1. 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

2. 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 …

3. 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

4. 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, 

5. 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 = (3)
WGe= (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,

6. 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 to 7, H+.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)

7. 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 to 7, 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 

8. 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 

9. 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
H+.cm-2
233.6 4
198 4
291 4
30 4
1.28
H+.cm-2
253.9 2,62
154 4
299 2
69 2
1.31
H+.cm-2
279.3 3,08
173 8
302 2
82 2
1.32
7, 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, H+.cm-2 :
2(irradiated H; 7, 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

10. Conclusions and Perspectives
Ge: N-type Ge (Sb doped) polished unannealed
Ge(300K) = 228 ps ; SGe = 0.462(8) ; WGe= (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, 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