pH sensitivity of nanocrystalline diamond films

The pH‐sensitive properties of hydrogen‐ and oxygen‐terminated nanocrystalline diamond (NCD) films have been investigated using a field‐effect‐based capacitive electrolyte‐diamond‐insulator‐semiconductor (EDIS) structure as transducer. The NCD thin films (100–500 nm) were grown on p‐Si–SiO2 substrates by microwave plasma‐enhanced chemical vapour deposition. The electrochemical characterisation of EDIS sensors with NCD films of different thicknesses has been performed in buffer solutions of pH 3 to pH 11 by means of capacitance–voltage and constant–capacitance methods. The developed EDIS sensors with O‐terminated NCD surfaces show an average pH‐sensitivity of 38 mV/pH. A slightly smaller pH‐sensitivity of 29–36 mV/pH was observed for the EDIS structure with H‐terminated NCD surfaces. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)