Dynamics of Gas-Surface Interaction

In recent decades surface science has experienced a large growth in connection with the development of various experimental techniques which are able to characterize solid surfaces through the observation of the scattering of ions, electrons, photons or atoms. These methods of investigation, known under different labels such as LEED, AES, XPS, UPS, etc. have been extensively applied in describing the structure, morphology, and chemical and physical properties of crystal surfaces and interfaces of a large variety of materials of interest in solid-state physics, electronics, metallurgy, biophysics, and heterogeneous catalysis. Among these methods we wish to emphasize molecular beam scattering from solid surfaces. ~lolecular beam scattering has gone through a large development in the last ten years. In this decade a large number of laboratories have used this method to study various clean and adsorbate-covered surfaces. The technique is nonetheless quite old. It dates back to the beginning of the thirties, when Estermann and Stern performed the first atom diffraction experiment proving the wave nature of atoms. In the following years the entire subject of gas-surface interaction was considered a branch of rarefied gas dynamics and developed in connection with aerospace research. Attention was then given to the integral properties of gas-solid interactions (sticking and energy accomodation, mean momentum transfer) rather than to atom-surface scatter­ ing from well-characterized surfaces.

I. Scattering of Atoms from Solid Surfaces.- Theory of Atom-Surface Scattering.- 1. Lecture I.- 1.1 Scattering from a Periodic Potential.- 1.2 Numerical Methods and Phase Shifts.- 1.3 Close Coupling Calculations.- 1.4 The Distorted Wave Born Approximation.- 2. Lecture II.- 2.1 Formal Scattering Theory.- 2.2 Partial Processes.- 3. Lecture III.- 3.1 Semiclassical Methods.- 3.2 Scattering from a Hard Corrugated Surface (HCS).- 3.3 Eikonal and Kirchoff Approximations.- 4. Lecture IV.- 4.1 Introduction.- 4.2 Kinematics.- 4.3 Resonant Scattering Formalism.- 4.4 Resonance Line Shapes.- References.- He Diffraction from Semiconductor Surfaces. Lecture I: Si(100).- 1. Introduction.- 2. Si (100): Disordered Dimer Array.- 2.1 Si(100) Periodicity.- 2.2 Diffraction Scans and a Qualitative Feature of the Si(100) Surface.- 2.3 Specular Intensities.- 3. Structural Models for Si(100).- References.- He Diffraction from Semiconductor Surfaces. Lecture II: CaAs(110): Calibration of the Atom-Diffraction Technique.- 1. Introduction.- 2. Diffracti on Scans.- 3. Specular Intensity Scans.- 4. Rigorous Calculation of Diffraction Intensities.- 5. The Origin of the He/GaAs Potential.- 6. Computation of Rarefied Charge Densities.- 7. Summary.- References.- He Diffraction from Semiconductor Surfaces. Lecture III: Si (111) 7×7.- 1. Introduction.- 2. Diffraction Scans.- 3. Specular Intensity Interference.- 4. A Model of the Si(111) 7×7.- 5. Summary.- References.- Helium Scattering from Clean and Adsorbate-Covered Metal Surfaces.- 1. Introduction.- 2. The He-Surface Interaction Potential and the Crystallographic Information Contained in the Corrugation Function.- 3. Data Analysis.- 3.1 Diffraction Geometry.- 3.2 The Hard Corrugated Wall Model.- 3.3 Calculation of Intensities for Given ?(R): The Direct Problem.- 3.4 Reconstruction of the Corrugation Function from Measured&&&Intensities: the Inverse Problem.- 3.5 Influences due to the Softness of the Potential.- 3.6 Influences due to the Thermal Motion of the Surface Atoms.- 4. Experimental Aspects.- 5. Examples.- 5.1 Metals.- 5.2 Adsorbate Structures.- References.- The Coherence Length in Molecular and Electron Beam Diffraction.- 1. Abstract.- 2. Introduction.- 3. The Formation of the Diffraction Pattern.- 3.1 The Simple-Minded Approach.- 3.2 The Rigorous Approach.- 4. Summary.- References.- Charge Density Waves Surface Deformation Studied by Helium Atom Diffraction.- 1. Introduction.- 2. Unreconstructed Structure of the Layered Compounds.- 3. Charge Density Waves Deformations.- References.- II. Characterization of Adsorbed Phases.- Phase Transitions in Surface Films.- 1. Introduction.- 2. Order-Disorder Transitions.- 2.1 Critical Exponents and Surface Symmetry.- 2.2 2D Gas-Solid Transition.- 2.3 2D Melting (Existence of a Self-Bound Liquid?).- 2.3.1 Mehtane/Graphite.- 2.3.2 Krypton/Graphite.- 3. Solid-State Transformation.- 3.1 Commensurate-Incommensurate (C-I) Transition.- 3.1.1 Kr/Graphite (0001).- 3.1.2 Xe/Cu(110).- 3.2 2D Polymorphism.- 3.3 Non Stoichiometric Surface Compounds.- 4. 2D Gas-Liquid Transition.- 4.1 Liquid-Gas Coexistence.- 4.2 Critical Index.- 5. Influence of Heterogeneities on Surface Phase Transitions.- 6. Conclusions.- References.- Universal Laws of Physical Adsorption.- 1. Introduction.- 2. Evidence for Universality.- 3. Analytical Forms of the Potential.- 4. Conclusion.- References.- The Dynamical Parameters of Desorbing Molecules.- 1. Abstract.- 2. Introduction.- 3. The Failure of the General Desorption Laws.- 4. The Associative Desorption of Permeating Atoms.- 5. Conclusions.- References.- Atomic Beam Diffraction as a Method for Studying Two-Dimensional Solids.- 1. Introduction.- 2. Atomic Diffraction.- 2.1 Surface Crystallography.- 2.2 Atom-Surface Interaction Potential.- 2.3 Inelastic Scattering.- 3. Atomic Diffraction from Adsorbates.- 4. Diffraction of H Atoms from a Xe Overlayer Adsorbed on the (0001) Surface of Graphite.- 5. Conclusions.- References.- Atom Scattering from Overlayers.- 1. Introduction.- 2. Experiments of Atom Scattering from Adsorbates.- 3. Theory of Atom Scatteri ng from Adsorbates.- 4. Inelastic Scattering.- References.- III. Spectroscopy of Surface Optical Excitations.- Surface Elementary Excitations.- 1. Introduction.- 2. Electrons at Metal Surfaces.- 3. Continuum Models of Bulk and Surface Elementary Excitatations.- 3.1 Radiative and Non-Radiative Modes.- 3.2 The Dispersion Relations.- 3.3 Matching Conditions in the Non-Retarded Limit.- 3.4 Surface Modes in a Crystal Slab.- 3.5 Quantization and the Hamiltonian Formalism.- 4. Microscopic Theory of Surface Electronic Excitations.- 4.1 Surface Plasmon Dispersion.- 4.2 Semiclassical Infinite Barrier Model (SCIBM).- 5. Optical Spectroscopy of Surface Excitations.- 5.1 Rough Surface and Gratings.- 5.2 Attenuated Total Reflection (ATR).- 6. Electron Energy Loss Spectroscopy of Surface Excitations.- 6.1 Introduction.- 6.2 Experimental Examples.- 6.3 Interaction of Electrons with Collective Surface Modes.- 6.4 Interaction of Electrons with Localized Vibrations.- 6.5 Solution of the Scattering Problem.- 6.6 Observation of Surface Optical Phonons and Surface Phonons.- 6.7 Observation of Adsorbed Molecule Vibrational Modes.- 7. Dynamical Screening-Image Potential.- References.- Surface-Enhanced Raman Scattering.- 1. Introduction.- 2. The Phenomenon of Surface Enhanced Raman Scattering, “Roughness” and Local Field Effects.- 3. Further Reading.- References.- Calculation of the Phonon Spectrum of the Ni(111) Surface Covered with Oxygen.- 1. Introduction.- 2. Dipole Coupling.- 3. Bulk Phonons.- 4. Surface Phonons.- 5. Interpretation of the EELS Experiment.- References.- IV. Surface Phonon Spectroscopy by Atom Scattering.- Phonon Interactions in Atom Scattering from Surfaces.- 1. Introduction.- 2. Review of Theoretical Studies of Surface Phonons.- 3. Kinematics of Inelastic Surface Scattering.- 4. Dynamical Theory of Inelastic Scattering.- 5. Inelastic Scattering Experiments.- 6. Role of Resonances in Phonon Interactions.- References.- Surface Phonons in Ionic Crystals.- 1. Introduction.- 2. Surface Elastic Waves.- 2.1 Theory.- 2.2 Isotropic Crystals.- 2.3 Anisotropic Cubic Crystals.- 3. Surface Polaritons.- 3.1 Introduction.- 3.2 Surface Phonon Polaritons.- 4. Surface Lattice Dynamics.- 4.1 Introduction.- 4.2 Dynamics of a Thin Slab.- 4.3 The Green’s Function Method.- 4.3.1 The Free Surfaces as a Perturbation.- 4.3.2 The Semi-Infinite Lattice.- 4.4 Examples and Comparison with Experimental Data.- 4.4.1 The Energy-Loss Profile of Inelastic Atom Scattering.- References.- Inelastic Scattering of Neon from the (001) LiF Surface.- 1. Introduction.- 1.1 Experimental Apparatus.- 1.2 Measurements and Analysis.- 1.3 Multiphonon Scattering.- 1.4 Conclusion.- References.- Inelastic Scattering from Metal Surfaces.- 1. What is so Exciting About Metal Surfaces.- 2. Basic Differences Between Metal and Insulator Surfaces.- 3. Experimental Results.- 3.1 Light Probing Atoms: He on Cu.- 3.2 Heavy Probing Atoms: Ne on Ni.- 3.3 Adsorbate Layers.- 4. Conclusion.- References.- Bound State Resonance in the Inelastic Scattering of He-Graphite.- 1. Introduction.- 2. Experimental Observations.- 2.1 Phonon-Assisted Bound State Resonance.- 2.2 Specular Phonon Assisted Bound State Resonance.- 2.3 Double Bound State Resonance.- 3. Calculation of the Specular Phonon Assisted Resonance.- 4. Information on Surface Phonon Dispersion Relation.- 5. Conclusions.- References.- Index of Contributors.