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What is the nature of the C-C complex in silicon?

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The structure of the C-C complex in silicon has been debated since long time. Different theoretical and experimental studies tried to shed light on the properties of these defects that are at the origin of the light emitting G-center. It is essential to understand structural and electronic properties of
these defects because they are relevant for applications in lasing and there is an increasing interest
to control their formation and concentration in bulk silicon. In this paper, we study structural, electronic, and optical properties of different possible configurations of the C-C complex in bulk
silicon by means of density functional theory (DFT) plus many-body perturbation theory (MBPT).
Our finding show that different competing structures could be at the origin of the experimental results.

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What is the nature of the C-C complex in silicon?

  1. 1. What is the nature of the C­C  complex in silicon? Claudio Attaccalite CNRS/CINAM Campus de Luminy, Case 913  13288 Marseille , France Insights from electronic  structure calculations
  2. 2. Silicon Laser : the problem Indirect band gap semiconductors are not good for  photonics/optoelectronics
  3. 3. Silicon Laser : solutions Nanostructures Defects (G­centers) and more…. hybryd lasers etc...
  4. 4. Silicon Laser in the news
  5. 5. The G­center in Silicon   D. Berhanuddin, M. Lourenco, C. Jeynes, M. Milosavljevic?, R.  Gwilliam, and K. Homewood, Journal of Applied Physics 112,  103110 (2012). D. D. Berhanuddin, M. A. Lourenc?o, R. M. Gwilliam, andK. P.  Homewood, Advanced Functional Materials 22, 2709 (2012).
  6. 6. The CiCs complex history ● Discovered in ‘60 in irradiated Silicon,  and associated to the G­center emission at 0.97 eV (1280 nm) ● Carbon isovalent to S occupies substitutional position Cs ● Cs binds carbon interstitials and forms CiCs couple! ● Experimental studies by means of: Electron­paramagnetic  resonance (EPR), Optical detection of magnetic resonance  (ODMR), Deep­level Transition­Spectroscopy (DLTS),  Photoluminescence Spectroscopy (PS), Infrared Spectroscopy(IS)
  7. 7. How to create G­centers…. Rotem, E., Shainline, J. M., & Xu, J. M. (2007). Electroluminescence of nanopatterned silicon with carbon implantation and solid phase epitaxial regrowth. Optics express, 15(21), 14099-14106. Carbon doping of silicon using conventional ion implantation is not feasible due to its low Carbon solubility. Solution: amorphization → ion implantation → Annealing
  8. 8. The suspects A-form: the interstitial silicon is three bounded B-form: Si is bounded to two C atoms C-form: two carbon atoms are situated in a vacancy and oriented in (100) direction D-form: is a torsion of C-form along the C-C bond axis
  9. 9. The suspects
  10. 10. First clue: binding energy Depending on approaching manner of Ci to Cs either A  or C can be formed. While A will directly transform to  B, as B is more stable and the energetic barrier is very  low 0.1 eV, transformation from either A or B to C is  less probable as the transformation barrier have been  estimated to be as high as 2­3 eV.
  11. 11. Second clue: vibrational frequiencies E. V. Lavrov, L. Hoffmann, and B. Bech Nielsen, Phys. Rev. B 60, 8081 (1999). Good agreement with experiments but lack of measurement above the  1000cm^­1. Measurement of the A and B form are obtained exciting the  system with light to make the transition B­>A
  12. 12. Third clue: defect concentration The experimental defect concentration are extracted from infrared spectra. (Annealing with different  carbon concentration) Simulation are based on “kinetic Mass Action Low” on lattice. Binding and migration energies from DFT
  13. 13. Forth clue: band structure/optics We started from the DFT­ PBE bans structure and  corrected it using Many­ Body Perturbation Theory  (MBPT) within the G0W0  approximation
  14. 14. Forth clue: band structure/optics The optical absortion is calculated by means  of the Bethe­Salpeter  equation 
  15. 15. Who is the murder ? We think that the responsible for  the G­center light emission is …...
  16. 16. Who is the murder ? We think that the responsible for  the G­center light emission is ….. the C­form of the CiCs complex but more experiments are needed  to clarify different points. Many clues point to the C­form but: 1) The C­form is magnetic, therefore its EPR response can be out of the  experimental range 2) Different form of CiCs complex could be present in the same sample 3) Vibration frequencies above 1000 cm^­1 not measured yet.
  17. 17. Acknoledgments  Pascal  Pochet Dilyara  Timerkaeva Damien Caliste  Brenet Gilles References  1) D. Timerkaeva, C. Attaccalite, B. Gilles, D. Caliste, P. Pochet, Which is the nature of the C-C complex in silicon? Insights from electronic structure calculations (submitted to PRB) 2) Brenet, G., Timerkaeva, D., Sgourou, E. N., Londos, C. A., Caliste, D., & Pochet, P. (2015). An atomistic vision of the Mass Action Law: Prediction of carbon/oxygen defects in silicon. Journal of Applied Physics, 118(12), 125706.
  18. 18. Mass Action Law :  carbon/oxygen defects in silicon Evolution concentration Constant rates

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