AVS 45th International Symposium
    Surface Science Division Thursday Sessions
       Session SS-ThP

Paper SS-ThP33
Atomic Force Microscopy Examination of the Evolution of the Surface Morphology of Bi@sub 4@Ti@sub 3@O@sub 12@ Grown by Molecular Beam Epitaxy

Thursday, November 5, 1998, 5:30 pm, Room Hall A

Session: Surface Science Division Poster Session
Presenter: G.W. Brown, Los Alamos National Laboratory
Authors: G.W. Brown, Los Alamos National Laboratory
M.E. Hawley, Los Alamos National Laboratory
C.D. Theis, Pennsylvania State University
J. Yeh, Pennsylvania State University
D.G. Schlom, Pennsylvania State University
Correspondent: Click to Email
Bi@sub 4@Ti@sub 3@O@sub 12@ is a candidate material for use in electro-optic devices and non-volatile ferroelectric-based memories. In these applications, obtaining the desired electronic or optical properties depends on the ability to deposit very smooth films. We have examined the molecular beam epitaxial nucleation and growth of these films on SrTiO@sub 3@ with ex-situ atomic force microscopy (AFM) to observe the thickness dependence of the surface morphology. From the AFM data we obtain the direct, real space surface morphology, the RMS surface roughness as a function of thickness, the amount of material present in the growing layers, and the height difference correlation function of the surface. Bi@sub 4@Ti@sub 3@O@sub 12@ growth begins with the nucleation of a layer that is 1/4 unit cell thick followed by growth of 1/2 unit cell thick layers. A transition to multilayer island (3-dimensional) growth occurs somewhere between deposition of 25 % of the second layer and the completion of the third layer. This implies that the film grows in a Stranski-Krastonov mode with a critical thickness between 0.325 and 1.250 monolayers. After 3-dimensional growth begins, the surface morphology can be described with the dynamic scaling hypothesis (DSH).@footnote 1,2@ The DSH scaling exponents, extracted from the AFM images, are compared to other thin film growth systems and should provide checks for future models or simulations of Bi@sub 4@Ti@sub 3@O@sub 12@ growth. We observe an interesting thickness dependence of one of the scaling exponents which may be related to the stress relief involved in the S-K growth mode. Possible models for the stress relief will be discussed. Finally, results of deposition on substrates providing different lattice mismatches will be shown and implications for the growth of thicker, smooth films will be discussed. @FootnoteText@ @footnote 1@F. Family and T. Viscek, J. Phys. A: Math. Gen. 18, L75 (1985). @footnote 2@J. Lapujoulade, Surf. Sci. Rep. 20, 191 (1994).