skip to main content
OSTI.GOV title logo U.S. Department of Energy
Office of Scientific and Technical Information

Title: First-principle study of quantum confinement effect on small sized silicon quantum dots using density-functional theory

Abstract

Density functional theory (DFT), as a first-principle approach has successfully been implemented to study nanoscale material. Here, DFT by numerical basis-set was used to study the quantum confinement effect as well as electronic properties of silicon quantum dots (Si-QDs) in ground state condition. Selection of quantum dot models were studied intensively before choosing the right structure for simulation. Next, the computational result were used to examine and deduce the electronic properties and its density of state (DOS) for 14 spherical Si-QDs ranging in size up to ∼ 2 nm in diameter. The energy gap was also deduced from the HOMO-LUMO results. The atomistic model of each silicon QDs was constructed by repeating its crystal unit cell of face-centered cubic (FCC) structure, and reconstructed until the spherical shape obtained. The core structure shows tetrahedral (T{sub d}) symmetry structure. It was found that the model need to be passivated, and hence it was noticed that the confinement effect was more pronounced. The model was optimized using Quasi-Newton method for each size of Si-QDs to get relaxed structure before it was simulated. In this model the exchange-correlation potential (V{sub xc}) of the electrons was treated by Local Density Approximation (LDA) functional and Perdew-Zungermore » (PZ) functional.« less

Authors:
; ;  [1]
  1. School of Applied Physics, Faculty of Science and Technology, Universiti Kebangsaan Malaysia, 43600, Bangi, Selangor (Malaysia)
Publication Date:
OSTI Identifier:
22308307
Resource Type:
Journal Article
Resource Relation:
Journal Name: AIP Conference Proceedings; Journal Volume: 1614; Journal Issue: 1; Conference: 2014 UKM FST postgraduate colloquium, Selangor (Malaysia), 9-11 Apr 2014; Other Information: (c) 2014 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSICS; APPROXIMATIONS; CRYSTALS; DENSITY FUNCTIONAL METHOD; ELECTRONS; FCC LATTICES; GROUND STATES; NEWTON METHOD; POTENTIALS; QUANTUM DOTS; SILICON; SPHERICAL CONFIGURATION

Citation Formats

Anas, M. M., Othman, A. P., and Gopir, G.. First-principle study of quantum confinement effect on small sized silicon quantum dots using density-functional theory. United States: N. p., 2014. Web. doi:10.1063/1.4895180.
Anas, M. M., Othman, A. P., & Gopir, G.. First-principle study of quantum confinement effect on small sized silicon quantum dots using density-functional theory. United States. doi:10.1063/1.4895180.
Anas, M. M., Othman, A. P., and Gopir, G.. Wed . "First-principle study of quantum confinement effect on small sized silicon quantum dots using density-functional theory". United States. doi:10.1063/1.4895180.
@article{osti_22308307,
title = {First-principle study of quantum confinement effect on small sized silicon quantum dots using density-functional theory},
author = {Anas, M. M. and Othman, A. P. and Gopir, G.},
abstractNote = {Density functional theory (DFT), as a first-principle approach has successfully been implemented to study nanoscale material. Here, DFT by numerical basis-set was used to study the quantum confinement effect as well as electronic properties of silicon quantum dots (Si-QDs) in ground state condition. Selection of quantum dot models were studied intensively before choosing the right structure for simulation. Next, the computational result were used to examine and deduce the electronic properties and its density of state (DOS) for 14 spherical Si-QDs ranging in size up to ∼ 2 nm in diameter. The energy gap was also deduced from the HOMO-LUMO results. The atomistic model of each silicon QDs was constructed by repeating its crystal unit cell of face-centered cubic (FCC) structure, and reconstructed until the spherical shape obtained. The core structure shows tetrahedral (T{sub d}) symmetry structure. It was found that the model need to be passivated, and hence it was noticed that the confinement effect was more pronounced. The model was optimized using Quasi-Newton method for each size of Si-QDs to get relaxed structure before it was simulated. In this model the exchange-correlation potential (V{sub xc}) of the electrons was treated by Local Density Approximation (LDA) functional and Perdew-Zunger (PZ) functional.},
doi = {10.1063/1.4895180},
journal = {AIP Conference Proceedings},
number = 1,
volume = 1614,
place = {United States},
year = {Wed Sep 03 00:00:00 EDT 2014},
month = {Wed Sep 03 00:00:00 EDT 2014}
}
  • Crystalline silicon quantum dots (Si QDs) were spontaneously grown in the silicon nitride films by plasma-enhanced chemical vapor deposition using SiH{sub 4} and NH{sub 3} as precursors. When the size of the Si QDs was reduced from 4.9 to 2.9 nm, the photoluminescence peak energy was shifted from 1.73 to 2.77 eV. The photoluminescence peak energy was fitted to the relationship, E(eV)=1.13+13.9/d{sup 2}, where d is the diameter of the Si QD in nanometers. The measured band-gap energies of the Si QDs were in good agreement with the quantum confinement model for crystalline Si QDs. These results suggest that themore » hydrogen dissociated from NH{sub 3} plays an important role in improving the crystallinity and surface passivation of Si QDs.« less
  • No abstract prepared.
  • We have previously proposed that further improved functionals for density functional theory can be constructed based on the Armiento-Mattsson subsystem functional scheme if, in addition to the uniform electron gas and surface models used in the Armiento-Mattsson 2005 functional, a model for the strongly confined electron gas is also added. However, of central importance for this scheme is an index that identifies regions in space where the correction provided by the confined electron gas should be applied. The electron localization function (ELF) is a well-known indicator of strongly localized electrons. We use a model of a confined electron gas basedmore » on the harmonic oscillator to show that regions with high ELF directly coincide with regions where common exchange energy functionals have large errors. This suggests that the harmonic oscillator model together with an index based on the ELF provides the crucial ingredients for future improved semi-local functionals. For a practical illustration of how the proposed scheme is intended to work for a physical system we discuss monoclinic cupric oxide, CuO. A thorough discussion of this system leads us to promote the cell geometry of CuO as a useful benchmark for future semi-local functionals. Very high ELF values are found in a shell around the O ions, and take its maximum value along the Cu–O directions. An estimate of the exchange functional error from the effect of electron confinement in these regions suggests a magnitude and sign that could account for the error in cell geometry.« less
  • A procedure is proposed to predict electronic structures in thin films from bulk properties using density functional kcentre dotp perturbation method. This procedure is based on the phenomenological expression of zero-point energy using effective mass approximation. It is found that the results by this procedure and those calculated using slab models agrees very well. A prediction is also demonstrated for the electronic structures of <110> uniaxially strained silicon thin films in the <001> confinement.