Difference in Formation of Ferromagnetic MnAs Nanoclusters on Ⅲ -Ⅴ Semiconducting Nanowire Templates

摘要

The authors report on the differences in ferromagnetic MnAs nanocluster formation on GaAs, GaAs/AlGaAs, GaAs/GaAsP, and InAs nanowire templates by combing selective-area metal-organic vapor phase epitaxy of semiconducting nanowires and endotaxial nanoclustering of MnAs. To characterize the dependences of MnAs nanocluster formation on semiconducting materials of the nanowire templates, GaAs, GaAs/AlGaAs core-shell, and GaAs/GaAsP core-shell nanowires have been grown at 750 ℃, whereas InAs nanowires have been grown at 580 ℃. MnAs nanoclusters are commonly and most frequently formed at six ridges between two {0-11} crystal facets on hexagonal prisms of Ⅲ-Ⅴ semiconducting nanowires. That is presumably because many atomic steps exist between the crystal facets. Here, MnAs nanoclusters are grown "into" the nanowires, as a result of the phenomenon of "endotaxy". Manganese atoms on the nanowires surface form chemical bonds mainly with arsenic atoms of the nanowires, because only manganese organometallic source and hydrogen are supplied, i.e. no supply of arsenic hydride source during the endotaxy of MnAs. In the case of GaAs/GaAsP core-shell and InAs nanowires, however, MnAs nanoclusters are formed on the top {111}B surfaces of the nanowires, as well as at six ridges of the hexagonal prisms. The results obtained in the current work possibly show that the endotaxy of MnAs depends on the thermal stability of the nanowires and/or the strength of atomic bonds in the host materials of nanowires.