Morphology and strain-induced defect structure of ultrathin epitaxial Fe films on Mo(110)

Abstract

Fe films in a coverage range of 0.4рр4.7 ML were deposited on a Mo͑110͒ substrate in the 300рT р700 K temperature range. It is found that growth around 300 K is mediated by the step-flow growth mechanism, in contrast with previous studies of the Fe/Mo͑110͒ and Fe/W͑110͒ systems, where growth at 300 K was mediated by two-dimensional island nucleation and coalescence. This difference is attributed to the slightly higher substrate temperature ͑between 300 and 345 K͒ during deposition. A transition from layer-bylayer to Stranski-Krastanov growth is observed in films grown in the 300рTр345 K range at around a 1.8 ML coverage. Strain-relieving dislocation defects appear along the ͓001 ͔ direction in the second Fe layer and develop with increasing film thickness into a dislocation network at around a 2.4 ML coverage. The dislocation defects in the second Fe layer act as preferential nucleation sites for third layer islands. At elevated temperatures (495рTр700 K), the first and second Fe layers are formed by the step-flow growth mechanism. Subsequent coverages are characterized by the formation of distinctive wedge-shaped islands supported on an Fe monolayer. A two-dimensional dislocation network is formed in the fourth Fe layer of these islands, from an array of closely-spaced dislocation lines in the third layer. Similar to the Fe/W͑110͒ system, the magnetic properties of these films are expected to vary significantly on the nanometer scale and they are therefore potential candidates for spin-polarized scanning tunneling microscopy studies.

Anisotropic transport behavior in ultrathin epitaxial Fe films on vicinal oxide substrates

“…We have clearly demonstrated the influence of step edges on the island shape in the model system of Fe islands grown on vicinal Mo ͑110͒ substrate. 13,14 …”

Developments in surface magneto-optical Kerr effect setup for ultrahigh vacuum analysis of magnetic ultrathin films

“…The growth proceeds by the step-flow mechanism producing 2 ML thick Fe stripes aligned along the atomic steps. 5 The stripes cover the entire surface of the substrate forming a structure that can be considered as a good experimental approximation of a twodimensional ferromagnetic system. Longitudinal hysteresis loops displayed in Fig.…”

Study of ferromagnetic–paramagnetic phase transition in two-dimensional Fe/Mo(110) epitaxial films

“…The cleaning procedure described in Ref. [5] was repeated until the surface produced a sharp 1 × 1 LEED pattern, consistent with the bulk termination of the Mo(110) surface (Fig.1b). Fe films were deposited by electron beam evaporation of a 4N purity Fe rod.…”