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.

Using the technique of photoluminescence imaging, self-organized patterns of high-electron density in homogeneous n-GaAs layers under homogeneous microwave irradiation are studied. The structures are shown to be analogous to current filaments in a static electric field. The symmetry of the microwave induced patterns is not constrained by the current feeding electrodes. It is, however, concluded that a feedback mechanism exists between the formation of high-conducting structures and the homogeneity of the incident microwave irradiation.

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Irish scientists have spent years putting Ireland on the map. Is Physics World now doing the opposite by depicting an Ireland-less world (November 1996 p35)?

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