Single-crystalline AlGaN:Mn nanotubes and their magnetism

A new class of 1D DMS nanostructures, Mn-doped nanotubes that has advantages such as low dimensionality, nanoscale size and perfect single crystalinity was investigated. The nanotubes were grown on nickel-coated sapphire substrates by using a chloride chemical vapor deposition (CVD) process. The XRD pattern showed that the nanotubes have a wurtzite structure without any secondary phases. It was observed that the growth of nanotubes depends on the thickness of the catalyst coated on the substrates. The large catalysts on the substrates coated with 5 nm of Ni are slowly etched out and leave a liquid film and the temperature gradient across the catalyst results in the generation of low and high interfacial tension. It was observed from the XAS and XMCD analyses that the origin of ferromagnetism is not metallic but based on ionic Mn and modulation can provide a way toward the development of a new class of 1D DMS nanostructures.