Electrochemical properties of undoped hydrogen terminated CVD diamond

The electronic properties of hydrogen terminated intrinsic single crystalline CVD diamond in redox–electrolytic solutions are characterized by cyclic voltammetry experiments and pH-sensitive measurements of ion-sensitive field effect transistor (ISFET) structures. The data show insulator-metal transitions of diamond if immersed into redox–electrolyte solutions with chemical potentials (unoccupied states) below the valence-band maximum. Cyclic voltammetry current peaks are electron exchange rate limited due to the small density of holes in a few Ångström thick conducting layer at the surface of diamond. H-terminated diamond is sensitive to pH of electrolytes, following the Nernst prediction with about − 58 mV/pH. Due to Coulomb repulsion of H+-ions from the H-terminated diamond surface, the enlarged tunneling distance works like a gate insulator and is indicated as reason for the confinement of holes in ISFET structures.