Direct Current Conductivity Measurement on Anthracene Single Crystal

Electrical conductivity measurement on high resistivity samples has been of a great concern in the past. The data vary with the state of the sample, viz. amorphous, polycrystalline, thin film and crystal forms. For the last several decades non-reproducible results are very common on a single sample in different runs and worker to worker. A compensation plot between activation energy (Eact) and pre-exponential factor (s0) has been incorporated in the past, to justify the different values of the parameters on a sample during different runs of the measurement. Therefore, it has been attempted to perform ideal measurement on high quality single crystals grown for the present study. A reproducible value of activation energy equal to 2.0 eV (the highest value), for 30 runs was obtained in this investigation, on the extremely high quality crystals grown from ultrapure material (zone refined, 60 passages), which represents a remarkable achievement. We have developed a model which justifies the highest activation energy observed in our experiment.