Schottky contact of nano-BiO_x thin film synthesized galvanostatically on stainless steel in acetonitrile

In this study, the nanosized-BiO_x thin film (mostly Bi₂O₃ with a trace amount of Bi₂O₅) is electrochemically synthesized on stainless steel (SS) surface at room temperature. The coating process is carried out using the galvanostatic pulse deposition method in an acetonitrile solution containing bismuth tetrafluoroborate, tartaric acid, tetrabutylammonium hydroxide, and tetrabutylammonium tetrafluoroborate. The structural and morphological characterizations of thin film are performed by XRD, XPS, SEM-EDX, and AFM techniques. Accordingly, α- and δ-Bi₂O₃-based coating with oxygen vacancies contains a small amount of Bi₂O₅ on the SS surface. The BiO_x thin film exhibits a rough surface with many nano-sized hills homogeneously distributed. Electrical characterization is conducted with electrochemical impedance spectroscopy, current-voltage, and Hall effect measurements. The pseudoresistance with the most drastic change increases with rising potential and decreases again after reaching its maximum value at the open circuit potential. It could be inferred that the composition (oxidation states or oxygen deficiency) of the Bi₂O₃-based film varies according to the applied potential. The n-type Schottky behavior is observed at the SS/BiO_x interface. Furthermore, the n-type SS/BiO_x-based Schottky diode tested for endurance shows significant stability over 200 cycles.