Evaluation of the Electrical Properties of MnO/ZnO:Zn Thin-Films for Potential Applications in Solid-State Supercapacitors

In this work, a bi-layer MnO/ZnO:Zn structure with an approximate thickness of 100 nm for each layer has been successfully synthesized by sputtering. Changes in the electrical properties were evaluated for the potential application for solid-state capacitors as electrodes. The characterization of the layers is carried out through X-Ray Diffraction (XRD), which provides valuable insights into the structural properties. An electrical study employing Frequency Response Analysis (FRA), Bode plots, Voltagetime (V-t), and Current-Voltage (I-V) graphs is conducted to thoroughly examine and understand the electrical behavior of the synthesized layers. XRD results show a MnO phase for the Mn sputtered layer and a mild distortion of the ZnO lattice for the ZnO:Zn co-sputtered layer due to Zn atoms. The electrical study provides a Bode plot where at f<100 KHz the films behave as a conductor and its resistivity increases as the frequency rises. It is also noted that a phase mismatch exists, implying capacitive and inductive effects at f>100 KHz. At the cutoff frequency (fc) a capacitance value of 142 pF is calculated. The attenuation and reactance effects are also showed in the V-t and I-V graphs. Finally, the time constant (τ) is calculated with a square +5V input signal where also a value of capacitance is obtained as 134 pF, indicating a ±10% of tolerance for the value of capacitance at high frequencies (f≥500 KHz) for the film, where reactance effects can be improved with several MnO/ZnO:Zn nanostructures as electrodes in series to add the capacitor value revealing a potential application for the structure for solid-state supercapacitors.