From Nanoparticles to Single Atoms, EDS of Electron Transparent Samples. M. Falke, et al.

Transcription

1 From Nanoparticles to Single Atoms, EDS of Electron Transparent Samples M. Falke, et al. 1

2 Presenters Dr. Meiken Falke Product Manager EDS/TEM, Bruker Nano Analytics, Berlin, Germany Dr. Igor Nemeth Application Scientist, Bruker Nano Analytics, Berlin, Germany 2

3 From Nanoparticles to Single Atoms, EDS of Electron Transparent Samples M. Falke, et al. Outline Nanoparticles / Nanoobjects what is this about SDD Technology Examples of nanoanalysis using various combinations of EDS and EM Conclusions: options to characterize NP, their distribution and environment 3

4 From Nanoparticles to Single Atoms, EDS of Electron Transparent Samples STEM T-SEM CNT+catalyst NP SENi C CNT+catalyst NP 300 nm Cs-corr. STEM Cell+NP Cs-corr. STEM Core-shell NP SEM Single atom 1 nm nanoclay in polymer 4

5 Detector Types for SEM/T-SEM and TEM/STEM and Solid Angle for X-Ray collection FEI d Ω wikipedia Ω! A surf / r 2 [sr] Single/multiple stand alone Systems: Ω EDS-SEM ~ sr Ω EDS-S/TEM ~ sr Nion+Bruker ~ 0.7sr (0,91sr) Spezial Systems with radial symmetry: FEI 0.9 sr (4 x 30 mm 2 ) FEI High res. PP 0.7 sr (4 x 30 mm 2 ) FlatQuad 1.2 sr (4 x 15 mm²) 5 5

6 Geometric limits (TEM/STEM) solid angle TOA TOA TOA Inverse solid angle! how much of the surroundings do we see? A small collimator opening is better to avoid system peaks. Solid angle by Nestor Zaluzec: 6

7 Detector quantum efficiency and Windows of in situ reaction cells Detector w/wo window + reaction species sticking to cell walls Window of reaction cell gas Contact layer Moxtek window: Polymer + Si support grid Si dead layer Si detector crystal 7

8 Lines above 50 kev can be used Powder of pure Dy 2 InSb0 7 Sample courtesy: Maria Bacia, CNRS Grenoble; Data courtesy: Philippe Lasson, Synergie 4 8

9 In situ: Comparing EDS spectra at RT, 800, and 900 o C ---- RT o C o C Noise mostly at low E, from radiation The window material of the SDD blocks 99% of the light Yes, we can do spectrum imaging up to ~ 800 o C SDD Jane Y. Howe (ORNL), Christianne Beekman (Florida State Uni) Bruker 30mm 2 SDD on SEM (Zeiss Merlin) 9

10 EDS for Life Science Yeast Cell: Element mapping of protein labels and light and heavy elements 30 mm 2, 0.12 sr (Standard EDS); Conventional STEM BF 500nm Ag Os N S P C O 10

11 EDS for Life Science at 0.1sr Malaria Parasite: Plasmodium Falcip. in erythrocyte treated with Chloroquine science.nationalgoegraphic.com The parasite multiplies by destroying red blood cells. Iron intake in food vacuole, since the parasite is digesting hemoglobin Malaria can be treated e.g.by Chloroquine Anopheles mosquito science.nationalgoegraphic.com Data courtesy: C. Biot and C. Slomianny, Laboratory of Cell Physiology, University of Lille, France; STEM CM300 11

12 Peak Separation measured Os P Os+P+ 12

13 Peak Separation measured Os P Os+P+ 13

14 TEM EDS Quantification; R. Egerton 1994, line intensity for a particular element line / transition Zeta- Factor I x = N A σ A ω A (Ω/4π) ε N e = n A t σ A ω A (Ω/4π) ε N e Cliff and Lorimer: I A I B = kab C A C B k AB can be determined experimentally or theoretically I x N n t number of X-ray photons in a characteristic peak of species A number of atoms per unit volume number of atoms per unit area times thickness σ ionization cross section (Casnati et al., 1982, Bote et al., 2009) ω fluorescence yield (Hubbell et al., 1994, Krause, 1979) Ω/4π solid angle / geometrical collection efficiency ε detection quantum efficiency number of incident electrons N e + absorption 14

15 TEM EDS Quantification Zeta vs CL For testing we used Si 3 N 4 a single layer (30nm) as the sample a double layer (60nm) as the standard STEM probe current: 344pA CL: Si at% N at% d nm Si3N4_expected 42,86 57,14 Si3N4_60nm_st. 42,86 57,14 Si3N4_30nm 43,84 56,16 Zeta: Si3N4_30nmZeta 41,96 58,04 30 Zeta Method: M. Watanabe J. of Micr Further tests with Al 2 O 3, TiO 2, GaAs Very sensitive to - probe current and - thickness variations 30nm Si 3 N 4 60nm 15

16 EDS for Catalysis, Quantification Pt-Pd Core Shell Particles mass%, 30 mm 2, 0.12 sr (Standard EDS); Cs-corr. STEM Data courtesy: Dogan Ozkaya, Johnson Matthey Technology Center. Jeol STEM Pt shell not closed due to fabrication procedure 16

17 Simultaneous EDXS and EELS from a single Si atom 30mm 2, SLEW; CFEG, Cs corrected STEM Tracking movie of 1 Si atom on graphene as recorded during EDS spectrum acquisition ED(X)S ADF image of a defect in monolayer graphene recorded after spectra were acquired. Arrow points to a tracked Si impurity atom. E ELS EDXS and EELS data recorded simultaneously. I p = 190 pa, 0.09sr, 224 s acquisition; Thereof ~10s beam close to the atom. Nion UltraSTEM100, 60 kev, Daresbury UK. Bruker SDD EDXS, Gatan Enfina EELS 17

18 Single atom spectra C 115 counts Si 51 counts 224s single Si atom spectrum Grid? Cu 23 counts T. C. Lovejoy et al., APL 100, (2012) C+Pt 374 counts Pt s single Pt atom spectrum Polepiece? Fe 45 Co 48 Grid? Cu 208 Pt 18

19 EDS with 100 mm 2 windowless oval detector area; Nion UltraSTEM, Cs-corrected, high brightness source EDXS at ~0.7 sr flat, collimated 100mm 2 / (10.5mm) 2 = 0.91sr TOA: mm 2 Wikipedia: solid angle 19

20 Identifying atoms by EDXS, one-by-one x 0.001cps/eV Si S Cu Cu HAADF image of meteorite nanodiamond with impurities > not as ideal as graphene! Nion UltraSTEM200, 60 kev, Bruker Quantax XFlash UHV windowless SDD. courtesy Rhonda Stroud, NRL, M&M (2015) R. M. Stroud et al., APL 108, (2016) E / kev EDXS of atom 1, 9.4 sec, 74 Si counts E / kev EDXS of atom 2, 8 sec, 33 S counts* 100 mm 2 SDD at 10.5 mm => 0.7 sr *tracking area was ~2x larger for S, hence the lower counts. Cu is a system peak due to sample holder & polepiece caps.

21 XFlash QUAD vs Single detector in SEM: Polymer composite containing organo clay 2 µm XFlash Flat QUAD detector 3 kv, 220pA, 10 kcps, 320 s, 1024x768 pixel Single 30mm 2 XFlash 3 kv, 220pA, 0.8 kcps, 320 s, 1024x768 pixel Shadow effects due to rough surface Sample courtesy by Dalto et al., Universidade Federal do Rio de Janeiro, Data courtesy T. Salge (Bruker / NHM, London); 21

22 Flat Quad XFlash 5060 N. J. Zaluzec, Detector solid angle Formulas for use in EDS, Microsc. Microanal., 15 (2009)

23 Flat Quad XFlash 5060 Solid angle and OCR vs distance d Cu, 1nA, 5kV max solid angle at d = 2.5mm: Ω > 1.1 sr d Ω 23

24 T-SEM-EDX of NP Typical Overview Analysis: T. Salge (Bruker/NHM) 24

25 TSEM-EDX of fluorescent core shell NP; Silica nanoparticles coated with Alexa dye XFlash FlatQUAD, 5 kv, 520 pa, 22.5 kcps, 250x250 pixel, 2 nm pixel size, 377 s K. Natte, T. Behnke, G. Orts-Gil, C. Würth, J. F. Friedrich, W. Österle and U. Resch-Genger, J Nanopart Res, 2012, 14, 680; Analysis: T. Salge; Hitachi SEM 25

26 T-SEM-EDX of SiO 2 NP; PA: Classification, Statistics unclassified NP SDD Flat 10 mm 2 QUAD Acq time (s per NP) ICR (kcps) Solid angle (sr) NP identified bulk NP hollow NP 3nm Analysis: T. Salge (Bruker/NHM); Hitachi SEM 26

27 EDS; Characterization of Nano-Objects; Possible Steps SEM/T-SEM > Overview / embedding/ statistics on mm-nm scale > Using annular detector > Combine with other analysis techniques (TKD, µxrf, µct) Standard / Cs-corrected STEM + Standard EDS > Q-Mapping in at% and nm for materials and life science Cs-corr. STEM + high Ω EDS > Single atoms > in situ (liquids, gases, temp.) 27

28 Q&A Are There Any Questions? Please type in the questions you have in the Q&A box, select Ask: All panelists and press Send. 28

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