Undoped diamond is normally an excellent electrical insulator. Its bandgap is about 5.5 eV, too big for a substantial number of electrons to enter the conduction band from the valence band. But in 1989 Maurice Landstrass and Kramadhati Ravi noticed that their synthetic diamond films conducted electricity much better than they expected. 1 Many researchers since then have tried to work out the origin of diamond films’ conductivity, but a convincing proof of a mechanism has been slow in coming, even as the effect has been exploited in designs for diamond-based electronics.

Now, Case Western Reserve University’s John Angus, his student Vidhya Chakrapani, and their colleagues have shown that diamond immersed in water can establish a charge-transfer equilibrium with the surrounding liquid. 2 They interpret their results to support an earlier explanation of Landstrass and Ravi’s 1989 experiment: Electrons transfer from the diamond to a film of atmospheric moisture adsorbed...

You do not currently have access to this content.