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The controllable growth and properties of self-assembly Ni-BaTiO3/ SrTiO3 nano-composite epitaxial film by laser molecular beam epitaxy

Weidong Wu 1,  Zhengwei Xiong ,  Xueming Wang 

1. Research Center of Laser Fusion, CAEP, MianYang 621900, China

Abstract
  Complex oxide epitaxial films with embedded magnetic metal nano-crystals (MNCs) have attracted more and more attention. On one hand, this interest has been driven by the exciting possibility of using those films for electronic and optic applications. On the other hand, problems associated with applications of those films, such as controllable growth, structure, dielectric and electronic transport properties, third order nonlinear optical properties etc., generated intensive research of the fundamental properties of the complex oxide films with embedded MNCs. In this report, growth behaviors, structure, electronic and optical properties of the epitaxial BaTiO3/ SrTiO3 super-lattice films with embedded Ni-MNCshave been reviewed in detail.

  The main contents of this report contain the following aspects:

 1. Ni nanocrystals (NCs) were embedded in BaTiO3 epitaxial films using LMBE method. The processes involving the self-organization of Ni NCs and the epitaxial growth of BaTiO3 were discussed. With the in situ monitoring of RHEED, the nanocomposite films were controllably engineered by the fine alternation of the self-organization of Ni NCs and the epitaxial growth of BaTiO3. The transmission electron microscopy  and the X-ray diffraction characterization confirmed that the composite film consist of the Ni NCs layers alternating with the (001)/(100)-oriented epitaxial BaTiO3 separation layers. In addition, Ni-BaTiO3/ SrTiO3 nanocomposite films (Ni NCs are embedded in BaTiO3/ SrTiO3 superlattice films) were also fabricated with the same method.

2. The third order nonlinear optical properties of Ni-BaTiO3 nanocomposite films were investigated by the z-scan technique. It was observed that the embedding of Ni NCs would significant improve the nonlinear optical property compare to BaTiO3 single crystal films.

3. The stress of the composite films was increased with the increasing concentration of embedded Ni NCs, as investigation in stress calculation. The influence with the various concentrations of Ni NCs embedded in BaTiO3/SrTiO3 superlattices was also discussed. The internal stress of the films was too strong to epitaxial growth of BaTiO3/SrTiO3 superlattices. Compared with the pure BaTiO3/SrTiO3 superlattices, the BaTiO3/SrTiO3 superlattices with lower concentration of embedded Ni NCs had higher permittivity and dielectric loss. Furthermore, the dielectric enhancement of BaTiO3/SrTiO3 superlattices with embedded Ni NCs was proposed to explain by Drude quasi-free-electron theory.

4. The increasing sizes and irregular shapes of nickel nanoparticles were observed as the increase of laser energy density. By the absorption spectra investigation, the absorption peak presented red-shift and broadening phenomenon with the increase of the sizes. The results were explained by the calculation of real and imaginary permittivity of bulk nickel.

5. The electronic transport properties of Ni-BaTiO3/ SrTiO3 nanocomposite films were also studied with different concentration of embedded Ni NCs.

 

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Presentation: Oral at 17th International Conference on Crystal Growth and Epitaxy - ICCGE-17, General Session 10, by Weidong Wu
See On-line Journal of 17th International Conference on Crystal Growth and Epitaxy - ICCGE-17

Submitted: 2013-04-14 16:32
Revised:   2013-07-29 22:56