Sep 7, 2010
At the nanoscale, defects help
Computer simulations based on realistic models of graphene nanoribbons doped with boron have shown that a large number of defects randomly distributed along the system lead to a large polarization of the current, paving the way to a new family of spintronic devices.
Researchers at Universidade Federal do ABC and São Paulo University, both in Brazil, have discovered that one-dimensional systems such as carbon nanoribbons could be used as spin filters with potential applications in spintronic devices.
Defects are usually seen as having deleterious effects on device design. However, by substituting a number of boron atoms randomly distributed along a piece of graphene nanoribbon, the group observed an increase in the ability of such systems to select the spin of the electrons entering the device. The investigation was performed using first principles computational methods.
The team has shown that the presence of a large number of impurities drives the system into the Anderson localization regime. The important point is that the scattering for electrons of different spins has a different probability and thus a different localization length. The exponential behaviour, which is a well known characteristic of the conductance in the localized regime, leads to a staggering increase of the degree of polarization to the extent that the system becomes fully spin-polarized for specific system sizes.
More details can be found in the journal Nanotechnology.
About the author
This work was conducted by researchers from Universidade Federal do ABC and Universidade de São Paulo. Alexandre R Rocha, is a professor at the Natural Sciences Center, Universidade Federal do ABC, Brazil, and leader of the Transport Simulations Group (TranSim). Currently he is working on the simulation of disordered nanoscopic devices. Prof. Adalberto Fazzio and Prof. Antônio José Roque da Silva are professors at the Physics Institute of Universidade de São Paulo and both lead the Sampa Research Group. Prof. da Silva is currently head of the National Synchrotron Facility. Dr Thiago B Martins is a research fellow working in the Sampa Research Group.