Large-scale first principles and tight-binding density functional theory calculations onhydrogen-passivated silicon nanorods

Abstract

We present a computational study by density functional theory (DFT) of entire siliconnanorods with up to 1648 atoms without any periodicity or symmetry imposed. Thenanorods have been selected to have varying aspect ratios and levels of surface passivationwith hydrogen. The structures of the nanorods have been optimized using a densityfunctional tight-binding approach, while energies and electronic properties have beencomputed using linear-scaling DFT with plane-wave accuracy with the ONETEP (Skylariset al 2005 J. Chem. Phys. 122 084119) program. The aspect ratio and surface passivation (1 × 1 and2 × 1 reconstructions) along with the size of the nanorods which leads to quantum confinementalong all three dimensions, significantly affect their electronic properties. The structures ofthe nanorods also show interesting behaviour as, depending on their characteristics, theycan in certain areas retain the structure of bulk silicon while in other parts significantlydeviate from it.