Quantum Control Of Diamond Structures

Quantum effects may govern the formation of nanostructures on the surface of boron-doped diamond microcrystals, reports a group led by Igor B. Altfeder of the Air Force Research Laboratory and Jacqueline Krim of North Carolina State University (Phys. Rev. Lett. 2009, 102, 136104). Quantum control of structures, thought to be governed by the wavelengths of electrons, has previously been observed in molecular assembly on a copper surface and in thin metal films. In the new study, the researchers used scanning tunneling microscopy (STM) to investigate the surface structures of pure and boron-doped diamond microcrystals. On the boron-doped crystals they found parallelogram-shaped grains that were 10.5 nm long, 8.3 nm wide, and at least 1.5 nm tall. Because the features are not observed on pure diamond, the scientists postulate that the boron dopant, which gives diamond metallic properties, induces quantum effects that control the growth of the nanostructures. Within the parallelograms are features spaced 3.5 nm apart. The features are due to lateral standing electron waves, the likely driving force of the electronic growth mechanism, the researchers say.