Nanotech 2011

Charge Confinement in Silicon Nanowires by Surface Functionalization

Y.-C. Shih, J.-H. Lee, C.-T. Lin, C.-S. Chen, K.-C. Wu
National Center for High-performance Computing, TW

Keywords: silicon nanowires, surface functionalization, charge confinement

Abstract:

Silicon nanowires (SiNWs) are expected to play an important role in nanotechnology because they possess remarkable physical property and compatibility with current Si-based fabrication. They have been successfully used in advance applications such as biosensors, nanotransistors, and optoelectronic devices. With the diameter down to ~1nm, SiNWs exhibit the direct nature of band gap and strong blueshift of photon emission due to quantum confiement effect. Interestingly, small diameter SiNWs with large surface-to-volume ratio were found to be sensitive to surface chemical passivation. This enable us to tune the electronic and optical properties of SiNWs by surface functional group. We use the self-consistent-charge density functional tight binding (DFTB) method implemented in DFTB+ to study the charge confinement in SiNWs by surface functionalization. The SiNW used in this study consist of two segments having 5 unit cells with surface terminated with different chemical species H (SiNW-H) or F (SiNW-F). Our calculated lattice length of 3.87Å of unit cell SiNW-H is in good agreement with the experimental value (3.8Å). We will show that holes and electrons can be confined in a particular SiNW segment, i.e. the SiNW-F. This controllable position of holes and electrons in SiNWs by terminating different chemical species could further be further profitable to novel nano-electronic and optical devices.
 

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