High-temperature sensitivity complex dielectric/electric modulus, loss tangent, and AC conductivity in Au/(S:DLC)/p-Si (MIS) structures

Abstract

Complex dielectric (ε* = ε′ − jε″)/electric modulus (M* = M′ + jM″), loss tangent (tanδ), and ac conductivity (σac) properties of Au/(S-DLC)/p-Si structures were investigated by utilizing admittance/impedance measurements between 80 and 440 K at 0.1 and 0.5 MHz. Sulfur-doped diamond-like carbon (S:DLC) was used an interlayer at Au/p-Si interface utilizing electrodeposition method. The capacitance/conductance (C/G) or (ε' ~ C) and (ε″ ~ G) values found to be highly dependent on both frequency and temperature. The increase of them with temperatures was attributed to the thermal-activated electronic charges localized at interface states (Nss) and decrease in bandgap energy of semiconductor. The observed high ε′ and ε″ values at 0.1 MHz is the result of the space/dipole polarization and Nss. Because the charges are at low frequencies, dipoles have sufficient time to rotation yourself in the direction of electric field and Nss can easily follow the ac signal. Arrhenius plot (ln(σac) vs 1/T) shows two distinctive linear parts and activation energy (Ea) value was found as 5.78 and 189.41 from the slope; this plot at 0.5 MHz is corresponding to low temperature (80–230 K) and high temperature (260–440 K), respectively. The observed higher Ea and ε′ (~ 14 even at 100 kHz) show that hopping of electronic charges from traps to others is predominant charge transport mechanism and the prepared Au/(S:DLC)/p-Si structure can be used to store more energy.