Insulator−Metal Transition of Intrinsic Diamond

Abstract

Insulator-metal transitions are translations characterized by a sudden change in electron transport properties from localized to itinerant behavior of electrons. In most cases, it is detected in strongly disordered semiconductors as a function of temperature with statistically distributed donors and/or acceptors. Here, we show that reversible insulator-metal transitions take place in H-terminated intrinsic (undoped) single crystalline diamond, if immersed into redox-electrolyte solutions at room temperature. The change is generated by valence-band electrons of diamond, which tunnel into the redox-electrolyte, where they occupy empty electronic sites. We applied cyclic voltammetry experiments to characterize the insulator-metal transition in combination with different redox couples. The experiments show that transfer doping accounts for the experimentally detected phenomena, and that intrinsic diamond is a promising candidate for chemical sensing in a variety of applications.