The micro-structural studies of Ni-BaTiO₃ nanocomposite films by TEM and EELS

Abstract

Epitaxial BaTiO₃ films with embedded metallic Ni nanocrystal (Ni-BaTiO₃) were successfully fabricated on SrTiO₃ (001) single-crystalline substrate through the laser molecular beam epitaxial (L-MBE) technique. High resolution transmission electron microscopy (HRTEM) and electron energy loss spectrum (EELS) with Kramers-Kronig analysis methods were employed to characterize the microstructures, elementary distribution and the electron structure of these films. HRTEM results suggested that the structure of BaTiO₃ was tetragonal with lattice parameters of a=0.399 nm and c=0.403 nm. Energy dispersive X-Ray spectroscopy (EDX) confirmed metallic Ni nanocrystal embedded successfully in BaTiO₃ epitaxial films. The Ni-BaTiO₃ composite films were compound of the epitaxial BaTiO₃ (110) layers alternating with Ni NCs array (111) layers. Furthermore, the existence of the misfit dislocations induced by the embedding of Ni nanoparticles was also clearly demonstrated by the HRTEM images. The Ni L_2,3 edges of EELS revealed that Ni NCs in their metallic state were embedded uniformly in the BaTiO₃ matrix. A chemical shift of about 7 eV regarding L₃ edges in the Ni EELS was also observed. The optical band gap of BaTiO₃ in these films was about 3.84 eV, higher than 3.55 eV for pure BaTiO₃ films at room temperature.

Keywords

Laser molecular beam epitaxial / transmission electron microscopy / electron energy loss spectrum / Kramers-Kronig analysis

References

[1] Cuppens R., Larsen P. K., Spierings G. A. C. M., . Ferroelectrics for Non-Volatile Memories[J]. Microelectron Eng., 1992, 19: 245-252.

[2] Scott J. F., Araujo C. A., Meadows H. B., . Radiation Effects on Ferroelectric Thin-Film Memories: Retention Failure Mechanisms[J]. J. Appl. Phys., 1989, 66: 1 444-1 452.

[3] Larsen P. K., Krampshoer G. L. M., Ulenaers M. J. E., . Nanosecond Switching of Thin Ferroelectric Films[J]. Appl. Phys. Lett., 1991, 59: 611-613.

[4] Wang Y. H., Zhao N., Zhang M., . Optical Waveguide and Nonlinear Properties of Bi₃NdTi₃O₁₂ Thin Films[J]. Journal of Wuhan University of Technology-Mater. Sci. Ed., 2010, 25(5): 743-746.

[5] Wessels B. W. Metal-Organic Chemical Vapor Deposition of Ferroelectric Oxide Thin Films for Electronic and Optical Applications[J]. A Rev. Mater. Sci., 1995, 25: 525-546.

[6] Zhang W. F., Huang Y. B., Zhang M. S., . Nonlinear Optical Absorption in Undoped and Cerium-Doped BaTiO₃ Thin Films Using Z-Scan Technique[J]. Appl. Phys. Lett., 2000, 76(8): 1 003-1 005.

[7] Shi W. S., Chen Z. H., Liu N. N., . Nonlinear Optical Properties of Self-Organized Complex Oxide Ce: BaTiO₃ Quantum Dots Grown by Pulsed Laser Deposition[J]. Appl. Phys. Lett., 1999, 75: 1 547-1 549.

[8] Wang W. T., Chen Z. H., Yang G., . Resonant Absorption Quenching and Enhancement of Optical Nonlinearity in Au: BaTiO₃ Composite Films by Adding Fe Nanoclusters[J]. Appl. Phys. Lett., 2003, 83: 1 983-1 985.

[9] Yang G., Guan D. Y., Wang W. T., . The Inherent Optical Nonlinearities of Thin Silver Films[J]. Opt. Mater., 2004, 25: 439-443.

[10] Wang W. T., Yang G., Chen Z. H., . Iron Nanopariticles in Amorphous BaTiO₃ Thin Films with Large Third-Order Optical Nonlinearity[J]. J. Appl. Phys., 2002, 92: 7 242-7 245.

[11] Yang G., Wang W. T., Zhou Y. L., . Linear and Nonlinear Optical Properties of Ag Nanocluster/BaTiO₃ Composite Films[J]. Appl. Phys. Lett., 2002, 81: 3 969-3 971.

[12] Wang W. T., Yang G., Wu W. D., . Effects of the Morphology and Nanostructure on the Optical Nonlinearities of Au: BaTiO₃ Nanocomposite Films[J]. J. Appl. Phys., 2003, 94: 6 837-6 840.

[13] Yuen K. D., Law M. F., Yu K. W., . Enhancement of Optical Nonlinearity through Anisotropic Microstructures[J]. Opt. Commn., 1998, 148: 197-207.

[14] Wen W. J., Wang N., Ma H. R., . Field Induced Structural Transition in Mesocrystallites[J]. Phys. Rev. Lett., 1999, 82: 4 248-4 251.

[15] Wu W. D., Wang F., Ge F. F., . Optical Properities of Co-BaTiO₃/MgO(100) Nano-Composite Films Grown by Pulsed Laser Deposition Method[J]. Chin Phys. Lett., 2008, 25: 1 465-1 468.

[16] Wu W. D., He Y. J., Wang F., . Preparation and Characterization of Co-BaTiO₃ Nano-Composite Films by the Pulsed Laser Deposition[J]. J. Cryst. Growth, 2006, 289: 408-413.

[17] Ge F. F., Bai L., Wu W. D., . The Controllable Growth of Co-BaTiO₃ Nanocomposite Epitaxial Film by Laser Molecular Beam Epitaxy[J]. J. Cryst. Growth, 2010, 312: 2 489-2 493.

[18] Ge F. F., Wang X. M., Cao L. H., . Self-Organized Ni Nanocrystal Embedded in BaTiO₃ Expitaxial Film[J]. Nanoscale Res. Lett., 2010, 5: 834-838.

[19] Liao H. B., Fu J. S., Xiao R. F., . Large Third-Order Nonlinearity in Au:SiO₂ Composite Films Near Percolation Threshold[J]. Appl. Phys. Lett., 1997, 70(1): 1-3.

[20] Kelly K. L., Coronado E., Zhao L. L., . The Optical Properties of Metal Nanopartices: The Influence of Size, Shape, and Dielectric Environment[J]. J. Phys. Chem. B, 2003, 107(3): 668-677.

[21] Egerton R. F. Electron Energy Loss Spectroscopy[M], 1996 New York Plenum Press

[22] Lin J. F., Bird J. P., Rotkina L., . Classical and Quantum Transport in Focused-Ion-Beam-Deposited Pt Nanointerconnects [J]. Phys. Lett., 2003, 82: 802-804.

[23] Leapman R. D., Grunes L. A., Fejes P. L. Study of the L23 Edges in the 3 d Transition-Metals and Their Oxides by Electron-Energy-Loss Spectroscopy with Comparisons to Theory[J]. Phys. Rev. B, 1982, 26(2): 614-635.

[24] Tanawadee D., Yang G. Y., Clive A. R., . Chemical Solution-Deposited BaTiO₃ Thin Films on Ni Foils: Microstructure and Interfaces[J]. J. Am. Ceram. Soc., 2008, 91(6): 1 845-1 850.

[25] Tanc J., Grigorovici R., Vancu A. Optical Properties and Electronic Structure of Amorphous Germanium[J]. Phys. Status Solidi, 1996, 15: 627-637.

[26] Ye L. X. Semiconductor Physics[M], 2007 2nd Ed. Beijing Higher Education Press