Rainer Behrisch, Wolfgang Eckstein (Eds.) Sputtering by Particle Bombardment Experiments and Computer Calculations from Threshold to MeV Energies With 201 Figures e1 Springer
Contents Introduction and Overview Rainer Behrisch and Wolfgang Eckstein 1 1 Overview 1 2 The Sputtering Yield 3 3 Distributions of Sputtered Particles 4 4 Surface Topography 4 5 Sputtering Calculations 7 5.1 Analytic Theory 7 5.2 Computer Calculations 8 6 Sputtering Measurements 9 7 Applications of Sputtering 11 8 Summary, Conclusions 12 References 12 Index 19 Computer Simulation of the Sputtering Process Wolfgang Eckstein and Herbert M. Urbassek 21 1 Programs Based on the Binary Collision Approximation 21 1.1 The Binary Collision 22 1.2 The Interaction Potential for BCA 22 1.3 The Inelastic (Electronic) Energy Loss 23 1.4 The Surface Binding Energy 24 1.5 Problems of the Concept of BCA 24 1.6 Dynamic Monte Carlo Programs 24 1.7 Advantages of BCA Programs 25 2 Programs Based on Molecular Dynamits 25 2.1 Physics Input: Forces 25 2.1.1 Interatomic Potentials 25 2.1.2 Electrons 26 2.2 Technical Considerations 27 2.2.1 System Size 27 2.2.2 Boundary Conditions 27 2.2.3 Initial State 27 2.2.4 Sputtering 28 2.2.5 Simulation Time 28
X Contents 2.3 Reliability 28 References 29 Index 31 Sputtering Yields Wolfgang Eckstein 33 1 Experimental Methods 33 2 Calculational Methods 35 3 Mono-Atomic Targets 37 3.1 Energy Dependence of the Sputtering Yield at Normal Incidence 37 3.2 Fitting 38 3.3 Comparison of Calculated Values with Experimental Data 40 3.4 Angle of Incidence Dependence of the Sputtering Yield 101 3.5 Threshold Energy of Sputtering 125 4 Single Crystalline Materials 125 5 Multicomponent Targets 126 5.1 Fluence Dependence 127 5.2 Oscillations in the Partial Sputtering Yields 128 5.3 Sputtering of Compounds 129 5.4 Isotope Sputtering 130 6 Temperature Dependence of the Sputtering Yield 131 7 Yield Fluctuations 132 8 Time Evolution of the Sputtering Yield 133 9 Conclusions 133 References 171 Index 186 Results of Molecular Dynamits Calculations Herbert M. Urbassek 189 1 Introduction 189 2 Linear-Cascade Regime 191 2.1 Low-Energy Sputtering 193 2.2 Preferential Sputtering 193 3 Ionic Crystals 196 4 Effect of Electronic Energy Loss and Electronic Excitations in Atomic Collision Cascades 197 4.1 Stopping 198 4.2 Excitation 198 5 High-Energy-Density (Spike) Phenomena 198 5.1 Sputtering from Fast-Ion-Induced Tracks 200 5.2 Cluster Impact 201 5.2.1 Small Cluster Impact (n < 3) 202 5.2.2 Larger Cluster Impact (n, > 3) 202 5.2.3 Cluster-Induced Surface Smoothing 204
Contents XI 6 Cluster Emission 204 7 Surface Topography Formation 208 7.1 Surface Vacancy and Adatom Production 209 7.2 Crater Production 210 8 Effects of Surface Topography on Sputtering 211 8.1 Effect of Surface Steps on Sputtering 212 9 Fluence Dependence of Sputtering 215 10 Sputtering of Molecular and Organic Solids 216 10.1 Diatomic and Small Anorganic Molecular Solids 216 10.2 Sputtering of Organic Solids 217 10.3 Sputtering of Polymers 217 11 Chemical Effects 218 12 Conclusions 219 References 220 Index 227 Energy and Angular Distributions of Sputtered Species Hubert Gnaser 231 1 Introduction 231 2 Theoretical Concepts 233 2.1 Energy Dissipation, Recoil Generation, and Sputtering 233 2.2 Surface Binding Energy 236 3 Experimental Techniques 237 3.1 Post-Ionization of Sputtered Neutrals 237 3.2 Methods for the Determination of Energy Spectra 238 3.2.1 Electrostatic Energy Analysis 238 3.2.2 Fluorescence Techniques 239 3.2.3 Time-of-Flight Measurements 240 3.3 Methods for Angular Distribution Measurements 241 4 Energy and Angular Distributions in the Linear-Cascade Regime 244 4.1 Energy Spectra from Metals, Semiconductors, and Organic Materials 245 4.1.1 Energy Spectra of Ground- and Excited-State Atoms, and of Ions 245 4.1.2 Energy Distributions of Atoms Sputtered from Alloys 252 4.1.3 Energy Spectra of Sputtered Molecules 254 4.2 Energy Spectra from Alkali Halides and Condensed Gases 269 4.2.1 Alkali Halides and Related Materials 269 4.2.2 Condensed Gases 271 4.3 Angular Distribution of Sputtered Species 275 4.3.1 Angular Distributions from Amorphous and Polycrystalline Targets 275 4.3.2 Angular Spectra from Single Crystals 277 4.3.3 Angular Distributions from Multicomponent Targets 280 5 Energy and Angular Distributions in the Single-Knockon Regime 283
XII Contents 5.1 Energy Spectra and Direct Recoils 285 5.1.1 Normal Incidence Bombardment 285 5.1.2 Oblique Incidence Bombardment 288 5.2 Angular Distributions at Low-Energy Irradiation 291 6 Energy and Angular Spectra from High-Density Cascades 293 6.1 Cluster-Ion Bombardment 293 6.2 Yield Enhancement under Cluster Impact 294 6.3 Energy Distributions under Cluster Bombardment 295 6.4 Angular Distributions under Cluster Irradiation 298 7 Summary 300 References 301 Index 323 Chemical Sputtering Wolfgang Jacob and Joachim Roth 329 1 Introduction 329 2 Chemical Effects in Sputtering 330 3 Definitions 332 3.1 Physical Sputtering 332 3.2 Chemical Erosion 333 3.3 Chemical Sputtering 333 4 Experimental Methods 334 4.1 Weight Loss 335 4.2 Mass Spectrometry 335 4.3 Ellipsometry 339 4.4 Optical Emission Spectroscopy 339 4.5 Cavity Probes 340 4.6 Dedicated Multiple Beam Experiments 340 5 Chemical Erosion of Carbon by Atomic Hydrogen 342 5.1 Thermal Process 342 5.2 Species Released by Chemical Erosion 345 6 Chemical Sputtering 348 6.1 Chemical Sputtering with Reactive Ions 349 6.1.1 Temperature Dependence 349 6.1.2 Energy Dependence 350 6.1.3 Dependence an the Type of Graphite 354 6.1.4 Flux Dependence 355 6.1.5 Identification of Species Released by Chemical Sputtering 356 6.2 Combined Irradiation with Noble Gas Ions and Hydrogen Atoms 359 6.3 Effect of Doping 364 6.4 Chemical Sputtering with Molecular Ions at Low Energies 365 6.5 Summary of Experimental Results 367 7 Mechanisms and Modelling for Chemical Sputtering 369
Contents XIII 7.1 Empirical Analytic Description 369 7.1.1 Radiation Damage 369 7.1.2 Low-temperature Near-surface Process, Ysurf 370 7.1.3 Empirical Roth Garcia-Rosales Formula 371 7.1.4 Comparison with Erosion Data 372 7.1.5 Extrapolation to Thermal Energies 373 7.2 Chemical Sputtering Model by Hopf 374 7.3 Molecular Dynamits Simulations 377 7.4 Isotope Effect 380 7.5 Effects due to Out-diffusion of Hydrocarbons 382 7.6 Summary 383 8 Chemical Sputtering with Other Reactive Species 384 8.1 Oxygen 384 8.2 Nitrogen 386 8.3 Fluorine 389 References 389 Index 399 Electronic Sputtering with Swift Heavy Ions Walter Assmann, Marcel Toulemonde, and Christina Trautmann 401 1 Introduction 401 2 Sputtering Experiments 406 2.1 Special Problems in High-Energy Sputtering 406 2.2 Measuring Techniques for Sputtering Yields 407 2.3 Angular Distribution, Total Yield, and Fluence Effect 410 2.4 Experimental Arrangements 411 3 Experimental Results 416 3.1 Dependence of Sputtering Yield on Charge State of Incoming Ions 416 3.2 Dependence of Sputtering Yield on Angle of Beam Incidence 416 3.3 Metallic Materials 417 3.3.1 Angular Distribution of Sputtered Particles for Metallic Targets 418 3.3.2 Total Sputtering Yields for Metallic Targets 418 3.4 Insulating Oxides 421 3.4.1 Angular Distributions of Sputtered Particles for Oxides 421 3.4.2 Total Sputtering Yields for Oxides 422 3.5 Ionic Insulators 423 3.5.1 Angular Distributions of Sputtered Particles for Ionic Crystals 423 3.5.2 Total Sputtering Yields for Ionic Crystals 426 3.6 Summary of Experimental Sputtering Data of Different Materials 426
XIV Contents 4 Calculations Based an the Inelastic Thermal Spike Model 428 4.1 Application to Metals 434 4.2 Application to Insulators 437 4.3 Thermal Spike Conclusion 439 5 Concluding Remarks and Outlook 440 References 442 Index 449 Author Index 461