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

1. 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, China 2. 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 INTRODUCTION 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. MOTIVATION • Figure 2. Raman spectra and photoluminescence (PL) spectra (inset) (acquired at RT) of samples A, B, and C. • Figure 1. XRD spectra 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. EXPERIMENTAL AND COMPUTATIONAL 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. • Figure 4. (a) One carbon substituted ZnO in the structure of 2×2×2 supercell. (b) Structure of magnetic unit CZn4O12, and (c) DOS of Carbon-doped ZnO with no VO, and (d) DOS of Carbon-doped ZnO with a VOresiding in the magnetic unit. The spin-up and spin-down DOS is shown above and below the abscissa axis, respectively. • 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. RESULTS AND DISCUSSION CONCLUSIONS Table 1. Properties of ZnO and carbon-doped ZnO • 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.. REFERENCES [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.