Electrical and dielectric properties of chromotrope 2R in pellet and thin film forms

Abstract

The dark conductivity (dc and ac) and dielectric properties of chromotrope 2R (CHR) in pellet as well as in thin film forms have been investigated as function of frequency (100Hz to 5MHz) within the temperature range (293–423K). The ac conductivity of CHR pellet in sandwich structure employing two symmetrical gold ohmic contacts shows both temperature and frequency dependence with relatively stronger dependence in the higher temperature and lower frequency ranges respectively. It is found that σac(ω) obey Jonscher’s universal power law, σac(ω)=Aωs with s<1 and the results has been analyzed with reference to various theoretical models. The correlated barrier hopping model (CBH) with single polaron process is found to be the dominant conduction mechanism for charge carrier transport in CHR material within the investigated temperature range. The dc conductivity has been measured in the considered temperature range for as deposited and annealed films. The results are fitted to Arhenius equation and the activation energy has been deduced at different frequencies. The results showed also that heating the deposited CHR films may reveal films with more stable electrical properties. Moreover, both the dielectric constant ε1 and the dielectric loss ε2 are found to increase with temperature and decrease with frequency which reveal that the CHR samples exists in molecular dipole form. The behavior of ε2 as a function of both frequency and temperature is analyzed according to Giuntini et al. model.