MnP nanoclusters embedded in GaP epitaxial films grown by organometallic vapor-phase epitaxy: A reciprocal space mapping and transmission electron microscopy study

Full three dimensional x-ray diffraction reciprocal space maps combined with transmission electron microscopy measurements provide a systematic determination of the texture of GaP epilayers containing embedded MnP nanoclusters grown on GaP(001) by organometallic vapor phase epitaxy. This approach reveals that the texture of the MnP clusters depends on the growth surface morphology and bonding configuration and on the lattice mismatch at the cluster/matrix interfaces during growth. It demonstrates that the orthorhombic MnP nanoclusters are oriented along specific GaP crystallographic directions, forming six well defined families, whose population is influenced by the growth temperature and the film thickness. The clusters principally grow on GaP(001) and GaP{111} facets with a small fraction of clusters nucleating on higher-index GaP{hhl} facets. Most epitaxial alignments share a similar component: the MnP(001) plane (c-axis plane) is parallel to the GaP{110} plane family. Axiotaxial ordering between the MnP clusters and the GaP matrix is also observed. Furthermore, with this systematic approach, all phases present in these heterogeneous films can be identified. In particular, traces of hexagonal Mn2P precipitates have been observed while their formation can be avoided by lowering the growth temperature. Comparing the structural results presented here with magnetic measurement carried out on similar samples confirms that the effective magnetic properties of the heterogeneous layer can be tuned by controlling the texture of the ferromagnetic nanoclusters. (C) 2012 American Vacuum Society. [http://dx.doi.org/10.1116/1.4758132]