PLS-II s STXM and its application activities

Transcription

1 1 PLS-II s STXM and its application activities Hyun-Joon Shin Pohang Accelerator Laboratory, Pohang University of Science and Technology, Pohang, Korea shj001@postech.ac.kr

2 Two accelerators for x-rays... at Pohang... 2 East sea POSCO NCNT POSTECH RIST PLS - II 3.0 GeV 400 ma 34 beamlines 10.0 GeV 3 BLs (2 hard, 1 soft x-ray) PAL-XFEL (2016~present) Construction: 2011~2015 Pohang Light Source (1994~2010) Upgrade 2011 Pohang Light Source II (2012~ present)

3 X-rays techniques/ X-ray absorption spectroscopy (XAS) 3 photoelectrons: n (e) PES (XPS) scattering, diffraction: n (hn) XRD, XRS SAXS, WAXS x-rays: n(hn) transmittance: n (hn) XAS (XAFS), imaging photoemission, fluorescence: n (hn ) XES, XRF, XAS (XAFS) energy 2p 2s absorbance: n (hn) XAS (XAFS) vacuum level n = 2 PES: photoemission/ photoelectron spectroscopy XPS: X-ray photo-emission/-electron spectroscopy XRD: X-ray diffraction XRS: X-ray scattering SAXS: Small angle x-ray scattering WAXS: Wide angle x-ray scattering XAS: X-ray absorption XAFS: X-ray absorption fine structure XES: X-ray emission spectroscopy XRF: X-ray fluorescence XAS: X-ray absorption - probes unoccupied DOS 1s n = 1

4 X-ray absorption spectroscopy (XAS): practical application by soft x-rays... 4 O-TM-O Fe L edge W. C. Chueh et al, Sandia Report, Ti L edge (anatase) O K-edge 1.2 z 2, x 2 -y Absorbance (arb.) t 2g e g t 2g e g L 3 L 2 D. Y. Cho, J. Mater. Chem. C. 2013, 1, Photon Energy (ev) element, crystal structure, oxidation state, chemical states, magnetic moment, electronic structure,

5 Optoelectronic device K.J. Kim et al., Adv. Mater. 20, 3589 (2008) H. Lim, et al., ChemComm 47, 8608 (2011) 5 Si 2p Need of spectro-microscopy In 4d DMS Appl. Phys. A 78, 623 (2004) Graphene J. S. Kang, et al., Phys. Rev. Lett. (2005) I. Song et al., Angew. Chem. Int. Ed. 53, 1266 (2014) SPEM image W. Park et al., ACS Nano 8, 4961 (2014) PDP MoS 2 SEM image JJAP 44, 861 (2005) H. M. Jeong et al., Nano Lett. 11, 2472 (2011) I. S. Byun et al., NPG Asia Materials (2014) 6, e102 L 3 L 2 OLED 1.2 Absorbance (arb.) t 2g e g t 2g eg Kevlar (e) APL. 89, (2006), APL 93, (2008) S 2p C 1s, ev C 1s, ev Ti L edge Photon Energy (ev) Anatase TiO 2 Polymer PLED J. Chung et al., Org. Electron. 9, 869 (2008)

6 6 Scanning transmission x-ray microscopy (STXM) ; spectro-microscopy Scanning imaging mode focusing ZP OSA sample (scanning) Detector Monochromatic light STXM XAS schematic: improvement of focal power/ focusing lens... minimal variation of focal position... detectors for fast imaging... nice softwares... Spectroscopy and imaging with ~ tens of nm space resolution!!!

7 10A beamline for PLS-II (Pohang Light Source II) 7 Enough flux in wide energy range: ev Energy resolving power: E/DE > 2,000 X-ray source: EPU (control of polarization) Small virtual source size: ~ 10 um x 10 um High demagnification geometry: ~1000:1 EPU VIA-PGM Flux (ph/s/320 ma, 50 um x 50 um exit slit), R ~ 5000(G1000), 400 ev 1E13 G400-1st G400-3rd G1000-re-1st G1000-re-3rd 1E12 1E11 1E Energy (ev) E/DE ~ ~ 400 ev

8 STXM hardware: ~ same model as those of CLS & ALS,..., Bruker Ltd. 8 Zone plate moves as x-ray energy changes (OSA (x,y) is fixed) Accurate and fast scanning stages: laser interferometry for fast and accurate position monitoring and feedback Detector: PMTube (efficient and fast) & Bruker Ltd.

9 PLS-II: Hardware near sample position 9 easy to operate easy to find ROI within sample and best focus easy and fast sample loading (5 samples in a holder) sample holder: upto 5 samples 1~10 mm Detector ZP OSA sample f (ZP sample) = D Dr / l short working distance (OSA sample) sample needs to be thin!!!

10 PLS-II: single image acquisition acquisition time: ~ tens of second ~ minutes 10 Field of view : 6 um x 6 um (250 x 250 points)

11 PLS-II: stack images acquisition... acquisition time: ~ tens of minute ~ hours 11

12 PLS-II: performance (basic) 12 Space resolution: 25 ~ 50 nm (17 nm features are discriminated with a dr n = 25 nm ZP) Energy range: 150 1,600 ev sample scan range: < 12 mm (h) x 8 mm (v) Spectral resolving power (E/DE): ~ 5,000 detection time per pixel: > ~ 0.2 ms ZP: dr n = 25 nm electronic biasing, electromagnet field application: ok Absorbance (arb.) Photon Energy (ev)

13 STXM: performance (application) 13 rotation, cooling, permanent magnetic field application : not optimized...

14 PLS-II STXM applications: Enhancement of Catalytic Activity of N-doped nanorods, TM Doped TiO2 Nanoparticles, NTR-150 NTR-60 Ti 3+ defect structure! (a) anatase TiO 2, 5 mole % TM-TiO 2 : (b) Cr-TiO 2, (c) Mn-TiO 2, (d) Fe-TiO 2, (e) Co-TiO 2, (f) Ni-TiO 2. Y. J. Hwang, H. Lee (Sookmyung Univ.)

15 Magnetic domain 15 (0.47nm Co/ 0.77nm Pt) 15 Left Right Difference aligned striped magnetic domain 500 nm in-plane, 2kOe D. H. Kim (Chungbuk Univ.)

16 16 nano & bio O K-edge Fe L-edge 10 um unpublished data; J. -K. Kim (Cath. Univ.)

17 nano & bio: cells between SiNx windows (scale bar: 5 um) 17 S. U. Yu et al, Nanoscale, in press

18 Issues: thick samples better spatial resolution??? 18 ZP OSA Scintillator/ PM tube CCD: Ptychography soft x-rays sample scanning Soft X-Ray Fluorescene (SXRF) schematic:

19 STXM; ptychography to improve space resolution 19 Increase of N.A. : ~ 5 nm space resolution is possible D. Shapiro, T. Tyliszczak et al., Nat. Photonics (2014). Nat. Mater. (2014). Nano Lett. (2015). Coherent soft x-ray 1.5 nm line resolved 3 nm line 50 nm

20 Photos of Ptychography setup and data example... Andor CCD 20 Beam size at sample = 50, 70, ~1000 nm Sample to CCD distance = ~80 mm Andor CCD Linear scale images (20 ms, 200 ms)

21 ZP OSA sample Soft x-ray fluorescence (soft-xrf) measurement setup 21 A. Gianoncelli,et al., NIMA 608 (1), 195. X-ray ZP holder PMT MCA detector Low fluorescence yields for soft X-rays!! Multi element information in a single scan... Acquisition time: ms/pixel for imaging...

22 Soft-XRF measurement on FeO x particles 22 Absorption and Fe and O XRF images obtained at 710 ev absorption Fe O FOV: 8 um x 8 um Fe L-edge XRF spectrum (Fe fluorescence yield) Intensity (Arb. Unit) Photon Energy (ev) Slower in measuring speed than that of normal transmission measurement mode..., but can probe thicker samples that can not be measured by transmission mode!!!

23 Soft-xrf measurement on NCM particles Li,Ni,Co,MnO 2 Ni,Co,MnO 2 STXM and xrf images obtained at 854 ev 23 absorption Ni Co Mn O NEXAFS Spectra measured by soft-xrf: Ni, Co, Mn, and O Ni L edge Co L edge XRF spectra measured at 854 and 848 ev 13 Ni Intensity (Arb. Unit) Intensity (Arb. Unit) Intensity (Arb. Unit) O Mn Channel number Co Intensity (Arb. Unit) Photon Energy (ev) Mn L edge L 3 4+ L 2 Intensity (Arb. Unit) Photon Energy (ev) 1.2 O K edge Photon Energy (ev) Photon Energy (ev)

24 24 Conclusions PLS-II STXM (scanning transmission x-ray microscopy) is running OK for normal applications (2 D imaging). ~ 30 nm space resolution/ ev energy range. Soft XRF probing setup has been added. Ptychography setup has been added. in-situ electrochemical cell is under development...

25 Acknowledgements 25 Dr. N. Kim, S. Lee, H. Kim: PLS members. Dr. T. Tyliszczak (ALS) Y. J. Hwang, Prof. H. Lee (Sookmyung Univ.) Prof. D. H. Kim (Chungbuk Univ.) M. Kim, Prof. B. Kim (POSTECH) L. Zhou, Prof. L. Zhang, Prof. Zijuan Xi, (SSRF/ SIAP/ CAS) Thank you!