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Multiscale Approach for the Analysis of Channeling Profile Measurements of Ion Implantation Damage G. Hobler, G. Otto, D. Kovac L. Palmetshofer 1, K. Mayerhofer², K. Piplits² 1 Inst. Semiconductor and Solid State Physics, Univ. Linz ² Inst. Chem. Technol. and Analytics, TU Vienna Institute of Solid-State Electronics

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Damage Models in BC Simulations Traditional model: –defect positions: generated statistically –atom positions: random interstitial model –dynamic annealing: „recombination factor“ Proposed model: –defect positions: trace each defect during the whole simulation –atom positions: take from ab-initio simulations –dynamic annealing: kinetic lattice Monte Carlo simulation (kLMC) after each collision cascade

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Overview Introduction BC-kLMC approach Application to channeling profile measurement (CPM) experiments

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Damage Measurements RBS Channeling profile

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Channeling Implantations Fit dose dependence of channeling implantation profiles recombination factor f rec =0.125 N sat =4 cm -2 (G.Hobler et al., J. Vac. Sci. Technol B14 (1) 272, 1996)

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Channeling Profile Measurements Measure pre-existing crystal damage with a low-dose channeling implant (M. Giles et al., MRS Symp. Proc. 469, 253, 1997)

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The Role of Dynamic Annealing in Si Temperature dependence of implant damage: (J.E. Westmoreland et al., Appl. Phys. Lett. 15, 308, 1969)

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The Role of Dynamic Annealing in Si Dose-rate dependence of implant damage: T=300K (O.W. Holland et al., Rad. Eff. 90, 127, 1985) 70µA/cm² 0.14µA/cm²

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Overview Introduction BC-kLMC approach Application to channeling profile measurement (CPM) experiments

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Coupled BC-kLMC Approach Traditional approach: BUT: type and amount of defects influence BC trajectories (dechanneling) kLMC BC loop over cascades 1 cascade point defects point defects + clusters

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Coupled BC-kLMC Approach Proposed new approach: kLMC BC loop over cascades old defects + new point defects point defects + clusters atom positions for each defect defects

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Details of kLMC Each defect is associated with one or more lattice sites Defects: V n, I n (n=1,2,3,...) Events: –Diffusion hops (I, V) –Reactions of defects located within capture radius V n +V V n+1 V n +I V n-1 I n +I I n+1 I n +V I n-1 Parameters: –D V =3 cm²/s D I =6.35 cm²/s –(Capture radii)

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Details of kLMC „Old“ defects: restricted to column (periodic boundary conditions) „New“ defects: anywhere Interaction between „new“ and „old“ defects: Using periodicity of „old“ defects

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Details of BC Read defects from kLMC (columnar domain) Use periodicity to generate defects around projectile Atom positions from ab-initio calculations (VASP) –defect structure –strain around defect All defects composed of individual I and V (currently)

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Overview Introduction BC-kLMC approach Application to channeling profile measurement (CPM) experiments

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CPM Experiments Damage implant: N, 30 keV, 3 cm - ², 10° tilt CPM implant: B, 30 keV, cm -2, 0° tilt shield (110)-Si

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CPM Experiments Results :

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CPM Simulation Results Simulation results without strain:

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CPM Simulation Results Strain from vacancies:

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CPM Simulation Results Strain from interstitials:

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What is wrong? Defects: V n, I n (n=1,2,3,...) Events: –Diffusion hops (I, V) –Reactions of defects located within capture radius V n +V V n+1 V n +I V n-1 I n +I I n+1 I n +V I n-1 Parameters: –D V =3 cm²/s D I =6.35 cm²/s –(Capture radii) Lack of amorphous pockets?

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What is wrong? Defects: V n, I n (n=1,2,3,...) Events: –Diffusion hops (I, V) –Reactions of defects located within capture radius V n +V V n+1 V n +I V n-1 I n +I I n+1 I n +V I n-1 Parameters: –D V =3 cm²/s D I =6.35 cm²/s –(Capture radii) Lack of amorphous pockets? NO Approximate treatment of I-Clusters?

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What is wrong? I-Clusters: Similar study on RBS-C: Efficiency of I 2, I 3, I 4 within 40% of split- 110 interstitial I I2I2 I3I3 I 4a I 4b (G. Lulli et al., Phys. Rev. B69, , 2004)

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What is wrong? Defects: V n, I n (n=1,2,3,...) Events: –Diffusion hops (I, V) –Reactions of defects located within capture radius V n +V V n+1 V n +I V n-1 I n +I I n+1 I n +V I n-1 Parameters: –D V =3 cm²/s D I =6.35 cm²/s –(Capture radii) Lack of amorphous pockets? NO Approximate treatment of I-Clusters? Probably not Attraction of I+V n, V+I n and/or Repulsion of I+I n, V+V n

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Conclusions New approach for implant damage simulations –coupled BC and kLMC –atom positions from ab-initio Consistent simulation of both defect generation and analysis Simulations yield too much damage need to use –interaction radii to favor recombination and/or –reaction barriers to impede clustering

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