Bonding modes and electronic properties of single-crystalline silicon nanotubes

The structural characteristics, bonding modes, and electronic properties of single-crystalline silicon nanotubes (sc-SiNTs) are investigated by using the first-principles method. These pristine sc-SiNTs with s p3 hybridization, constructed by the bulklike tetrahedrally coordinated Si atoms, are found to be energetically stable. The electronic property is sensitive to the external diameter, tube-wall thickness, and tube-axis orientation due to quantum confinement effects. A direct band gap is observed in SiNTs with smaller sizes. The band gap increases monotonically with decreasing tube-wall thickness, in accord with the substantial blueshift observed in the experiment. It is suggested that this type of SiNTs would have promising practical applications in nanoscale light-emitting devices and electronic devices.