Comparison of confinement characters between porous silicon and silicon nanowires

Nacir Tit, Zain H. Yamani, Giovanni Pizzi, Michele Virgilio

Research output: Contribution to journalArticlepeer-review

Abstract

Confinement character and its effects on photoluminescence (PL) properties are theoretically investigated and compared between porous silicon (p-Si) and silicon nanowires (Si-NWs). The method is based on the application of the tight-binding technique using the minimal sp3-basis set, including the second-nearest-neighbor interactions. The results show that the quantum confinement (QC) is not entirely controlled by the porosity, rather it is mainly affected by the average distance between pores (d). The p-Si is found to exhibit weaker confinement character than Si-NWs. The confinement energy of charge carriers decays against d exponentially for p-Si and via a power-law for Si-NWs. This latter type of QC is much stronger and is somewhat similar to the case of a single particle in a quantum box. The excellent fit to the PL data demonstrates that the experimental samples of p-Si do exhibit strong QC character and thus reveals the possibility of silicon clustering into nano-crystals and/or nanowires. Furthermore, the results show that the passivation of the surface dangling bonds by the hydrogen atoms plays an essential role in preventing the appearance of gap states and consequently enhances the optical qualities of the produced structures. The oscillator strength (OS) is found to increase exponentially with energy in Si-NWs confirming the strong confinement character of carriers. Our theoretical findings suggest the existence of Si nanocrystals (Si-NCs) of sizes 1-3 nm and/or Si-NWs of cross-sectional sizes in the 1-3 nm range inside the experimental p-Si samples. The experimentally-observed strong photoluminescence from p-Si should be in favor of an exhibition of 3D-confinement character. The favorable comparison of our theoretical results with the experimental data consolidates our above claims.

Original languageEnglish
Pages (from-to)2422-2429
Number of pages8
JournalPhysics Letters, Section A: General, Atomic and Solid State Physics
Volume375
Issue number24
DOIs
Publication statusPublished - Jun 13 2011

Keywords

  • Nanocrystalline materials
  • Photoluminescence
  • Porous materials
  • Quantum dots
  • Quantum wires
  • Silicon

ASJC Scopus subject areas

  • Physics and Astronomy(all)

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