Skin dominanceof the dielectric-electronic-phononic-photonic attribute of nanoscaled Silicon

《Surf Sci Rep》Volume 68, Issues 3–4, November–December 2013, Pages 418–445

http://www.journals.elsevier.com/surface-science-reports/                                                              

Synopsis

Skin-resolved bond contraction, quantum entrapment, and electron localization due to bond-order imperfection, metallization, and passivation differentiate nanoscaled Si from itsbulk in the tunability of the dielectric, electronic, phononic, and photonic properties.

Abstract

ABSTRACT

Nanoscaled or porous silicon (p-Si) with and withoutsurface passivation exhibits unusually tunable properties that its parent bulkdoes never show. Such property tunability amplifies the applicability of Si inthe concurrent and upcoming technologies. However, consistent understanding ofthe fundamental nature of nanoscaled Si remains a high challenge. This articleaims to address the recent progress in this regard with focus on reconciling thetunable dielectric, electronic, phononic, and photonic properties of p-Siin terms of skin dominance. We show that the skin-depth bond contraction, localquantum entrapment, and electron localization is responsible for thesize-induced property tunability. The shorter and stronger bonds betweenundercoordinated skin atoms result in the local densification and quantumentrapment of the binding energy and the bonding electrons, which in turnpolarizes the dangling bond electrons. Such local entrapment modifies theHamiltonian and associated properties such as the band gap, core level shift,Stokes shift (electron-phonon interaction), phonon and dielectric relaxation. Therefore,given the known trend of one property change, one is expected to be able topredict the variation of the rest based on the notations of the bondorder-length-strength correlation and local bond average approach (BOLS-LBA).Furthermore, skin bond reformation due to Al, Cu, and Ti metallization and Oand F passivation adds another freedom to enhance or attenuate the size effect.The developed formulations, spectral analytical methods, and importantly, theestablished database and knowledge could be of use in engineering p-Siand beyond for desired functions.