First-principles calculations for si nanostructures

Knowledge of the band structure of a material is the first necessary step to understanding and predicting its electronic properties. With the recent advancement in semiconductor microfabrication technologies, novel device architectures, coupled with nano-structures such as ultrathin films and nanowires, have been proposed. The band structure plays a fundamental role in determining both the electrostatics and the dynamics of carriers in those nano-structures. This chapter presents the band structures computed for Si nano-structures using first-principle density-functional theory, and discusses atomistic effects in Si nano-structures. The band structure calculations were performed by using a first-principles simulation package based on the density-functional theory (DFT), VASP, where the electron-electron exchange and correlation interactions were treated within the generalized gradient approximation (GGA). One of the most important technological roadblocks for further miniaturization is the high-quantum mechanical tunneling current through the gate oxide, which greatly increases VLSI power consumption.