Semiconducting -FeSi2 Presented by Srujana Aramalla
Silicides • Metallic Silicides e.g. CoSi2, NiSi2, TiSi2 • Semiconducting silicides e.g. b-FeSi2 (bandgap of 0.85 eV), CrSi2 (0.35 eV)and ReSi2 (0.12 eV).
Advantages of Transition metal silicides • Temperature stability • Oxidation resistance • Low electrical resistivity
FeSi2-Phases Exists in two phases • Semiconducting low temperature phase • Metallic high temperature phase -FeSi2 - FeSi2 ~937C
Bandgap of -FeSi2 Quasi direct bandgap ~0.83 eV - ~0.87 eV (at RT)
Optical characterization • Raman spectroscopy -provides information related to structure and bonding
Samples investigated • -FeSi2 (undoped) • -(Fe(1-X)Crx)Si2 (x=0.003, 0.01) • -(Fe(1-X)Cox)Si2 (x=0.009, 0.066, 0.14)
Growth method Molecular beam epitaxy The deposition can consist of 1.Pure metal deposition at room temp, followed by annealing (SPE) 2.pure metal deposition at high temp (RDE) 3.codeposition of metal and silicon
Raman Spectroscopy Specifications: • 0.85m Double monochromator equipped with a pair of 1200 grooves/mm holographic gratings • 5145 Ar ion laser as excitation source with output power at 300 mW • Photo multiplier detector tube.
Information obtainable from Raman spectrum • Raman intensity • The frequency shift • The linewidth
Conclusion • Observed overall red shift if the peaks is related to tensile stress in the samples. • Tensile stress observed in these samples may result in sufficient strain to cause Y-point transition to become the fundamental direct transition, thus allowing light emission.