New pH-sensitive TaO_xN_y membranes prepared by NH₃ plasma surface treatment and nitrogen incorporated reactive sputtering

For low cost, easy fabrication and low process temperature, Ta₂O₅ and TaO_xN_y pH-sensing membranes were prepared by reactive RF sputtering. To incorporate nitrogen into Ta₂O₅ layer, two process techniques including NH₃ plasma treatment on Ta₂O₅ surface and TaO_xN_y layer directly deposited in reactive RF sputtering with various N₂ ratios were proposed. With NH₃ plasma treatment for 10 min, the sensitivity of Ta₂O₅-EIS structure can be increased to 54.9 mV/pH. The similar result can be obtained TaO_xN_y layer directly deposited in the nitrogen incorporated reactive RF sputtering. For the long-term stability, both two process techniques could be applied to minimize the drift coefficient. With proper nitrogen incorporation process, an excellent sensitive membrane can be obtained by low temperature process based on NH₃ plasma treatment.