Impurity pays off
doi:10.1038/nindia.2009.17 Published online 30 January 2009
Inserting highly energetic manganese (Mn) ions into the structure of gallium-arsenide (GaAs) semiconductor renders it ferromagnetic1. On exposure to heat, the semiconductor packed with the magnetic Mn ions forms nanoclusters reshaping its architecture. Such doped semiconductors have potential applications in building new generation of classical information processing devices.
Dilute magnetic semiconductors (DMS) are a class of material which use both spin and charge of the electrons. To exploit this property, the researchers implanted highly energetic Mn ions in semi-insulating GaAs substrates at room temperature. Then the samples were heated at high temperature in an atmosphere of nitrogen gas.
High dose and high current implantation gave rise to alloy formation. Due to implantation of Mn, an alloy of Ga-Mn-As may have formed. Sophisticated imaging technique showed generation of nanowires of varying diameters. These nanowires are formed due to defects generated by implantation of Mn ions and heat treatment.
Magnetoresistance study indicates the formation of MnAs nanoclusters, which are ferromagnetic in nature. These nanoclusters reside inside the paramagnetic GaAs:Mn matrix.
"The MnAs clusters can be controlled by varying temperature, implant dose and time of heating," says lead researcher Chacko Jacob.
The authors of this work are from: Materials Science Centre, Indian Institute of Technology, Kharagpur, and Institute of Physics, Sachivalaya Marg, Bhubaneswar, India.