Development and application for X-ray excited optical luminescence (XEOL) technology at STXM beamline of SSRF

Transcription

1 Development and application for X-ray excited optical luminescence (XEOL) technology at STXM beamline of SSRF

2 Content Introduction to XEOL Application of XEOL Development and Application of XEOL in STXM Beamline at SSRF XANES-XEOL Spectroscopy detection Time-Resolved XEOL detection

3 Introduction to XEOL an X-ray photon in, optical photon out technique synchrotron radiation Ultraviolet-visible-near infrared ( nm) The physical process of XEOL

4 Main application fields of XEOL XEOL study object Light emitters Semiconductor light emitting material Organic Light-emitting Diodes (OLED) Scintillator Fluorescent dyes

5 The advantage of XEOL Origin of luminescence Kinetic process of luminescence XANES- XEOL Observation of surface/defect states; Depth distribution of near surface defects XANES- TRXEOL Effect of morphology, size and structure on Luminescence Properties Luminescence decay time

6 Energy domain XEOL: specific excitation energy 2D XANES-XEOL: Tuning excitation energy to a particular absorption edge of an element Spatial resolved XEOL Time domain (Time-Resolved XEOL) Luminescence Lifetime Time-gated XEOL: Detect XEOL spectra under different time gates TRXEOL Imaging The development of XEOL Energy domain + Time domain Time-gated 2D XANES-XEOL: 2D XANES-XEOL detection under different time gates

7 Energy domain The application of XEOL Study on luminescence mechanism of porous silicon Results showed that the luminescence from porous silicon does not derive from siloxane, and thus suggest that the quantum-confinement model seems to provide the only viable explanation. T. K. Sham et al., Nature, 363, (1993)

8 The application of XEOL 2D XAFS-XEOL Mapping of Ga 1-x Zn x N 1-x O x Nanostructured Solid Solutions The luminescence exhibits a single peak with a maximum at 630 nm ( 2 ev). This energy is too small and the width is too broad for the NBG emission. It is attributed to emission from defects. M. J. Ward et al., J. Phys. Chem. C 2011, 115,

9 The application of XEOL Origin of luminescence from ZnO/CdS core/shell nanowire arrays Combining XANES and XEOL, it is concluded that the UV luminescence is the near band gap emission (BGE) of ZnO; the green luminescence comes from both the BGE of CdS and defect emission (DE, zinc vacancies) of ZnO; the IR luminescence is attributed to the DE (bulk defect related to the S site) of CdS; ZnS contributes little to the luminescence of the ZnO/CdS NW arrays. Z.Q. Wang et al., Nanoscale, 2014; 6(16): 9783

10 The application of XEOL Luminescence of ZnO Nanostructures XEOL of ZnO nanostructures shows noticeable structure-dependent luminescence: ZnO nanowire has very strong green emission and relatively weak UV near band edge emission, while perfect single crystals of nanoneedles only show a UV near band edge emission. The strong green light emission is attributed to the defect involving an oxygen vacancy. X. H. Sun, et al., J. Phys. Chem. B, 2005, 109:

11 The application of XEOL Optical properties of silicon nanowires These chemical-and morphology-dependent luminescence are attributable to the emission from the encapsulating silicon oxide, the quantum-confined silicon crystallites of various sizes embedded in the oxide layer, and the silicon-silicon oxide interface. Both XEOL and XES show that the surface oxide plays a significant role in the electronic structure and optical properties of SiNW. T. K. Sham et al., PHYSICAL REVIEW B 70, (2004)

12 The application of XEOL Studies of fluorescein isothiocyanate (FITC) and FITC-labeled proteins The implication is that XEOL is excitation channel specific and that it can be used as a powerful tool in studying the optical properties of biomolecules. P. G. Kim et al., Chemical Physics Letters, 2004, 392:44 49.

13 The application of XEOL Energy domain + Time domain Time-resolved x-ray-excited optical luminescence characterization of onedimensional Si CdSe heterostructures The time-resolved luminescence spectrum consists of a short-lifetime band centered at 637 nm and a long-lived band at 530 nm. By monitoring the intensities of these bands following excitation of a Se 2p3/2 electron, the authors are able to show that the 637 nm band is associated with the CdSe sheath while the 530 nm band emanates from the Si core R. A. Rosenberg et al., Appl. Phys. Lett. 89, , 2006

14 The application of XEOL Time-resolved x-ray excited optical luminescence from SnO 2 nanoribbons: Direct evidence for the origin of the blue luminescence and the role of surface states The yellow-green luminescence has a long lifetime while the blue luminescence a short one. The luminescence is attributed to the radiative decay of trapped electrons in oxygen vacancies just below the conduction band and electrons in the conduction band to intrinsic surface states in the band gap. X. T. Zhou et al., Appl. Phys. Lett. 89, (2006)

15 The application of XEOL The lifetime of the optical decay of XEOL (TRXEOL) from GZNO has been investigated using an optical streak camera (OSC) with a fast sweep. Figure. (a) 5 ns streak image of XEOL ( nm) from GZNO excited at 550 ev. (b) XEOL decay lifetime taken from blue (400 nm) and red (550 nm) windows of the streak image respectively. (c) Fast and slow XEOL taken from ns and ns time windows, respectively. (d) XEOL of GZNO recorded using un-gated, ns, ns, and ns time windows with maximum intensity normalized to unity. T. Z. Regier et al., AIP Conf. Proc. 2010, 1234, 838.

16 Development and Application of XEOL in STXM Beamline at SSRF XANES-XEOL Spectroscopy detection ZnO sample

17 Development and Application of XEOL in STXM Beamline at SSRF Time-Resolved XEOL detection ZnO sample