Vacancy induced magnetism in N-doped 4H–SiC by first-principle calculations

doi:10.1016/j.solidstatesciences.2015.09.012

Solid State Sciences

Volume 49, November 2015, Pages 78-82

https://doi.org/10.1016/j.solidstatesciences.2015.09.012 Get rights and content

Highlights

•
Neither single N dopant nor single V_Si can introduce FM.
•
V_Si together with N_C would yield ferromagnetism.
•
The FM and AFM were competition for the charge states.
•
The overlap density of two C atoms and N atom leads to FM coupling.

Abstract

First-principles calculations were performed to investigate the electronic and magnetic properties of silicon vacancy (V_Si) and nitrogen doped silicon carbide (4H–SiC). V_Si or nitrogen-doping alone cannot form ferromagnetic ordering. V_Si together with the substitution of nitrogen for carbide would yield ferromagnetism in 4H–SiC crystal. The most stable configuration was identified by energy calculations. The magnetic coupling calculated results demonstrated that the ferromagnetic states and antiferromagnetic states competed with each other for the charge states. The magnetic orbital of two C atoms overlap around the V_Si and the nearby substituted N atom, the overlap density leads to a ferromagnetic coupling between the two C atoms.

Graphical abstract

Introduction

Dilute magnetic semiconductors (DMSs) that combine functions of semiconductors and magnetic materials have attracted much interest for their potential applications in spin-electronic devices [1], [2]. Among the various materials systems that have been considered as possible candidates for creating DMS, SiC, a wide bandgap semiconductor with light atoms and strong bonding, holds promise as a perspective spintronic material. Several reports have been published documenting experimental studies of magnetic properties of SiC with transition metal (TM) impurities [3], [4], [5]. However, the origin of ferromagnetic order is disturbed by the uncontrolled precipitation or secondary phase formation. These extrinsic magnetic behaviors are undesirable for practical applications.

The presence of native defects in nonmagnetic materials may induce spin polarization and form the local magnetic moments [6], [7], [8], [9], [10]. For clarifying microscopic origin of magnetic properties, non-metal implantation to trigger ferromagnetism (FM) in SiC-based DMSs is desirable. Nitrogen, a non-magnetic element, has roughly the same atomic radius as carbon [11]. Using first-principle calculations, Miao et al. [12] predicted that the ferromagnetic ordering can be developed in 3C–SiC by codoping of N impurity and Si vacancy (V_Si) (magnetic moment is about 2 μ_B). The magnetism induced by non-magnetic N would exclude the contribution from uncontrolled magnetic clusters. While for vacancy-free 3C–SiC, the substitution N impurity cannot trigger spin-polarization. That is, doping nitrogen atom and defect are both important for 3C–SiC based DMS.

Silicon carbide (SiC) has more than 200 known polytypes in structures. For SiC polytypes, the nearest neighbors of any Si or C atom are always four C or Si atoms, forming tetrahedral around the corresponding Si or C atom. There are two types of sites in the SiC lattice, that is, the so-called hexagonal and cubic sites and thus the corresponding hexagonal (h) and cubic (k) layers, different in their next-nearest-neighbor arrangement or the medium-range order. The 4H–SiC contain different numbers of both h and k layers [13]. How about the magnetism for 4H–SiC when doped nitrogen atom and defect? In this paper, we explored the electronic structure and magnetic properties investigations in nitrogen atom and defect codoped 4H–SiC system based on ﬁrst principles calculations. The calculated results confirmed that N-doped 4H–SiC cannot induce ferromagnetism while together with Si-vacancies would favor the FM states. Our work is expected to provide a theoretical basis and guidance to experimental for potential applications of 4H–SiC based DMS.

Section snippets

Computational methods and details

4H–SiC has a hexagonal structure (P6₃mc) with lattice constants a = 3.078 Å and c = 10.046 Å. The 72-atom 3 × 3 × 1 4H–SiC supercell was shown in Fig. 1. In our work, the test calculations with higher supercell were performed. The electronic structures of 3 × 3 × 2 supercell with 144 atoms (with two N atoms and two Vsi) were calculated. The results do not make much difference on the electronic and magnetic properties of 3 × 3 × 1 72 atoms supercells (with one N atoms and one Vsi), as shown in

Results and discussions

To determine the most stable N substitution site in 4H–SiC, we consider two kinds of possible configurations: N replaces C (N_C) or N replaces Si (N_Si), in which the concentration of N in 4H–SiC is about 2.28 at%. The formation energy of the substitution N in 4H–SiC can be calculated as follows [16]: $E_{f o r m}^{N_{-} X} = E_{d o p e d}^{N_{-} X} - E_{u n d o p e d} - μ_{N} + μ_{X}$ $μ_{S i C}^{b u l k} = μ_{s i} + μ_{c}$ where $E_{d o p e d}^{N_{-} X}$ is the total energy for the supercell with substitution N for X (Si or C), E_undoped is the total energy for the supercell of undoped

Conclusions

In summary, we have investigated the electronic structure and magnetic properties of V_Si and nitrogen-doped 4H–SiC by first-principles calculations. Neither single N dopant nor single V_Si can introduce spin polarization. When N dopant and V_Si were presented together, the spin-polarization would appear in the 4H–SiC supercell. The FM states and AFM states are competition with each other for different charge states. The spin-polarized 2p states of C atom and the N atoms overlap with the

Acknowledgments

This work was sponsored by National Natural Science Foundation of China under Grant Nos. 51372027, 51372026 and No. 51372056. This work also was supported by the Fundamental Research Funds for the Universities of Henan Province (NSFRF140140).

References (26)

L. Yu et al.
Chem. Phys. Lett.
(2010)
Y. Ohno et al.
Nature
(1999)
S. Wolf et al.
Science
(2001)
M. Syväjärvi et al.
Mater. Sci. Forum
(2004)
N. Theodoropoulou et al.
J. Vac. Sci. Technol. A
(2002)
F. Stromberg et al.
J. Phys.: Condens. Matter
(2006)
P. Lehtinen et al.
Phys. Rev. Lett.
(2004)
J.M. Carlsson et al.
Phys. Rev. Lett.
(2006)
O.V. Yazyev et al.
Phys. Rev. B
(2007)
A. Zywietz et al.
Phys. Rev. B
(1999)

M. Zhao et al.

Appl. Phy. Lett.

(2010)

Y. Ma et al.

Phys. Rev. B

(2005)

M. Miao et al.

Phys. Rev. B

(2006)

Cited by (14)

Electronic structures and magnetic properties of Co-, Mn-doped and (Co, Mn) co-doped 4H–SiC: A first-principles study
2020, Vacuum
Citation Excerpt :
The search for DMSs materials which show ferromagnetism (FM) at or above room temperature is an important problem for modern spintronics devices [8,9]. Among various materials that are considered to be likely to be used to create DMSs, silicon carbide (SiC) is a potential host candidate in DMS-based spintronics materials [10–13]. SiC is an important wide bandgap semiconductor with excellent performance such as high breakdown field strength, high thermal conductivity, high saturation drift speed, and excellent physicochemical stability [14–17].
Using first-principles calculations, we have systematically investigated the structural, electronic structures and magnetic properties of Co-, Mn-doped and (Co, Mn) co-doped 4H–SiC. All calculations have been performed with the help of density functional theory, and the strong correlation effects are introduced by means of generalized gradient approximation + U scheme. The energy difference between the ferromagnetic and anti-ferromagnetic has been evaluated. The results show that the substitution of Co–Co, Mn–Mn and Co–Mn couples in 4H–SiC have revealed ferromagnetic and half-metallic characteristics with the magnetic energy ( $△ E_{F M}$ ) of −417.5, −493.3 and −537.0 meV, respectively. The calculations show that Co-, and Mn-doped 4H–SiC systems have the large magnetic moments of 5.94 and 6.04 $μ_{B}$ , respectively. The major contribution to the magnetic moment stems from the 3d orbitals of Co atoms, 3d orbitals of Mn atoms and 2p orbitals of C atoms. Further analysis of the impurity orbitals near the Fermi energy reveals a strong spin-polarization feature in the three doped systems. Our results demonstrate that substitutional doping with Co and Mn in 4H–SiC represents an effective manner to modulate electronic and magnetic properties of 4H–SiC for spintronic applications.
Electronic structures and ferromagnetism in (Fe, Cr)-codoped 4H–SiC from first-principles investigations
2019, Vacuum
Citation Excerpt :
It is possible to introduce room-temperature ferromagnetism in the presence of inherent defects [34]. silicon vacancies plays an important role in ferromagnetic tuning in SiC based DMSs [35,36]. Consequently, it is essential to contemplate Si vacancy effect.
Electronic structures and magnetic properties for double impurities (Fe and Cr) doped 4H silicon carbide (SiC) are studied by first principles calculations within the generalized gradient approximation (GGA) +U scheme. For single Fe-doped 4H–SiC, the local magnetic moments of Fe atom is about 3.76 μ_B and the system exhibits half-metallic character. For single Cr atom doped 4H–SiC, the local magnetic moments of Cr atom is about 3.15 μ_B. The introduction of Cr impurities does not destroy the semiconducting nature of Cr-doped 4H–SiC system. For (Fe, Cr)-codoped 4H–SiC, the magnetic coupling between the moments induced by Fe and Cr dopants is ferromagnetic and the origin of strong ferromagnetic coupling can be attributed to p-d hybridization interaction. We discuss the effect of silicon vacancy on the magnetism as well. Our calculations results show that (Fe, Cr)-codoped 4H–SiC exhibit half-metallic behavior, which is suitable for spintronic devices applications.
Ferromagnetism induced by vacancies in (N, Al)-codoped 6H-SiC
2019, Solid State Communications
Citation Excerpt :
Though the configuration doped with NSi can induce magnetism, the formation energy of NC- is lower than that of NSi-, therefore, the configuration with NC is considered in later discussion. It is widely recognized that the ferromagnetism is closely connected with some kinds of vacancy defects [20,28]. Here, we considered two kinds of possible vacancies, VC and VSi by removing one C and one Si, respectively.
The electronic structures and magnetic properties of 6H-SiC doped with N, C vacancies (V_C), Si vacancies (V_Si) and Al are studied by first principles calculations. The results indicate that the N substituting C in 6H-SiC cannot order magnetism but V_Si can introduce magnetic moments effectively. Ferromagnetism coupling is obtained in (N, 2V_Si)-codoped 6H-SiC. The ferromagnetism can be mainly attributed to the interactions between the 2p orbitals of C atoms around Si vacancies. More interestingly, substituting Si with Al can enhance the ferromagnetic states in 6H-SiC in neutral states. We also studied the effect of charge on magnetic properties and provide an effective method of tuning magnetism in 6H-SiC.
Electronic structures and magnetic properties of (Ni,Al) co-doped 4H-SiC: A first-principles study
2018, Computational Materials Science
Citation Excerpt :
3C-SiC has a cubic structure with stacked style of ABCABC…, while 4H-SiC and 6H-SiC have a hexagonal structure with stacked styles of ABACAB…and ABCACBABC…, respectively. 4H-SiC has the largest band gap of 3.27 eV and other superior properties, such as the high thermal conductivity, fine breakdown field strength, good saturation drift velocity, and excellent physical and chemical stability [17–21]. Due to the outstanding properties, 4H-SiC has been extensively studied by theoretical and experimental researchers [22–26].
Based on density functional theory (DFT) first-principles method, we have investigated the electronic structures and magnetic properties of (Ni,Al) co-doped 4H-SiC system. Various configurations of Ni sites have been considered to confirm the most stable geometric construction. Comparing with pure 4H-SiC, the magnetic moment of Ni-doped 4H-SiC is increased, which is attributed to the hybridization of Ni:4s and C:2p orbitals. Moreover, we found that it is the 3d orbital of Ni that induces the spin-polarized state in Ni-doped 4H-SiC. In addition, the origin of ferromagnetic coupling between Ni-doped 4H-SiC has been predicted to be the ferromagnetic orders activated by the Ni₀:3d-C:2p-Ni₂:3d coupling chains. For (Ni,Al) co-doped system, we found that ferromagnetic stability is reduced significantly. For (2Ni, $V_{Si}$ ) co-doped 4H-SiC system, the antiferromagnetic state is more stable than ferromagnetic state with $△$ $E_{FM}$ of 97.2 meV, and the system changes from ferromagnetism to anti-ferromagnetism. These results provide a new route for the potential applications of dilute magnetic semiconductors in spintronic devices by employing doped 4H-SiC.
X-ray Absorption Fine Structural Study of Atomic Structures and Chemical States of Dopants in 4H-SiC(0001)
2023, ACS Applied Electronic Materials
Electron-Coupled Proton Transfer Governed Magnetic Spin Couplings and Switching in Defect Nano Silicon Carbide
2023, Journal of Physical Chemistry C

View all citing articles on Scopus

View full text

Vacancy induced magnetism in N-doped 4H–SiC by first-principle calculations

Highlights

Abstract

Graphical abstract

Introduction

Section snippets

Computational methods and details

Results and discussions

Conclusions

Acknowledgments

Chem. Phys. Lett.

Nature

Science

Mater. Sci. Forum

J. Vac. Sci. Technol. A

J. Phys.: Condens. Matter

Phys. Rev. Lett.

Phys. Rev. Lett.

Phys. Rev. B

Phys. Rev. B

Appl. Phy. Lett.

Phys. Rev. B

Phys. Rev. B