Transmission Electron Microscopy Design Fall 2023 Ondrej L. Shanel, Ph.D. CPO elements overview CPO Elements Electrostatic 𝐅 = βˆ’π‘’π„ βˆ’ 𝑒𝐯 Γ— 𝐁 Magnetic Elements PrismMultipolesLenses CavityMultipolesLenses Deflectors Stigmators MultiPoles Hexapoles Octupoles Deflectors Stigmators MultiPoles Hexapoles Octupoles Wien Filter Dodecapoles Apertures TEM Principle – Functional Decomposition TEM mode Magnification of illuminated sample to a camera Electron Beam Creation Creating illumination of the sample Providing interaction e- beam/sample interaction/detection space Transfer of created image Signal Detection STEM mode Scanning with electron probe over sample and imaging its diffraction plane to a detector Enable e-Beam Enable Detection Enable Sample interction Creating paralell illumination of the sample Magnification of created image (up to 1Mx) Detection on Camera Creating the smallest eprobem and scanning over of the sample Magnification back focal plane Detection on Detector Minimize disturbances Signal Visualization TEM Principle – Design Schematic β€’ TEM mode – Image of an illuminated sample is magnified onto a camera β€’ STEM Mode - Focused Beam scanning over the sample β†’ processed signal creates an image Camer Data Storage Projection Chamber Diffraction Lens Condenser Lens 2 Condenser Lens 1 Gun Deflectors Accelerator Condensor aperture Image Deflectors/Stigmator s Sample/ Sample holder Sample stage Objective lens Selective Area/Diffraction aperture Intermediate Lens Projective Lens 1+2 Condensor Deflectors/Stigmator s TEM Standard Parameters Parameter Value Accelerating voltage [kV] 30-300 Beam current [nA] 0.01-100 Chamber Vacuum 1e-5 – 1e-8 Resolution [nm] Cs corrected/uncorr ~0.05/~0.1 Sample size [mm3] 3.05^2 * 1E-5 - 1E-4 Projection Chamber Diffraction Lens Condenser Lens 2 Condenser Lens 1 Gun Deflectors Accelerator Condensor aperture Image Deflectors/Stigmator s Sample/ Sample holder Objective lens Selective Area/Diffraction aperture Intermediate Lens Projective Lens 1+2 Condensor Deflectors/Stigmator s Camer Stage TEM and SEM comparison sample Detector Chamber Objective lens Condenser Lens 2 Condenser Lens 1 Gun Deflectors Accelerator Final aperture Deflectors/Stigmator s TEM Value Parameter SEM Value 30-300 Accelerating voltage [kV] 0.5-30 0.01-100 Beam current [nA] 0.01-100 1e-5 – 1e-8 Chamber Vacuum 1e-3 – 1e-6 ~0.05/~0.1 Resolution [nm] ~0.5 3.05^2 * 1E-5 - 1E-4 Sample size [mm3] 90x90x20 Camera Projection Chamber Diffraction Lens Condenser Lens 2 Condenser Lens 1 Gun Deflectors Accelerator Condensor aperture Image Deflectors/Stigmators Objective lens Selective Area/Diffraction aperture Intermediate Lens Projective Lens 1+2 TEM Schematic SEM Schematic TEM modes TEM - Imaging TEM Diffraction STEM Imaging Back focal plane Diffraction lens Intermediate lens P1 lens P2 lens Sample Upper part of Objective lens Lower part of Objective lens Condensor 2 Gun Filament Sample Condensor 1 Camera/Detector Sample Condensor aperture Incoming wave (assumed parallel wave): πœ“0 Τ¦π‘Ÿ = 1 Sample-electron interaction: πœ“out Τ¦π‘Ÿ = 1 + Ο΅ Τ¦π‘Ÿ + iΟ† Τ¦π‘Ÿ Image in back focal plane: πœ“bfp Τ¦π‘ž = Ξ΄ Τ¦π‘ž + E Τ¦π‘ž + iΞ¦ Τ¦π‘ž Optics Aberration impact: β†’ Ο‡ Τ¦π‘ž, ΞΈ = Οƒn Οƒm 1 n+1 cos mΞΈ βˆ’ ΞΈn,m Cn,mΞ»n+1 Τ¦π‘žn+1 β†’ Ο‡ Τ¦π‘ž = 1 2 C1,0Ξ»2 Τ¦π‘ž2 + 1 4 C3,0Ξ»4 Τ¦π‘ž4 W(Τ¦π‘ž) = 2Ο€ Ξ» Ο‡(Τ¦π‘ž) πœ“bfp,ab Τ¦π‘ž = Ξ΄ Τ¦π‘ž + E Τ¦π‘ž eβˆ’iW π‘ž + iΞ¦ Τ¦π‘ž eβˆ’iW π‘ž πœ“det Τ¦π‘Ÿβ€² = M β‹… IFT πœ“bfp,ab Τ¦π‘ž/𝑀 Intenzita Τ¦π‘žβ€² = FT Intenzita Τ¦π‘Ÿβ€² = FT πœ“det Τ¦π‘Ÿβ€² πœ“det Τ¦π‘Ÿβ€² Contrast Transfer Function (CTF) CTF Τ¦π‘žβ€² =𝐸t π‘žβ€² 𝐸s Τ¦π‘žβ€² 𝐸d Τ¦π‘žβ€² 𝐸u Τ¦π‘žβ€² β‹… Intenzita Τ¦π‘žβ€² ∈ βˆ’1; 1 where 𝐸t π‘žβ€² - temporal coherency, 𝐸s Τ¦π‘žβ€² - spatial coherency, 𝐸d Τ¦π‘žβ€² - drift impact, 𝐸u Τ¦π‘žβ€² - vibration dumping TEM – PΕ™enosovΓ‘ funkce kontrastu - intenzita Point-to-point resolution Point-to-point resolution Information limitInformation limit Scherzer defocus – optimal for point-to-point resolution: Where 𝐢𝑠 is spherical aberrations, πœ† – electron wavelenght Spatial abberation envelope Chromatic abberation envelope Δ𝑓 = βˆ’1.2 𝐢𝑠 πœ† Tecnai T20 Thermionic Tecnai T20 FEG TEM imaging - CTF TEM imaging – Defocus impact STEM - Spot size calculation β€’ First order calculation where 𝜢 – is beam convergent semiangel, Cs – spherical aberration, Cc – chromatical aberration, H – stability factor, I - beam current, 𝝀 – electron wavelenght, Br – e-source brightness, 𝑼 - acceleration voltage, M – demagnification of source, 𝒅 𝟎 - original source size where πš«π‘° - objective current instability, πš«π‘¬ – energy source spread, πš«π‘Ό – instability of accelerating voltage β€’ Better approaches : Barthel, Kruit, Optics 1999 β€’ Absolute accuracy β†’ Wave calculation 𝒅 πŸ“πŸŽ = (𝟎. πŸ’πŸ‘π‘ͺ 𝒔 𝜢 πŸ‘) 𝟐+(π‘ͺ 𝒄 πœΆπ‘―) 𝟐 + ( 𝑰 π…πœΆ 𝑩𝒓𝑼 ) 𝟐 + (M 𝒅 𝟎) 𝟐+ ( 𝟎.πŸ”πŸ‘π€ 𝜢 ) 𝟐, sample 𝑯 = πŸ’( πš«π‘° 𝑰 ) 𝟐+( πš«π‘¬ 𝑼 ) 𝟐+( πš«π‘Ό 𝑼 ) 𝟐, Condensor aperture Condensor Deflectors/Stigmator s Sample/ Sample holder Objective lens Ξ± Image Deflectors/Stigmator Spot size calculation HT = 200kV, Cs=1.1mm,Cc=1.6mm, Ξ”E = 0.8eV, I = 20pA, H = 4e-6 1,00E-16 1,00E-15 1,00E-14 1,00E-13 1,00E-12 1,00E-11 1,00E-10 1,00E-09 1,00E-08 0,1 1 10 Diameterspotsized50[m] Convergent semiangle [mrad] Spot size dependancy on convergent semiangle of beam Cs addition Cc addition Brightness addition Total abberation squared approache Total acc Barth en Kruit Electron sources β€’ Using Thermionic, FEG and C-FEG sources E-source Thermoemission Schottky FEG C-FEG Cathode W LaB6/CeB6 W/ZrO Cold FEG Work function[eV] 4.5 2.4 2.7 4.5 Operating Temp [K] 2700 1700 1750 300 Virtual source size[Β΅m] 50 10 ~ 0.015 ~ 0.005 Energy spread [eV] 2-3 1.5 0.6-0.9 0.2-0.3 Operating vacuum [Pa] 10-3 10-4-10-5 10-6-10-7 10-8-10-9 Max beam current [Β΅A] 1- 3 1-3 0.3 0.1 Lifetime [h] 40-100 500-1000 >2000 >2000 Red. brightness [A/m2srΒ·eV] (1-3)*104 (3-10)*105 (0.2-2)*108 (0.5-5)*108 Accelerators/Emission Chamber β€’ Using Signle- and Two-aperture Electrostatic lenses with Multi Anodes design High Tension Insulation pad + - Anode Vacuum <1E-3Pa Tungsten harpin Emission chamber High Tension Insulation pad + - Anode Gun lens Vacuum <1E-5Pa Tungsten tip Type Single-aperture (5 - 120kV) Two-aperture + MultiCathodes E-source Thermionic FEG, C-FEG Pros Cheap Less aberrations, higher HT possible Camer a Anodes array Camer a Deflectors β€’ Function β€’ Centering optical elements – Gun, Beam, Image β€’ Image/Diffraction Shift, Tilt – Beam and Image β€’ Gun optimization – Gun β€’ Scanning/Descanning – Beam/Image β€’ Magnetic β€’ Gun deflection coils – centering e-beam from Acc to Condensor lenses β€’ Beam deflection coils β€’ DC - centering e-beam from Condensor lenses to Objective lens β€’ AC – Scanning over sample β€’ Image deflection coils β€’ DC - centering e-beam from Condensor lenses to Objective lens β€’ AC – Scanning over sample β€’ Driven by Optical Boards β€’ Signal to coils – AC (trending to DC directly) β€’ Processing DC β€’ Noise of Optical Boards translates to image instability or resolution lost (H) Optical boards AC/DC Gun Deflectors Image Deflectors/Stigmator s Condensor Deflectors/Stigmator s Deflectors – Beam Tilt and Beam Shift – Pivot Points β€’ Combinatin of two deflection coils pair to create independent beam Tilt and Shift Beam Tilt sample Ξ± Ξ± lens Beam Shift sample 2Ξ± Ξ± lens lens Beam Shift Pivot Point Beam Tilt Pivot Point Camer a Lenses β€’ Function β€’ Condensor – 2 or 3 condenser system, Make a sample illumination (TEM/STEM) β€’ Projector – 4 lenses system - Magnify a sample image or diffraction, providing non-rotating imaging β€’ Magnetic β€’ Condensor, Objective (immerse) and projector lenses β€’ Water cooling β€’ Electrostatic β€’ Accelerator only β€’ Driven by Optical Boards β€’ Signal to coils DC β€’ Feedback loops for coils stability β€’ Noise of Optical Boards translates to image instability or resolution lost (H) Optical boards AC/DC Condensor 1 + 2 Projector 1+2 Objective lens Diffraction lens Intermediate lens Stigmators Optical boards AC/DC β€’ Magnetic β€’ Objective or Gun stigmators β€’ Correcting 2-fold and 3-fold astigmatism β€’ Driven by Optical Boards β€’ Signal to coils – AC (trending to DC directly) β€’ Processing DC β€’ Noise of Optical Boards translates to image instability or resolution lost (H) Camer a Image Deflectors/Stigmator s Condensor Deflectors/Stigmator s Correctors Corrector boards AC/DC β€’ Spherical Correctors – Image or Probe β€’ Hexapole based – CEOS supplier β†’ Thermo Fisher Scientific, Jeol, Hitachi β€’ Octupole based - Nion β€’ Chromatic – Only Image β€’ Octupole based – CEOS – Thermo Fisher Scientific, Jeol β€’ Driven by Optical Boards β€’ Most stable boards (<0.1 ppm) β€’ AC drivers β€’ Processing DC β€’ Noise of Optical Boards translates to image instability or resolution lost (H) Camer Corrector boards AC/DC Probe corrector Image corrector Detectors β€’ Projection chamber area β€’ TEM – Cameras – CMOS, Hybrid, CCD β€’ STEM – HAADF, BF, DF, Pixelized β€’ Sample area β€’ EDS β€’ CL β€’ SE – SDD based β€’ BSE - SDD based β€’ Driven by Optical Boards β€’ Signals – AC/DC (trending to DC directly) β€’ Processing DC β€’ Noise of Optical Boards translates to image instability β€’ Sync with Scanning Deflection coils Detect ors boards AC/DC Camer a Detector in Projection Chamber Infrastructure I β€’ Vacuum β€’ Levels β€’ Chamber 1e-4Pa β€’ Accelerator 1e-4 Thermionic, 1e-9 CFEG β€’ Pumps β€’ TMP, IGP, NEG, Scroll, Diffusion, Rotary β€’ Valve β€’ Using to create separate vacuum volumes β€’ Linening Tubes β€’ Using to keep vacuum for electron trajectory β€’ Non-magnetic materials (glass, stainless steel) β€’ Stage β€’ 4 Axis stage, 5th axis done via holders β€’ Resolution 1-10nm β€’ Drift 0.5-1 nm/min β€’ Ultrasonic, Piezo design Vacuum pump Vacuum pump Vacuum pump Pre- Vacuum pump Camer a Stage Infrastructure II β€’ Chamber β€’ Vacuum level 1e-3 – 1e-6 β€’ Support column, stage, detectors β€’ Shielding of sample area from any disturbance (EMI) β€’ Frame, Dumping, Enclosure β€’ Supporting Chamber and the whole infrastructure β€’ Dumping (typically 1/10 of required resolution) β€’ Rubber pods β€’ Air dumpers β€’ Active dumping β€’ Sound and EMI enclosure – suppressing EMI and sound influence Dumping system Camer a Enclosure Electronics - Boards β€’ Optical Boards β€’ Signals – AC/DC (trending to DC directly) β€’ Processing DC β€’ Noise of Optical Boards translates to image instability β€’ Lens β€’ Typical currents 1-12A or 10-1000V β€’ Stability 0.5-10 ppm β€’ Deflectors/Stigmators β€’ Typical currents 10-100mA or 1-10V β€’ Stability 1-10 ppm β€’ Correctors β€’ Typical currents 10-1000mA or 1-100V β€’ Stability <0.1 ppm β€’ Detectors Boards β€’ Signals – AC/DC (trending to DC directly) β€’ Processing DC β€’ Depending on specific Detectors needs β€’ Infrastructure Boards β€’ Vacuum pump, vavles SW IOM FW DC/AC FW DC/AC FW DC/AC HEP Behavior layer Apps Apps Apps UI Apps UI HW HW HW TEM examples Name/Brand LVEM25E/ Delong UltraSTEM 200/Nion CryoArm 300 II /Jeol Tensor/Tescan HF5000/Hitachi Krios/TFS Resolution [nm/kV] <1 <0.08/200