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Vacancy defects induced by proton irradiation

Centre National de l’Energie, des Sciences et Techniques Nucléaires. Vacancy defects induced by proton irradiation. Bouchra Belhorma, Hicham Labrim Unité Sciences de la Matière, CNESTEN-Rabat MF.Barthe, E.Ntsoenzok, P,Desgardin CNRS-CEMHTI-Orléans H.Erramli FS Semlalia, Marrakech.

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Vacancy defects induced by proton irradiation

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  1. Centre National de l’Energie, des Sciences et Techniques Nucléaires Vacancydefectsinduced by proton irradiation Bouchra Belhorma, Hicham Labrim Unité Sciences de la Matière, CNESTEN-Rabat MF.Barthe, E.Ntsoenzok, P,Desgardin CNRS-CEMHTI-Orléans H.Erramli FS Semlalia, Marrakech

  2. Objectives • Principle of Positron Annihilation Spectroscopy • Study of vacancy defects induced in the track region Germanium substract • Conclusion

  3. Contexte & Objective Miniaturisation of electronic components 1/K Grille Main compound Si but : - High leakage current, - technical difficulties (manufacturing) Solutions : - modify the chip architecture - modify the chemical composition A good candidate = Ge, low gap and high mobility Caracterization of the defaults induced by irradiation on Ge Samples : pure Ge , Ge irradiated by H+ beam at different fluences Experimental techniques : cyclotron, PAS

  4. 511 keV Defect S Lattice counts W W 0 PL Lifetimes of positrons  STARTg source 1.28 MeV • Positron Annihilation Spectroscopy • The sample is irradiated with H+ beam • Interactions : inelastique chocs with atomique e-Thermalisation , scattering, annihilation with valence or core e- Doppler brodening (DE =cPL/2 ): Electron-positron pair momentum distribution (p) Eg1=511 keV DE e+ e+ DE 3 Annihilation • S = Nvalence/No(e+) • W = Ncore/No(e+) •  = lifetime of positrons Sample e+ fast, life time e+ slow , Doppler broadening STOP gannihilation Eg2=511 keV DE Vacancy defaults S, W, 

  5. Characteristics of positron annihilation in germanium lattice Substrats: Germanium doped Sb polished unannealed Mesurements of Doppler broadening (slow e+) Mesurements of lifetime (fast e+) VepFit SGe= 0.4629(3) WGe= 0.0465(1) ANAPC

  6. Hydrogen Irradiation • Substrates: N-type Ge (Sb doped) polished unannealed, width 300 µm • 1H+, 12 MeV, at differentfluences from 1.1014 to 7,6.10161H+.cm-2 (<40°C), with the Cyclotron du CEMHTI-CNRS d’Orléans Irradiationconditions • Mesures TRIM => Implantation profile for 12MeV H in Ge = 590 µm > 300 µm => Track region • Doppler (e+ slow) • lifetimes (e+ fast)

  7. • Creation of vacancy defaults with: • heterogeneous distribution of defects in the trace region of H • or • The vacancy defect concentration increaseswith fluence Effect of the irradiation fluence on the Doppler broadening (S, W) Hydrogen Irradiation 12 MeV, fluences 1.1014 to 7,6.1016 cm-2 • After irradiation and whatever the fluence: • Safter irradiation(E) > Sas-received • Wafter irradiation(E) < Was-received • when   : S(E)  et W(E) 

  8. FF MF D LF TF As-received  • the same vacancy defects are created in the track region whatever is the H fluence • Several types of defects detected in all samples irradiated at different fluences with homogeneousdistribution Effect of the fluence of irradiation on the Doppler broadening (S, W) • S(E)  et W(E)  when  • Scattering lenght When • => trapping of the positron Theory

  9. Effect of the fluence of irradiation on the lifetime of fast positrons(300°K) • 12 MeV Hydrogen irradiation : • moy> moy(pure) and moy when  Creation of vacancy defects by irradiation • 2(irradiated H; 1014 H+.cm-2)= 2(monvacancy Ge) low fluence  detection monvacancy • At higher fluence7,6.1016 H+.cm-2: • 2(irradiated H; 7,6.1016 H+.cm-2)=2(divacancy Ge) higher fluence  détection divacancy • 2(1014H+.cm-2, monolacune) <2(1015et 1016H+.cm-2) <2(7,6.1016H+.cm-2, bilacune) fluence 1015 et 1016H+.cm-2 a vacancy-impurties complex was detected

  10. Conclusions and Perspectives • Ge: N-type Ge (Sb doped) polished unannealed Ge(300K) = 228 ps ; SGe = 0.462(8) ; WGe= 0.0464(5) • 12 MeVHydrogen irradiation • the nature of defects in the trace region of H changes with the fluence • Atlow fluence 1014 H+.cm-2: Monovacancy (VGe) • At two fluences 1015 et 1016 H+.cm-2: vacancy-impurity complex • At higher fluence 7,6.1016 H+.cm-2: divacancy (VGe-Ge) • Polished Ge samples unannealed irradiated • Energy level of defects ( irradiation H+, 12 MeV) Photolum spectroscopy • Evolution of the distribution of defects of according to temperature Lifetimes of posiotrons of according to temperature • Evolution of the distribution of vacancy defects in both function of temperature and annealing atmosphere

  11. Thank you for your attention

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