Comparison of ZnO, Al₂O₃, AlZnO, and Al₂O₃-Doped ZnO Sensing Membrane Applied in Electrolyte-Insulator-Semiconductor Structures

In this study, ZnO, AlZnO, Al2O3, and Al2O3-doped ZnO-sensing membranes were fabricated in electrolyte–insulator–semiconductor (EIS) structures. Multiple material analyses indicate that annealing at an appropriate temperature of 500 °C could enhance crystallizations, passivate defects, and facilitate grainizations. Owing to their material properties, both the pH-sensing capability and overall reliability were optimized for these four types of membranes. The results also revealed that higher Al amounts increased the surface roughness values and enhanced larger crystals and grains. Higher Al compositions resulted in higher sensitivity, linearity, and stability in the membrane