110 likes | 211 Views
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.
E N D
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
Objectives • Principle of Positron Annihilation Spectroscopy • Study of vacancy defects induced in the track region Germanium substract • Conclusion
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
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,
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
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)
• 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)
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
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
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