IUVSTA 15th International Vacuum Congress (IVC-15), AVS 48th International Symposium (AVS-48), 11th International Conference on Solid Surfaces (ICSS-11)
    Electronics Tuesday Sessions
       Session EL-TuP

Paper EL-TuP19
The Morphology and Strain-induced Defect-structure of Ultrathin Epitaxial Fe Films Grown on Mo(110)

Tuesday, October 30, 2001, 5:30 pm, Room 134/135

Session: Electronic Materials Poster Session
Presenter: I. Shvets, Trinity College, Ireland
Authors: S. Murphy, Trinity College, Ireland
D. Mac Mathuna, Trinity College, Ireland
G. Mariotto, Trinity College, Ireland
I. Shvets, Trinity College, Ireland
Correspondent: Click to Email
The magnetic properties of ultrathin epitaxial Fe and Ni films can often be strongly subject to the film strain imposed by lattice mismatch with the substrate and the mechanisms by which this strain may be relieved. In this work, the morphology and defect-structure of Fe films grown with mismatch m = -8.9% on the Mo(110) surface was characterized by a combination of scanning tunneling microscopy, low-energy electron diffraction and Auger electron spectroscopy. Fe films in a thickness range of 0.5 @<=@ d @<=@ 8 Å were grown on a Mo(110) at substrate temperatures lying in the 300 @<=@ T @<=@ 525 K interval. Near room-temperature, films grow layer-by-layer through a combination of step-flow and two-dimensional island growth until the first two Fe layers are complete. Beyond this coverage, there is a transition to layer-plus-island growth. The first layer is pseudomorphically strained, but the film strain is partially relieved in the second layer by the formation of dislocation lines along the [00-1] direction. Because the film is relaxed in the local region about these dislocations, they form preferential sites for nucleation of third layer islands. The build-up in strain with increasing film thickness results in the formation of a strain-relieving dislocation network in the third layer of the film. At elevated temperatures (495 @<=@ T @<=@ 525 K), the first two Fe layers grow by the step-flow mechanism, leading to the formation of arrays of Fe nanostripes. Dislocations are formed along the [00-1] direction in second layer stripes that are wider than approx. 100 Å. At higher coverages, the Fe agglomerates into large wedge-shaped islands surrounded by an Fe monolayer sea. A dislocation network is formed on these islands, originating in the second layer and persisting to the maximum island thickness observed (approx. 10 layers). This network has a similar structure to that observed on islands grown near 300 K, but is 14% more relaxed along the [1-10] direction.