Impact of titanium content and postdeposition annealing on the structural and sensing properties of TbTixOy sensing membranes

Abstract

This paper describes the impact of the titanium content and postdeposition annealing on the structural properties and sensing characteristics of TbTi_xO_y sensing membranes deposited on Si substrates through reactive co-sputtering. X-ray diffraction, atomic force microscopy, secondary ion mass spectrometry, and X-ray photoelectron spectroscopy were used to study the structural, morphological and chemical features of these films as functions of the growth conditions (Ti plasma powers of 80 W, 100 W, and 120 W; temperatures ranging from 700 to 900 °C). The observed structural properties were then correlated with the resulting pH sensing performances. The TbTi_xO_y electrolyte–insulator–semiconductor device prepared under a Ti plasma condition of 100 W with subsequent annealing at 900 °C exhibited the best sensing characteristics, including pH sensitivity, hysteresis and drift. We attribute this behaviour to the optimal titanium content and annealing temperature in this oxide film forming a well-crystallized Tb₂Ti₂O₇ structure and a smoother surface.