In situ TEM studies of helium bubble/platelet evolution in Si based materials

Transcription

1 In situ TEM studies of helium bubble/platelet evolution in Si based materials M. Vallet 1, M.F. Beaufort 1, J.F. Barbot 1, E. Oliviero 2 and S.E. Donnelly 3 1 Institut Pprime, CNRS-Université de Poitiers, France. 2 CSNSM, CNRS-IN2P3, Orsay, France. 3 Electron Microscopy and Materials Analysis Group, University of Huddersfield, UK. Institut P UPR CNRS 3346 SP2MI Téléport 2 Boulevard Marie et Pierre Curie BP F86962 FUTUROSCOPE CHASSENEUIL Cedex

2 Part I. In Silicon Carbide Study the effects of the Au irradiation on the stability of He bubbles in the complex environment of a reactor Part II. In Silicon Study the interaction between implanted H ions with He platelets 2

3 Silicon Carbide SiC is a wide-band gap semi-conductor and a ceramic Excellent physical and chemical properties (High temperature stability, chemical inertness, small neutron capture cross section) Promising material for several applications Used as structural component for the first wall of the nuclear reactor (fusion)/ Encapsulating material for nuclear fuel (fission) - High temperature - Production of He atoms - Fast neutron fluxes (damage) No studies on the effect of neutron irradiation on He bubbles have been reported 3

4 Experimental details Preliminary step: Formation of He bubbles Wafers of n-type 4H-SiC (0001) Single crystal «Cree Inc.» 8 off-axis Thickness : 400 µm Helium implantation T impl : 400 C E = 160 kev Fluence: He.cm -2 Annealed at 1400 C during 30 min Layer of bubbles: 200 nm Bubble diameter: 4 12 nm In-situ irradiation in a TEM JANNuS Facility in Orsay + = XTEM BF image underfocused Use of the reactor Aramis Characterization in situ in a TEM 4

5 Experimental details In-situ irradiation in a TEM JANNuS Facility in Orsay 2 MeV Au irradiation Flux: /cm 2 /s Specimen normal to the ion line T irr : 350 C -Develop levels of atomic displacements in few hours -Equivalent to damage levels that reactor components will receive in an operating lifetime R p : 310 nm ΔR p : 56 nm Going through the samples V/A-ion 0.27 dpa/10 15 Au 5

6 Results XTEM BF images Off-zone Recorded with the objective lens underfocused Fluence Steps x10 15 Au.cm

7 Results XTEM BF images Off-zone Recorded with the objective lens underfocused Fluence Steps x10 15 Au.cm Shrinkage of bubbles 7

8 Results XTEM BF images Off-zone Recorded with the objective lens underfocused Fluence Steps x10 15 Au.cm Shrinkage of bubbles Quick shrinkage Sputtering effects 8

9 Shrinkage of He bubbles Determination of the radius of each bubble for each step Shrinkage rate 0.09 nm / Au.cm -2 XTEM BF images Off-zone Recorded with the objective lens underfocused 9

10 Toward a qualitative understanding of the effect of Au irradiation on He bubbles System was simulated by 1D model using the SRIM code: Experiment SRIM model Au Irradiation Au Irradiation He He He He SiC He He He He layer He SiC SiC Thickness of the He layer d of He bubbles Bubbles modeled by a layer of He + Dpa constant => no influence of the position of the He layer + Observation in very thin area (no overlapping of He bubbles) 10

11 Toward a qualitative understanding of the effect of Au irradiation on He bubbles System was simulated using the SRIM code: SRIM model Au Irradiation SiC SiC He Helium density obtained from the equation of state corresponds to pressure of an equilibrium bubble with r = 3.35 nm RL. Mills, PRB 21, 5137 (1980) He recoiled out of bubble Stopping of He ejected from a 6.7nm-thick helium layer following irradiation with Au ions at 2MeV. 11

12 Comparison with experiment Experimental rate : Model 1 : average rate

13 Comparison with experiment Experimental rate : Model 2: average rate Number of ejected He atoms is corrected by the number of recoiled He retrapping by the bubble layer Equilibrium radius calculated at each step by using EOS from Mills et al. Good agreement with the experimental result Model 1 : average rate Incertitude Position of the bubbles Measurement of the mean radius 13

14 Summary By the expulsion of He from bubbles, Au irradiation induces a linear shrinkage of bubbles The re-trapping of He in bubbles should be taken into account to explain the shrinkage of bubbles 14

15 Part II. Effects of the interaction between H ions and He platelet-like defects in Si 15

16 Effects of the interaction between H ions and He platelet-like defects in Si Smart-Cut process / Ion-cut technology Based on H defects to initiate cracks Application for the transfer of thin film (production of SOI structures) BUT He defects could replace H defects as precursor H ions And annealing (500 C) for H diffusion + = Bright field image of edge-on He-plates in (001)-oriented substrate Reboh S, APL 96, (2010) Study in-situ the effects of the interaction H/He-plates 16

17 Effects of the interaction between H ions and He platelet-like defects in Si Experimental details Preliminary step: formation of He-plates Helium implantation T impl : RT E = 45 kev Fluence: He.cm -2 Annealing at 350 C + = during 15 min H 2 + implantation in JANNuS facility T impl : RT E = 30 kev Inclination/Ion beam: 45 Fluence: He.cm -2 R p = 140 nm ΔR p = 48 nm Direct insertion of H in the defect Implantation performed thanks to the reactor IRMA 17

18 Effects of the interaction between H ions and He platelet-like defects in Si Results As-implanted observations No effect on the morphology of He-plates XTEM BF image of the asimplanted sample An in-situ thermal annealing up to 500 C To determine the position of H ions 18

19 Effects of the interaction between H ions and He platelet-like defects in Si Results In-situ thermal annealing up to 500 C Evolution of He-plates at 500 C without H After annealing at 500 C Cluster of bubbles 19

20 Effects of the interaction between H ions and He platelet-like defects in Si Results In-situ thermal annealing up to 500 C Stability in T of the platelet structure increases up to 500 C 20

21 Effects of the interaction between H ions and He platelet-like defects in Si Results Increase of the mean diameter by addition of H2 in He-plates from 200 C 150 nm 170 nm 210 nm 280 nm It is favorable for the formation of cracks Work in progress 21

22 Conclusions Studied the shrinkage of He bubbles under Au irradiation Specified the role of the H in He-plate THANK YOU FOR YOUR ATTENTION 22

23 Effects of the interaction between H ions and He platelet-like defects in Si Results No modification of the structure after H implantation a RT 23

24 Experimental details In-situ irradiation in a TEM JANNuS Facility in Orsay Electron beam off during irradiation Possible synergistic effects under electrons/ions co-irradiation (200 kev electrons and 4MeV Au) Pawley CJ, J. Phys.: Conf. Ser. 371, (2011) He desorption from bubbles under e - beam (EELS experiments) David ML, APL 98, (2011) Step at given fluence to study the evolution of bubbles ϕ = 1, 2, 4, 7, 10, 13, Au.cm -2 24