Fundamentals of Fundamentals of X X-ray micr ay microscop oscopy - PowerPoint PPT Presentation

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