Spin-Dependent Transport and Optical Properties of Transparent Half

Subscriber access provided by Brought to you by ST ANDREWS UNIVERSITY LIBRARY

Article

Spin Dependent Transport and Optical Properties of Transparent Half Metallic g-CN Films 4

3

Arqum Hashmi, M. Umar Farooq, Tao Hu, and Jisang Hong J. Phys. Chem. C, Just Accepted Manuscript • DOI: 10.1021/jp510179p • Publication Date (Web): 05 Dec 2014 Downloaded from http://pubs.acs.org on December 7, 2014

Just Accepted “Just Accepted” manuscripts have been peer-reviewed and accepted for publication. They are posted online prior to technical editing, formatting for publication and author proofing. The American Chemical Society provides “Just Accepted” as a free service to the research community to expedite the dissemination of scientific material as soon as possible after acceptance. “Just Accepted” manuscripts appear in full in PDF format accompanied by an HTML abstract. “Just Accepted” manuscripts have been fully peer reviewed, but should not be considered the official version of record. They are accessible to all readers and citable by the Digital Object Identifier (DOI®). “Just Accepted” is an optional service offered to authors. Therefore, the “Just Accepted” Web site may not include all articles that will be published in the journal. After a manuscript is technically edited and formatted, it will be removed from the “Just Accepted” Web site and published as an ASAP article. Note that technical editing may introduce minor changes to the manuscript text and/or graphics which could affect content, and all legal disclaimers and ethical guidelines that apply to the journal pertain. ACS cannot be held responsible for errors or consequences arising from the use of information contained in these “Just Accepted” manuscripts.

The Journal of Physical Chemistry C is published by the American Chemical Society. 1155 Sixteenth Street N.W., Washington, DC 20036 Published by American Chemical Society. Copyright © American Chemical Society. However, no copyright claim is made to original U.S. Government works, or works produced by employees of any Commonwealth realm Crown government in the course of their duties.

Page 1 of 25

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

The Journal of Physical Chemistry

1

Spin dependent transport and optical properties of

2

transparent half-metallic g-C4N3 films

3

Arqum Hashmi, M. Umar Farooq, Tao Hu, and Jisang Hong

4

Department of Physics, Pukyong National University, Busan 608-737, Korea

5

ABSTRACT

6

Half-metallic materials play an essential role in the spin dependent transport study and so far it is

7

believed that the 3d transitional metal elements are necessary to obtain ferromagnetic state.

8

Herein, we demonstrate that the metal free two-dimensional graphitic carbon nitride (g-C4N3)

9

film show half metallic state and this is independent of the film thickness and stacking order. We

10

find that the half-metallicity results in a very large magnetoresistance even at finite bias.

11

Moreover, we have also investigated various optical properties. The g-C4N3 thin films have a

12

very high refractive index for parallel polarization and extremely weak reflectivity for

13

perpendicular polarization. Additionally, the g-C4N3 thin films are optically transparent because

14

of very weak absorption coefficients. Overall, our findings suggest that the transparent half-

15

metallic g-C4N3 thin films can be used for both spintronics and optical applications because of

16

potential multifunctionality.

17

ACS Paragon Plus Environment

1


1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 2 of 25

18 19

INTRODUCTION

20

Spintronics is one of the most promising fields in condensed matter physics because the spin

21

degree of freedom can provoke various applications of innovative technologies. Regarding the

22

spintronics, half-metallic materials have many advantages because one spin channel is

23

conductive, but the other spin channel is insulating.1,2 This will result in a giant

24

magnetoresistance which is an essential quantity for spintronics. Various types of materials show

25

half-metallic state, but most of them are based on the conventional 3d transition metal

26

elements.3–8

27 28

In general, 2p electron systems show a non-magnetic behavior in a bulk state. Of course, several

29

studies proposed defect induced magnetic state in two-dimensional geometry.9–11 However, those

30

studies were about local magnetic state, not ferromagnetism arising from long range ordering. In

31

the spin dependent transport study, a long spin relaxation time is an important factor for spin

32

information delivery. By virtue of the fact that the spin relaxation time is inversely proportional

33

to the strength of spin-orbit coupling, the half-metallicity in 2p electron system will bring an

34

interesting issue in the spin dependent transport property. Nonetheless, it is rare to find such

35

reports on the half-metallicity from pure 2p electronic materials.12,13

36 37

Interestingly, the graphitic carbon nitride, namely g-C4N3, was synthesized and showed a half-

38

metallic state in free standing monolayer.14,15 After then, many other works were reported on

39

free standing structure.16–20 Recently, the influence of Li adsorption and the mechanism of stable

40

adsorption of hybridized system with BN layer were presented as well.21,22 However,


2

Page 3 of 25

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


41

manipulating a single layer structure will require highly precise experimental technique and also

42

complex fabrication process for device applications. It will be more practical, realistic, and easier

43

to treat thicker layers than free standing monolayer. So far, no studies on this issue have been

44

performed. In this respect, our objective is to propose that the g-C4N3 film can maintain half-

45

metallic state even in multilayer structure and this half-metallicity can be applied for spintronics.

46

We will prove this by calculating the spin dependent current and magnetoresistance at finite bias.

47

Along with these magnetic properties, if the multilayer g-C4N3 system can be utilized for optical

48

device applications, it will be a remarkable finding and attract great research interests in diverse

49

fields in condensed matter physics because of potential multifunctionality. Thus, we will study

50

the frequency dependent optical properties such as dielectric functions, refractive index,

51

reflectivity, and absorption coefficients.

52 53

NUMERICAL METHOD

54

We employed the Vienna ab initio simulation package (VASP) using a plane wave basis

55

set.23,24 The core electron interactions were described using the projector augmented wave

56

(PAW) method. For layer structured materials, it is of necessity to include van der Waals

57

interaction. Thus, in this report, we explore the structural, adsorption, electronic and magnetic

58

properties of multilayer g-C4N3 using non-empirical vdW-DF method proposed by Dion et al.25

59

as implemented in the VASP code. We used most recently developed less repulsive optB88-like

60

exchange functional method

61

interlayer distances were achieved.25,27,28 A vacuum distance of 15 Å was imposed and we

62

carried the self-consistent calculations with 9x9x1 k-mesh. All results have been obtained with

63

very high plane-wave energy cut-off of 700 eV. The structure optimization has been performed

26

because significant improvements in binding energies and


3


1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 4 of 25

64

until the residual forces on individual atoms were smaller than 0.01 eVÅ-1. The convergence

65

criterion for energy was set to 0.1 meV. It is worth noting that the g-C4N3 is known to have a

66

(2x2) reconstructed surface geometry. Thus, the ground state lattice constant of g-C4N3 is 9.68 Å

67

and entire calculations were performed with this lattice constant. In addition, ferromagnetic

68

(FM), antiferromagnetic (AFM) and non-magnetic (NM) spin configurations were considered to

69

find out the magnetic ground state. The thickness varies from bilayer to 4 monolayers (MLs). In

70

this type of layer structured material, it is necessary to find the stacking order. Thus, three

71

different stacking orders, so called, AA, AB and AC for bilayer system and ABA, ABB and

72

ABC stacking orders for the trilayer film were examined. Using the result of trilayer structure,

73

we adopted the stacking order of ABAB for 4 ML film. For the transport calculations, we

74

employ the non-equilibrium Green's function (NEGF) method based on density functional

75

theory. All of the electron transport calculations were performed using the density functional

76

theory code OpenMX, which is based on localized pseudoatomic orbitals (PAOs) and norm-

77

conserving pseudopotentials.29,30 Two primitive orbitals (s and p orbitals) generated by a

78

confinement scheme with cutoff of 5 Bohr radius are employed.31,32 The Perdew-Burke-

79

Ernzerhof (PBE) exchange-correlation functional, which is derived within the generalized

80

gradient approximation (GGA) is used.33 To obtain bias dependent current, we have divided the

81

sheet of g-C4N3 into three parts; two leads and scattering part.34 The central sheet sandwiched

82

between two g-C4N3 leads is used for the NEGF calculations. For spin dependent transport study,

83

we changed the relative spin direction in the two leads and the bias dependent current in both

84

parallel and antiparallel configurations is obtained

85


4

Page 5 of 25

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


86

NUMERICAL RESULTS

87

The g-C4N3 bilayer structure can have three different configurations such as AA, AB, and AC

88

stacking as shown in Figure 1 (a) - (c). For clarification, we also present the (1x1) cell of free

89

standing g-C4N3 layer in Figure 1(d). The C and N atoms located on the hexagonal ring are

90

referred as C1 and N1, respectively, whereas C atom located outside the ring is denoted as C2. In

91

AA stacking, carbon and nitrogen atoms of two layers have the same lateral positions. In AB

92

stacking, C1 and N1 atoms are on the hexagonal rings of the other layer while C2 atoms have no

93

direct coupling. In AC stacking, carbon and nitrogen atoms of both layers are on the bridge sites

94

of each other. Figure 1 (e) – (g) shows three different stacking orders for the trilayer film. Here,

95

we considered ABA, ABB, and ABC stacking. Since the AB stacking was the most stable

96

configuration in bilayer system, we constructed trilayer structure by adding one more layer to the

97

AB stacked bilayer g-C4N3. Table 1, the ABA stacking became the most stable structure. Thus,

98

this suggests that the multilayer film may display ABAB stacking with increase of the film

99

thickness. So, we only considered ABAB stacking in 4 ML film.

100 101

Table I presents the total energy differences among FM, AFM and NM spin arrangements and

102

magnetic moment per (1x1) cell. Here, it should be remarked that we have calculated the total

103

energy with (2x2) cell and the same spin configurations are considered as Du et al. did.15 In

104

bilayer and trilayer systems, the total energy of AB and ABA stacking in FM state was set to

105

zero, respectively as a reference energy.

106


5


1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 6 of 25

107

TABLE 1: Stacking order dependent total energy difference (in meV/cell) and energy

108

difference per atom (in meV) shown in parentheses. The magnetic moment (in µB) per (1x1)

109

unit cell . FM

AFM

NM

µB / cell

AB

0

365 (6.5)

357 (6.3)

1.000

AC

29 (0.5)

340 (6.1)

342 (6.1)

0.968

AA

42 (0.8)

328 (5.8)

328 (5.8)

0.921

ABA

0

518 (6.2)

552 (6.6)

1.000

ABB

62 (0.7)

532 (6.3)

534 (6.3)

0.935

ABC

71 (0.8)

563 (6.7)

568 (6.8)

0.969

0

700 (6.3)

735 (6.6)

1.000

Stacking 2ML

3ML

4ML ABAB 110 111

The most stable bilayer structure is found in the AB stacking. FM ground state was still

112

preserved in the bilayer structure and the magnetic ground state is independent of the stacking

113

order. The calculated total magnetic moment of the bilayer g-C4N3 film in 2x2 supercell is 8.00

114

µB , 7.75 µB and 7.37 µB in AB, AC and AA stacking respectively. Note that the magnetic

115

moment of pristine free standing g-C4N3 monolayer is 1.0 µB per (1x1) unit cell.15,19,22 In bilayer

116

system, we found an integer magnetic moment in AB stacking. This implies that the most stable

117

AB stacking film has a half-metallic state. On the other hand, we find the same behavior even in

118

3 and 4 ML films. This result tells that the g-C4N3 displays half-metallic state in multilayer

119

films. From Table I, we find that the order of spin polarization in bilayer is AB>AC>AA while it

120

becomes ABA>ABC>ABB in trilayer structures. There is an interesting relationship between


6

Page 7 of 25

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


121

spin polarization and stacking order. First of all, the AB stacking order produces the largest spin

122

polarization and the smallest spin polarization is obtained in identical stacking (AA order) in

123

bilayer system. If we add one more layer on AB bilayer structure to form a trilayer film, the ABB

124

stacking will have the least spin polarization because of the identical BB stacking. In addition,

125

the BC arrangement in ABC stacking is like an AC bilayer stacking if we start from the layer B.

126

On the other hand, BA arrangement in ABA stacking is equivalent to AB bilayer stacking with

127

respect to the B layer. Thus, we find the order of spin polarization such as ABA>ABC>ABB.

128 129

It is noteworthy that the stability of FM state seems increasing as the film thickness increases.

130

However, in reality, the energy difference per atom remains almost the same as shown in

131

parentheses of Table 1. Hence, the ferromagnetic stability shows no significant thickness

132

dependency. Indeed, we have checked another AFM configuration. In this case, the AFM

133

interaction between different layers of g-C4N3 is considered. The FM state is still stable spin

134

configuration and the calculated energy difference was almost 20 meV as compared with AFM

135

state. In addition, this value is also thickness and stacking order independent. We now show the

136

geometric feature and adsorption energy,

137

Ntot represent the total energy of the fully optimized N layer g-C4N3 film, the energy of free

138

standing single layer g-C4N3, the number of layers and the total number of atoms in the supercell,

139

respectively. The optimized interlayer distances and adsorption energies are presented in Table 2.

140

TABLE 2: Optimized interlayer distances (in Å) and adsorption energies (Ea in meV/atom) 2ML AB stacking AC stacking AA stacking

=

( ( × )

where EN, , N and

Interlayer Distance

3.27

3.30

3.32

Ea

-0.032

-0.031

-0.031


7


1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 8 of 25

3ML

ABA stacking

ABB stacking

ABC stacking

Interlayer Distance

(AB) 3.27

(AB) 3.30

(AB) 3.30

(BA) 3.27

(BB) 3.31

(BC) 3.31

Ea

-0.044

-0.043

-0.043

4ML

ABAB stacking

_

_

Interlayer Distance

3.27

_

_

Ea

-0.051

_

_

141 142

We have observed that the multilayer films still maintain corrugated layer structure as found in

143

free standing single layer g-C4N3 structure.15,21 From the calculated adsorption energy, one can

144

understand that the g-C4N3 multilayer is a weakly bounded system. This suggests that the main

145

interaction among layers should be described by the van der Waals interaction because the

146

adsorption energy per atom is very small as compared with that of bilayer graphene.35

147 148

Figure 2 and 3 shows the band structures and density of states (DOS) for bilayer and trilayer

149

respectively. Indeed, the band structures and DOS in 4ML films were almost the same as those

150

of bilayer and trilayer systems, thus we here only presented the results of bilayer and trilayer

151

films. Band structure and DOS of AB and ABA stacking of bilayer and trilayer show the half

152

metallic behavior as shown in Figure 2(a) and 3(a), respectively. One can clearly find that the

153

majority spin electrons are fully occupied below the Fermi level, whereas the minority spin

154

bands cross the Fermi level. In AA and AC configurations for bilayer and ABB and ABC

155

configurations for trilayer, we find a similar trend although the majority spin bands barely cross

156

the Fermi level. Nonetheless, the minority spin bands maintain the same features as found in AB

157

and ABA stacking. This can be confirmed by the spectral shape of DOS. This half-metallic


8

Page 9 of 25

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


158

characteristic in thin film geometry will bring an interesting issue in the spin dependent transport

159

phenomenon because a giant magnetoresistance can be achieved.

160 161

We now discuss the spin dependent transport properties at finite bias. In Figure 4 (a) and (b), the

162

schematic illustration for two leads and scattering part for both parallel and antiparallel

163

configurations is displayed, respectively. We apply the bias voltages along the negative x-axis,

164

so the electrons move to the positive x-axis. The periodic boundary condition is used along the y-

165

axis and the vacuum distance of 12 Å is applied along the perpendicular to the film surface. We

166

performed the NEGF calculation by taking 150 numbers of poles along the x-direction and 9 k-

167

points along the y direction and the convergence criterion is kept 10-8 Hartree. It is obvious that

168

the electronic band structure controls the transport property of a material. As we discussed

169

already, the most stable configuration of multilayer g-C4N3 shows the half-metallic state and no

170

substantial changes in their ground state band structures were found. Thus, we expect that the

171

essential transport properties for multilayer g-C4N3 will be the same. Hence, we only calculated

172

the transport properties of single layer g-C4N3. In Figure 4 (c), we present the spin dependent I-V

173

curve originated from each spin component as a function of external bias. In parallel spin

174

configuration, the majority spin current is completely suppressed and this is a straightforward

175

result because the majority spin band has a gap as shown in Figure. 2 and only the minority spin

176

electrons contribute to the current. In antiparallel spin configuration, the current is significantly

177

suppressed because of the reversed spin direction in the opposite lead. From these I-V curves of

178

each spin component, we calculate bias dependent magnetoresistance (MR) ratio defined by

179

MR(%) = (Ip-Iap)/Ip where the Ip(ap) represents the total current of parallel (antiparallel) spin

180

configuration. Then, the maximum MR ratio is 100 % in the theoretical point of view when the


9


1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 10 of 25

181

total current in an antiparallel configuration is zero at any bias voltage. However, in general, the

182

Iap can be measured at finite bias, so the 100 % MR ratio is hardly achievable at finite bias. In

183

our system, we find that the MR ratio is still large enough even at bias voltage of 0.5 eV and this

184

giant MR ratio suggests that the g-C4N3 film can be an ideal candidate for spintronics.

185 186

To explore the optical properties, the most important quantity is the frequency dependent

187

dielectric function () = () + () because various optical properties such as

188

refractive index, reflectivity, and absorption function can be extracted from this value. Here, we

189

have considered both parallel (E‫ )׀׀‬and perpendicular (E⊥) electric field polarization to the film

190

surface. From the calculated electronic band structures, one can easily understand that the

191

contribution to the dielectric function due to the intraband transition is negligible if the photon

192

energy is larger than approximately 0.6 eV. Thus, the interband transition plays an essential role

193

in a wide range of photon energy for the frequency dependent dielectric function. Additionally,

194

we expect very weak interband optical transition in the visible range because of the band

195

characteristic. This implies that the g-C4N3 films will be optically transparent. Thus, the g-C4N3

196

films can be utilized for both spintronics and optical application purposes.

197 198

Figure 5 shows the real and imaginary part of frequency dependent dielectric functions for both

199

bilayer and trilayer by changing the stacking order. At a zero frequency, the static dielectric

200

functions (ε1(0)) are subject to the thickness and polarization. In bilayer, the ε1(0) is in the range

201

from 13 to 25 for parallel polarization while it is about 4 for perpendicular polarization. In

202

trilayer, the ε1(0) is in the range from 35 to 50 for parallel polarization while it is about 6 for

203

perpendicular polarization. As the photon energy increases, the thickness and stacking order


10

Page 11 of 25

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


204

dependence of the dielectric function disappear, but only the electric field polarization

205

dependence remained. One can see noticeable asymmetric behavior in the imaginary part of the

206

dielectric function. This may indicate an anisotropic optical behavior with respect to the electric

207

polarization. In Figure 6 (a) and (b), the calculated refractive index is presented for bilayer and

208

trilayer films, respectively. The real part of the refractive index of parallel electric polarization

209

was larger than that of perpendicular polarization and the refractive index of perpendicular

210

polarization is frequency dependent, but it is almost constant of 1.2 in the visible range for

211

parallel polarization. Interestingly, we find very large refractive index of 2.6 near the blue light

212

for parallel polarization. This large value of refractive index can have potential application for

213

optical device. The reflectivity value is also an important quantity for reflecting and anti-

214

reflecting applications. For instance, it is highly desirable to obtain zero reflectivity for anti-

215

reflection coating purposes. As shown in Figure 6(c) and (d), the perpendicular polarization

216

component has very weak reflectivity. On the other hand, we can find high reflectivity in the

217

ultraviolet region for parallel polarization. In Figure 6(e) and (f), we present the frequency

218

dependent absorption coefficients. We also find an anisotropic behavior in the frequency

219

dependent functions. As displayed, the absorption coefficient for perpendicular polarization is

220

quite small compared with that of parallel polarization. Since the intensity of propagating light

221

decays exponentially as a function of length, the calculated absorption coefficients indicate that

222

the g-C4N3 films can be optically transparent even in much thicker films.

223 224

CONCLUSION

225

In summary, we investigated the structural, magnetic, optical and spin dependent transport

226

properties of g-C4N3 films. The most stable structure was found in AB type stacking order. The


11


1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 12 of 25

227

adsorption energy calculations indicated that the interlayer interaction should be described by the

228

van der Waals interaction. We found metal free half metallic behavior and the essential

229

electronic structure was insensitive to the film thickness and stacking order. Due to the half-

230

metallic behavior, the minority spin electrons contribute to the spin dependent current at finite

231

bias in parallel spin configuration whereas the current is strongly suppressed in an antiparallel

232

configuration. Consequently, we find very large magnetoresistance up to the bias voltage of 0.5

233

eV. Along with these magnetic properties, we also explored the optical properties. In general,

234

the optical properties are insensitive to the film thickness and stacking order, but they are

235

strongly subjective to the electric polarization. For instance, the refractive index for

236

perpendicular polarization seems frequency independent in the visible range. Interestingly, a

237

large refractive index of 2.6 was found in parallel polarization, whereas an extremely low

238

reflectivity was obtained in perpendicular polarization. In addition, the multilayer g-C4N3 films

239

are optically transparent. Overall, we propose that the metal free transparent half metallic g-C4N3

240

films can be utilized for spintronics and optical device applications.

241


12

Page 13 of 25

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


242

AUTHOR INFORMATION

243

Corresponding Author

244

*E-mail: [email protected]

245

Notes

246

The authors declare no competing financial interest.

247

ACKNOWLEDGMENT

248

This research was supported by Basic Science Research Program through the National

249

Research Foundation of Korea(NRF) funded by the Ministry of Education, Science and

250

Technology (No. 2013R1A1A2006071) and by the Supercomputing Center/Korea Institute of

251

Science and Technology Information with supercomputing resources including technical support

252

(KSC-2014-C3-015)


13


1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

253 254 255 256

Page 14 of 25

REFERENCES (1)

De Groot, R. A.; Mueller, F. M.; Engen, P. G. van; Buschow, K. H. J. New Class of

Materials: Half-Metallic Ferromagnets. Phys. Rev. Lett. 1983, 50, 2024–2027. (2)

Groot, R. A. de; Mueller, F. M.; Engen, P. G. van; Buschow, K. H. J. Half‐metallic

257

Ferromagnets and Their Magneto‐optical Properties (invited). J. Appl. Phys. 1984, 55, 2151–

258

2154.

259

(3)

Kang, J.-S.; Park, J.-G.; Olson, C. G.; Youn, S. J.; Min, B. I. Valence Band and Sb 4d

260

Core Level Photoemission of the XMnSb-Type Heusler Compounds (X=Pt,Pd,Ni). J. Phys.

261

Condens. Matter 1995, 7, 3789.

262 263 264 265 266

(4)

Hanssen, K. E. H. M.; Mijnarends, P. E. Positron-Annihilation Study of the Half-Metallic

Ferromagnet NiMnSb: Theory. Phys. Rev. B 1986, 34, 5009–5016. (5)

Galanakis, I.; Dederichs, P. H.; Papanikolaou, N. Slater-Pauling Behavior and Origin of

the Half-Metallicity of the Full-Heusler Alloys. Phys. Rev. B 2002, 66, 174429. (6)

Medvedeva, J. E.; Freeman, A. J.; Cui, X. Y.; Stampfl, C.; Newman, N. Half-Metallicity

267

and Efficient Spin Injection in AlN/GaN∶Cr (0001) Heterostructure. Phys. Rev. Lett. 2005, 94,

268

146602.

269

(7)

270 271

Mallajosyula, S. S.; Pati, S. K. Vanadium−Benzimidazole-Modified sDNA: A One-

Dimensional Half-Metallic Ferromagnet. J. Phys. Chem. B 2007, 111, 13877–13880. (8)

Du, C.; Adur, R.; Wang, H.; Hauser, A. J.; Yang, F.; Hammel, P. C. Control of

272

Magnetocrystalline Anisotropy by Epitaxial Strain in Double Perovskite Sr2FeMoO6 Films.

273

Phys. Rev. Lett. 2013, 110, 147204.


14

Page 15 of 25

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

274 275 276 277 278 279 280 281


(9)

Kim, D.; Hashmi, A.; Hwang, C.; Hong, J. Magnetization Reversal and Spintronics of

Ni/Graphene/Co Induced by Doped Graphene. Appl. Phys. Lett. 2013, 102, 112403. (10) Yang, J.; Kim, D.; Hong, J.; Qian, X. Magnetism in Boron Nitride Monolayer: Adatom and Vacancy Defect. Surf. Sci. 2010, 604, 1603–1607. (11) Si, M. S.; Xue, D. S. Magnetic Properties of Vacancies in a Graphitic Boron Nitride Sheet by First-Principles Pseudopotential Calculations. Phys. Rev. B 2007, 75, 193409. (12) Li, Y.; Zhou, Z.; Shen, P.; Chen, Z. Spin Gapless Semiconductor−Metal−Half-Metal Properties in Nitrogen-Doped Zigzag Graphene Nanoribbons. ACS Nano 2009, 3, 1952–1958.

282

(13) Dutta, S.; Pati, S. K. Half-Metallicity in Undoped and Boron Doped Graphene

283

Nanoribbons in the Presence of Semilocal Exchange-Correlation Interactions. J. Phys. Chem. B

284

2008, 112, 1333–1335.

285

(14) Lee, J. S.; Wang, X.; Luo, H.; Dai, S. Fluidic Carbon Precursors for Formation of

286

Functional Carbon under Ambient Pressure Based on Ionic Liquids. Adv. Mater. 2010, 22, 1004–

287

1007.

288 289 290 291 292 293

(15) Du, A.; Sanvito, S.; Smith, S. C. First-Principles Prediction of Metal-Free Magnetism and Intrinsic Half-Metallicity in Graphitic Carbon Nitride. Phys. Rev. Lett. 2012, 108, 197207. (16) Sun, S.-J. Interior Edges Induced Half-Metallic Ferromagnetism in Graphitic Carbon Nitride Structures. J. Magn. Magn. Mater. 2013, 344, 39–43. (17) Li, Y.; Sanvito, S.; Hou, S. Origin of the Half-Metallic Properties of Graphitic Carbon Nitride in Bulk and Confined Forms. J. Mater. Chem. C 2013, 1, 3655–3660.


15


1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

294 295 296 297 298 299 300 301 302 303 304 305 306 307 308 309 310 311

Page 16 of 25

(18) Li, X.; Zhou, J.; Wang, Q.; Kawazoe, Y.; Jena, P. Patterning Graphitic C–N Sheets into a Kagome Lattice for Magnetic Materials. J. Phys. Chem. Lett. 2013, 4, 259–263. (19) Li, X.; Zhang, S.; Wang, Q. Stability and Physical Properties of a Tri-Ring Based Porous G-C4N3 Sheet. Phys. Chem. Chem. Phys. 2013, 15, 7142–7146. (20) Wu, M.; Wang, Q.; Sun, Q.; Jena, P. Functionalized Graphitic Carbon Nitride for Efficient Energy Storage. J. Phys. Chem. C 2013, 117, 6055–6059. (21) Hashmi, A.; Hu, T.; Hong, J. Transition from Half Metal to Semiconductor in Li Doped G-C4N3. J. Appl. Phys. 2014, 115, 124312. (22) Hashmi, A.; Hong, J. Metal Free Half Metallicity in 2D System: Structural and Magnetic Properties of G-C4N3 on BN. Sci. Rep. 2014, 4. (23) Kresse, G.; Furthmüller, J. Efficiency of Ab-Initio Total Energy Calculations for Metals and Semiconductors Using a Plane-Wave Basis Set. Comput. Mater. Sci. 1996, 6, 15–50. (24) Kresse, G.; Furthmüller, J. Efficient Iterative Schemes for Ab Initio Total-Energy Calculations Using a Plane-Wave Basis Set. Phys. Rev. B 1996, 54, 11169–11186. (25) Dion, M.; Rydberg, H.; Schröder, E.; Langreth, D. C.; Lundqvist, B. I. Van Der Waals Density Functional for General Geometries. Phys. Rev. Lett. 2004, 92, 246401. (26) Klimeš, J.; Bowler, D. R.; Michaelides, A. Chemical Accuracy for the van Der Waals Density Functional. J. Phys. Condens. Matter 2010, 22, 022201.


16

Page 17 of 25

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


312

(27) Graziano, G.; Klimeš, J.; Fernandez-Alonso, F.; Michaelides, A. Improved Description of

313

Soft Layered Materials with van Der Waals Density Functional Theory. J. Phys. Condens.

314

Matter 2012, 24, 424216.

315

(28) Liu, W.; Carrasco, J.; Santra, B.; Michaelides, A.; Scheffler, M.; Tkatchenko, A. Benzene

316

Adsorbed on Metals: Concerted Effect of Covalency and van Der Waals Bonding. Phys. Rev. B

317

2012, 86, 245405.

318 319 320 321 322 323 324 325 326 327 328 329 330 331

(29) The Code, OpenMX, Pseudo-Atomic Basis Functions and Pseudopotentials Are Available on Web Site (http://www.openmx-Square). (30) Troullier, N.; Martins, J. L. Efficient Pseudopotentials for Plane-Wave Calculations. Phys. Rev. B 1991, 43, 1993–2006. (31) Ozaki, T. Variationally Optimized Atomic Orbitals for Large-Scale Electronic Structures. Phys. Rev. B 2003, 67, 155108. (32) Ozaki, T.; Kino, H. Numerical Atomic Basis Orbitals from H to Kr. Phys. Rev. B 2004, 69, 195113. (33) Perdew, J. P.; Burke, K.; Ernzerhof, M. Generalized Gradient Approximation Made Simple. Phys. Rev. Lett. 1996, 77, 3865–3868. (34) Ozaki, T.; Nishio, K.; Kino, H. Efficient Implementation of the Nonequilibrium Green Function Method for Electronic Transport Calculations. Phys. Rev. B 2010, 81, 035116. (35) Birowska, M.; Milowska, K.; Majewski, J. A. Van Der Waals Density Functionals for Graphene Layers and Graphite Acta Physica Polonica A 2011, 845.


17


1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 18 of 25

332

Figure 1. Schematic illustrations of (a) AA stacking (b) AB stacking (c) AC stacking in bilayer

333

film (d) 1x1 unit cell of g-C4N3 (e) ABA stacking (f) ABB stacking (g) ABC stacking in trilayer

334

film.

335

Figure 2. Calculated Band structures of (a) AB stacking (b) AC stacking (c) AA stacking and

336

DOS of (d) AB stacking (e) AC stacking (f) AA stacking.

337

Figure 3. Calculated Band structures of (a) ABA stacking (b) ABB stacking (c) ABCstacking

338

and DOS of (d) ABA stacking (e) ABB stacking (f) ABC stacking.

339

Figure 4. Schematic illustrations of device components for transport calculations with two leads

340

and scattering part (central region). The arrow indicates the direction of electron flow in (a)

341

parallel spin configuration (b) antiparallel spin configurations. (c) I-V curve and

342

magnetoresistance (MR) with the applied voltage. The left and right scales are for current and

343

MR ratio, respectively.

344

Figure 5. Real part of the frequency dependent dielectric function of (a) bilayer (b) trialyer

345

and imaginary part of the frequency dependent dielectric function of (c) bilayer (d) trilayer.

346

Figure 6. Frequency and polarization dependent (a) - (b) refractive index (c) - (d) reflectivity (e)

347

–(f) absorption coefficient for bilayer and trilayer, respectively.

348 349 350 351


18

Page 19 of 25

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

352


Table of Contents (TOC)

353


19


1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53


Page 20 of 25

Page 21 of 25 3

3

2

2

2

E n e r g y (e V )

(a )

(b )

(c )

1

1

1

0

0

0

-1

-1

-1

-2

-2

-2

G

-3

K

G

M

G

-3

4 0

M

G

-2 0

-2

0

E n e r g y (e V )

2

G

M

(f)

2 0

2 0

0

0

-2 0

-2 0

-4 0 4

K

4 0

0

-4

G

(e )

2 0

-4 0

K

-3

4 0

(d )

D O S ( S t a t e s /e V .a t o m .s p in )

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44

The Journal of Physical Chemistry 3

-4

-2 0 2 ACS ParagonE Plus Environment n e r g y (e V )

-4 0 4

-4

-2

0

E n e r g y (e V )

2

4

The Journal of Physical Chemistry 3

3

3

2

2

2

E n e r g y (e V )

(a )

(b )

(c )

1

1

1

0

0

0

-1

-1

-1

-2

-2

-2

G

-3

4 0

D O S ( S t a t e s /e V .a t o m .s p in )

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44

Page 22 of 25

K

G

M

G

-3

4 0

(d )

K

M

G

G

-3

4 0

(e )

2 0

2 0

0

0

0

-2 0

-2 0

-2 0

-4 0

-4 0

-4 0

-2

0

E n e r g y (e V )

2

4

-4

-2 0 2 E n Plus e r g y Environment (e V ) ACS Paragon

4

G

M

(f)

2 0

-4

K

-4

-2

0

E n e r g y (e V )

2

4

Page 23 of 25

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36




5 0

E

(a )

5 0

//

A A -s ta c k in g A B -s ta c k in g A C -s ta c k in g

4 0

E

//

A B A -s ta c k in g A B B -s ta c k in g A B C -s ta c k in g E

⊥

3 0


2 0

E

(b )

4 0

⊥

3 0

ε1(ω)

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44

Page 24 of 25

A B A -s ta c k in g A B B -s ta c k in g A B C -s ta c k in g

1 0

2 0

1 0

0

0

-1 0

-1 0 0

1

2

3

4

5

3 0

0

1

2

3

4

5

3 0

E

//

(c )

A A -s ta c k in g A B -s ta c k in g A C -s ta c k in g E

2 0

⊥

E

//

(d )

A B A -s ta c k in g A B B -s ta c k in g A B C -s ta c k in g E

2 0

⊥

ε2(ω)


1 0


1 0

0

0 0

1

2

3

P h o to n E n e rg y (e V )

4

5 ACS Paragon Plus 0 Environment 1

2

3


4

5

Page 25 of 25


8

R e f r e a c t i v e I n d e x N ( ω)

(a ) 6

Im g

4

E

E

//

A A -s ta c k in g A B -s ta c k in g A C -s ta c k in g E //

A A -s ta c k in g A B -s ta c k in g A C -s ta c k in g E ⊥

6



4

Im g

2

E

//

⊥

A B A -s ta c k in g A B B -s ta c k in g A B C -s ta c k in g E ⊥



0 1

2

0 .6

3

4

5

0

1

2

0 .6 E

A A - s t a c k in g A B - s t a c k in g A C - s t a c k in g

0 .4 E

E

(d )

//

(c ) R ( ω)

E

A B A -s ta c k in g A B B -s ta c k in g A B C -s ta c k in g E //

2

0

R e fle c tiv ity

R e a l

(b )

⊥

0

3

4

5

3

4

5

3

4

5

//

A B A - s t a c k in g A B B - s t a c k in g A B C - s t a c k in g

0 .4

⊥

E

⊥



0 .2

0 .2

0 .0

0 .0 0

1

2

3

4

5

0

8

A b s o rp tio n c o e ffic ie n t / 1 0 5 (c m -1 )

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44

8 R e a l

1

2

8 E


6 E

//


6 E

⊥

A A - s t a c k in g A B - s t a c k in g A C - s t a c k in g 4

E

(f)

//

(e )

⊥

A B A - s t a c k in g A B B - s t a c k in g A B C - s t a c k in g 4

2

2

0

0 0

1

2

3


4

5

0


1

2


Spin-Dependent Transport and Optical Properties of Transparent Half

Recommend Documents