Studies on AC Response of MPc Thin Films Molecular Materials

GRAPHICAL ABSTRACT

Abstract

Thin films of zinc phthalocyanine, ZnPc, are prepared by thermally evaporated method at room temperature on precleaned glass substrates under the pressure of (10⁻⁵–10⁻⁶) Torr by slowly varying the current. The rate of evaporation is controlled and maintained constant during all the evaporations. AC electrical properties of Au-ZnPc-Au and Au-ZnPc-Al devices are investigated over the frequency range (1–10⁶) Hz, temperatures range (120–298) °K, and superimposed voltages range (0–5) V. The observed AC conductance showed strong dependence on frequency and it is found to vary with respect to ω^s with the exponent s ≤ 1, indicating a dominant hopping transport model of conduction. The temperature dependence of the AC conductance shows Arrhenius type with three thermal activation energies. The activation energies are determined for selected frequencies and calculated from the linear slope zone of logarithmic conductance versus the inverse of temperature. The results show that hopping transport is dominant at high frequencies and low temperatures and remains significant than in the band model (DC measurements).

Keywords:

• Organic molecular
• contact
• conduction process
• hopping