Surface Analysis - The Principal Techniques

Transcription

1 Surface Analysis - The Principal Techniques Edited by John C. Vickerman Surface Analysis Research Centre, Department of Chemistry UMIST, Manchester, UK JOHN WILEY & SONS Chichester New York Weinheim Brisbane Singapore Toronto

2 Contents List of Contributors Preface xiii xv Chapter 1 Introduction 1 JOHN С VICKERMAN 1 How do we define the surface? 1 2 How many atoms in a surface? 2 3 Information required 3 4 Surface sensitivity 5 5 Radiation effects surface damage 6 Chapter 2 Vacuum Technology for Applied Surface Science... 9 ROD WILSON 1 Introduction: gases and vapours 9 2 The pressure regions of vacuum technology and their characteristics 15 3 Production of a vacuum Types of pump Evacuation of a chamber Choice of pumping system Determination of the size of backing pumps Flanges and their seals 31 4 Measurement of low pressures Gauges for direct pressure measurement Gauges using indirect means of pressure measurement Partial pressure measuring instruments 39 Chapter 3 Electron Spectroscopy for Chemical Analysis 43 BUDDY RATNER DAVID CASTNER

3 vi CONTENTS 1 Overview The basic ESCA experiment A history of the photoelectric effect and ESCA What information is learned from ESCA? 45 2 X-ray interaction with matter, the photoelectron effect, and photoemission from solids 46 3 Binding energy and the chemical shift Koopmans' Theorem Initial state effects Final state effects Binding energy referencing Charge compensation in insulators Peak widths Peak fitting 57 4 Inelastic mean free path and sampling depth 58 5 Quantitation Quantitation methods Quantitation standards Quantitation example 66 6 Spectral features 67 7 Instrumentation Vacuum systems for ESCA experiments X-ray sources Analyzers Data systems Accessories 79 8 Spectral quality 80 9 Depth profiling X-Y Mapping Chemical derealization Valence Band Perspectives Energy resolution and spectral interpretation Low-temperature ESCA studies Photoelectron diffraction Low-cost ESCA Imaging ESCA Conclusions 92

4 CONTENTS Chapter 4 Auger Electron Spectroscopy 99 HANS JÖRG MATHIEU 1 Introduction 99 2 Principle of the Auger Process Kinetic energies of Auger peaks Ionization cross-section Comparison of Auger and photon emission Electron backscattering Escape depth Chemical shifts Instrumentation Electron sources Ill 3.2 Spectrometers Modes of acquisition Detection limits Quantitative analysis Depth profile analysis Thin film calibration standard Depth resolution Sputter rates Preferential sputtering A-correction Chemical shifts in AES profiles Summary 132 vii Chapter 5 Secondary Ion Mass Spectrometry-the Surface Mass Spectrometry 135 JOHN С VICKERMAN ANDREW SWIFT 1 Introduction Basic concepts The basic equation Monolayer lifetime and the static limit Surface charging Experimental requirements Primary beam Electron bombardment Plasma 143

5 viii CONTENTS Surface ionisation Field ionisation sources Mass analysers Magnetic sector The quadrupole mass analyser Time of Flight Mass Spectrometers Mechanism of secondary ion generation Models of sputtering Ionisation Nascent ion molecule model The desorption ionisation model Static SIMS-the relationship between spectra and surface structure Surface science studies of the adsorbate state CO adsorption on metals Adsorption of complex hydrocarbons Surface reactions Surface chemistry of organic materials Static conditions for organic analysis Spectral interpretation Examples of surface characterisation Surface analysis of an adhesive system Quantification of surface composition MS/MS studies of the ion generation process SIMS imaging or scanning SIMS Depth profile analysis by dynamic SIMS The dynamic SIMS experiment Depth Profiling the Ion Beam Depth Profiling the mass analyser Quantitative analysis Sensitivity Dynamic range Depth resolution Instrumental effects Surface topography Radiation induced effects 195

6 CONTENTS ix 8 Sputtered Neutral Mass Spectrometry Electron post-ionisation Electron beam post-ionisation SNMS basic equation for elemental analysis Electron plasma SNMS Photon induced post-ionisation SNMS by resonant multi-photon ionisation (REMPI) SNMS using non-resonant multi-photon ionisation Summary 208 Chapter 6 Low-energy Ion Scattering and Rutherford Backscattering 215 EDMUND TAGLAUER 1 Introduction Physical basis The scattering process Collision kinematics Interaction potentials and cross-sections Shadow cone Rutherford backscattering Energy loss Apparatus Beam effects Quantitative layer analysis Structure analysis The value of RBS and comparison to related techniques Low-energy ion scattering Neutralisation Apparatus Surface composition analysis Adsorbates Catalysts Alloys Structure analysis Principles (ICISS) Surface reconstruction Direct recoil spectroscopy (DRS) Conclusions 262

7 X CONTENTS Chapter 7 Vibrational Spectroscopy from Surfaces 267 MARTYN PEMBLE 1 Introduction Infrared spectroscopy from surfaces Transmission IR spectroscopy Photoacoustic spectroscopy Reflectance methods Attenuated total (internal) reflection (ATR) Diffuse reflectance Reflection-absorption IR spectroscopy (RAIRS) The RAIRS experiment Signal enhancement techniques in RAIRS Spatial resolution in surface IR spectroscopy Electron energy loss spectroscopy (EELS) Inelastic or impact scattering Elastic or dipole scattering The EELS experiment Spatial resolution in EELS The group theory of surface vibrations The general approach Group theory analysis of ethyne adsorbed on to a flat surface Group theory analysis of ethyne adsorbed on a (100) surface of an FCC metal The form of the RAIRS and dipole EELS spectrum Laser Raman Spectroscopy from surfaces The theory of Raman scattering The study of collective surface vibrations (phonons) Raman spectroscopy from metal surfaces Spatial resolution in Raman Spectroscopy Fourier transform Raman techniques Inelastic neutron scattering (INS) Introduction to INS The INS spectrum INS spectra of hydrodesulphurisation catalysts Sum-frequency generation methods 307

8 CONTENTS Chapter 8 Surface Structure Determination by Interference Techniques 313 WENDY R. FLAVELL 1 Introduction Basic theory of diffraction three dimensions Extension to surfaces two dimensions Notation for surface structures The Ewald sphere construction in two dimensions Electron diffraction techniques General introduction Low energy electron diffraction (LEED) Development Experimental arrangement Elements of the theory of LEED Applications of LEED Reflection high energy electron diffraction (RHEED) Introduction Experimental arrangement Elements of the theory of RHEED Applications of RHEED: Temporal intensity variations in RHEED patterns during film growth of semiconductors by Molecular Beam Epitaxy (MBE) Absorption/Scattering techniques Introduction X-ray absorption in solids Fine structure in X-ray absorption spectra Extended X-ray absorption fine structure (EXAFS) The importance of EXAFS Basic theory of EXAFS Experimental techniques Data handling Applications of EXAFS Extension to surfaces surface exafs (SEXAFS) Experimental techniques 364 xi

9 xii CONTENTS Chapter Applications of SEXAFS NEXAFS (XANES) in surface structure determination Additional techniques for surface structure determination Two-dimensional X-ray diffraction (surface X-ray diffraction) X-ray standing waves (XSW) or standing X-ray wavefield absorption (SXW) Photoelectron diffraction (PD) 379 Scanning Tunnelling Microscopy and Atomic Force Microscopy 393 GRAHAM LEGGETT 1 Introduction Basic principles of operation Operation of the STM Quantum tunnelling The role of tip geometry Instrumentation and basic operating parameters Operation of the AFM Atomic resolution and spectroscopy: surface crystal and electronic structure Studies of gold surfaces Graphite surfaces The silicon (111) 7 x 7 reconstruction Scanning tunnelling spectroscopy Crystal growth Lithography and micromanipulation Atomic resolution by AFM Molecules at surfaces Liquid crystals and organic liquids Self-assembled monolayers Other adsorbate and film structures Studies of polymer surfaces Biological applications Conclusions 444 Index 451