Dopant location in Mn- and Al-doped iron disilicides

J. DESIMONI; S. M. COTES; J. MARTÍNEZ; J. RUNCO; M. A. TAYLOR

La Plata, Argentina

Conferencia; XI Latin American Conference on the Applications of the Mössbauer Effect; 2008

The strong and continual interest on the ecological-friendly low temperature semiconductor b-FeSi2 phase, with a wide spectrum of interesting physical properties, rests on the fundamental issues related to the stability of the phases, growth kinetics, interface structure, and on the technological applications to microelectronic, thermoelectric, photovoltaic and optoelectronic. For technological applications, the control of the electrical conductivity of the system is critical and the intrinsic semiconductor needs to be doped to form either n-type or p-type b-FeSi2. Additives like Pt, Mn and Al can turn the material into a p-type semiconductor. In spite of the effort performed on the subject, the doping of the iron disilicide semiconductor phase is still an open question since encloses intriguing fundamental issues related to dopant location in the two crystallographically inequivalent Fe sites of the orthorhombic structure of -FeSi2. Then, in the present contribution, iron disilicides of the type Fe1−xRxSi2 (R = Mn, Al, 0.00  x  0.12) prepared by ball milling and subsequent annealed at 1123K are study using X-ray diffraction and Mössbauer spectroscopy. Supported by the calculations performed using a model that accounts for the vacancy concentration, site occupation and sample composition, a preferential substitution of Fe by Mn atoms at the regular lattice Fe site II, in the b-FeSi2 structure could be inferred from the present results. Nevertheless, nor replacement of Al atoms in  iron sites can be conjectured from the present results. Although, replacement of Si atoms by Al ones could not be deduced from the XRD patterns.