Sensing Performance of Stable TiN Extended-Gate Field-Effect Transistor pH Sensors in a Wide Short Annealing Temperature Range

In this letter, the structural properties and sensing performances of TiN sensing films deposited on a n⁺-type Si through the reactive DC sputtering method with rapid thermal annealing at a wide temperature range of 200 °C to 800 °C were investigated for extended-gate field-effect transistor (EGFET) pH sensors. We used X-ray diffraction, X-ray photoelectron spectroscopy, and atomic force microscopy to study the structural characteristics of these films. These TiN EGFET sensors exhibited almost the same sensing performances, such as pH sensitivity 58 mV/pH), hysteresis voltage 2 mV), and drift rate (0.45 mV/h), indicating that they contained similar or identical in the film composition and surface roughness.