Electronic and magnetic properties of graphene quantum dots doped with alkali metals

被引：52

作者：

Osman, Waleed ^{[1
,2
]}

Abdelsalam, H. ^{[2
,3
]}

Ali, M. ^{[4
]}

Teleb, N. H. ^{[5
]}

Yahia, I. S. ^{[6
,7
,8
]}

Ibrahim, M. A. ^{[9
]}

Zhang, Q. ^{[2
]}

机构：

[1] Beni Suef Univ, Fac Sci, Phys Dept, Bani Suwayf 62514, Egypt

[2] Yancheng Inst Technol, Sch Mat Sci & Engn, Yancheng 224051, Peoples R China

[3] Natl Res Ctr, Theoret Phys Dept, El Buhouth Str, Giza 12622, Egypt

[4] Misr Univ Sci & Technol, Basic Sci Dept, Giza 77, Egypt

[5] Natl Res Ctr, Electron Microscope & Thin Films Dept, El Buhouth Str, Giza 12622, Egypt

[6] King Khalid Univ, Res Ctr Adv Mat Sci RCAMS, POB 9004, Abha 61413, Saudi Arabia

[7] King Khalid Univ, Fac Sci, Dept Phys, Adv Funct Mat & Optoelect Lab AFMOL, POB 9004, Abha, Saudi Arabia

[8] Ain Shams Univ, Fac Educ, Semicond Lab,Met Lab,Phys Dept 2, Nanosci Lab Environm & Biomed Applicat NLEBA, Cairo 11757, Egypt

[9] Natl Res Ctr, Spect Dept, El Buhouth Str, Giza 12622, Egypt

来源：

JOURNAL OF MATERIALS RESEARCH AND TECHNOLOGY-JMR&T | 2021年 / 11卷

关键词：

Graphene quantum dots; DFT; Doping; Alkali metals; Electronic and magnetic properties; Spin polarization; 1ST PRINCIPLES; FUNCTIONALIZATION; ABSORPTION; NANOTUBE; PROGRESS;

D O I：

10.1016/j.jmrt.2021.01.119

中图分类号：

T [工业技术];

学科分类号：

08 ;

摘要：

The electronic and magnetic properties of armchair-hexagonal (AHEX) and zigzag triangular (ZTRI) graphene quantum dots doped with alkali metals are investigated using density functional theory. The binding energy confirms the stability of the undoped systems. Although doping decreases stability of single layer structures, in bilayer ones the binding energy between the layers increases. The former is due to the broken bonds and the deformation at the surface, while the later is due to the chemical bonds formation between the layers. We found that the lowest ground state energy for AHEX/AHEX-doped is the singlet/quadruplet spin state. Therefore, AHEX dots experience transformation from diamagnetic to ferromagnetic state after doping. In addition, the optimized spin state for ZTRI/ZTRI-doped is the quintet/sextet spin-polarized state. In few cases, the doped AHEX/ ZTRI dots have doublet/quadruplet spin state due to the strong interaction between the flake atoms that passivates some unpaired electrons. Magnetic properties depend also on stacking, for instance pristine bilayer triangular flakes become antiferromagnetic due to pairing between edge states. The energy gap significantly affected by doping, for instance the gap decreases from similar to 3.7 eV in hexagonal flakes to 1.5 eV when it is doped with Na in the upper position. Electrons from the broken bonds around the doped metal form orbitals loosely bound to the flake consequently decreasing the energy gap. On the other hand, stacking increases the energy gap in bilayer triangular flakes due to the mutual passivation of the reactive edge states from both the layers. The calculated spin up/down density ratio is high in hexagonal flakes leading to high spin polarization (P), for instance P 1/4 0.64 in hexagonal flakes doped with K atom. The found enhanced spin polarization, in addition to the tunable magnetic properties, makes doped graphene flakes promising candidates for spintronic devices.(c) 2021 The Author(s). Published by Elsevier B.V.

引用

页码：1517 / 1533

页数：17

共 40 条

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