Low Energy Electrons and Surface Chemistry

Transcription

1 G. Ertl, J. Küppers Low Energy Electrons and Surface Chemistry VCH

2 1 Basic concepts Introduction Principles of ultrahigh vacuum techniques Why is UHV necessary? Production of ultrahigh vacuum Pressure measurement Gas handling Preparation of clean surfaces Interaction of low energy electrons with matter Electron energy analyzers Retarding field grid analyzer (RFA) Cylindrical mirror analyzer (CMA) analyzer Concentric hemisphere analyzer (СНА) References 15 2 Auger electron spectroscopy Historical development Instrumentation Source of excitation Sample Analyzer and detector system Further refinements Mechanism of the Auger process Energies and shapes of the Auger peaks Free atoms Condensed matter Chemical effects Intensity of the Auger electron emission Auger yield Ionization cross section Auger electron emission from condensed matter Detected volume Qualitative analysis Quantitative analysis Determination of relative surface quantities Absolute surface quantities Alloys Depth profiling Kinetic studies 56

3 2.9 Deconvolution technique and band structure References 61 3 X-ray photoelectron spectroscopy (XPS) Introduction Instrumentation Light sources Analyzer and detector Data analysis Physical principles Qualitative surface analysis Identification of elements Core-level chemical shifts Quantitative analysis Final state effects Relaxation effects Multiplet splitting Multi-electron excitations Core-level satellites Angular effects References 83 4 Ultraviolet photoelectron spectroscopy (UPS) Introduction Instrumentation Light sources Resonance sources Continuous sources Sample Analyzer and detector Photoionization process Photoionization of atoms Photoionization of molecules Photoemission from solids UPS from clean surfaces Angle integrated photoemmission Angle resolved photoemission UPS from adsorbate covered surfaces Adsorbed atoms Adsorbed noble gases Adsorbed molecules 128

4 IX 1 Adsorbed CO Adsorbed polyatomics 138 References 143 Electron spectroscopy with noble gas ions and metastable atoms 147 Introduction 147 Instrumentation 147 Deexcitation mechanisms 148 Auger neutralization 150 Auger deexcitation (Penning ionization) 153 References 156 Appearance potential spectroscopy 157 Introduction 157 Instrumentation 158 Mechanism 160 Core-level binding energies 163 Surface analysis 165 Band structure and deconvolution 165 Adsorbate studies/chemical effects 170 Extended fine structure 171 References 173 Inverse photoemission (IPE, BIS) 175 Introduction 175 Instrumentation 175 Mechanism of IPE 176 Clean surfaces 178 Adsorbate studies 181 References 183 Electron energy loss spectroscopy (ELS, EELS) 185 Introduction 185 Instrumentation 186 Ionization losses 187 Plasmon losses and intraband transitions 190 Extended loss fine structure 195 Adsorbate induced losses 197 References 199

5 X Contents 9 Low energy electron diffraction (LEED) Introduction and historical development Classification of periodic surface structures Substrate and surface structures Surfaces with periodic steps and kinks Formation of the diffraction pattern Instrumentation Introduction Electron gun Detector system Geometrical theory of diffraction Introduction The reciprocal lattice Interference conditions and the Ewald construction Analysis of a simple diffraction pattern Domain structures LEED patterns of incommensurate structures Kinematic theory Introduction Scattering at two-dimensional lattices Kinematical structure factor Intensity-voltage (I/V) curves Disordered structures Introduction The transfer width Size effects and one-dimensional disorder Lattice gas systems Antiphase domains Facets Stepped surfaces Simulation of diffraction patterns Dynamical theories Introduction Physical parameters entering a dynamical theory Multiple scattering Data evaluation Temperature effects Spin-polarized LEED References X-ray absorption fine structure (EXAFS) Introduction Instrumentation 268

6 IX 1 Adsorbed CO Adsorbed polyatomics 138 References 143 Electron spectroscopy with noble gas ions and metastable atoms 147 Introduction 147 Instrumentation 147 Deexcitation mechanisms 148 Auger neutralization 150 Auger deexcitation (Penning ionization) 153 References 156 Appearance potential spectroscopy 157 Introduction 157 Instrumentation 158 Mechanism 160 Core-level binding energies 163 Surface analysis 165 Band structure and deconvolution 165 Adsorbate studies/chemical effects 170 Extended fine structure 171 References 173 Inverse photoemission (IPE, BIS) 175 Introduction 175 Instrumentation 175 Mechanism of IPE 176 Clean surfaces 178 Adsorbate studies 181 References 183 Electron energy loss spectroscopy (ELS, EELS) 185 Introduction 185 Instrumentation 186 Ionization losses 187 Plasmon losses and intraband transitions 190 Extended loss fine structure 195 Adsorbate induced losses 197 References 199

7 XII Contents 12.5 Angular distribution of desorbing ions (ESDIAD) References Appendix Fundamental constants Properties of selected elements Line positions in XPS using Al-K d radiation XPS atomic sensitivity factors Kinetic energies of Auger electrons Relative Auger sensitivity factors Character tables Characteristic group frequencies Abbreviations and acronyms 369 Index 371