changes in the band structure by optical absorption spectroscopy.Measuring in parallel the tubes electrical conductivity and optical absorption spectra, we found that conduction mechanism in SWCNT is comparable to that of intrinsically conducting polymers. We identified, in analogy to conducting polymers, in the infrared spectra a new absorption band which is responsible for the increased conductivity, leading to a closing gap in semiconducting SWCNT.We could show that by different functionalizations of the same SWCNT starting material the properties like conductivity can be dramatically changed, leading to different imaginable applications. We investigated here, an ultraviolet sensor with weakly modified SWCNT

Electronic and Ionic Electric Field Screening and Persistent Built‐In Electric Field in Carbon Nanotube/PCBM Films

“…Electrons and holes can hardly cause processes lasting for hours and days; therefore, we attribute the long‐lasting built‐in electric field to the motion of ions. A similar attribution was made analyzing the environmental influence on the electrical conductivity of SWCNT films where such long‐lasting processes were assigned to adsorbed oxygen . As the temperature dependences in Figure show, this motion requires thermal assistance of about 200 K (16 meV), which, according to Arrhenius equation, converts into 5–10 meV activation energy.…”

Capacitive and Charge Transfer Effects of Single‐Walled Carbon Nanotubes in TiO2 Electrodes

“…The electronic transport properties of SWCNT thin films, which were prepared by spray coating from the starting 0‐SWCNT dispersion and the chromatographic fractions as well, were studied through measurements of DC resistance ( R ) in the temperature range of 4 to 400 K (Figure ). It is known that R values are influenced by ambient conditions such as moisture and the filling gas in the measurement chamber ,. The present measurements were performed under vacuum, after waiting for at least 2 h at room temperature, during which the film resistance increased until stabilization.…”

“…It is known that R values are influenced by ambient conditions such as moisture and the filling gas in the measurement chamber. [26,27] The present measurements were performed under vacuum, after waiting for at least 2 h at room temperature, during which the film resistance increased until stabilization. For all the i-SWCNT films, R increases as temperature decreases, particularly below 70 K. Independently of the individual SWCNT conformations, all the SWCNT networks show a semiconductor behaviour, even though the resistance variation with temperature is much slower than in classical semiconductors such as germanium.…”

The Effect of the Gaseous Environment on the Electrical Conductivity of Multi-Walled Carbon Nanotube Films over a Wide Temperature Range

“…It can be explained by the desorption of dopants present on the surface, which in the ambient conditions enhance the conductivity of CNT networks. The doping species that could come off the CNT films readily at such a low pressure are water [32,33] and oxygen [34] molecules. Their removal is particularly difficult as they are confined within the framework and structure of the CNT films and require a significant pressure difference to desorb them fully.…”