X-ray Photoelectron Spectroscopy for Chemical …

1 X-ray Photoelectron Spectroscopy for Chemical Analysis J. ANIBAL BOSCOBOINIK MSAE E8235x: Selected Topics In Materials Science. Columbia University, Oct 14th 2015 Ambient Pressure X-ray Photoelectron Spectroscopy (AP-XPS) endstation at NSLS-II Photon Energy: 250 eV to 2000 eV Pressures up to 5 Torr. Temperatures up to 900 C Capillary tube into Mass Spec. AP-XPS End Station BS Chemistry San Luis PhD Chemistry Wisconsin PostDoc Chemical Physics Berlin Materials Scientist New York Who is this guy? Columbia University, Oct 14th 2015. Anibal Boscoboinik - CFN, Brookhaven Lab 3 Anibal Boscoboinik - CFN, Brookhaven Lab Our Playground Columbia University, Oct 14th 2015.

2 Anibal Boscoboinik - CFN, Brookhaven Lab 4 What will you learn today? X-ray Photoelectron Spectroscopy (XPS) Ambient Pressure XPS. What you can do with it. Some examples. Columbia University, Oct 14th 2015. Anibal Boscoboinik - CFN, Brookhaven Lab 5 X-ray Photoelectron Spectroscopy Background Photoelectric Effect The photoelectric effect is the observation that many metals emit electrons when light shines upon them. (Hertz 1887) = In 1905 Albert Einstein published a paper that explained experimental data from the photoelectric effect as being the result of light energy being carried in discrete quantized packets (Photon).

3 Nobel Prize 1921. The energy of the light must exceed certain value for emission of electrons to occur. The intensity of the light doesn t affect the energy of the electrons, but it affects the number of emitted electrons Columbia University, Oct 14th 2015. Anibal Boscoboinik - CFN, Brookhaven Lab 7 = + KE Structure on an atom A photon (E= ) is absorbed by an electron The electron is emitted from the atom with certain KE Columbia University, Oct 14th 2015. Anibal Boscoboinik - CFN, Brookhaven Lab 8 Periodicity Table, binding Energies Columbia University, Oct 14th 2015. Anibal Boscoboinik - CFN, Brookhaven Lab 9 Columbia University, Oct 14th 2015.

4 Anibal Boscoboinik - CFN, Brookhaven Lab 10 X-ray Photoelectron Spectroscopy Background Principles Karl Manne Georg Siegbahn. Nobel Prize in Physics in 1924 "for his discoveries and research in the field of X-ray Spectroscopy . Kai Manne B rje Siegbahn. Nobel Prize in Physics in 1981 for developing the method of Electron Spectroscopy for Chemical Analysis (ESCA), now usually described as X-ray Photoelectron Spectroscopy (XPS) Columbia University, Oct 14th 2015. Anibal Boscoboinik - CFN, Brookhaven Lab 12 = + KE Photon ( X-ray ) Source Electron Energy Detector Columbia University, Oct 14th 2015.

5 Anibal Boscoboinik - CFN, Brookhaven Lab 13 Vacuum Level Work Function Valence Band 1s 2s 2p 3s 3p 3d K L1 L2,3 M, etc Emitted Photoelectron Kinetic Energy (KE) X-ray hv X-ray Photoelectron Spectroscopy (XPS) Courtesy of O. Furlong (UNSL) Columbia University, Oct 14th 2015. Anibal Boscoboinik - CFN, Brookhaven Lab 14 = + = + KE Lab X-ray source Synchrotron Electron Analyzer Columbia University, Oct 14th 2015. Anibal Boscoboinik - CFN, Brookhaven Lab 15 Why is XPS surface sensitive? Columbia University, Oct 14th 2015. Anibal Boscoboinik - CFN, Brookhaven Lab 16 Electron Escape Depth Columbia University, Oct 14th 2015.

6 Anibal Boscoboinik - CFN, Brookhaven Lab 17 = + KE Lab X-ray source Synchrotron Electron Analyzer Columbia University, Oct 14th 2015. Anibal Boscoboinik - CFN, Brookhaven Lab 18 1s binding energies for these elements: B, C, O, Be, F, Li, N 1 2 3 4 5 6 7 Columbia University, Oct 14th 2015. Anibal Boscoboinik - CFN, Brookhaven Lab 19 1s binding energies for these elements: B, C, O, Be, F, Li, N 1 2 3 4 5 6 7 Columbia University, Oct 14th 2015. Anibal Boscoboinik - CFN, Brookhaven Lab 20 Aluminum Plate O 1s C 1s Al 2s Al 2p O 2s O Auger William Durrer, Department of Physics at the Univertsity of Texas at El Paso N(E) Binding Energy (eV) XPS Survey EV/Step: 1 eV, Time/Step: 50 mSec, Sweeps: 10 Source: Mg K , Pass Energy: 100 eV Columbia University, Oct 14th 2015.

7 Anibal Boscoboinik - CFN, Brookhaven Lab 21 Columbia University, Oct 14th 2015. Anibal Boscoboinik - CFN, Brookhaven Lab 22 Metallic Aluminum Columbia University, Oct 14th 2015. Anibal Boscoboinik - CFN, Brookhaven Lab 23 Metallic Aluminum What happens if we oxidize it? Columbia University, Oct 14th 2015. Anibal Boscoboinik - CFN, Brookhaven Lab 24 eV eV Oxidation State Columbia University, Oct 14th 2015. Anibal Boscoboinik - CFN, Brookhaven Lab 25 Columbia University, Oct 14th 2015. Anibal Boscoboinik - CFN, Brookhaven Lab 26 How can you determine the oxide thickness? Columbia University, Oct 14th 2015.

8 Anibal Boscoboinik - CFN, Brookhaven Lab 27 Al - F Al - O Columbia University, Oct 14th 2015. Anibal Boscoboinik - CFN, Brookhaven Lab 28 Al - F Al - O Chemical Shift Columbia University, Oct 14th 2015. Anibal Boscoboinik - CFN, Brookhaven Lab 29 Columbia University, Oct 14th 2015. Anibal Boscoboinik - CFN, Brookhaven Lab 30 XPS tells you What elements you have How much you have of each of them Their oxidation state Their coordination to other elements How deep they are from the surface Columbia University, Oct 14th 2015. Anibal Boscoboinik - CFN, Brookhaven Lab 31 Some fact about XPS Surface sensitive Traditionally carried out in UHV Many relevant systems require higher pressures.

9 Catalysis Environmental and Atmospheric Chemistry Ambient Pressure XPS Elevated Pressures Developing tools at BNL Pressure Photoelectron Spectroscopy (AP-PES) AP-XPS & AP-NEXAFS Infrared Reflection Absorption Spectroscopy (PM-IRAS) Tunneling Microscopy (r-STM) Columbia University, Oct 14th 2015. Anibal Boscoboinik - CFN, Brookhaven Lab 34 Ambient Pressure X-ray Photoelectron Spectroscopy (AP-XPS) endstation at NSLS-II Pressures up to 5 Torr. Capillary tube into Mass Spec. AP-XPS End Station Starr, Tenney, Boscoboinik AP-XPS D. E. Starr, Z. Liu, M. H vecker, A. Knop-Gericke, H.

10 Bluhm. Chem. Soc. Rev., 2013,42, 5833-5857 > > > > UHV AP Differential Pumping Refocussing Lenses d z > d Importance of a tightly focused beam Cone Sample The smaller z, the higher P0 What can we use this for? Columbia University, Oct 14th 2015. Anibal Boscoboinik - CFN, Brookhaven Lab 38 Catalyst Model System Simplified version of a commercial catalyst allows to disentangle different factors that can potentially affect the Chemical reaction. used for surface science mechanistic studies There is a vast set of surface science tools to study model systems: Scanning Tunneling Microscopy X-ray Photoelectron Spectroscopy Etc.