Electrochemical properties of undoped hydrogen terminated CVD diamond

Abstract

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.