Effect of evaporation on surface morphology of epitaxial ZnO films during postdeposition annealing

• Published in: Applied surface science Vol. 241; no. 1; pp. 179 - 182
• Main Authors: Kim, I.W., Doh, S.J., Kim, C.C., Je, Jung Ho, Tashiro, J., Yoshimoto, M.
• Format: Journal Article Conference Proceeding
• Language: English
• Published: Amsterdam Elsevier B.V 28.02.2005; Elsevier Science
• Subjects: Annealing; Condensed matter: structure, mechanical and thermal properties; Cross-disciplinary physics: materials science; rheology; Evaporation; Exact sciences and technology; Materials science; Methods of deposition of films and coatings; film growth and epitaxy; Physics; Structure and morphology; thickness; Surface morphology; Surfaces and interfaces; thin films and whiskers (structure and nonelectronic properties); Theory and models of film growth; Thin film structure and morphology; ZnO; 61.10.Nz; Annealing; 68.43.Vx; 68.35.Md; Surface morphology; 68.35.−p; ZnO; 68.55.Ac; Evaporation; Atomic force microscopy; 68.35.-p; Epitaxial layers; Grain growth; 68.55.Ac ZnO: Evaporation; Surface structure; Zinc oxides; X-ray scattering
• ISSN: 0169-4332; 1873-5584
• DOI: 10.1016/j.apsusc.2004.09.087

We investigated the effect of evaporation on the surface morphology of c-oriented epitaxial ZnO (40 nm thick)/Al 2O 3(0 0 0 1) films during postdeposition annealing using real time synchrotron X-ray scattering and atomic force microscopy (AFM). We find that evaporation as well as grain coalescence play crucial roles on the surface morphology of the ZnO/Al 2O 3(0 0 0 1) films. Grain growth occurring in initial stage of annealing forms facets with higher surface energies than the (0 0 0 1) planes. By the preferential evaporation of the prism planes, the surface morphology of the ZnO film eventually evolves into 2D flat (0 0 0 1) surface at 800 °C, as confirmed by AFM. The real time measurement of the film thickness during annealing also supports the effect of the evaporation on the morphology. The evaporation rate is high in initial stage by the preferential evaporation from high energy facets but slows down after transition to the flat (0 0 0 1) surface.