Self-assembled semiconducting nanowires (NW) are promising candidates to design and to fabricate new and advanced devices for nanotechnology. In particular, the synthesis of magnetic Ge NWs is still in its infancy even if highly Mn doped Ge1-xMnx (x > 0.7) are ferromagnetic up to 400 K while at high Mn dilution in the Ge matrix the system can behaves as a true Diluted Magnetic Semiconductor. Ge Nws have been grown at low temperature by Molecular Beam Epitaxy on Ge (111) substrates using Mn as catalytic seed. The size and distribution of the Mn particles have been investigated by AFM after annealing at high temperature of Mn films. These evidenced nano droplets on the Ge surface with a morphology dependent on the thickness of Mn layer, temperature and duration of annealing. Ge NWs have been growing by using Mn based nano-droplets via Vapor Liquid Solid (VLS) and Vapor Solid Solid (VSS) growth methods. Conversely, nanowires have been provided also by co-evaporation of the Mn and Ge at substrate temperatures below 400 °C. Transmission Electron Microscopy (TEM) of the grown films showed the presence of Ge NWs, kinetically induced from the formation of a GeMn phase with a low eutectic point, not stabilized at low deposition temperature. Analysis suggests that a reduction of the interfacial free energy of the Ge1-xMnx/Ge system drives the uniaxial growth of Ge NWs along specific crystallographic directions.
Growth of diluted magnetic germanium nanowires using manganese nano-droplets
Rezvani S. J.;PINTO, Nicola;GUNNELLA, Roberto;
2012-01-01
Abstract
Self-assembled semiconducting nanowires (NW) are promising candidates to design and to fabricate new and advanced devices for nanotechnology. In particular, the synthesis of magnetic Ge NWs is still in its infancy even if highly Mn doped Ge1-xMnx (x > 0.7) are ferromagnetic up to 400 K while at high Mn dilution in the Ge matrix the system can behaves as a true Diluted Magnetic Semiconductor. Ge Nws have been grown at low temperature by Molecular Beam Epitaxy on Ge (111) substrates using Mn as catalytic seed. The size and distribution of the Mn particles have been investigated by AFM after annealing at high temperature of Mn films. These evidenced nano droplets on the Ge surface with a morphology dependent on the thickness of Mn layer, temperature and duration of annealing. Ge NWs have been growing by using Mn based nano-droplets via Vapor Liquid Solid (VLS) and Vapor Solid Solid (VSS) growth methods. Conversely, nanowires have been provided also by co-evaporation of the Mn and Ge at substrate temperatures below 400 °C. Transmission Electron Microscopy (TEM) of the grown films showed the presence of Ge NWs, kinetically induced from the formation of a GeMn phase with a low eutectic point, not stabilized at low deposition temperature. Analysis suggests that a reduction of the interfacial free energy of the Ge1-xMnx/Ge system drives the uniaxial growth of Ge NWs along specific crystallographic directions.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
