Fundamentals of Fundamentals of X X-ray micr ay microscop oscopy y and spectr and spectro-micr microscop oscopy May 8 th 2018 ICTP School on Synchrotron and FEL Applications Maya Ma a Ki Kiskin inov ova
An Invitation to Enter a New Field of Physics & Material Science There's Plenty of Room at the Bottom Richard P. Feynman - 1959!!! ‘NANO’ by natu ture re, desi sign gn or r exte terna rnally lly- induced ced ch chan ange ges s • Materials properties vary at various depth and length scales: atomic, nano or meso dimensions. • Structure and chemical composition uually is different at the surface and in the bulk. • New properties expected with decreasing the dimensions stepping into nanoworld. What we NEED: Chemical sensitivity, spatial resolution & morphology & structure, varying probing depth, temporal resolution when possible. Majority of these methods are based on interaction of the matter with photon, electron or ion radiation . May 8 th 2018 ICTP School on Synchrotron and FEL Applications Maya Ma a Ki Kiskin inov ova
Why Microscopy needs Synchrotrons % coherent tunable High Brightness Accelerated electrons radiate electromagnetic n = c/ l energy in very wide range polarized Synchrotron light advantages Very bright, wave-length tunable (cross sections and atomic edges), multiply polarized (dichroic effects, bonding orientation), partly coherent. Great variety of spectroscopies - elemental, chemical, magnetic information. Variety of imaging contrasts based on photon absorption, scattering or spectroscopic feature. Higher penetration power compared to charged particles - less sensible to sample environment . May 8 th 2018 ICTP School on Synchrotron and FEL Applications Ma Maya a Ki Kiskin inov ova
All methods using SR are based on the interaction of photons with the matter and find applications in all domains of science and technology l l q nul d l X-ray Absorption Spectroscopy (XAS) and InfraRed Absorption Spectroscopy q (IRAS) l q d X-ray Photoelectron Spectroscopy (XPS) Auger Electron Spectroscopy (AES) and XAS Fluorescence Spectroscopy (FS), RXES and XAS May 8 th 2018 ICTP School on Synchrotron and FEL Applications Maya Ma a Ki Kiskin inov ova
Spectroscopies @ synchrotron light sources: XPS-AES, XES, XAS Photoelectric effect & de-excitation processes = chemical specific spectroscopies E h n is constant & energy filtering of emitted h n photons and electrons AES out FS and RXES FS XPS PES+AES PES=XPS+AES XAS: based on absorption coefficient m = f(h n -E core ) and resonant electronic transitions governed by selection rules. e - and h n detection. E h n scanned May 8 th 2018 ICTP School on Synchrotron and FEL Applications Maya Ma a Ki Kiskin inov ova
X-ray PhotoElectron Spectroscopy detects the electron emission, known as XPS, PES or ESCA (Electron Spectroscopy for Chemical Analysis) . Incident X-ray Conduction Band Conduction Band Fermi Fermi Level Level Valence Band Valence Band 2p L2,L3 2p L2,L3 2s L1 2s L1 1s K 1s K XPS spectral lines are identified by KLL Auger electron emitted to the shell from which the electron conserve energy released. was ejected (1s, 2s, 2p, etc.). The KE of the emitted Auger The ejected photoelectron has electron is: KE=E(K)-E(L2)-E(L3) . kinetic energy: KE=hv-BE-f ‘Chemical shifts’ due to chemical bond in solid state or different coordination of emitting atom. May 8 th 2018 ICTP School on Synchrotron and FEL Applications Maya Ma a Ki Kiskin inov ova
Sampling depths: depend on the detected signal (electrons or photons) Fluorescence emission (XAS and FS): TEY& Auger electron emission (XAS), Probe depth > 100 nm = f(E ph , matrix) core&valence PES: Probe depth 1- 10 nm FS X- ray transmission: ‘bulk’ May 8 th 2018 ICTP School on Synchrotron and FEL Applications Ma Maya a Ki Kiskin inov ova
Microscopy Approaches : X-ray or electron optics; X-ray or electron detection XRF, XPS, XAS = elemental and chemical information; X-ray transmission and scattering = morphology; Topology – electron emission Scanning X-ray Microscopy Transmission X-ray Microscopy X-ray PhotoElectron Emission SXM (SPEM, STXM) SPEM TXM Microscopy (XPEEM) Lateral resolution using Lateral resolution provided by photon optics electron optics May 8 th 2018 ICTP School on Synchrotron and FEL Applications Maya Ma a Ki Kiskin inov ova
X-ray focusing optics: zone plates, mirrors, capillaries KP-B mirrors each focusing in one direction: soft & hard: ~ 1000 nm Soft & hard x-rays! Zone Plate optics: from ~ 200 to ~ XFS,XPS, achromatic focal point, easy 10000 eV XANES energy tunability, comfortable Monochromatic: working distance Resolution achieved 15 nm in Resolution ≤ 100 nm transmission Capillary: multiple reflection Refractive lenses concentrator Normal incidence: spherical mirrors with multilayer interference coating (Schwarzschild Objective) Hard x-rays ~ 4-70 keV Monochromatic, good for E < 100eV Resolution: > 1000 nm Hard x-rays ~ 8-18 keV Resolution: best ~ 100 nm Resolution: > 3000 nm May 8 th 2018 ICTP School on Synchrotron and FEL Applications Maya Ma a Ki Kiskin inov ova
Zone plate : circular diffraction grating of N lines with radially decreasing line width operating in transmission dr N OSA m=0 1 2 t 3 f -1 f 1 f -2 f -3 f 3 f 2 D f m = D.dr/ l m Important parameters: Finest zone width, dr N (10-100 nm) - determines the Rayleigh resolution (microprobe size) t =0.61 l /( q ) =1.22 r N Diameter, D (50-250 m m) determines the focal distance f. Efficiency % of diffracted x-rays: 10-40% (4-25%) Monochromaticity required: l /d l ≥ N (increases with dr and D). May 8 th 2018 ICTP School on Synchrotron and FEL Applications Maya Ma a Ki Kiskin inov ova
X-ray transmission microscope (TXM-FFIM) Full-field X-ray imaging or “direct” X-ray image acquisition can be considered CCD camera as an optical analog to visible light transmission microscope. Günther Schmahl, 1st experiment DESY 1976 Objective ZP to magnify the image Aperture: onto the detector removes (i) unwanted diffraction orders and straylight, and serves (ii) with condenser as monochromator X-ray light from a Specimen Synchrotron or environment: to be Lab light adapted to application source Condenser illuminating the object field Resolution achieved better than 15 nm. May 8 th 2018 ICTP School on Synchrotron and FEL Applications Maya Ma a Ki Kiskin inov ova
Spectro-microscopy (XANES) with TXM-FFIM: requires collection of a set of images at different photon energy Study dealing with genetic determinism of h n immobilization induced bone loss with the FFIM at ID21, ESRF, France (Ca XANES) M.Salome et al. 1.1 2mm 1 0.9 0.8 Absorption (arb.) 0.7 0.6 0.5 0.4 0.3 0.2 Trabecular bone of a mouse femur 4000 4020 4040 4060 4080 4100 Energy (eV) sample (10µm thick); Image field is 27 x 21 µm 2 Hydroxy-apatite spectrum recovered from a stack of 200 images May 8 th 2018 ICTP School on Synchrotron and FEL Applications Maya Ma a Ki Kiskin inov ova
Cryogenic 3D imaging of biological cells May 8 th 2018 ICTP School on Synchrotron and FEL Applications Ma Maya a Ki Kiskin inov ova
Following dynamic processes during temperature treatment, applying magnetic/electric field or pumping with optical lasers X Fe38Rh62 nanoparticles XAS-XMCD X-Ray Magnetic Circular Dichroism May 8 th 2018 ICTP School on Synchrotron and FEL Applications Ma Maya a Ki Kiskin inov ova
X-ray Scanning Microscopy: uses focusing x-ray optics (preferred zone plates) Imaging in Transmission & Emission + Nano-micro spot spectroscopy Can use all detection Janos Kirz, 1st operating STXM 1983 modes! SPEM 1990, STXM+XRF 1995 Resolution achieved better than 25 nm in transmission. e - or x-ray detectors incl. spectroscopy Image contrast Density, thickness, morphology (incl. phase Microspectroscopy: contrast and ptychography); μ - XPS, μ - XANES or μ -XES (XRF) from selected Element presence and concentration; spots - detailed chemical and electronic Chemical state, band-bending, charging; structure of coexisting micro-phases. Magnetic spin or bond orientation. May 8 th 2018 ICTP School on Synchrotron and FEL Applications Maya Ma a Ki Kiskin inov ova
SXM: contrast based on photon detection Bulk sensitive COMPLEMENTARY: transmission & XRF + XANES Specimen Segmented detector Integrating detector X-ray Scattering: or CCD camera IS X-ray Absorption (photodiode) is not morphology sensitive to scattering sensitive to scattering • Density • Phase contrast – phase change encoded by refracrive index, . • Chemical-magnetic contrast: XAS • Ptychography The number of photons absorbed within thickness x is given as number N of photons penetrating to depth x, times the number n of absorbers per unit volume and the absorption cross section σ : dN/dx = – Nn σ or N = N 0 exp( – n σ x). May 8 th 2018 ICTP School on Synchrotron and FEL Applications Maya Ma a Ki Kiskin inov ova
S imultaneous acquisition of absorption and phase-sensitive X-ray transmitted signals & XRF Prim. Na Mg C O Absorption Diff. phase contrast 10 m m Mg Na Epatocytes from human liver May 8 th 2018 ICTP School on Synchrotron and FEL Applications Maya Ma a Ki Kiskin inov ova
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