Electrical conduction mechanisms and dielectric constants of nanostructured methyl violet 2B thin films

Abstract

The uniform thin films of methyl violet 2B, MV2B, with thicknesses ranged from 96 to 300 nm, have been successfully prepared by spin coating technique. X-ray diffraction showed that the powder and pristine thin film of MV2B have amorphous structure. The amorphous pristine films become polymorphous nanocrystallites after annealing at 433 K. The electrical properties of MV2B thin films have been studied. There are a number of operational environments where the performance of MV2B thin films is likely to be affected significantly on their electrical properties and dielectric constants such as the differences of film thicknesses, temperatures and frequencies. It was found that the DC conductivity of MV2B films increases with increasing temperature. The extrinsic conduction mechanism is operating in temperature range of 288–360 K with activation energy of 0.16 eV, and the conduction in extrinsic region is explained via applying Mott model for variable range hopping. The intrinsic conduction mechanism is operating in temperatures >360 K with activation energy of 0.91 eV. The conduction in intrinsic region is explained by applying band to band transitions theory. The AC electrical conductivity and dielectric relaxation of MV2B thin films in the temperature range 365–473 K and in frequency range 0.1–100 kHz has been also studied. It has been shown that theoretical curves generated from correlated barrier hopping, CBH, model gives the best fitting with experimental results. Analysis of these results proved that conduction occurs by phonon-assisted hopping between localized states and it is performed by bipolaron hopping mechanism. The temperature and frequency dependence of both the real and imaginary parts of dielectric constant have been investigated.