Films of Fe, with coverages ranging from θ = 0.4 to 4.7ML, were deposited onto a Mo(110) substrate at 300 to 700K. It was found that growth at around 300K was mediated by a step-flow growth mechanism; in contrast to previous studies of the Fe/Mo(110) and Fe/W(110) systems, where growth at 300K was mediated by 2-dimensional island nucleation and coalescence. This difference was attributed to the slightly higher substrate temperature (between 300 and 345K) during deposition. A transition from layer-by-layer to Stranski-Krastanov growth was observed in films grown at 300 to 345K to give around 1.8ML of coverage. Strain-relieving dislocation defects appeared along the [00¯1] direction in the second Fe layer and developed, with increasing film thickness, into a dislocation network at about 2.4ML of coverage. The dislocation defects in the second Fe layer acted as preferential nucleation sites for third-layer islands. At 495 to 700K, the first and second Fe layers formed via the step-flow growth mechanism. Subsequent coverages were characterized by the formation of distinctive wedge-shaped islands, supported on an Fe monolayer. A 2-dimensional dislocation network was formed, in the fourth Fe layer of these islands, from an array of closely-spaced dislocation lines in the third layer.

Morphology and Strain-Induced Defect Structure of Ultrathin Epitaxial Fe Films on Mo(110). S.Murphy, D.M.Mathúna, G.Mariotto, I.V.Shvets: Physical Review B, 2002, 66[19], 195417 (10pp)