Magnetic Properties of Edge Hydrogenated Zigzag Black

Phosphorene Nanoribbon by Fe Doping

Xinfeng Li

, Kai Zhang

, Shanling Ren

, Yunhui Wang

and Zhihong Yang

College of Electronic Science and Optical Engineering, Nanjing University of Posts and Telecommunications, Nanjing,

China

Faculty of Science, Nanjing University of Posts and Telecommunications, Nanjing, China

Keywords: two-dimensional material, black phosphorene nanoribbon, magnetic, first-principles calculation

Abstract: Using first-principles based on density functional theory within the GGA+U framework, we investigated the

structural states, energy, and magnetic properties of edge hydrogenated Zigzag black Phosphorene

Nanoribbon (H-ZPNR) with P atom substituted by Fe atom in different site. Undoped Edge hydrogenated

ZPNR has no magnetic moment, however our results show that the magnetic moment of doped systems

varied from 1μB to 4μB, and the coupling between the Fe atom and adjacent P atoms is either ferromagnetic

or anti-ferromagnetic.

1 INTRODUCTION

Two-dimensional(2D) material displayed great

potential applications in optoelectronic devices,

spintronic, lithium batteries and gas sensors (Liu et

al., 2017; Sun et al., 2016). Single layer black

phosphorus is a two-dimensional structure followed

by graphene and transition metal dichalcogenides

(MoS

), stanene and germanene, which had attracted

extensive research efforts. Many two-dimensional

materials are composed of nonmagnetic atoms, and

no magnetic state appeared in the 2D system.

Studies has shown that magnetic properties of

two-dimensional materials can be induced by doping,

vacancy defects, and edge effects (Cao et al., 2018;

Sharma et al., 2018; Son, 2006). For example, magnetic

properties are induced by doping transition metal

atom for MoS2, germanene, and graphene.

Phosphorene monolayer exhibits pleated structure

and is semiconductor with a direct band gap of

0.91eV

(Luan et al., 2017). The field effect transistor

fabricated with phosphorene exhibits a high-speed

carrier mobility (~1000cm

-1

) and gives a high

switching ratio of ~10

at room temperature (Li et al.,

2014), indicating the great potential application to

micro-electronic devices. So we explore the physical

properties of edge hydrogenated zigzag black

phosphorene nanoribbon (H-ZPNR) using

first-principles calculation. Latest studies indicated

H-ZPNR does not show edge magnetism and the

system is a direct band gap semiconductor (Zhou et

al., 2017). Moreover, due to the quantum

confinement effect, the band gap of H-ZPNR varies

greatly with the width of the nanoribbon (Peng et al.,

2014). Compare with other transitional atom Co and

Ni, the Fe atom has smaller mass so it can be easily

cooperated into ZPNR and the magnetic

configuration is simple compared with the Mn atom.

In this paper, we explore the electronic structure for

H-ZPNR doped with Fe atom, especially in

magnetic properties.

2 CALCULATION MODEL AND

PARAMETERS

The bare edge zigzag black phosphorus nanoribbon

(ZPNR) show either semiconductor or metallic

behavior in dependence on their edge chemical

groups (Peng et al., 2014), and edge hydrogenated

ZPNR transformed into a direct band gap

semiconductor (Zhu et al., 2014). H-ZPNR are more

stable than the ZPNR, and it is found that the ZPNR

band gap decreases with the increase of the

nanoribbon width (Zhu et al., 2014), we consider the

effect of inequivalent dopant position from the

centre of the nanoribbon to the margin, so we

choose 8 as the width of ZPNR (H-8ZPNR) as

228

Li, X., Zhang, K., Ren, S., Wang, Y. and Yang, Z.

Magnetic Proper ties of Edge Hydrogenated Zigzag Black Phosphorene Nanoribbon by Fe Doping.

DOI: 10.5220/0008188002280231

In The Second International Conference on Materials Chemistry and Environmental Protection (MEEP 2018), pages 228-231

ISBN: 978-989-758-360-5

narrow as possible. We have employed the method

of projector augmented wave based on density

functional theory as implemented in the Vienna

Ab-initio Simulation Package (VASP) (Kresse and

Furthmüller, 1996), and selected the projection

augmented wave (PAW) to describe the mutual

interaction between the ions. Meanwhile, we use the

generalized Gradient Approximation (GGA) of the

Perdew Burke Ernzerhof (PBE) functional form to

process the exchange-correlation energy between

electrons (Perdew et al., 1996a; Perdew et al.,

1996b). Considering that the localized d orbital

electrons will have a significant electron correlation

effect on the transition metal magnetism, correction

method GGA+U is applied to the doping system

(Dudarev et al., 1998). U=2.5eV is used as the

available value for obtaining the magnetic moment

of the transition metal atom in the study of transition

metal doped in single layer black phosphorus (Zhai

et al., 2017). We selected GGA+U (U=2.5eV)

framework to check the magnetic states of doped

systems.

(a)ZFe01 (b)ZFe02 (c)ZFe03

Figure 1: Schematic illustration: (a) ZFe01, (b) ZFe02, (c)

ZFe03. The Fe , P and H atoms are represented by the red,

purple and white color. O, B and A represent P atoms

adjacent to Fe atom.

As shown in Figure 1, the width is defined by the

number of P atoms along the x-axis. We construct

H-8ZPNR with periodic boundary, the vacuum

region of 15Å along the z-axis to avoid the influence

of interaction between the periodic nanoribbons.

And the 6Å vacuum region along the edge of the

hydrogenated nanoribbon to avoid interaction

between H atoms, lattice constant of a = 15.00 Å, b

= 19.80 Å and c = 15.0 Å are used. H-8ZPNR

contains 48 P atoms, the doping concentration of Fe

atom is 2.83%. These inequivalent doping sites were

chosen to research the effect on nanoribbion, three

doped systems substituted Fe atom for original P

atom are defined ZFe01, ZFe02 and ZFe03 from

margin to centre of nanoribbon respectively. The

kinetic energy cutoff of 450eV for the plane wave

expansion, and the structure relaxation was executed

until force on each atom less then 0.01 eV/Å, and

the energy convergence criterion of the each

electron was kept 10

-5

eV. The spin is considered in

the calculation performance. The Monkhorst-Pack

k-point sampling with a 1×7×1 k-mesh is used in the

Brillouin zone integration. And 1×31×1 k-mesh is

used for density of the state.

3 CALCULATION MODEL

Structural States and Energy. The top view of the

ZFe01, ZFe02 and ZFe03 are listed in Figure 1, P-P

bond transforms into Fe-P bond after doping. Three

P atoms adjacent to Fe atom are denoted as ‘O’, ‘A’

and ‘B’. Table 1 shows bond length and energy of

doped system, focus on position ‘O’ in ZFe01, the

P-P(O) bond length is 2.255 Å, the bond length of

Fe-P(O) is 2.222 Å after doping, the difference is

0.033 Å, the difference in ‘B’ and ‘A’ are 0.042 Å

and 0.041Å respectively. The total bond length

difference is 0.116 Å, 0.105 Å and 0.129 Å for

ZFe01 ZFe02 and ZFe03, and ZFe02 has the

smallest change of bond length indicating that the

bond length is likely to be impacted by doping

position. By comparing the energy difference of the

system, ZFe03 has the lowest energy of -299.280eV.

Results indicated that ZFe03 is the most stable.

Table 1: Optimized Bond Lengths ((P-P and Fe-P)in Å),

Energy (in eV).

P(O)

P(B)

P(A)

Energy

ZFe01

2.255

2.259

2.26

-297.225

2.222

2.301

ZFe02

2.255

2.224

-296.737

2.311

2.247

2.25

ZFe03

2.25

2.224

-299.280

2.26

2.28

2.287

Table 2: Magnetic moment of the Fe doped system

under GGA+U(in μB).

P(O)

P(B)

P(A)

total

ZFe01

2.701

0.09

-0.077

2.781

ZFe02

3.426

0.109

0.12

0.118

4.034

ZFe03

1.154

-0.028

-0.042

-0.026

1.07

Magnetic Properties of Edge Hydrogenated Zigzag Black Phosphorene Nanoribbon by Fe Doping

229

Magnetic Properties: Charge Analysis and

Density of States. The total magnetic moments of

ZFe01, ZFe02 and ZFe03 are 2.78μB, 4.034μB and

1.070μB respectively, ZFe02 has the largest total

magnetic moment, as shown in Table 2. The

magnetic moments of the three doped systems are

mainly arised from the Fe atom. The three P atoms

adjacent to the Fe atom in ZFe02 exhibit spin-up

magnetic moment, indicates that the three adjacent P

atoms are ferromagnetic coupling. In contrast, the

three P atoms adjacent to the Fe atom in the ZFe01

and ZFe03 exhibit spin-down status as a whole in

Figure 2, indicating antiferromagnetic coupling

between Fe atom and adjacent P atoms. The average

magnetic moment of adjacent P atoms and second

nearest P atom’s are 0.081μB and 0.013μB for

ZFe01, 0.116μB and 0.018μB for ZFe02, and

0.032μB, 0.013μB for ZFe03. So the most magnetic

moment are mainly from the Fe and adjacent P

atoms and we can take the magnetic moment of

doped system are localized. The magnetic moment

is relavent to the bond length, with the shorter Fe-P

bond length in ZFe02, the wave function overlapped

more compared with the others, so the magnetic

moment of ZFe02 is larger than others. Especially

the coupling between the Fe atom and the adjacent P

atoms can be either ferromagnetic or

antiferromagnetic indicates the coupling is intricate,

which need further research like multi-dopant

investigation.

(a)ZFe01 (b)ZFe02 (c)ZFe03

Figure 2: Spin charge density for Fe-doped system within

the GGA+U framework. The gold and cyan color have

iso-values of ±0.005 e/A

The Bader charge analysis has used to

investigate properties of the magnetic moment

between Fe and adjacent P atoms. The localized spin

charge density of the Fe atoms and three adjacent P

atoms were listed, gold color represents the spin-up

density, and cyan color represents the spin-down

density. In ZFe01 and ZFe03, the gold areas are

mainly accumulated around the Fe atom, the cyan

areas are small and concentrated in P atoms adjacent

to the Fe atom. Therefore, the adjacent P atoms of

Fe atoms in ZFe01 and ZFe03 are antiferromagnetic

coupling. However, ferromagnetic coupling is

exhibited in the ZFe02, which is consistent with the

conclusion from magnetic moment analysis. Thus

the spin charge density of the system is mainly

concentrated around the Fe atom, there are only a

few spin charge densities around the adjacent P

atoms, and there are almost no spin charge densities

in the adjacent position and locations far away from

the Fe atom. It also shows that the magnetic

properties in the doped system are mainly from the

Fe atom. Bader charge analysis also illustrate the

charge transfer, the Fe atom in three doped systems

are all electronegative, and electrons transfer from

the d orbital of the Fe atom to the p orbital of the P

atoms, and the charge transfer electrons are 0.37e,

0.44e, and 0.33e, respectively.

Figure 3: DOS illustration: (a) ZPNR, (b) ZFe01, (c)

ZFe02, (d) ZFe03.

Density of states (DOS) for ZFe01, ZFe02 and

ZFe03 are listed in Figure 3. In H-8ZPNR, the band

gap is 2eV. However, dopant energy state appeared

in ZFe01, ZFe02 and ZFe03 so reduce the band gap,

their band gap is 0.76eV, 0.74eV and 1.04eV

respectively. The majority spin density of state and

the minority spin density of state are asymmetric,

Compared with the width of band gap, central doped

is greater than the edge doped. As shown in Figure 4,

the partial wave hybridization between d orbital of

the Fe atom and the p orbital of P atoms make most

contribution to density of states (PDOS) clearly

indicate the influence of electron orbital of the

atom on the magnetic properties. The magnetic

moment is derived from d orbital of the Fe atom, p-d

orbital the total magnetic moment and this coupling

is localized.

MEEP 2018 - The Second International Conference on Materials Chemistry and Environmental Protection

230

Figure 4: PDOS illustration: (a) ZPNR, (b) ZFe01, (c)

ZFe02, (d) ZFe03.

4 CONCLUSIONS

In summary, based on the density functional

calculations, we have explored the structure and

magnetic properties of doped black phosphorene

nanoribbon. The result show that doped nanoribbon

had lattice distortion but the structure is stable. The

substitution of Fe for P induce magnetic moment

and this moment is localized. The coupling between

the Fe atoms and adjacent P atoms can be either

ferromagnetic or anti-ferromagnetic coupling,

relavent to the magnetic value of Fe atom, which is

required further research.

ACKNOWLEDGEMENTS

This research was supported by Basic Science

Research Program through the Natural Science

Foundation of China (No. 11804169 and 11747029)

and by the Research initiation funds of Nanjing

University of Posts and Telecommunications No.

NY216029. In addition, I appreciate the help from

Dr. Huang Xin for useful discussion.

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