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 I will present to you the vacancy … on Ge samples

Vacancy defects induced by proton irradiation Plan Objectives Principle of Positron Annihilation Spectroscopy Study of vacancy defects induced in the track region Germanium substract Conclusion At the begining I will give the contexte of this work, then the principe of the main experimental technique After the characteristics of Positron annihilation in Ge lattice And I will then give the resultats of the vacancy defects induced …

A good candidate = Ge, low gap and high mobility Contexte & Objective Miniaturisation of electronic components Grille 1/K 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 In the miniaturisation of electronic ships, the objective is to get a components with high frequency and low power. With Si, the main problem is the curent leakage and some technical realisation difficulties. The solutions that are explored by industrials and reseachers consist on modifying the junction geometry or modify the material. A team of Berkeley have tried a new composition with 3nm Ge (good candidate to overcome this difficulties) on Si substract, and have shown that the leak curent has desapered. The objective if our work is to study the efect of structure and chemical composition on electronic properties of Ge. For this we have used the technique of Positron annihilation spectroscopy on Ge. The sample are Ge irradiated with He ions at different fluences Caracterization of the defaults induced by irradiation on Ge Samples : pure Ge , Ge irradiated by H+ beam at different fluences Experimental techniques : cyclotron, PAS

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 3 Annihilation Sample STOP g annihilation Eg2=511 keV DE e+ Lifetimes of positrons  START g source 1.28 MeV W S PL counts 511 keV Defect Lattice e+ DE S = Nvalence/No(e+) W = Ncore/No(e+)  = lifetime of positrons The technique of PAS is based on measurements of the lifetime of positrons between their production and their annihilation-recombination with an electron of valence or core. The difference between the detection time of the gamma rays produced by the annihilation informe us about path that each photon have passed through. The used quantities are width doppler proadening noted as S and the tails lengnts of the distribution. e+ fast, life time e+ slow , Doppler broadening Vacancy defaults S, W, 

Substrats: Germanium doped Sb polished unannealed Characteristics of positron annihilation in germanium lattice Substrats: Germanium doped Sb polished unannealed Mesurements of Doppler broadening (slow e+) Mesurements of lifetime (fast e+) Ge doped Sb, polished and unannealed 1(ps) As-received 227.9 3 VepFit SGe = 0.4629 (3) WGe= 0.0465 (1) ANAPC In this figures you ca see the distributions of these parametres S and W v.s the incident particule’s energies This measurmenets have been performed on Ge doped with antimoine irradiated with protons Hydrogen ions,

Vacancy defects induced by proton irradiation Irradiation Hydrogène à 12 MeV Hydrogen Irradiation Substrates: N-type Ge (Sb doped) polished unannealed, width 300 µm 1H+, 12 MeV, at different fluences from 1.1014 to 7,6.1016 1H+.cm-2 (<40°C), with the Cyclotron du CEMHTI-CNRS d’Orléans Irradiation conditions Sample Particle Energy (MeV) depth (µm) Temperature °C Fluence H+.cm-2 MLGEN2E10E11 H 12 590 <40 1014 MLGEN1E8E9 1015 MLGEN2E14E15 1016 MLGEN2E3E4 7,6.1016 Mesures TRIM => Implantation profile for 12MeV H in Ge = 590 µm > 300 µm => Track region Doppler (e+ slow) lifetimes (e+ fast)

Hydrogen Irradiation 12 MeV, fluences 1.1014 to 7,6.1016 cm-2 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)  Creation of vacancy defaults with: heterogeneous distribution of defects in the trace region of H or The vacancy defect concentration increases with fluence 

Effect of the fluence of irradiation on the Doppler broadening (S, W) Sample L+(nm) TF : 1014H+.cm-2 95.72 LF : 1015H+.cm-2 89.16 MF :1016H+.cm-2 60.67 FF : 7,6.1016H+.cm-2 43.92 As-received 145 FF LF TF As-received MF D S(E)  et W(E)  when   Scattering lenght  When   => trapping of the positron Theory 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 homogeneous distribution 

2(irradiated H; 1014 H+.cm-2)= 2(monvacancy Ge) Effect of the fluence of irradiation on the lifetime of fast positrons (300°K) Ge doped Sb, polished unanealed moy (ps) Composantes 2/pure 1(ps) lattice 2 (ps) default I2 % pure 227.9 3 1.1014 H+.cm-2 233.6 4 198 4 291 4 30 4 1.28 1.1015 H+.cm-2 253.9 2,62 154 4 299 2 69 2 1.31 1.1016 H+.cm-2 279.3 3,08 173 8 302 2 82 2 1.32 7,6.1016 H+.cm-2 284.9 9,16 227 13 316 7 64 9 1.38 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 fluence 7,6.1016 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(1015 et 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 MeV Hydrogen irradiation the nature of defects in the trace region of H changes with the fluence At low 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

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