Influence of Oxygen to Argon Ratio on the Structural and Morphological Properties of Nb-Doped SrTiO₃ Epitaxial Films Grown by Reactive Ion Beam Sputter Deposition

Gasidit Panomsuwan, Nagahiro Saito

Department of Materials, Physics and Energy Engineering, Graduate School of Engineering, Nagoya, Japan.

DOI: 10.4236/csta.2013.21005                

Abstract

Nb-doped SrTiO₃ (STNO) films were grown on (001)-oriented LaAlO₃ substrates by a reactive ion beam sputter deposition at various mixing ratios (OMRs) with a substrate temperature of 800^oC. The STNO films exhibited good crystallinity with an epitaxial orientation as characterized by high-resolution X-ray diffraction, grazing-incidence X-ray diffraction, and in-plane pole figure analysis. A decrease of out-of-plane and in-plane lattice constants was observed with an increase of OMR. The surface morphology of the STNO films showed a very dense fine-grain structure. The root-mean-square roughness was found to be increased as the OMR increased. Moreover, the elemental compositions of the STNO films were examined by X-ray photoelectron spectroscopy.

Keywords

Nb-Doped SrTiO₃; Epitaxial Films; Crystal Structure; Ion Beam Sputter Deposition

Conflicts of Interest

The authors declare no conflicts of interest.

References

[1]	C. W. Schneider, R. Schneider and H. Rietschel, “High Dielectric Constant and Tunability of Epitaxial SrTiO3 Thin Film Capacitors,” Journal of Applied Physics, Vol. 85, No. 10, 1999, pp. 7362-7369. doi:10.1063/1.369363
[2]	K. Eisenbeiser, J. M. Finder, Z. Yu, J. Ramdani, J. A. Curless, J. A. Hallmark, R. Droopad, W. J. Ooms, L. Salem, S. Bradshaw and C. D. Overgaard, “Field Effect Transistors with SrTiO3 Gate Dielectric on Si,” Applied Physics Letters, Vol. 76, No. 10, 2000, pp, 1324-1326.
[3]	J. Robertson, “High Dielectric Constant Gate Oxides for Metal Oxide Si Transistors,” Reports on Progress in Physics, Vol. 69, No. 2, 2006, pp. 327-396. doi:10.1088/0034-4885/69/2/R02
[4]	T. Tomio, H. Miki, H. Tabata, T. Kawai and S. Kawai, “Control of Electrical Conductivity in Laser Deposited SrTiO3 Thin Films with Nb Doping,” Journal of Applied Physics, Vol. 76, No. 10, 1994, pp. 5886-5890. doi:10.1063/1.358404
[5]	D. Olaya, F. Pan, C. T. Roger and J. C. Price, “Electrical Properties of La-Doped Strontium Titanate Thin Films,” Applied Physics Letters, Vol. 80, No. 16, 2002, pp. 2928- 2930. doi:10.1063/1.1470694
[6]	S. Y. Wang, B. L. Cheng, C. Wang, S. Y. Dai, H. B. Lu, Y. L. Zhou, Z. H. Chen and G. Z. Yang, “Reduction of Leakage Current by Co Doping in Pt/Ba0.5Sr0.5TiO3/ Nb–SrTiO3 Capacitor,” Applied Physics Letters, Vol. 84, 2004, pp. 4116-4118. doi:10.1063/1.1755421
[7]	S. Ohta, T. Nomura, H. Ohta, M. Hirano, H. Hosono and K. Koumoto, “Large Thermoelectric Performance of Heavily Nb-Doped SrTiO3 Epitaxial Film at High Temperature,” Applied Physics Letters, Vol. 87, No. 9, 2005, Article ID: 092108.
[8]	A. Biswas, A. K. Poswal, R. B. Tokas and D. Bhattacharyya, “Characterization of Ion Beam Sputter Deposited W and Si Flms and W/Si Interfaces by Grazing Incidence X-Ray Reflectivity, Atomic Force Microscopy and Spectroscopic Ellipsometry,” Applied Surface Science, Vol. 254, No. 11, 2008, pp. 3347-3356. doi:10.1016/j.apsusc.2007.11.025
[9]	G. Panomsuwan, O. Takai and N. Saito, “Fabrication and Characterization of Epitaxial SrTiO3/Nb-Doped SrTiO3 Superlattices by Double ECR Ion Beam Sputter Deposition,” Vacuum, Vol. 89, 2013, pp. 35-39. doi:10.1016/j.vacuum.2012.08.011
[10]	N. Sakudo, K. Tokiguchi, H. Koike and I. Kanomata, “Microwave Ion Source,” Review of Scientific Instruments, Vol. 48, No. 7, 1977, pp. 462-466. doi:10.1063/1.1135144
[11]	K. Fukushima and S. Shibagaki, “Nb Doped SrTiO3 Thin Films Deposited by Pulsed Laser Ablation,” Thin Solid Films, Vol. 315, No. 1-2, 1998, pp. 238-243. doi:10.1016/S0040-6090(97)00752-9
[12]	E. J. Tarsa, E. A. Hachfeld, F. T. Quinlan and J. S. Speck, “Growth-Related Stress and Surface Morphology in Homoepitaxial SrTiO3 Films,” Applied Physics Letters, Vol. 68, No. 4, 1996, pp. 490-492. doi:10.1063/1.116376
[13]	H. L. Cai, X. S. Wu and J. Gao, “Effect of Oxygen Content on Structural and Transport Properties in SrTiO3-x Thin Films,” Chemical Physics Letters, Vol. 467, No. 4-6, 2009, pp. 313-317. doi:10.1016/j.cplett.2008.11.071
[14]	R. Reshmi, M. K. Jayaraj and M. T. Sebastian, “Influence of Oxygen to Argon Ratio on the Properties of RF Magnetron Sputtered Ba0.7Sr0.3TiO3 Thin Films,” Journal of the Electrochemical Society, Vol. 158, No. 5, 2011, pp. G124-G127. doi:10.1149/1.3566094
[15]	T. Ohnishi, K. Takahashi, M. Nakamura, M. Kawasaki, M. Yoshimoto and H. Koinuma, “A-Site Layer Terminated Perovskite Substrate: NdGaO3,” Applied Physics Letters, Vol. 74, No. 17, 1999, pp. 2531-2533. doi:10.1063/1.123888
[16]	W. Martienssen and H. Warlimont, “Springer Handbook of Condensed Matter and Materials Data,” Springer, Berlin, 2005.