Synthesis and characterization of self-assembled c-axis oriented Bi2Sr3Co2Oy thin films by the sol–gel method

Xuebin Zhu; Xianwu Tang; Dongqi Shi; Hongbin Jian; Hechang Lei; Wai Kong Yeoh; Bangchuan Zhao; Jie Yang; Qi Li; Rongkun Zheng; Shixue Dou; Yuping Sun

doi:10.1039/C0DT01731K

Synthesis and characterization of self-assembled c-axis oriented Bi₂Sr₃Co₂O_y thin films by the sol–gel method

Xuebin Zhu,*^ab Xianwu Tang,^a Dongqi Shi,^b Hongbin Jian,^a Hechang Lei,^c Wai Kong Yeoh,^d Bangchuan Zhao,^a Jie Yang,^a Qi Li,^b Rongkun Zheng,^d Shixue Dou^b and Yuping Sun^a

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* Corresponding authors

^a Key Laboratory of Materials Physics, Institute of Solid State Physics, Chinese Academy of Sciences, Hefei, P. R. China
E-mail: xbzhu@issp.ac.cn
Fax: +86 5515591434
Tel: +86 5515591439

^b Institute for Superconducting and Electronic Materials, University of Wollongong, Wollongong, Australia

^c Condensed Matter Physics and Materials Science Department, Brookhaven National Laboratory, Upton, New York, USA

^d Australian Centre for Microscopy and Microanalysis, University of Sydney, Sydney, Australia

Abstract

Bi₂Sr₃Co₂O_y thin films are prepared on SrTiO₃ (100), (110) and (111) single crystal substrates using the sol–gel method. All the thin films are c-axis oriented regardless of the orientation of the substrate suggesting self-assembled c-axis orientation, and X-ray photoelectron spectroscopy results give evidence of coexistence of Co³⁺ and Co²⁺ ions in the derived films. Transmission electronic microscopy observations reveal that all samples are c-axis oriented with no obvious differences for different samples, and the c-axis lattice constant is determined as ∼15 Å suggesting the misfit structure. A phenomenological thermodynamic phase diagram for self-assembled c-axis orientation is established for misfit cobaltate-based films using chemical solution deposition. All samples behave like semiconductors due to the coexistence of Co³⁺/Co²⁺ ions, and the resistivity at 350 K is ∼47, 39 and 17 mΩ cm for the thin films on SrTiO₃ (100), (110) and (111), respectively, whereas the Seebeck coefficient at 300 K is 97, 89 and 77 μV K⁻¹. The successful attainment of Bi₂Sr₃Co₂O_y thin films with self-assembled c-axis orientation will provide an effective prototype for investigation of growth mechanisms in complex oxide thin films with a misfit structure.

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Synthesis and characterization of self-assembled c-axis oriented Bi₂Sr₃Co₂O_y thin films by the sol–gel method

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Synthesis and characterization of self-assembled c-axis oriented Bi₂Sr₃Co₂O_y thin films by the sol–gel method

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