Vanadium:Silicon - an ion-beam generated diluted magnetic semiconductor? Vanadium diffusion and concentration predictions in Silicon

The generation of dilute magnetic semiconductors (DMS) by ion-beam implantation of magnetic centres into semiconducting materials has experienced renewed interest since the generation of magnetic thin films from the Cobalt-doped wide-gap semiconductor TiO2. Since the magnitude of the magnetic moment in such films is strongly varying and since the implementation in a standard, Silicon-based semiconductor device is challenging, we have concentrated on the binary and fully integrable system Vanadium:Silicon. Vanadium form several binary compounds in Silicon at higher doping concentrations; the most well characterised structures have the compositions V:Si= 3:1, 5:3, 6:5, 1:2, and bear the potential to exhibit magnetism. At higher dilution, Vanadium may form point defects in the crystalline Silicon host matrix. Here, we investigate different combinations of substitutional and interstitial vanadium atoms in crystal matrix as well as its diffusion. Spin dependent density functional band-structure calculations with the Projector Augmented Wave (PAW)-method (with Abinit, VASP) in LDA and GGA have been carried out to investigate magnetism for all configurations. For special structures also the all-electron full-potential local-orbitals (FPLO)-method (with FPLO) have been used, to confirm the magnetic properties. At the same time first experiments (RBS, XRD, SQUID) have been arranged to support the simulations.