Density functional calculation for electronic structure properties of graphene adsorbed with GaAs nanostructure

Graphene and GaAs nanostructures are well-known materials that have potential application in modern high-speed electronic devices, due to high electron mobility which makes their properties desirable. Until now, the adsorption mechanism of GaAs nanostructure on graphene with a view to change its ele...

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Main Author:	Abubakar, Shamsu
Format:	Thesis
Language:	English
Published:	2014
Subjects:	Mathematical physics Density functionals
Online Access:	http://psasir.upm.edu.my/id/eprint/75937/1/FS%202014%2089%20IR.pdf
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id	my-upm-ir.75937
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spelling	my-upm-ir.759372019-11-22T01:06:36Z Density functional calculation for electronic structure properties of graphene adsorbed with GaAs nanostructure 2014-06 Abubakar, Shamsu Graphene and GaAs nanostructures are well-known materials that have potential application in modern high-speed electronic devices, due to high electron mobility which makes their properties desirable. Until now, the adsorption mechanism of GaAs nanostructure on graphene with a view to change its electronic structure properties has yet to be understood. For that reason, this study is conducted on altering the electronic structure properties of graphene, as semi-metallic material using GaAs nanostructures. This semi-metallic nature needs to be overcome before graphene can be proposed as a metal-substrate for nanoscale growth. In this work, density functional calculation employed is based on quantum mechanical method, used to examine the possible effect of small number of adsorbed Ga and As adatoms as well as their dimer on graphene. This calculation is performed using exchange-correction functional to obtain the structural stabilities and electronic properties of graphene adsorbed with GaAs nanostructure. A simplifying approach of k-points sampling and pseudopotentials approximation are also used in the calculation. The computational software package used based on density functional theory for this calculation is QUANTUM ESPRESSO. The results of the calculation have indicated that the convergences with respect to plane-wave energy cutoff and with k-points sampling grids have been achieved. This calculation is performed in order to determine the stable height between the Ga and As adatoms on graphene and subsequently, the most stable adsorption sites of the individual atoms and dimer on graphene are obtained. After optimization, the lattice constant for a pristine graphene, a = 2.46 Å is in agreements with the experimental value found in literatures. For the calculated adsorption site of Ga adatom on graphene, H-site is found to be energetically stable. The bond distance between gallium adatom and the neighboring carbon atoms in the graphene structure on H-site is 2.26Å, which is in closer agreement with the value of 2.20Å, found in other previous study. In the case of arsenic adatom on graphene, B-site is the most stable adsorption site and the electronic structure of graphene is affected significantly, as a result of the charge transfer and weak hybridization. The magnetic moment for gallium and arsenic adatoms as well as their dimer is found to be 0.00, which signify the non-magnetic behavior in graphene that is adsorbed with GaAs nanostructure. It has also been found that the orbital contributions for C-GaAs bond are mainly dominated by pz orbitals of carbon and px and py orbitals of GaAs. This study has significantly found that the semi-metallic behavior in graphene is changed to metallic as a result of orbitals-hybridization with GaAs nanostructure. Therefore, these new features make graphene a wonderful material for potential uses in electronic device and also as prepared substrate, used for the epitaxial growth of nanowires. Mathematical physics Density functionals 2014-06 Thesis http://psasir.upm.edu.my/id/eprint/75937/ http://psasir.upm.edu.my/id/eprint/75937/1/FS%202014%2089%20IR.pdf text en public masters Universiti Putra Malaysia Mathematical physics Density functionals
institution	Universiti Putra Malaysia
collection	PSAS Institutional Repository
language	English
topic	Mathematical physics Density functionals
spellingShingle	Mathematical physics Density functionals Abubakar, Shamsu Density functional calculation for electronic structure properties of graphene adsorbed with GaAs nanostructure
description	Graphene and GaAs nanostructures are well-known materials that have potential application in modern high-speed electronic devices, due to high electron mobility which makes their properties desirable. Until now, the adsorption mechanism of GaAs nanostructure on graphene with a view to change its electronic structure properties has yet to be understood. For that reason, this study is conducted on altering the electronic structure properties of graphene, as semi-metallic material using GaAs nanostructures. This semi-metallic nature needs to be overcome before graphene can be proposed as a metal-substrate for nanoscale growth. In this work, density functional calculation employed is based on quantum mechanical method, used to examine the possible effect of small number of adsorbed Ga and As adatoms as well as their dimer on graphene. This calculation is performed using exchange-correction functional to obtain the structural stabilities and electronic properties of graphene adsorbed with GaAs nanostructure. A simplifying approach of k-points sampling and pseudopotentials approximation are also used in the calculation. The computational software package used based on density functional theory for this calculation is QUANTUM ESPRESSO. The results of the calculation have indicated that the convergences with respect to plane-wave energy cutoff and with k-points sampling grids have been achieved. This calculation is performed in order to determine the stable height between the Ga and As adatoms on graphene and subsequently, the most stable adsorption sites of the individual atoms and dimer on graphene are obtained. After optimization, the lattice constant for a pristine graphene, a = 2.46 Å is in agreements with the experimental value found in literatures. For the calculated adsorption site of Ga adatom on graphene, H-site is found to be energetically stable. The bond distance between gallium adatom and the neighboring carbon atoms in the graphene structure on H-site is 2.26Å, which is in closer agreement with the value of 2.20Å, found in other previous study. In the case of arsenic adatom on graphene, B-site is the most stable adsorption site and the electronic structure of graphene is affected significantly, as a result of the charge transfer and weak hybridization. The magnetic moment for gallium and arsenic adatoms as well as their dimer is found to be 0.00, which signify the non-magnetic behavior in graphene that is adsorbed with GaAs nanostructure. It has also been found that the orbital contributions for C-GaAs bond are mainly dominated by pz orbitals of carbon and px and py orbitals of GaAs. This study has significantly found that the semi-metallic behavior in graphene is changed to metallic as a result of orbitals-hybridization with GaAs nanostructure. Therefore, these new features make graphene a wonderful material for potential uses in electronic device and also as prepared substrate, used for the epitaxial growth of nanowires.
format	Thesis
qualification_level	Master's degree
author	Abubakar, Shamsu
author_facet	Abubakar, Shamsu
author_sort	Abubakar, Shamsu
title	Density functional calculation for electronic structure properties of graphene adsorbed with GaAs nanostructure
title_short	Density functional calculation for electronic structure properties of graphene adsorbed with GaAs nanostructure
title_full	Density functional calculation for electronic structure properties of graphene adsorbed with GaAs nanostructure
title_fullStr	Density functional calculation for electronic structure properties of graphene adsorbed with GaAs nanostructure
title_full_unstemmed	Density functional calculation for electronic structure properties of graphene adsorbed with GaAs nanostructure
title_sort	density functional calculation for electronic structure properties of graphene adsorbed with gaas nanostructure
granting_institution	Universiti Putra Malaysia
publishDate	2014
url	http://psasir.upm.edu.my/id/eprint/75937/1/FS%202014%2089%20IR.pdf
_version_	1747813099728011264

Density functional calculation for electronic structure properties of graphene adsorbed with GaAs nanostructure

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