Ab INITIO CALCULATIONS OF HYDROGEN IMPURITES IN Zn
Ab INITIO CALCULATIONS OF HYDROGEN IMPURITES IN Zn. O A. Useinov 1, A. Sorokin 2, Y. F. Zhukovskii 2, E. A. Kotomin 2, F. Abuova 1, A. T. Akilbekov 1, J. Purans 2 L. N. Gumilyov Eurasian National University, 3 Munaitpasova, Astana, Kazakhstan Institute of Solid State Physics, 8 Kengaraga str. , University of Latvia, Riga This study was supported by ERAF project Nr. 2010/0272/2 DP/2. 1. 1. 1. 0/10/APIA/VIAA/088 Introduction Details of calculation method Zinc oxide modified by varios metallic dopants can be used as suitable low-cost substitute for indium-tin oxide when manufacturing the solar batteries and optoelectronic devices [1]. Therefore, the atomic and electronic structure of defective Zn. O continues to attract great attension due to a number of promising technological applications. In this study, we present analyze the influence of neutral H impurity defects on the redistribution of the electronic charge, the band structure and energy of defect in the Zn. O bulk. Special attention is paid to an interstitial hydrogen atom (Hi) [3]. Interstitial and substitutional H have been shown by first-principles calculations to be shallow donors, large-scale ab initio DFT calculations have been performed using the formalism of linear combination of localized atomic functions (LCAO) including optimized atomic basis sets combined PBE 0 hybrid exchange-correlation functional, as implemented into CRYSTAL 09 code [2]. For periodic system, The reciprocal space integration was performed by sampling the Brillouin zone with an 2 × 1 Pack-Monkhorst mesh. To achieve high accuracy, large enough tolerances of 7, 7, and 14 were chosen for the Coulomb overlap, Coulomb penetration, exchange overlap, first exchange pseudooverlap, and second exchange pseudo-overlap, respectively. which contribute to the n-type conductivity in Zn. O. When Zn. O is doped by H, its electrical conductivity increases simultaneously with retain of high optical transparency. To describe the electron density redistribution we have been constricted a difference charge density maps projected on characteristic plane of defect as shown in Fig. 3 Interstitial H in Zn. O bulk In this study the Zn. O bulk described with periodic 3 × 2 supercell models (see Fig. 1). The lattice parameters of supercell a = 3. 28 and c = 5. 18 Å. The H dopants concentration 1. 4%. Fig. 3 The total and difference electronic density distributions for H impurity. Redistribution of the electronic density to describe of ground impurity H atom clearly Fig. 1. Arrangement of the interstitial hydrogen atom Hi in the 3× 3× 2 supercell of Zn. O shows some transfer of charge toward the channel inside Zn. O lattice which contributes to the n – type conductivity in accordance with earlier performed theoretical study [4], thus electrical conductivity increase. To estimate electronic properties of interstitial hydrogen atom, we optimize position of Hi per 3× 3× 2 supercell with frozen geometry of lattice. We have constricted the electronic charge redistribution (see Fig. 3) under influence of H impurity and density of states (see Fig. 2). b a Conclusions Hybrid exchange-correlation functionals provide much better correlation of calculated band structures with experiment, including width of band gap and position of defect levels. • Our calculations showed that hydrogen creates a H-O with O atom and leads to the delocalization of electronic charge on the nearest atoms. Fig. 2. Density of states (DOS) of a perfect (a) and the one H impurity (b) in Zn. O 3 × 2 supercell Bond length between the oxygen atom and hydrogen is 1. 561 Å. The shift of the hydrogen atom in the bulk Zn. O is x = 0. 09052 Å – energy of a perfect crystal and conductivity. References For calculate of defect formation energy we have consider follow expression: – defect formation energy, to the conduction band minimum of Zn. O, which can explain the increase of the electrical in the opposite direction of the nearby oxygen atom. Where • As in earlier studies, we confirm that the impurity hydrogen Hi give rise to shallow levels, close – total energy of defective structure, – energy of isolated H atom. The calculated formation energy of defect is found to be 1. 13 e. V. 1. D. C. Reinolds, D. C. Look, B. Jogai, C. W. Litton, G. Gantwell, W. C. Harsch, Phys. Rev. B 60, 2340 (1999). 2. R. Dovesi, V. R. Saunders, C. Roetti, et al. CRYSTAL-2009 User’s Manual (University of Torino, 2009). 3. Mao-Hua Du and Koushik Biswas, Phys. Rev. Letters, PRL 106, 115502 (2011) 4. Federico Gallino, Gianfranco Pacchioni, and Cristiana Di Valentin, J. Chem. Phys. , 133, 144512 (2010)
- Slides: 1