Electrodeposition Parameters Dramatically Influence the Morphology, Stability, and Performance of n-Si/Pt Light-Addressable Electrochemical Sensors

Light addressable electrochemical (LAE) sensors have seen great utility in the past several years because they enable multiple localized electrochemical measurements to be performed on a single macroscopic electrode, opening up applications in imaging, biosensing, surface patterning, and multiplexing. In this study, we investigated the effects of electrodeposition on the formation of LAE sensors formed between n-Si and electrodeposited Pt. We prepared sensors by electrodepositing Pt onto freshly-etched n-Si under a variety of conditions, varying the Pt precursor concentration, electrodeposition time, supporting electrolyte, and potential waveform. We characterized the sensors using a combination of atomic force microscopy, electrochemical impedance spectroscopy, and cyclic voltammetry. This study shows that the electrodeposition parameters have a dramatic impact on the morphology of the electrodeposited surfaces, sensor stability, and sensitivity towards H₂O₂. Specifically, we observed that continuous Pt films prepared with a higher Pt precursor concentration were more stable and had better linearity, higher sensitivity, and broader dynamic range than those prepared with a lower Pt precursor concentration. The stability and increased H₂O₂ sensing performance correlate strongly with an increase in the Pt islands which make up the film. These data highlight that the morphology of the metal in semiconductor/metal junction LAE sensors has an impact on important performance metrics like stability and sensitivity. They also demonstrate the need for semiconductor/metal LAE sensors to be studied using micro- and nanoscale imaging techniques in order to more deeply understand their performance characteristics.