Conductivity of Diamonds

We were surprised to read in "Diamond's Surface Conductivity" the statement: "Pure diamond is insulating, but it can be made conductive by doping or exposure to air" (C&EN, Dec. 3, 2007, page 15). Actually, it has never been shown that an undoped diamond becomes conductive by exposure to air. This point must have escaped the author's notice. In fact, the groups reporting on the surface conductivity in diamond used, without exception, hydrogenated (H-doped) diamond. We recently demonstrated in Crystal Growth & Design (2007, 7, 2298) that the conductivity caused by H-doping is not restricted to the surface: After surface hydrogenation, diamond films become bulk-conductive—a new observation raising concerns on the phenomenon of surface conductivity in diamond.

Andrei P. Sommer, Dan ZhuUlm
Germany