RF Magnetron Co-Sputtered TiN-Ga₂O₃ Thin Films for EGFET pH Sensor Applications

In this study, a TiN-Ga<sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub>O<sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> composite thin films were deposited using RF magnetron co-sputtering and investigated for its structural characteristics and pH-sensing capabilities. The composite material was integrated into an Extended Gate Field-Effect Transistor (EGFET) pH sensor, which was evaluated for its sensitivity, linearity, and stability. The fabricated sensor demonstrated a voltage sensitivity of 59.4 mV/pH, approaching the theoretical Nernstian limit, demonstrating high pH sensitivity and electrochemical stability. The device exhibited an exceptional linearity (R²) of 0.997, confirming its accuracy in pH detection over a broad pH range from 2 to 10. Minimal hysteresis of 3.2 mV was recorded, indicating high repeatability and stability under varying measurement conditions. The structural analysis of the TiN-Ga<sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub>O<sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> film revealed a uniform surface morphology, which contributed to enhanced sensing performance. The presence of Ga<sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub>O<sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> improved the chemical stability and surface reactivity of the film, while TiN provided high conductivity and durability. The synergy between these two materials resulted in improved charge transfer efficiency, which is crucial for reliable pH sensing. The wide pH detection range makes this sensor suitable for various fields, including biomedical diagnostics, environmental monitoring, and industrial process control.