Effect of substrate orientation on the crystal quality and surface roughness of Nb-doped TiO{sub 2} epitaxial films on TiO{sub 2}
- Environmental Molecular Sciences Laboratory, Pacific Northwest Laboratory, P. O. Box 999, MS K2-12, Richland, Washington 99352 (United States)
We have grown Nb-doped TiO{sub 2} epitaxial films on (100) and (110)-oriented TiO{sub 2} rutile substrates by molecular beam epitaxy. Nb substitutionally incorporates at cation sites in the rutile lattice, forming Nb{sub {ital x}}Ti{sub 1{minus}{ital x}}O{sub 2} 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 {ital 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 TiO{sub 2} to NbO{sub 2}; there are 1{percent} and 12{percent} 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{percent} 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 Nb{sub {ital x}}Ti{sub 1{minus}{ital x}}O{sub 2} epitaxial films. {copyright} {ital 1996 Materials Research Society.}
- Research Organization:
- Pacific Northwest National Lab. (PNNL), Richland, WA (United States)
- DOE Contract Number:
- AC06-76RL01830
- OSTI ID:
- 280132
- Journal Information:
- Journal of Materials Research, Vol. 11, Issue 4; Other Information: PBD: Apr 1996
- Country of Publication:
- United States
- Language:
- English
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