Reverse bias dependent impedance and dielectric properties of Al/n-NC FeSi₂/p-Si/Pd heterostructures formed by facing-targets sputtering

Al/n-NC FeSi₂/p-Si/Pd heterostructures were formed by facing-targets sputtering. From the dark J-V results, the device showed rectifying action with leakage current. In this work, impedance spectroscopy was employed to study the electrochemical characteristics of the heterostructures, which were inspected within a frequency (f) range from 20 Hz to 2 MHz. The range of the biased voltage (V) was −1 V to 0 V. All plots of real and imaginary impedances possessed single semi-circular arcs for all bias V values. The relaxation time was 2.00 μs at −1 V, and it became faster at 0 V with 0.42 μs. The equivalent circuit for the heterostructures consisted of series resistance (R_s) combined with three sets of shunt circuits of resistance (R_p) and a constant phase element (CPE), representing grain, grain boundary, and junction, respectively. The simulated R_s and R_p values decreased, while all CPE values increased as the biased V increased. For the dielectric properties, the real permittivity (ε′) values of 86.70 at 0 V and 20.22 at −1 V were disclosed at 100 Hz; all ε′ values decreased as the f value was increased. The loss tangent revealed to be very high due to dielectric loss being much higher than ε′ values, indicating the device to be leaky. The alternating conductivities plotted against f started at a low level in low f zones and grew exponentially when f reached higher values for all V values. Direct current conductivity was observed at 1.66 × 10⁻⁴ S m⁻¹ at 0 V, which reduced to 2.67 × 10⁻⁵ S m⁻¹ at −1 V. The dimensionless exponent of the conductivity results was higher than 1, indicating the hopping movement within the local site.