A Brief History of Atom Probe

Transcription

1 A Brief History of Atom Probe Thomas F. Kelly and John A. Panitz Pre-meeting Congress, M&M 2016

2 Ancestry of the Modern Atom Probe 2

3 Erwin Wilhelm Müller Photograph of Professor Erwin W. Müller ( ): Father of High Field Nanoscience 3

4 1935 Field Electron Emission Microscopy - electron E + Fluorescent Screen E. W. Müller, Z. Phys. 120 (1943) 270 4

5 Field Electron Emission Microscopy Field electron emission microscopy (FEEM) was developed as a point projection microscope FEEM patterns showed clear crystallographic information Ba atoms and phthalocyanine molecules were observed on W needles with FEEM Image resolution improved through the late 1940 s Müller sought to resolve atoms with FEEM Eventually it was concluded that FEEM would resolve no better than ~2 nm Field desorption (and evaporation?) was shown in

6 FEEM tips were routinely cleaned by reversing the bias Practitioners of FEEM noticed: Field ions were emitted during reverse bias Müller sought, and found, a way to increase the signal of field ions: H, He gas Intensity of field ion signal varied with gas pressure In early 1950s, this was pursued for imaging the tip surface Atoms at ledges were seen Early field ion images (FIM) had higher resolution than FEEM Field Ion Microscopy Erwin Müller at Penn State 6

7 1951 Field Ion Microscopy Gas supply + ion Fluorescent Screen + E First images ever of atoms (on ledges of tip surface): Summer 1951, Müller First atomically resolved lattice on surface: October 11, 1955, Bahadur and Müller 7

8 Surface atoms and defects are visible in FIM E.g. Self-interstitial atoms produce large image in FIM Imaging Crystal Defects in FIM 8

9 Vacancies imaged in FIM! Vacancies observed Knock-on damage cascades were mapped by cinematography of FIM 9

10 1960s FIM 10

11 40 K Tungsten Needle Helium Gas Phosphor Screen FIM & Field Evaporation Movie Best Imaging Voltage Slight Laser Heating Field Evaporation Adsorbed gas atoms field ion image Specimen atoms atom probe Movie Courtesy Baptiste Gault

12 3D FIM Comes to Life! 100% of atoms positioned High precision on atom locations Crystal structure and defects readily visible 12

13 Compositional Contrast in FIM In this field ion micrograph of boron-doped nickel aluminide (Ni 3 Al), the bright dots are individual boron atoms that have segregated to a grain boundary (arrowed). 13

14 Müller sought a way to identify atoms in the specimen Barofsky was asked to built a magnetic sector mass spectrometer He later suggested that they should try ToF Panitz was assigned the job How to detect single atoms? Never been done The Atom Probe John A. Panitz Mueller, Panitz, McLane, Rev. Sci. Instrum. (1968) vol. 39, p

15 Much of the following from Panitz th International Field Emission Symposium Atom Probe Tomography and Microscopy Stuttgart, Germany

16 The Müller Group ~ 1968 Names in bold are part of the atom probe effort 16

17 1967 Original Atom-Probe Field Ion Microscope 17

18 Single Atom Detection Was Invented Photograph of oscilloscope screen 18

19 Data File: Oscilloscope Trace Polaroid picture of oscilloscope screen Atom Hit 19

20 First Publication on Atom Probe 20

21 The Second Atom Probe

22 Muller and Panitz 22

23 Imaging Atom Probe: the Progenitor of Atom Probe Tomography MRP of 14 was achieved! Tip tilting not needed Flight distance cm to center Observe field ion image or field desorption image Mass analyze all atoms within a field of view 23

24 Imaging Atom Probe 2.0: Curved MCPs Tip at center of MCP curvature All parts of detector have same flight length High mass resolution over entire field of view Tomographic imaging possible Detector technology for recording each ion impact position was not yet invented 24

25 Field Desorption Images of Single Specie Time gate on MCPs 25

26 Pulsed Laser Atom Probe A laser was adapted to the Imaging atom probe at Sandia Laboratories First time non-metals were atom probed Laser pulsing has become the dominant pulsing mode in APT 26

27 PLAP data - Molybdenum Flight path was not optimized No correction for flight distance across detector Demonstrated laser pulsing for metals, insulators Correct isotopic abundances 27

28 New Groups Develop University of Oxford Professor George Smith Congratulations to George MSA Distinguished Scientist Award First atom probe expert Early atom probe at Oxford 28

29 1975 The Vacuum Generators APFIM 100 Developed in conjunction with Smith et al. at Oxford First commercial atom probe 29

30 1988 The Position-Sensitive Atom Probe Adapted a Wedge-and-Strip detector from astronomy to a VG APFIM Fall MRS presented by George Smith First operational 3DAP 30

31 The Position-Sensitive Atom Probe (PoSAP) 31

32 The Commercial PoSAP Manufactured by Kindbrisk (Oxford NanoScience) 32

33 Tomographic Atom Probe D. Blavette, A. Bostel, J. M. Sarrau, B. Deconihout, and A. Menand: An atom-probe for three dimensional tomography. Nature 363: (1993). 33

34 TAP Detector 34

35 Electron-Beam-Pulsed Atom Probe Thermal pulsing can be route to high repetition rates Need to heat very small volumes for rapid cooling Needed for high mass resolving power Electron beams can be focused to very small diameter ~100 nm heated volume Specimen in atom probe is positive electrode Thermal pulsing with electron beam 35

36 Atom Probe and (S)TEM Electron beam pulsing and atom probe naturally suggest imaging during analysis There are many advantages of having a TEM image of the specimen Kelly, 1990 IFES meeting, Albuquerque 36

37 Electron-Beam-Pulsed Atom Probe Larson, Camus and Kelly, Applied Surface Science 67 (1993)

38 The Atom Probe Microscope 38

39 There were Challenges to overcome Vibration-free cooling Field emission from electrode With Cryopump on 39

40 Scanning Atom Probe Nishikawa, O., Kimoto, M., Applied Surface Science (1994) vol. 76, pp

41 Basic conundrum: Origins of Local Electrode Atom Probe 3DAP is superlative analytical tool but 3DAP of 1990 is too slow to be practical (1 atom/s) The field of view was limited to about 20 nm Scanning Atom Probe used an aperture electrode close to specimen Field emitter arrays had demonstrated field enhancement factors of 10 relative to remote electrode Lower voltage pulsers can achieve much higher repetition rates Two key results: Use local electrode to obtain high data rates Relative reduction in energy spread can be compensated by post A Brief History of Atom Probe acceleration => high mass resolution over full field of view July 24,

42 Local Electrode Specimen Local Electrode Enables: Analysis of microtips and needles High data collection rates Large field of view 42

43 Microtips in the LEAP 1 mm Local Electrode Microtip Array Sharp Flat Top 43

44 Solid Model of Alpha Prototype Cryopump Specimen and local electrode Detector 44

45 Alpha Prototype to LEAP 3000 Circa

46 The LEAP 4000 X

47 Near Full page on gradient background The LEAP

48 There Are Many LEAP Models Anticipated Quantum LEAP LEAP Frog LEAP of Faith Lambeau LEAP 48

49 EIKOS IS Atom Probe Tomography July 24, 2016

50 Focused Ion Beam: General Liftout Method a) b) 1 a) b) 3 2 c) d) c) d ) e) f) e) f) David Larson led the way on FIB preparation of specimens All scale bars are 5 μm All scale bars are 1 μm (except f which is 200nm) 50

51 STEM+LEAP The ATOM Project Build objective lens assembly with atom probe inside Position Sensitive Detector O. Krivanek et al., Ultramicros. 108 (2008) 179. Side-entry liquid He sample stage 51

52 TEM+LEAP Project Tomo Build objective lens assembly with atom probe inside 52

53 Specimen Holder for Project TOMO Electron Beam Evaporated Ions 53

54 AST EELS Atomic Structure Electronic Structure Electronic Structure Atom Probe Diffraction ASAT STEM Computed Image Properties Structure-Properties Microscopy

55 In the History of Microscopy, We are at an Inflection Point Log (Length Scale of Knowledge) Mega Macro Micro Prehistory Human eye Telescopes Microscopes 1600 Today Time Inflection point 55

56 The History of Microscopy The history of microscopy is the pursuit of learning more and more about less and less We have reached the atomic scale This marks an inflection point The future of microscopy will be the pursuit of learning more and more about more and more 56

57 Ancestry of the Modern Atom Probe 57

58 We ve made progress: From Müller FEM FIM APFIM 58

59 To Commercial Atom Probes 1975 VG APFIM PoSAP 2016 LEAP 5000, EIKOS 59

60 D Atomic-Scale Tomography, an Achievable Vision January 26,