Influence of oxygen content on the structural and sensing characteristics of Y_2O_3 sensing membrane for pH-ISFET

摘要

This paper describes the physical and sensing characteristics of Y_2O_3 sensing membrane grown on Si substrates through reactive rf sputtering. The structural and morphological features of these films were investigated using X-ray diffraction, atomic force microscopy and X-ray photoelectron spectroscopy. We find that the electrolyte-insulator-semiconductor structure with Y_2O_3 sensing membrane prepared under an argon-to-oxygen flow ratio of 25/5 and annealed at 800 ℃ exhibited a higher sensitivity of about 54.5mV/pH in the solutions from pH 2 to pH 12, a smaller drift rate of 2 mV/h in the pH 7 buffer solution, and a lower hysteresis voltage of 4.78 and 6.39 mV in the pH 7→ 4→ 7→ 10→ 7 and pH 7→10→7→4→7 loops, respectively. We attribute this behavior to (a) the presence of small amounts of oxygen in the sensing film preventing Y-silicate or amorphous silica from forming at the Y_2O_3/Si interface and (b) the low surface roughness.