A route to tunable direct band-gap diamond devices: Electronic structures of nanodiamond crystals

Electronic structures of nanodiamond crystals are elucidated by means of first principles calculations. It is found that the lowest unoccupied molecular orbital of diamond molecules forms the conduction band with a parabolic dispersion centered at the momentum origin. This results in a direct band gap in the nanodiamond crystal, which contrasts sharply with the indirect gap in bulk diamond. The corresponding light absorption/emission energy can be tuned within the ultraviolet wavelength range by choosing different nanodiamonds, which provides significant potential for their optoelectronic applications. (C) 2008 American Institute of Physics. [DOI: 10.1063/1.2986637]