Experimental and theoretical studies on the magnetic property of carbon-doped ZnO

X. J. Ye1, C. S. Liu2, W. Zhong1, H. A. Song1, C. T. Au3, and Y. W. Du1

1. Nanjing National Laboratory of Microstructures, Nanjing University, Nanjing 210093, China2. Key Laboratory of Materials Physics, Institute of Solid State Physics, Chinese Academy of Sciences, Hefei 230031, China

3. Department of Chemistry, Hong Kong Baptist University, Hong Kong

Figure 1. XRD spectra of carbon- doped ZnO.

The Carbon-doped ZnO samples with nominal carbon concentration of 5, 10, and 15 mol% (denoted as sample A, B, and C hereinafter) were prepared by means of solid-state reaction in a rapid thermal process.

The calculations were performed at level of generalized gradient approximation (GGA) [2] via Perdew-Burke-Ernzerhof (PBE) [3] exchange-correlation functional. An all electron double numerical atomic orbital augmented by d-polarization functions (DNP) [4] as basis set is used. The computation was carried out in DMol3 software package.

[1] S. A. Wolf, D. D. Awschalom, R. A. Buhrman, J. M. Daughton, S. von Molnár, M. L. Roukes, A. Y. Chtchlkanova, and D. M. Treger, Science 294 (2001) 1488-1495. [2] M. Schluter and L. J. Sham, Phys. Today 35 (1982) 36-43.[3] P. Perdew, K. Burke, and M. Ernzerhof, Phys. Rev. Lett. 77 (1996) 3865-3868.[4] B. Delley, J. Chem. Phys. 113 (2000) 7756-7764.

1. Carbon-doped ZnO powder samples are ferromagnetic at RT experimentally.2. CZn4O12 unit is the origin of magnetic moment in carbon-doped ZnO system confirmed by theoretical calculations.3. Oxygen vacancy defects and nitrogen favor residing in the magnetic unit and destroying the magnetic moment.4. The varied configurations of carbon in approximately same energy, i.e., induced distinct carrier densities, play a key role on magnetic moment of Carbon-doped ZnO..

In order to study the effects of carbon distribution and defects (oxygen vacancy) in this system on magnetic properties and explore the ferromagnetic interaction mechanism, we investigated carbon-doped ZnO system in experiment and theoretical calculation .

INTRODUCTION

MOTIVATION

CONCLUSIONS

REFERENCES

Table 1. Properties of ZnO and carbon-doped ZnO

ZnO Sample A Sample B Sample C

a (Å)c (Å)

Real carbon concentration (mol%)Percentage of C in carbide state (%)

Magnetization at RT (10-4 emu/g)Moment per C in carbide state (B)

3.25005.2050

------------

3.24945.2030

2.843.129.3

0.0153

3.25005.2044

4.982.8111.8

0.0123

3.24995.2097

8.212.7515.2

0.0098

Figure 2. Raman spectra and photoluminescence (PL) spectra (inset) (acquired at RT) of samples A, B, and C.

Figure 3. RT M-H curves of samples A, B, and C. Inset (a): M-H curve of sample A measured at 389 K. Shown in inset (b) is the M-T curves of sample A in magnetic field of 500 Oe.

Figure 4. (a) One carbon substituted Figure 4. (a) One carbon substituted ZnO in the structure of 2×2×2 ZnO in the structure of 2×2×2 supercell. (b) Structure of magnetic supercell. (b) Structure of magnetic unit CZnunit CZn44OO1212, and (c) DOS of Carbon-, and (c) DOS of Carbon-

doped ZnO with no VO, and (d) DOS doped ZnO with no VO, and (d) DOS of Carbon-doped ZnO with a VOof Carbon-doped ZnO with a VO residing in the magnetic unit. The residing in the magnetic unit. The spin-up and spin-down DOS is shown spin-up and spin-down DOS is shown above and below the abscissa axis, above and below the abscissa axis, respectively.respectively.

EXPERIMENTAL AND COMPUTATIONAL

RESULTS AND DISCUSSION

Recently, ZnO based diluted magnetic semiconductors (DMS) have been studied extensively because of their potential functionalities as spintronics devices [1]. However, different and even contradictory results were reported over same type of samples prepared by different methods or fabricated by different procedures.