Electron Density-Change in Semiconductor by Ion-Adsorption at Solid–Liquid Interface

The change in electrical properties of electrodes by adsorption or desorption at interfaces is a well-known phenomenon required for signal production in electrically transduced sensing technologies. Furthermore, in terms of electrolyte–insulator–semiconductor (EIS) structure, several studies of energy conversion techniques focused on ion-adsorption at the solid–liquid interface have suggested that the electric signal is generated by ionovoltaic phenomena. However, finding substantial clues for the ion-adsorption phenomena in the EIS structure is still a difficult task because direct evidence for carrier accumulation in semiconductors by Coulomb interactions is insufficient. Here, a sophisticated Hall measurement system is demonstrated to quantitatively analyze accumulated electron density-change inside the semiconductor depending on the ion-adsorption at the solid–liquid interface. Also, an enhanced EIS-structured device is designed in an aqueous-soaked system that works with the ionovoltaic principle to monitor the ion-dynamics in liquid electrolyte media, interestingly confirming ion-concentration dependence and ion-specificity by generated peak voltages. This newly introduced peculiar method contributes to an in-depth understanding of the ionovoltaic phenomena in terms of carrier actions in the semiconductors and ionic behaviors in the aqueous-bulk phases, providing informative analysis about interfacial adsorptions that can expand the scope of ion-sensing platforms.