Amorphous boron carbon nitride as a pH sensor

Amorphous boron carbon nitride (a-BCxNy) has been used as the sensing membrane in an extended gate field effect transistor for the measurement of pH of solutions. The a-BCxNy material was produced by dual gun magnetron sputtering and has been found to be a stable and sensitive pH sensor with sensitivities in the range of 40 mV/pH. The pH sensitivity, however, increased with increasing carbon content of the a-BCxNy sensing membrane and reached a maximum of 46 mV/pH for a carbon concentration of 47 at. %. The response times of these sensors are close to 6 s. The drain current, which is an indicator of the pH, remained stable (fluctuation of few microamperes) over a period of 10 min in the phosphate solution with varied pH, demonstrating a good stability of the sensing membrane.