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Semiconducting -FeSi 2. Presented by Srujana Aramalla. Silicides. Metallic Silicides e.g. CoSi 2 , NiSi 2 , TiSi 2 Semiconducting silicides e.g. b -FeSi 2 (bandgap of 0.85 eV), CrSi 2 (0.35 eV)and ReSi 2 (0.12 eV). Advantages of Transition metal silicides. - PowerPoint PPT Presentation
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Semiconducting Semiconducting -FeSi-FeSi22
Presented by
Srujana Aramalla
SilicidesSilicides
• Metallic Silicides
e.g. CoSi2, NiSi2, TiSi2
• Semiconducting silicides
e.g. -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
FeSiFeSi22-Phases-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)
Nature of bandgap
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
Results
Results
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.
Thank You…Thank You…
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