科研之友
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摘要
Defects were characterized in epitaxial (001) CeO2 films deposited and planarized in situ on patterned (001) LaAlO3 substrates by ion beam assisted deposition (IBAD). A hill and valley structure with steps running parallel to the [100] LaAlO3 axis was produced on the surface of the substrate by photolithography and ion beam etching prior to film deposition. A conformal epitaxial CeO2 layer of similar to 100 nm thickness was deposited on the heated substrate by e-beam evaporation. Lattice-matching between the e-beam film and the substrate was of the type: (001) CeO2\\(001) LaAlO3 and [110] CeO2\\[100] LaAlO3. Evaporative deposition of additional film onto the conformal layer was accompanied by bombardment with a 500 eV argon/oxygen ion beam to promote in situ planarization. Extreme lattice misfit for the orientation (001) CeO2\\(001) LaAlO2 and [001] CeO2\\[001] LaAlO3 caused formation of dislocations in the e-beam CeO2 film in the vicinity of individual ledges in the substrate surface. Coherence of the CeO2 film was locally lost in the step regions of the hill and valley structure. The large patterned steps, which are composed of numerous adjacent ledges in the LaAlO3 surface, caused nucleation of CeO2 with a tilt misalignment of up to similar to 5 degrees about the substrate [100]. Nucleation and growth of nonepitaxial CeO2 crystallites was observed along the step regions of the film during the IBAD portion of deposition. Defect formation in the e-beam ceria layer due to substrate surface relief indicates that ''lattice engineering'' of multilayer epitaxial structures may not be possible when nonplanar surfaces are created during device fabrication. The IBAD CeO2 layer was more defective than the conformal layer deposited without the impinging ion beam, even in the portions of the film where epitaxy was maintained throughout both layers.
- 出版日期1995-6
