Growth, reaction and nanowire formation of Fe on the ZnS(1 0 0) surface

The growth and reaction of Fe on a ZnS(1 0 0) substrate are studied in situ and with high lateral resolution using low energy electron microscopy (LEEM), micro low energy electron diffraction ( μLEED), x-ray photoemission electron microscopy (XPEEM), microprobe x-ray photoelectron spectroscopy ( μXPS) and x-ray magnetic circular dichroism PEEM (XMCDPEEM) for complementary structural, chemical, and magnetic characterization. Initially, a two-dimensional (Fe, Zn)S reaction layer forms with thickness that depends on growth temperature. Further growth results in the formation of a variety of three-dimensional crystals, most of them strongly elongated in the form of 'nanowires' of two distinct types, labeled as A and B. Type A nanowires are oriented near the ZnS[1 1 0] direction and are composed of Fe. Type B nanowires are oriented predominantly along directions a few degrees off the ZnS[0 0 1] direction and are identified as Greigite (Fe3S4). Both types of nanowires are magnetic with Curie temperatures above 450 °C. The understanding of the reactive growth mechanism in this system that is provided by these investigations may help to develop growth methods for other elemental and transition metal chalcogenide nanostructures on ZnS and possibly on other II-VI semiconductor surfaces.