Dielectric constant, AC conductivity and impedance spectroscopy of zinc-containing diamond-like carbon film UV photodetector

Abstract

We report on the dielectric constant, conductivity, impedance spectroscopy and current-voltage characteristic of zinc contain diamond-like carbon (Zn-DLC) films prepared by a combination of plasma source ion implantation with magnetron sputtering of a zinc target. The frequency variation of the AC conductivity follows Jonscher's power law. The temperature variation of the frequency exponent indicates that the charge carriers follow a correlated barrier hopping conduction mechanism. The frequency dispersion of real and imaginary part of the dielectric constant obeys a modified Cole-Cole equation. The space charge conductivity, free charge conductivity and relaxation time of the Zn-DLC thin films are temperature dependent. The relaxation time decreases with increase in temperature. The Nyquist plot of complex impedance spectroscopy is simulated by a simple electrical equivalent circuit. The imaginary part of the complex impedance shows a relaxation peak, which shifts towards the high frequency side with an increase in temperature. The temperature dependent current-voltage (I-V) characteristic shows a non-linear type behaviour which follows the Poole-Frenkel (PF) emission model. To investigate the photosensitivity of an Ag/Zn-DLC/Si device, we placed it in dark and UV light condition and measured the (I-V) characteristic at room temperature. The dark current density and photocurrent density follow the PF model and a modified PF model respectively.