Abstract
We have grown Nb-doped TiO2 epitaxial films on (100) and (110)-oriented TiO2 rutile substrates by molecular beam epitaxy. Nb substitutionally incorporates at cation sites in the rutile lattice, forming NbxTi1−xO2 solid solutions. However, the crystal quality and surface roughness of the films depend strongly on the substrate orientation. Surface roughening and defect formation occur at lower values of x on (100) than on (110). This result is due to anisotropic changes in the metal-oxygen bond lengths within the rutile structure in going from TiO2 to NbO2; there are 1% and 12% changes in the metal atom to octahedron-base oxygen and metal atom to octahedron-vertex oxygen bond lengths, respectively. Every metal atom in the (100) growth surface has in-plane components of the 12% mismatch. However, only half of the metal atoms in the (110) growth plane have such components. Thus, there is substantially larger in-plane lattice mismatch when the growth surface is (100) compared to (110), resulting in surface roughening and formation of defects at a lower doping level for (100)-oriented NbxTi1−xO2 epitaxial films.
Similar content being viewed by others
References
A. Fujishima, and K. Honda, Nature (London) 238, 37 (1972).
V. E. Henrich, and P. A. Cox, The Surface Science of Metal Oxides (Cambridge University Press, Cambridge, 1994).
G. C. Bond and R. Burch, in Catalysis 6, edited by G. C. Bond and G. Webb (Royal Soc. Chem., London, 1983), p. 27.
V. E. Henrich and R. L. Kurtz, Phys. Rev. B. 23, 6280 (1981).
P. W. Murray, F. M. Leibsle, C. A. Muryn, H. J. Fisher, C. F. J. Flipse, and G. Thornton, Phys. Rev. Lett. 72, 689 (1994).
M. Ramamoorthy, R. D. King-Smith, and D. Venderbilt, Phys. Rev. B 49, 7709 (1994).
M. Sander and T. Engel, Surf. Sci. Lett. 302, L263 (1994).
B. Grossman, and P. Piercy, Phys. Rev. Lett. 74, 4487 (1995).
K. E. Smith and V. E. Henrich, Surf. Sci. 217, 445 (1989).
M. A. Henderson, Surf. Sci. 319, 315 (1994).
A. L. Linsebigler, G. Q. Lu, and J.T. Yates, Jr., Chem. Rev. 95, 735 (1995).
W. Lee, Y. R. Do, K. Dwight, and A. Wold, Mater. Res. Bull. 28, 1127 (1993).
Y. R. Do, W. Lee, K. Dwight, and A. Wold, J. Solid State Chem. 108, 198 (1994).
S. Okazaki and T. Okuyama, Bull. Chem. Soc. Jpn. 65, 914 (1983).
Y. Matsumoto, T. Shimizu, A. Toyoda, and E. Sato, J. Phys. Chem. 86, 3581 (1982).
H. Cui, K. Dwight, S. Soled, and A. Wold, J. Solid State Chem. 115, 187 (1995).
B. G. Hyde and S. Andersson, Inorganic Crystal Structures (John Wiley & Sons, New York, 1989).
R. W. G. Wyckoff, Crystal Structures, 2nd ed. (John Wiley & Sons, New York, 1963), Vol. 1.
A. K. Cheetham and C. N. R. Rao, Acta Crystallogr. Sect. B 32, 1579 (1976).
CRC Handbook of Chemistry and Physics, edited by R. C. Weast, M. J. Astle, and W. H. Beyer, 66th ed. (CRC Press, Boca Raton, FL, 1986).
Y. Gao, Y. Liang, and S. A. Chambers, Surf. Sci. (1996, in press).
S. Thevuthasan, unpublished result.
S. A. Chambers, T. T. Tran, and T. A. Hileman, J. Mater. Res. 9, 2944 (1994).
Author information
Authors and Affiliations
Rights and permissions
About this article
Cite this article
Gao, Y., Chambers, S.A. Effect of substrate orientation on the crystal quality and surface roughness of Nb-doped TiO2 epitaxial films on TiO2. Journal of Materials Research 11, 1025–1029 (1996). https://doi.org/10.1557/JMR.1996.0128
Received:
Accepted:
Published:
Issue Date:
DOI: https://doi.org/10.1557/JMR.1996.0128