TRANSMISSION ELECTRON MICROSCOPY Danqi Wang Swagelok Center for Surface Analysis of Materials (SCSAM) Case Western Reserve University 1 OUTLINE SCSAM TEM Instrument Introduction Scanning TEM Imaging XEDS EELS TEM Bright-field/Dark-field Imaging High-resolution Imaging Diffraction Energy-filtered TEM Transmission Kikuchi Diffraction/ASTAR system Sample Preparation – Nanomill SCSAM TEM Instruments FEI Tecnai F30 (300 kV) Zeiss Libra 200EF (200 kV) TEM Sample Preparation Focused Ion Beam NanoMill Model 1040 Precision Ion Polishing System Twin Jet Electropolishing System FEI TECNAI F30 Operating at 300 kV Resolution Limit ≈ 0.17 nm High-resolution imaging 4 ZEISS LIBRA 200EF Operating at 80, 120, and 200 kV Energy Resolution < 0.5 eV Analytical chemical analysis 5 OUTLINE INTRODUCTION Resolving Power of Microscopes Transmission Electron Microscope Useful Signals Generated from Electron–Matter Interaction Major Contrast Mechanisms for imaging Mass thickness contrast, Diffraction contrast, Phase contrast (HRTEM). It is essential that specimens for TEM be extremely thin, i.e, a few tens of nms or less, so as for the energetic electron beam to penetrate and generate useful signals. 8 Modes of Imaging Scanning Microscopy Full Frame Imaging Scanning electron microscopy Scanning transmission electron microscopy Focused Ion Beam Source ↓ Object imaged ↓ Detector – image pixel by pixel Transmission electron microscopy Regular light microscopy X-ray imaging Visible light photography Source ↓ Object imaged ↓ Image forming lens ↓ Recording 2D media –– CCD, negative 9 What do can we learn? Structure Information Elastic scattering Morphology and microstructure. Crystallographic structure High Resolution Transmission Electron Microscopy Scheu et. al., Phil Mag A, 78(2) 1998, 439. Composition Inelastic scattering/XEDS Elemental composition Bonding state Electron Energy Loss Spectroscopy (EELS) 10 XEDS Elemental Mapping Solid Oxide Fuel Cell Purple –Zr; Yellow – LSM; Green – Mn. OUTLINE SCANNING TRANSMISSION ELECTRON MICROSCOPY (STEM) Imaging EDS EELS STEM Gold on Carbon film DF BF 13 Atomic Resolution STEM 20 nm Carburized Ferrite in 17-7 PH Stainless Steel 1 nm XEDS Elemental Mapping Solid Oxide Fuel Cell Purple –Zr; Yellow – LSM; Green – Mn. XEDS Line Scan in STEM Cu-Al2O3 Composite Si Ca 16 ELECTRON ENERGY-LOSS SPECTROSCOPY EELS Analysis- Valence State Grain-1 Grain-2 O-K edge results show the presence of precipitates in 2 valence states 18 Electron Spectroscopy Imaging (ESI) Elemental Mapping Ti – 452 eV N – 398 eV Oxygen map Ti map High Temperature MEMS Device Color Mix: Red:Ti, Green:O 19 Life Science Applications Dark-field STEM Image of Fe Deposit in a Erythroid Precursor Cell 20 XEDS Spectrum of Fe Deposit Grid 21 EELS Spectrum of Fe in Different Oxidation States Fe2+ FeCO3 (Siderite) Fe2+ + Fe3+ Fe3O4 (Magnetite) 707 eV OUTLINE TEM Bright-field/Dark-field Imaging Diffraction High-resolution Imaging Energy-filtered TEM Diffraction Imaging Full Frame Imaging TEM imaging system can be operated in two modes: diffraction mode (left), imaging mode (right). Shown here are simplified ray diagrams of both modes. 24 Bright-field and Dark-field Imaging in TEM BF DF DF 25 Bright-field vs Dark-field Imaging To identify grain size and distribution in the microstructure Nanocrystalline Al. Scale markers are 500 nm. 26 Bright-field vs Dark-field Imaging To identify a second phase in the microstructure Nitrided ferrite in 17-7 PH Stainless Steel High-resolution TEM (HRTEM) A HRTEM image of an interface between a Cu particle and alumina grain. Grain Boundary 28 Electron Diffraction Analyze the Lattice Spacing and Orientation 29 Convergentbeam electron diffraction (CBED) 3.620 Å ZA  HOLZ lines used for lattice parameter 3.620 Å determination 3.622 Å ZA  3.624 Å Austenitic stainless steel ZA  ZA  MEASURED SAMPLE THICKNESS FROM AUSTENITIC STAINLESS STEEL Simulated Simulated Experimental ENERGY-FILTERED TEM (EFTEM) IMAGING Zero-loss EFTEM images: Dislocations in 316 Stainless Steel after Low-temperature Gas-phase Carburization. Specimen prepared by electropolishing Un-Filtered Zero-loss Image 33 EFTEM Images from Co-Polymer Polystyrene and PVDF Zero loss Image 20 eV Loss Image* With F Without F * Energy of plasmon excitation for Fluorine OUTLINE TRANSMISSION KIKUCHI DIFFRACTION (TKD): STEM IN A SEM EBSD VS TKD Bulk material Surface information Tilted to 70° Interaction volume 30-50 nm Thin TEM foil Can resolve 3-5 nm -20° - 0° tilt Exiting surface structure 70° Tim Maitland and Scott Sitzman Scanning Microscopy for Nanotechnology, Springer René de Kloe - EDAX WHY USE TKD? Improved spatial resolution compared to EBSD: 30-50 nm ⇒ 3-5 nm. Actual resolution will depend on sample composition and preparation. Users that have a FIB system together with EDS/EBSD, can carry out this analysis at practically no extra cost. Carburized Low-alloy Steel (15 nm/step) XEDS OUTLINE ASTAR SYSTEM PRECESSION ELECTRON DIFFRACTION (PED) ADVANTAGES OF ASTAR TEM diffraction patterns easier to interpret Less sensitive to sample thickness variations More diffraction spots → higher precision measurements Automated analysis becomes possible INDEXING TEM DIFFRACTION PATTERNS Stereographic projection (cubic ) 111 Pre-calculated templates Angular step size ~1° ~ 3000 templates 001 1-11 Correlation index Acquired pattern ASTAR ORIENTATION MAPPING Similar results to SEM-EBSD but with much higher spatial resolution. Down to 1 nm with FEG! SEM image Deformed Ta6V EBSD map (20-100 nm step size) TEM map (1-30 nm step size) Al (9 nm) –TiN (1 nm) multilayer system Al Phase Map Orientation Map ASTAR system could both identify the phases and orientations. Note that the Al layers are finely twinned. ASTAR ORIENTATION MAPPING Quality Map Orientation Map 40 nm Gold nanoparticles OUTLINE TEM SAMPLE PREPARATION FISHIONE NANOMILL MODEL 1040 ADVANTAGES OF NANOMILL Low energy ion source (up to 2kV Ar) Removes amorphous and implanted layers AS-FIBBED TEM FOIL High-resolution TEM image of Si showing the effect of Ga implantation and surface amorphization on phase contrast imaging AFTER NANOMILLING Same specimen after Ga implantation and amorphization removal by the NanoMilling process SUMMARY TEM can provide information regarding to Structure Defects (dislocations, twins, etc.) Morphology Composition Valence state Orientation THANK YOU!