ISSN:
1573-482X
Source:
Springer Online Journal Archives 1860-2000
Topics:
Electrical Engineering, Measurement and Control Technology
,
Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
Notes:
Abstract We have previously shown that a new class of quasi-one-dimensional p-type semiconductors can be created by dissolving small amounts of oxidising agents into the hydrocarbon chain matrix of discotic liquid crystals. This paper reports the elucidation of the mechanism of conduction in these new materials. In particular, the ac conductivity of 2,3,6,7,10,11 -hexahexyloxytriphenylene (HAT6) doped with the Lewis acid AlCl3, has been measured as a function of frequency (10−3–107 Hz), and temperature in its crystalline solid (K), hexagonal discotic liquid crystal (Dho) and isotropic liquid (I) phases. In macroscopically aligned K and Dho phases, the conductivity measured along the column axes is approximately 103 greater than that in the perpendicular direction. Both components of the conductivity are found to be independent of frequency at low frequencies, but show a power law dependence on frequency (Σ(Ω)∼Ωs, s∼0.8) at higher frequencies. This behaviour is characteristic of charge carrier transport by a hopping mechanism. The conductivity data have been analysed in terms of the Scher and Lax theory of hopping transport to obtain the parameters describing this process. The conduction along the columns is identified with a single charge transport process in which the carriers hop between localized states (radical cations) associated with counterions (perceived as AlCl4 −) linearly distributed off-axis along the columns.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF00187117
