First-principles study of structural and electronic properties of ultrathin silicon nanosheets

Silicon (Si) is currently the basis of most of our nanodevice technology and ultrathin materials based on Si would have the great advantage of easy integration into existing circuitry. Recently, it has been demonstrated using molecular-dynamics calculations that two-dimensional ultrathin layered Si can be formed by cooling fluid Si confined in a slit pore [T. Morishita et al., Phys. Rev. B 77, 081401 (R) (2008)]. Here we investigate, using ab initio density-functional theory, the structural and electronic properties of ultrathin double layer Si with and without hydrogenation or substitutional doping. We show that such materials have very desirable electronic properties, being able to be changed from metallic to semiconducting. They may also act as p-type or n-type semiconductors upon partial hydrogenation or substitutional doping of phosphorus. We suggest that these materials may be of great importance to production of nanoelectronic devices and sensors.