Recent advances ofMEIS (medium-energy ion scattering)     (medium-      for near surface analysis           Pedro. L. Gran...
Outline1.       Introduction (MEIS)2.       Recent Advances     •        Nanoparticles (NPs) Analysis          •      Simp...
Techniques           (Surfaces/Interfaces/Nano)•XPS•AES•LEED•STM•Electron microscopic•EXAFS,•Raman,•...   Ion Beam Techniq...
Ion Beam Techniques  http://lnmsf.irb.hr/techniques.htm
Ion Scattering - MEIS                      ImprovedH+                    depth and mass                      resolution   ...
MEIS - Advantages Penetrating (can access buried interfaces!) Mass specific Known interaction law (cross sections are  ...
MEIS data collection                                    Schulte H. (Private communication)    Energy Spectrum             ...
MEIS Spectrum                                       3.0                                                                   ...
MEIS user Community  • Depth profiling (amourphous)      •High-k materials      •Thin films  …  • Structural determination...
Recent Developments (MEIS) New detectors (MEIS 3D, TOF-MEIS)Strain measurementsOrganic and biological materials analysi...
MEIS for Nanoparticles
MEIS Potentiality            Depth profiling elements            inside a NP
Energy-     Energy-loss asymmetry                            1.5        Backscattred Ions                            1.0  ...
0.020                                                                                                          distributio...
Where does the asymmetry come from ?       • Statistical : # of collisions                      correlated or uncorrelated...
Asymmetry very important           for ultra-thin films !               ultra-Pezzi at al. Surface Science 601 (2007) 5559
Nanoparticle analysis
Nanoparticles           Full Monte-Carlo Simulation• any geometrical shape (sphere, cylinder,..)• density distribution• si...
Full 3D Monte-Carlo Integration        Monte-(PowerMeis program)                              E0    EoutE1      E0    E in...
Sample descriptionPowerMeis GUI
Giant 3D matrix (of matrices)  Pair correlation function g(r)
Shape sensitivity
Influence of the asymmetry:       backscattering collisionAu
Nanoparticles   (asymmetrical lineshape)                 lineshape) Diameter   t > 5nm Diameter   t < 5nm         false ...
For the full 2D MEIS spectrum !                                    Asymmetric                                             ...
Nanoparticle analysis - applications    I – Au NPs in polyelectrolytes          multilayered films
Polyelectrolyte (PE)   charged polymers   films can be tuned with    desired composition and    thickness   can be depo...
Au NPs adsorbed in polyelectrolyte
TEMNPs on the surface
MEIS results (100 keV         H+)M.A. Sortica et al. JAP (2009)
Energy spectrum (1D)      Geometrical shape      Size distribution   Good agreement with TEM !M.A. Sortica et al. JAP (2009)
NP interaction with PE film Depends   on both Au colloid and PE assembling    procedure   MEIS  characterization of nan...
Further MEIS results (100 keV H+)G. Machado et al. Nanoscale 3, (2011)1717
Nanoparticle analysis – applications     II – Core-shell characterization of          CdSe/ZnS quantum dots
Quantum dots CdSe/ZnS                 CdSe/ Nanocrystals   Absorption and  emission depends on    composition and size  ...
Core-         Core-shell analysis of CdSe/ZnS                                CdSe/         quantum dots   Liquid sample –...
MEIS analysis (150 keV He+)
MEIS analysis – 3 angles           400                                        Cd         Experimental     Cd              ...
MEIS analysis Core  stoichiometry  Cd0.65Se0.35 Core diameter  5.0 nm Shell stoichiometry  Zn0.41S0.59 Shell thickn...
40                                  TEM Results        30# NPs        20        10        0             3   4   5    6   7...
Dr. DaeWon Moon
Buried Nanoparticles ?
Nanoparticle analysis – applications          III – Burried Pb NPs             ion implantation
Pb nanoislands at SiO2 / Si                                                   2 D array             SiO2             Si• P...
Pb nanoislands : TEM imagesCross-section     Plan view                3.7x1011 NPs/cm2
MEIS results (100 keV         He+)  thinner (45nm)   thicker (65nm) SiO2
Experiment       Pb Film           Simulations                                   (PowerMeis program)                      ...
Usual data analysis            60                   Experiment                       11      -2                   2.10 NPs...
Advanced data analysis
Experimental vs. Simulations                                                  Experimental                 1000           ...
TEM plan view                  3.7 x 1011 NPs/cm2MEIS (best fit)        (4.5 ± 1.5) x1011 NPs/cm2
Where do they deviations come from ?Multiple Scattering Effects ?some NPs in Si (bulk)                                    ...
Energy SpectraMS important for   < 115 deg !
Shape Sensitivity                                                          11         2                                   ...
Nanoparticle analysis – applications                                Au (sputtering)          IV – Burried Au NPs          ...
Porto Alegre,                                  Brazil                                                     ~40 nm          ...
57
44 %                 9.0 × 1011 NP/cm2          25sAu dissolvedinto the SiO2                                     58
Nanoparticle analysis – applications           V – Burried Fe NPs               Ion implantation
As implanted                   1 minute                                                   MEIS →                          ...
Statistics and shape fromTEM as input to obtainshell stoichiometry fromMEIS analysis                            2 Rshell  ...
XPS + MEIS/TEM  Fe@FexSi33-xO67          33-  SiO2 density (atoms/cm3) Fe@Fe14Si19O67  Fe                Fe  Si           ...
Simple approach for thefull description of the 2D –MEIS        spectrum-        spectrum- Crystals
Cu(111):[100] In
Blocking curves – Cu(111) surface
VEGAS Monte Carlo Simulation  well   established in MEIS          just the area of the surface peak          Phit and Pde...
Extending the VEGAS code to include ion scattered energiesImprove surface determination    •Bimetallic surfaces    •Therma...
Energy Loss                                            single collision                    0.020                    0.018 ...
Cu (111) single crystal     •single atomic type     •very small relaxation     •previously analyzed by MEISA,.Hentz et al....
Comparison with ab-initio                  ab- energy- energy-loss calculations
Skimming Effect
Nice but…Coupled-channel calculations arevery time consuming ! A simple model is needed !
Simple Model for the impact    parameter dependent   energy loss distribution            Gaussian( E - Q(b), (b))        b...
Simple model               Skimming Effect
Experimental Data                    Simple model
Summary       MEIS for NP characterization1) On the surface : Excellent (using asymmetrical lineshape)2) Buried NPs : sens...
Summary II   This opens new perspectives for nanostructure analysis in situ thatcan of great interest.   Pitfall : Dissolv...
Summary IIISimple approach for the full 2D MEIS spectrum (Crystal)                      (VEGAS extended) • Visibility of e...
Gregor Schiwietz                                   Helmholtz-                                   Helmholtz-Zentrum Berlin  ...
Thank you for your attention !        Obrigado !
Recent advances of MEIS for near surface analysis
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Recent advances of MEIS for near surface analysis

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Apresentação do professor Pedro Grande, da seção UFRGS do Instituto Nacional de Engenharia de Superfície. Palestra convidada do Simpósio Engenharia de Superfície do X Encontro da SBPMAT. Realizada no dia 26 de setembro de 2011 em Gramado (RS).

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Recent advances of MEIS for near surface analysis

  1. 1. Recent advances ofMEIS (medium-energy ion scattering) (medium- for near surface analysis Pedro. L. Grande (UFRGS-Brazil)
  2. 2. Outline1. Introduction (MEIS)2. Recent Advances • Nanoparticles (NPs) Analysis • Simple NPs : Au NPs on Polyeletroyides • Core-shell NPs: CdSe • Buried NPs: Pb Nanoisland and Fe NPs • Simple approach for the 2D MEIS spectra for crystal3. Conclusions
  3. 3. Techniques (Surfaces/Interfaces/Nano)•XPS•AES•LEED•STM•Electron microscopic•EXAFS,•Raman,•... Ion Beam Techniques
  4. 4. Ion Beam Techniques http://lnmsf.irb.hr/techniques.htm
  5. 5. Ion Scattering - MEIS ImprovedH+ depth and mass resolution (amorphous) Surface sensitivity (crystal)
  6. 6. MEIS - Advantages Penetrating (can access buried interfaces!) Mass specific Known interaction law (cross sections are known) – quantitative technique – can determine absolute number of atoms in the sample Excellent depth resolution Non-destructive
  7. 7. MEIS data collection Schulte H. (Private communication) Energy Spectrum Angular Spectrum Yield gl g An ter i n e at Sc Energy d el Yi MC ion scattering simulation of Deconvolution of ES gives depth angular yield provides surface profile (primarily for amorphous structure. thin films).
  8. 8. MEIS Spectrum 3.0 o 2.5 = 60 Counts (arb. units) 2.0Energy 1.5 1.0 0.5 0.0 Angle 93.0 93.5 94.0 94.5 95.0 proton energy Summed over 2 degrees around = 60o
  9. 9. MEIS user Community • Depth profiling (amourphous) •High-k materials •Thin films … • Structural determination •Heterogeneous catalysis •Surface reconstruction …
  10. 10. Recent Developments (MEIS) New detectors (MEIS 3D, TOF-MEIS)Strain measurementsOrganic and biological materials analysis Better understanding of the energy-loss processes (ab-inito, simple-models) Nanoparticle/Nanoislands/Quantum dots analysisFull description of the 2D MEIS spectrum for crystals
  11. 11. MEIS for Nanoparticles
  12. 12. MEIS Potentiality Depth profiling elements inside a NP
  13. 13. Energy- Energy-loss asymmetry 1.5 Backscattred Ions 1.0 0.5 0.0 60 80 100 120 EnergyDepth profile or energy-loss asymmetry ??? or energy-
  14. 14. 0.020 distributions Investigations on Exponentially Modified Gaussian (EMG) Moyal + M-shell H (100keV) + Al f(x) = exp(-(a x + exp(-ax))/2) 0.015 Gaussian not Gaussian Exp. decay Exp. decay dP/d E(eV ) the asymmetry of energy-loss distribution energy- -1 0.010 d d Asymmetric Gaussian Lognormal (Grande and Schiwietz) Schiwietz) L-shell 2 f(x) = exp(-(ln(x)- ) /2 2 )/x 0.005 1 2 0.000 0 50 100 150 200 250 300 350 400 450 500 550 600 distributions Energy Transfer ( E) (eV)  Ab-initio (coupled-channel calculations)  Analytical formula NIMB 256 (2007) 92 Surface Science 601 (2007)5559 PRL 102 (2009) 096103  Simple models (CasP program)P.L. Grande, G. Schiwietz, Ionization and energy loss beyond perturbation theory,Advances in Quantum Chemistry, Vol 45 (2004) 7-46.
  15. 15. Where does the asymmetry come from ? • Statistical : # of collisions correlated or uncorrelated • Single hard collision (b ~ 0)
  16. 16. Asymmetry very important for ultra-thin films ! ultra-Pezzi at al. Surface Science 601 (2007) 5559
  17. 17. Nanoparticle analysis
  18. 18. Nanoparticles Full Monte-Carlo Simulation• any geometrical shape (sphere, cylinder,..)• density distribution• size distribution• asymmetrical lineshape
  19. 19. Full 3D Monte-Carlo Integration Monte-(PowerMeis program) E0 EoutE1 E0 E inE out K i ( ) E1 E out E1
  20. 20. Sample descriptionPowerMeis GUI
  21. 21. Giant 3D matrix (of matrices) Pair correlation function g(r)
  22. 22. Shape sensitivity
  23. 23. Influence of the asymmetry: backscattering collisionAu
  24. 24. Nanoparticles (asymmetrical lineshape) lineshape) Diameter t > 5nm Diameter t < 5nm false geometrical shape false size distribution
  25. 25. For the full 2D MEIS spectrum ! Asymmetric Gaussian 80% 1 nm + 20% 4 nm Au spheres - Gaussian lineshape 1nm Au spheres - EMG lineshape 1.485E6 1.585E6 99.5 99.5 1.392E6 1.486E6 1.276E6 1.362E6 99.0 99.0 1.160E6 1.238E6 1.044E6 1.114E6 98.5 98.5 9.906E5 9.281E5Energy (keV) Energy (keV) 8.668E5 8.121E5 98.0 98.0 7.430E5 6.961E5 6.191E5 5.801E5 97.5 97.5 4.953E5 4.641E5 3.715E5 3.480E5 97.0 97.0 2.477E5 2.320E5 1.238E5 1.160E5 96.5 96.5 0 120 140 160 180 200 220 240 260 280 300 320 0 120 140 160 180 200 220 240 260 280 300 320 Angle (deg) Angle (deg)
  26. 26. Nanoparticle analysis - applications I – Au NPs in polyelectrolytes multilayered films
  27. 27. Polyelectrolyte (PE) charged polymers films can be tuned with desired composition and thickness can be deposited onto different substrates can be easily removed after nanomaterials synthesis
  28. 28. Au NPs adsorbed in polyelectrolyte
  29. 29. TEMNPs on the surface
  30. 30. MEIS results (100 keV H+)M.A. Sortica et al. JAP (2009)
  31. 31. Energy spectrum (1D) Geometrical shape Size distribution Good agreement with TEM !M.A. Sortica et al. JAP (2009)
  32. 32. NP interaction with PE film Depends on both Au colloid and PE assembling procedure MEIS  characterization of nanoparticles on the PE surface
  33. 33. Further MEIS results (100 keV H+)G. Machado et al. Nanoscale 3, (2011)1717
  34. 34. Nanoparticle analysis – applications II – Core-shell characterization of CdSe/ZnS quantum dots
  35. 35. Quantum dots CdSe/ZnS CdSe/ Nanocrystals  Absorption and emission depends on composition and size  Higher efficiency in fluorescence process  Thin band gap
  36. 36. Core- Core-shell analysis of CdSe/ZnS CdSe/ quantum dots Liquid sample – EviDots (maple red-orange) in toluene solution – 2.2 mg/L  Dilutedin toluene at 3.82 g/L  Deposited on SiO2/Si(100) substrate
  37. 37. MEIS analysis (150 keV He+)
  38. 38. MEIS analysis – 3 angles 400 Cd Experimental Cd Cd 350 Simulated 300 = 112 degrees = 120 degrees = 128 degrees 250 Counts 200 150 Se Se Se 100 Zn Zn Zn S S 50 0 100 110 120 130 100 110 120 130 100 140 110 120 130 140 Energy (keV)
  39. 39. MEIS analysis Core stoichiometry  Cd0.65Se0.35 Core diameter  5.0 nm Shell stoichiometry  Zn0.41S0.59 Shell thickness  0.6 nm
  40. 40. 40 TEM Results 30# NPs 20 10 0 3 4 5 6 7 nm TEM  spatial and size distribution MEIS  core and shell characterization
  41. 41. Dr. DaeWon Moon
  42. 42. Buried Nanoparticles ?
  43. 43. Nanoparticle analysis – applications III – Burried Pb NPs ion implantation
  44. 44. Pb nanoislands at SiO2 / Si 2 D array SiO2 Si• Produced by ion implantation (300 keV Pb)• Thermal annealing : 200oC (100 hours) + 1100oC (1 hour)• Two SiO2 thicknesses (different etching times) 45 and 65 nm
  45. 45. Pb nanoislands : TEM imagesCross-section Plan view 3.7x1011 NPs/cm2
  46. 46. MEIS results (100 keV He+) thinner (45nm) thicker (65nm) SiO2
  47. 47. Experiment Pb Film Simulations (PowerMeis program) Same amount of Pb 3.3 x1022 Pb/cm2 • Film (thickness = 0.7nm)2x1011 NPs/cm2 6x1011 NPs/cm2 • NPs 1. V = 350 nm3 (2x1011 NPs/cm2) 2. V = 100 nm3 (6x1011 NPs/cm2)
  48. 48. Usual data analysis 60 Experiment 11 -2 2.10 NPs cm 11 -2 6.10 NPs cm 40 = 130 deg S 20 0 60 70 80 Energy (keV)
  49. 49. Advanced data analysis
  50. 50. Experimental vs. Simulations Experimental 1000 Film 11 2 2.0x10 NPs/cm Counts (a.u.) 11 2 3.5x10 NPs/cm 11 2 6.0x10 NPs/cm 500 0 66 68 70 72 74 76 78 80 Energy (keV)
  51. 51. TEM plan view 3.7 x 1011 NPs/cm2MEIS (best fit) (4.5 ± 1.5) x1011 NPs/cm2
  52. 52. Where do they deviations come from ?Multiple Scattering Effects ?some NPs in Si (bulk) atomic Pb ? NP Size Distribution ? Experimental 1000 Simulation some NPs in SiO2 Counts (a.u.) 500 0 66 68 70 72 74 76 78 80 Energy (keV)
  53. 53. Energy SpectraMS important for < 115 deg !
  54. 54. Shape Sensitivity 11 2 2x10 NPs/cm Experimental Film TEM Sphere 11 2 3.5x10 NPs/cm Experimental Film Counts (a. u.) TEM Sphere 11 2 6 x10 NPs/cm Experimental Film TEM Sphere 68 70 72 74 76 78 80 Counts (a. u.)D.F. Sanchez et al. Surface Science 605 (2011) 654
  55. 55. Nanoparticle analysis – applications Au (sputtering) IV – Burried Au NPs SiO2 sputtering Si (bulk)
  56. 56. Porto Alegre, Brazil ~40 nm SiO2 (sputtering) Au (sputtering)7.4 × 1015 Au atoms/cm2 SiO23.1 × 1015 Au atoms/cm2 Si (bulk)1.8 × 1015 Au atoms/cm2 56
  57. 57. 57
  58. 58. 44 % 9.0 × 1011 NP/cm2 25sAu dissolvedinto the SiO2 58
  59. 59. Nanoparticle analysis – applications V – Burried Fe NPs Ion implantation
  60. 60. As implanted 1 minute MEIS → 109º 109º H+ 150 keV Scattered Intensity (a. u.) 120º 120ºLower Hutt, New Zealand 131º Si 131º Si Fe Fe Fe surface1.0 x 1016 atoms/cm2 132 136 140 144 132 136 140 144 Energy (keV) Fe surface J. Kennedy et. al., Nanotechnology, 22, 115602 (2011) 60
  61. 61. Statistics and shape fromTEM as input to obtainshell stoichiometry fromMEIS analysis 2 Rshell 2 Rcore 61
  62. 62. XPS + MEIS/TEM Fe@FexSi33-xO67 33- SiO2 density (atoms/cm3) Fe@Fe14Si19O67 Fe Fe Si Si 62
  63. 63. Simple approach for thefull description of the 2D –MEIS spectrum- spectrum- Crystals
  64. 64. Cu(111):[100] In
  65. 65. Blocking curves – Cu(111) surface
  66. 66. VEGAS Monte Carlo Simulation  well established in MEIS just the area of the surface peak Phit and Pdet (only the blocking curves !) 66
  67. 67. Extending the VEGAS code to include ion scattered energiesImprove surface determination •Bimetallic surfaces •Thermal vibration correlations •Dechanneling background
  68. 68. Energy Loss single collision 0.020 0.018 0.016 0.014 dP/d E(eV ) 0.012 -1 0.010 0.008 0.006 0.004 0.002 0.000 0 50 100 150 200 250 300 350 400 450 500 550 600 68 Energy Transfer ( E) (eV)
  69. 69. Cu (111) single crystal •single atomic type •very small relaxation •previously analyzed by MEISA,.Hentz et al. PRL 102, 096103 (2009)
  70. 70. Comparison with ab-initio ab- energy- energy-loss calculations
  71. 71. Skimming Effect
  72. 72. Nice but…Coupled-channel calculations arevery time consuming ! A simple model is needed !
  73. 73. Simple Model for the impact parameter dependent energy loss distribution Gaussian( E - Q(b), (b)) b>0F( E,b) = exp(- E) ( E) b =0 1/ 0
  74. 74. Simple model Skimming Effect
  75. 75. Experimental Data Simple model
  76. 76. Summary MEIS for NP characterization1) On the surface : Excellent (using asymmetrical lineshape)2) Buried NPs : sensitivity for the areal density no sensitivity for the geometrical shape MS effects are important
  77. 77. Summary II This opens new perspectives for nanostructure analysis in situ thatcan of great interest. Pitfall : Dissolved atomic species affect MEIS analysis
  78. 78. Summary IIISimple approach for the full 2D MEIS spectrum (Crystal) (VEGAS extended) • Visibility of each layer • Electronic energy-loss at hard-collision (asymmetric) • Impact parameter dependent energy-lossInput parameters : , dE/dx, dW2/dxUseful to improve surface determination
  79. 79. Gregor Schiwietz Helmholtz- Helmholtz-Zentrum Berlin Phil Woodruff Daewon Moon Warwick KRISSMauricio, Dario,Agenor, Paulo, AdrianoGiovanna, ClaudioUFRGS – Porto Alegre Jêróme Leveneur, John Kennedy, National Isotope Centre, GNS Science New Zealand 80
  80. 80. Thank you for your attention ! Obrigado !

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