Subject Index

Ab-initio calculations 182, 252, 256 Abnormal images 82 Activation barrier 190 Adatom - apparent size 15 - on jellium 3 Adhesion 185, 207, 270 - avalanche in 188 Adhesive bonding 226 Adhesive contact 214 Adhesive energy 185 Adhesive neck 218 Adiabatic approximation 197 Adsorbates 7, 72 - alkali atoms 48 Adsorbed molecular liquid film 235 Adsorbed surface layers 326 AI(II1) 42, 43, 44 Alkanes 35 - layers 36 Angle Resolved Ultraviolet Photoemission

Spectroscopy (ARUPS) 78 Anomalous corrugation 26 Anti-corrugating effect 43 Apex atom 83 Apparent barrier height 19,26,150-152,

170, 171 Apparent radius 165, 167 Apparent size 15 Asymmetric interaction 191 Atomic-Force Microscopy (AFM) 208 Atomic forces 169 Atomic resolution 142 Atomic scale Friction 4 Atomic-scale probing 207 Atomic stress tensor 216 Atomic structural transformation 227 Atom transfer 182, 190 Atom tunneling 190 Attraction of cohesion 213 Attractive force 153, 170

atomic 158 - regime 170

Ballistic transport 197, 198

Bardeen approach 143, 144 - modified (MBA) 146, 147, 155 Barrier

collapse 195 double rectangular 125 effective 198 height 195 infinite 115 lowering 151 negative 197 rectangular 116 square 151 time-modulated 123

BCS-theory 143 Bell's theorem 111 Binding energy 185 Bohm trajectories 105,117,122,126,127,

131 - non intersection property of 112, 121 Bohm's interpretation of quantum

mechanics 110, 137 Bond formation 189 Bonding and antibonding states 68, 153 Born-Oppenheimer approximation 153 Boundary conditions 25, 27 Biittiker-Landauer traversal time 109, 124

c-axis compressibility 253 Capillarity 207 Capillary - forces 235, 351 - phenomena 235 Casimir limit 300 Casimir-Polder result 302, 318 Center of interaction 310 Charge

depletion 265 - regulation process 340 - transfer 263 Charge density 43 - local sample 23, 24, 31 Charge-density contour 164 Charging effect 193 Clausius-Mosotti equation 348 Closed -shell repulsion 262

362 Subject Index

Cluster models for the tip 80 Co Axial Impact-Collision Ion Scattering

Spectroscopy (CAlC ISS) 96 Computer simulation 209 Concave meniskus 352 Conductance

10 203 3D 203 distribution 166 dynamic 173

Conductivity 44 Confined complex films 230 Connected Vacuum Tail method (CVT) 80 Connective neck 189, 223, 226 Contact 43

area 199, 200 atomic-size 218 formation 207, 224 intermetallic 235 mechanical 181, 189 mechanics 212 point of 44

Contact force microscopy 4 Constant force simulation method 243 Constriction 196, 197 - effect 181, 197, 198 Contact value theorem 337 Continuum elasticity theory 253, 289 Conventional tunneling regime 180 Corrugation 43, 47, 167 - amplitudes 46, 47, 168 Counterion concentration profile 337 Cu(110) 46, 47, 48 Current carrying states 195 Current density 10, 29 - 31

d states 16 Dangling-bond 2, 91 Debye-Hiickel approximation 342 Debye length 340 Debye-Kessom contributions 299 Debye rotational relaxation process 312 Deformations 188

elastic 169, 180, 188, 289 - hysteric 200 - plastic 189, 200, 220, 289 Degree of layering 235 Density Functional Theory 256 Density of States (DOS) 65 - tip 172 - sample 172 Derivative rule 162 Derjaguin approximation 307, 342 Derjaguin-Landau-Verwey-Overbeck (DLVO)

theory of lyophobic colloid stability 343 Dielectric permittivities 297, 312

Dielectric properties 312 Differential power law index 309 Dimer rows 85 Disjoining pressure 237 - of wetting films 339 Distance dependence of corrugation

amplitudes 142 Dividing surface 24 DLP theory 296, 299 Double layer 337 - forces 343 Drainage 230, 233 - molecular 235 Ductile extension 218 Dwell time 106 Dynamic conductance 173 Dynamic electronic polarizabilities 300 Dyson's equation 28

Effect of the atom kind 84 Effective electronic absorption

wavelength 312 Effective excess dynamic polarizability of an

individual molecule 304 Effective layer thickness 253 Effective measure of curvature 306 Effective potential 198 Effects of attractive and repulsive

forces 142 Elastic deformation 169, 180, 188, 289 Electromagnetic interaction 297 Electromigration 192 Electronic absorption peak 312 Electronic contact regime 181 Electronic instability 44 Electrostatic forces 336 Embedded Atom Method (EAM) 210 Energy absorption spectrum 312 Energy dissipation 188, 297 Entropic contribution 299 Equi-current contours Equiforce mode 251 Excess polarizabilities 302 - dielectric 302 Exchange-correlation energy density 256 Exchange interaction 146 Exchange of electrons 146

Fermi-level - LDOS corrugation of 167 Fermi wavelength 182 Fermi's golden rule 28, 143 Feynman path integral techniques 107 Field desorption 190, 192 Field emission 146 Field-emission microscopy 145

Field Ion Microscopy (FIM) 77, 145 First-principles 256 Fluid-film lubrication 230 Force-distance curves 252 Force gradient 44, 46 Four-slab problem 327 Fowler-Nordheim regime 59 Free electron gas 312 - plasma frequency of 313 Free electron model 62 Friction 187, 207, 213, 269

coefficient 270, 281, 285 force 243, 244, 279 origins of 269 phenomena 188 sliding 269, 272, 276 rolling 269, 277 with wear 270, 271 without wear 270, 271

Friction Force Microscopy (FFM) 270, 272

Generalized Debye screening length 344 Generalized Ehrenfest theorem 25, 27, 29,

31, 33, 34 Generalized Lifshitz approach 183 Gouy-Chapman approach 341 Grahame relation 340 Graphite Intercalation Compounds (GIC)

253 - donor 263 Graphite surface 81 Green operator 28 Green's function 3, 23, 33, 39, 52, 150,

198 - of the tip 28 Group velocity 63

Hamaker approach 296, 303 constants 184,262, 312, 348 density modulated constant 350 entropic constant 299, 300 non-retarded constant 300 renormalized approach 296 retarded constant 301

Hard sphere liquid 347 Harmonic lattice spring model 258 Hartree potential 256 He-scattering 23, 38 Healing length 259 Heaviside step Function 254 Honeycomb-Chained-Trimer (HCT)

model 96 Hopping energy 192 Hydration forces 351 Hydrogen molecular ion 152, 174

Subject Index 363

Hydrophilic and hydrophobic interactions 351

Hysteresis 181, 217, 226 effects 189

- in the force vs. distance curve 226

Ideal friction machines 272 Image effects 41 Image force 151 Image inversion 47, 48 Image potential 150, 151 Indentation 219 Independent-atomic-orbital method 165,

168 Independent conduction channels 196 Independent-electrode approximation 3 Inelastic tunneling 99 Instabilities 184 - mechanical 198, 199 - structural 199 Insulators 35 Interaction energy 185 Interaction forces 40 Interaction between a sphere and a

semi-infinite slab 329 Interaction between two spheres 329 Interatomic interactions 210 Intercalants 253 Interfacial - adherence 208 - systems 212 Interference effects 43 Interference between electric and magnetic

quadrupole photons 332 Interference of ionic and VdW forces 343 Inter-materials junctions 208 Intermolecular interactions 302 Interphase-interface 208 Interstitial-layer partial dislocations 228 Inverse decay length 194 Ion-electron attraction 187 Ion-ion repulsion 187 Ionic excess osmotic pressure 337 Ionic forces 336 Ionic materials 237

Jellium - model 7, 202, 203 - edges 195 Jump-to-Contact (JC)

formation 231 instability 223, 231 phenomenon 216

KCs 263 Kelvin equation 352

364 Subject Index

Kelvin mean radius 352 Kohn-Sham equations 256 Korringa-Kohn-Rostocker band theory

(KKR) 39 Kramers-Kronig relation 297

Langmuir-Blodgett films (LB) 35, 231 Langmuir relation 339 Laplace pressure 352 Larmor clock 109, 116, 129 Lateral forces 187 Layered materials 253 Layer-KKR formalism 39 Leading Bloch waves 163 Lennard-Jones liquid 355 Lever 251 LiC6 263 Lifshitz formula 184 Light emission from STM 78, 98 Linear Combination of Atomic Orbitals

(LCAO) 79 Lippman-Schwinger equation 28 Load 251 Local barrier-height 19 Local Density (LOD) - Capacitor Projected (CAP-LOD) 32, 31,

42 - Sample Projected (SAP-LOD) 33 - Tip Projected (TIP-LOD) 32, 33, 41, 42 Local Density Functional Theory 78, 256, 280 Local Density Of States (LDOS) 8, 51, 84 - Modified (MLDOS) 71 Local exchange-correlation potential 256 Local Gaussian-type orbitals 257 Local hydrostatic pressure 216 Local negative differential resistance 78 Local surface rigidity 253 London - formula 302 - limit 300 Long-range interaction 180, 183 Lorentz harmonic oscillator model 312 Low-permittivity approximation 319 Lubrication 207, 208, 270

Many-body effects 302 Matching procedure 51 Material - elastic and plastic response 207 - transport 44 Matrix element 149 - tunneling 159, 161, 172 Maximum repulsive retarded dispersion

force 319 Measurement of mean transmission and

reflection times 136

Measurement of particle momentum 132 Measurements of tunneling barrier 170 Metal

close packed surface 163 - micro-contacts 214 - surface 41, 46 Microindentation 209 Microscopic friction force 181 Microscopic view 2 Minority carrier injection 99 Missing-row reconstruction 46, 47 Modified wave functions 149 Molecular-dynamics simulations (MD) 4,

209, 210 Molecular-scale analysis 332 Molecular tip array 334 Molecule physisorption process 308 Monovalent electrolyte solution 340 Morse - curve 169 - force 157 Multilayer configuration 326

Nanoindentation 189, 207, 214 Nanotribology 208, 269 Negative differential resistance 91, 92 Negative resistance 14 Negative tip displacement 11 Nickel tip wetted by a gold monolayer 223 Non-retarded limit 302

Offdiagonal current 84 Onset of plastic yielding 212 Optical refractive index 312 Ordering of the molecular film 235 Organic layers 35 Oscillating refractive index 350

Paraffin layers 35 Particle-substrate dispersion interaction 305,

308 Pauling's theory of the chemical bond 141,

153 Pd - (100) 30, 31, 41, 42 - (111) 43 Perturbation theory 2, 24, 33, 51, 141 - stationary-state 146, - time dependent 143, 148 Phase time 109 Plastic yielding 222 Point contact 17, 198, 200 Poisson-Boltzmann equation 345 Polarized interaction 146 Potassium 47 Plasmon 99

Pressure - contours 217 - distribution 217 Prevention of degradation and wear 230 Pseudopotential method 185, 197, 202, 256

Quantized step 196 Quantum conductance 196, 198 Quantum mechanical dispersion 299 Quantum oscillations 183 Quantum potential 111, 116, 123, 130, 136 Quantum transmission 147, 148

Radiation field retardation 300 Reflection time 106,111,113,115,116 - distribution 106, 113, 119, 120 - measurement 136 Relative humidity 355 Relaxation mechanisms of adsorbed organic

thin films 231 Renormalization 302 Repulsion 299 Repulsive force 146, 153, 156 - regime 170 Resistance

negative 14 negative-differential 91, 92 quantum limit 36 tunnel 34, 36, 37

Resonance 34, 141, 153, 155 - conductivity 35 - energy 146, 149 Resonant states 65, 193 Resonant tunneling 94 Retardation wavelength 320 Retarded limit 302 Rigidity

flexural 253 local flexural 263 local surface 260 transverse 253

Rotational absorption peak 312 Rydberg function 185

Scanning Force Microscopy (SFM) 251, 269 Scanning microscopies 212 Scanning Tunneling Optical Microscopy

(STOM) 98 Scanning Tunneling Spectroscopy (STS) 78 Scattering

He 23,28 process 26 theoretical approach 23 three-dimensional 23

Second-harmonic generation 78 Self-assembled films 231

Subject Index 365

Self-consistency 256 Self-Consistent Field (SCF) pseudopotential

calculations 180 Sharvin contact conductivity 35 Shear modes 187 Short-range forces 186 Si

(100) reconstructed surface 85 (111) V3 x V3-Ag surface 95 (111) V3xV3-B 91

Size and shape effects 328 Sliding process 332 Solvation forces 345 Spatial resolution 310 Spectral distribution 46 Spectral resolution 45 Spectroscopic mode 51 Spectroscopy 14 Spherical modified Bessel function 159 Spontaneous capillary condensation of

vapours 351 Spreading 230 Square-barrier problem 151 Stability of STM 169 Standing-wave excitation 78 Stick-slip - atomic-scale phenomenon 214, 241, 243 - motion 181, 188 Strain energy 222 Stress deviator 222 Structural deformation profile 217 Structural transformation 227 Surface

deformations 207, 208 electrostatic potential 340 energy 185 graphite 80 manipulation 332 melting 189 nano-mechanical-properties 208 Si (100) reconstructed 85 Si (111) V3 x V3-Ag 95

Tensile stress 219 Tersoff-Hamann theory 144, 145, 169 Thermally activated desorption 190 Thin-film 230 - drainage 208 Three-dimensional theories 25 Time-dependent SchrOdinger equation 154 Time-of-flight experiment 132 Tip

based force 212 cluster models 80 coated 223 compression 228

366 Subject Index

Tip (cont.) DOS 172 elastic deformation 40 electronic states 141 electronic structure 172 elongation 225 induced drainage 232 induced modification 192 induced states 193 orbitals 26, 45, 46 pressure 38 resonance states 193 shape 25 structure 39, 142 wave function 160 wear 244

Tip-Induced Localized States (TILS) 3, 72, 182

Tip-sample absolute distance 164 adhesive interaction 208 interaction 23, 38, 47, 141, 179, 208, 212 reactive system 241 separation after indentation 220

Topography 10, 23 Transfer Hamiltonian 31, 51, 58, 179 Transition matrix element 24, 25, 28, 144,

149 Transition matrix method 203 Transition probability 149 Transmission factor 66 Transmission probability 202 Transmission time 106, 111, 113, 116

distribution 106, 113, 119, 120, 123, 127, 132 measurement 136

Traversal time 106, 108 Tribology 212 Tunnel conductivity 32, 34, 44 Tunnel resistance 34, 36, 37

Tunneling 1D 201 inelastic 95 matrix element 159, 161, 172 non-destructive interactions resonant 94

Tunneling current 51 - distribution 84 Tunneling Hamiltonian 8 Tunneling time 105, 106, 137, 157 Two-component incident wave packet 121 Two-slab problem 297 Two-slab renormalization 304 Two terminal theory 196

UV region 299

Van Hove singularities 63 Van der Waals (VdW) force 146, 153, 180,

183, 262, 294 - asymptotic pressure 299 - pressure 297 Velocity distribution 133, 134, 135 Very small tunneling gaps 142 Voltage dependence of STM images 141 Von Mises shear strain-energy criterion 212

W tip atom 46 Wave function distortion 146 Weak overlap approximation 342 Wear 207, 209 - of the tip 244 Wetting 189, 192, 230, 232 WKB - approximation 203 - theory 144 Work function 19

Young-Laplace equation 237

Zero frequency force 299 Zero-point quantum fluctuations 299

Contents of

Scanning Tunneling Microscopy I (Springer Series in Surface Sciences, Vol. 20)

1. Introduction By R Wiesendanger and H.-J. Guntherodt (With 5 Figures) 1 1.1 Historical Remarks on Electron Tunneling . . . . . . . . . . . . . . . 1 1.2 STM and Related Techniques. . . . . . . . . . . . . . . . . . . . . . . . . 4

1.2.1 Local Proximal Probes . . . . . . . . . . . . . . . . . . . . . . . . . . 4 1.2.2 Modes of Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5

1.3 Development of the Field . . . . . . . . . . . . . . . . . . .. . . . . . . . . 8 1.4 Prospects for the Future . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11

2. Tbe Rise of Local Probe Metbods By H. Rohrer. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13

3. STM on Metals By Y. Kuk (With 19 Figures). . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17 3.1 Tunneling Tip . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18 3.2 Tunneling Spectroscopies ............................ 20

3.2.1 Current Versus Gap Distance. . . . . . . . . . . . . . . . . . . . . 20 3.2.2 Electronic Structure by dl/dV. . . . . . . . . . . . . . . . . . . . . 22

3.3 Examples on Metal Surfaces . . . . . . . . . . . . . . . . . . . . . . . . . . 25 3.3.1 Surface Structures. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25 3.3.2 Dynamics. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30

3.4 Conclusion. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35 References ...... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35

4. Adsorbate Covered Metal Surfaces and Reactions on Metal Surfaces By J. Wintterlin and RJ. Behm (With 22 Figures). . . . . . . . . . . . . 39 4.1 Imaging of Adsorbates by STM ....................... 40

4.1.1 Representation of Individual Adsorbates . . . . . . . . . . . . 40 4.1.2 Resolution and Corrugation in Closed Adlayers ...... 47 4.1.3 Spectroscopy of Adsorbates .. . . . . . . . . . . . . . . . . . . . . 50

4.2 Processes at the Metal-Gas Interface . . . . . . . . . . . . . . . . . . . 54 4.2.1 Adsorption, Dissociation, Surface Diffusion . . . . . . . . . . 54 4.2.2 Formation of Ordered Adsorbate Layers. . . . . . . . . . . . 58

4.3 Structure Modifications of Metal Surfaces ............... 60 4.3.1 Adsorbate-Induced Reconstructive Transformations ... 60 4.3.2 Oxidation Reactions. . . . . . . . . . . . . . . . . . . . . . . . . . . . 68

368 Contents of Scanning Tunneling Microscopy I

4.4 Epitaxial Growth of Metals on Metal Substrates . . . . . . . . . . 70 4.5 Conclusions. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 79 References ......................... . . . . . . . . . . . . . . . . . . 79

5. STM on Semiconductors By R.J. Hamers (With 29 Figures). . . . . . . . . . . . . . . . . . . . . . . . . 83 5.1 Experimental Technique . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 83

5.1.1 Topographic Imaging. . . . . . . . . . . . . . . . . . . . . . . . . . . 83 5.1.2 Tunneling Spectroscopy. . . . . . . . . . . . . . . . . . . . . . . . . 85

5.2 Scanning Tunneling Microscopy/Spectroscopy on Surfaces .. 87 5.2.1 Clean Group IV Semiconductors. . . . . . . . . . . . . . . . . . 87 5.2.2 Clean Compound Semiconductor Surfaces. . . . . . . . . . . 106 5.2.3 Adsorbates and Overlayers on Semiconductors . . . . . . . 113 5.2.4 Chemical Reactions on Semiconductor Surfaces. . . . . . . 119

5.3 Other Tunneling Techniques Applied to Semiconductors. . . . 120 5.3.1 Surface Photo voltage . . . . . . . . . . . . . . . . . . . . . . . . . . . 120 5.3.2 Tunneling-Induced Luminescence . . . . . . . . . . . . . . . . . 123 5.3.3 Potentiometry. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 124 5.3.4 Ballistic Electron Emission Microscopy (BEEM). . . . . . 125

References .............. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 126

6. STM on Layered Materials By R. Wiesendanger and D. Anselmetti (With 44 Figures) . . . . . . . 131 6.1 STM Studies of Graphite. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 132

6.1.1 Site Asymmetry, Energy-Dependent Corrugation, Tunneling Spectroscopy and Electronic Structure of the Graphite Surface ......................... 133

6.1.2 Giant Corrugations, Tip-Sample Interaction and Elastic Response of the Graphite Surface . . . . . . . . 136

6.1.3 Anomalous STM Images . . . . . . . . . . . . . . . . . . . . . . . . 138 6.1.4 STM Imaging of Defects. . . . . . . . . . . . . . . . . . . . . . . . . 140 6.1.5 STM Studies of Clusters on the Graphite Surface . . . . . 142

6.2 STM Studies of Graphite Intercalation Compounds. . . . . . . . 145 6.2.1 Donor Graphite Intercalation Compounds. . . . . . . . . . 149 6.2.2 Acceptor Graphite Intercalation Compounds ........ 154 6.2.3 Interpretation and Comparison

with Theoretical Predictions ..................... 154 6.3 STM Studies of Transition Metal Dichalcogenides . . . . . . . . . 157 6.4 STM Studies of Charge Density Waves. . . . . . . . . . . . . . . . . . 161

6.4.1 Charge Density Waves in Transition Metal Dichalcogenides . . . . . . . . . . . . . . . 161

6.4.2 Charge Density Wave Defects and Domains. . . . . . . . . 165 6.4.3 Charge Density Waves

in Quasi-One-Dimensional Systems . . . . . . . . . . . . . . . . 170 6.5 STM Studies of High-Tc Superconductors ............... 172

Contents of Scanning Tunneling Microscopy I 369

6.6 Concluding Comments ...................... . . . . . . . . 175 References .... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 175

7. Molecular Imaging by STM By S. Chiang (With 19 Figures) . . . . . . . . . . . . . . . . . . . . . . . . . . . 181 7.1 Introduction to STM of Molecules. . . . . . . . . . . . . . . . . . . . . 181 7.2 STM of Chemisorbed Molecules in Ultrahigh Vacuum. . . . . . 182

7.2.1 Co adsorbed Benzene and CO on Rh(111) . . . . . . . . . . . 182 7.2.2 Copper-Phthalocyanine on Cu(l00) and GaAs (110) .. . 186 7.2.3 Naphthalene on Pt(111) . . . . . . . . . . . . . . . . . . . . . . . . . 188

7.3 STM of Alkanes and Their Derivatives. . . . . . . . . . . . . . . . . . 191 7.3.1 Cadmium Arachidate

and Other Langmuir-Blodgett Films. . . . . . . . . . . . . . . 191 7.3.2 n-Alkanes on Graphite . . . . . . . . . . . . . . . . . . . . . . . . . . 194 7.3.3 Alkylbenzenes on Graphite. . . . . . . . . . . . . . . . . . . . . . . 195

7.4 STM of Liquid Crystals. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 197 7.4.1 Alkylcyanobiphenyls............. . . . . . . . . . . . . . . . 197 7.4.2 Other Liquid Crystals. . . . . . . . . . . . . . . . . . . . . . . . . . . 199

7.5 STM of Polymers ...... . . . . . . . . . . . . . . . . . . . . . . . . . . . . 200 7.5.1 PODA, PMMA, and PMPS on Graphite. . ... .. .. . . 200 7.5.2 Polyethylene on Graphite ................... . . . . 202

7.6 Other Molecules. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 202 7.7 Conclusions. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 203 References ......................................... . . 203

8. STM on Superconductors By P.J.M. van Bentum and H. van Kempen (With 21 Figures). . . . 207 8.1 Theory of Tunneling into Superconductors. . . . . . . . . . . . . . . 208

8.1.1 Coulomb Blockade. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 214 8.2 Low Temperature STM Spectroscopy

on Classical Superconductors . . . . . . . . . . . . . . . . . . . . . . . . . 215 8.3 Vortices. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 216 8.4 Organic Superconductors ............................ 220 8.5 STM Topography on High-Tc Superconductors. . . . . . . . . . . 221

8.5.1 Granularity and Growth Structures. . . . . . . . . . . . . . . . 221 8.5.2 Potentiometry. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 223 8.5.3 Incommensurate Modulation. . . . . . . . . . . . . . . . . . . . . 224

8.6 STM Spectroscopy on High- Tc Superconductors . . . . . . . . . . 226 8.6.1 Normal State Spectroscopy. . . . . . . . . . . . . . . . . . . . . . . 226 8.6.2 STM Spectroscopy of the Superconducting State. . . . . . 229 8.6.3 Energy Gap .................................. 230

8.7 Concluding Remarks. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 238 References ......... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 239

Subject Index. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 243

Contents of

Scanning Tunneling Microscopy II (Springer Series in Surface Sciences, Vol. 28)

1. Introduction By R. Wiesendanger and H.-J. Giintherodt . . . . . . . . 1 1.1 STM in Electrochemistry and Biology . . . . . . . . 1 1.2 Probing Small Forces on a Small Scale . . . . . 2 1.3 Related Scanning Probe Microscopies . . . . . . 3 1.4 Nanotechnology . . . . 4 References . . . . . . . . . . . . . . . . . . . . . . . . . 5

2. STM in Electrochemistry By H. Siegenthaler (With 13 Figures) . . . . . . . 7 2.1 Principal Aspects. . . . . . . . . . . . . . . . . 9 2.2 Experimental Concepts for Electrolytic STM

at Potential-Controlled Electrodes . . . . . . 12 2.2.1 Potential Control Circuitry, STM Cell Design,

Counter and Reference Electrodes. . . . . . . 12 2.2.2 Tunneling Tips . . . . . . . . . . . . . . . . . . 19 2.2.3 Sample Preparation and Transfer Procedures 26

2.3 Electrochemical Applications of In Situ STM at Potential-Controlled Electrodes . . . . . . . . . . 31 2.3.1 STM Studies at Metal Electrodes . . . . . . . 31 2.3.2 STM Studies at Carbon and Semiconductor Electrodes 42 2.3.3 Miscellaneous Investigations . 45

2.4 Outlook . . . 45 References . . . . . . . . . . . . . . . . . . 45

3. The Scanning Tunneling Microscope in Biology By R. Guckenberger, T. Hartmann, W. Wiegriibe, and W. Baumeister (With 23 Figures) . . 51 3.1 Instrumentation . . . . . . . . . . . . 53

3.1.1 The STM Head . . . . . 53 3.1.2 Auxiliary Microscopes . . . . . 54 3.1.3 Electronics . . . . . . . . . . . . . . . . 55 3.1.4 Controlling the Environment of the STM Head. 58 3.1.5 Tunneling Tips. . . . . . . . . . . 58

3.2 Processing of STM Images. . . . . . . 61 3.2.1 Correction of Imaging Faults. . 61

372 Contents of Scanning Tunneling Microscopy II

3.2.2 Evaluation of STM Images . 61 3.2.3 Representation of the Images 63

3.3 Preparation . . . . . . . . . . . 63 3.3.1 Substrates ........ 63 3.3.2 Specimen Deposition . . 67 3.3.3 Specimen Dehydration . 68 3.3.4 Coating with Conductive Films. 69 3.3.5 Examining the Quality of Preparations 70

3.4 Applications. . . . . 70 3.4.1 Nucleic Acids . . . . . 70 3.4.2 Proteins. . . . . . . . . 74 3.4.3 Biological Membranes 79

3.5 Imaging and Conduction Mechanisms . 84 3.5.1 Practical Observations in STM Imaging

of Uncoated Biological Material . . . . . 84 3.5.2 Measurements of Conductivity and Related Parameters 85 3.5.3 Basic Electron Transfer Mechanisms. . . . . . . . . . 88 3.5.4 Intrinsic Conduction in Organic

and Biological Material: Theoretical Considerations 89 3.5.5 External Conduction Mechanisms 90 3.5.6 Image Formation. 91

3.6 Conclusions. 92 References . . . . . . . . . . . 93

4. Scanning Force Microscopy (SFM) By E. Meyer and H. Heinzelmann (With 31 Figures) 99 4.1 Experimental Aspects of Force Microscopy. . . 101

4.1.1 Preparations of Cantilevers . . . . . . . . . 101 4.1.2 Techniques to Measure Small Cantilever Deflections 103 4.1.3 Modes of Operation . . . . . . . . . . . . . . 107

4.2 Forces and Their Relevance to Force Microscopy. . . . 111 4.2.1 Forces Between Atoms and Molecules. . . . . . . . 111 4.2.2 Forces in Relation to Scanning Force Microscopy. 112

4.3 Microscopic Description of the Tip-Sample Contact 117 4.3.1 Empirical Potentials . . . . . 117 4.3.2 Molecular Dynamics . . . . . 119 4.3.3 Continuum Elasticity Theory 123 4.3.4 Ab Initio Calculations . . . . 123

4.4 Imaging with the Force Microscope 127 4.4.1 SFM on Layered Materials 127 4.4.2 Ionic Crystals . . . . . . . . . . 133 4.4.3 Organic Molecules . . . . . . . 139 4.4.4 Applications of SFM on a Nanometer Scale 141

4.5 Conclusions and Outlook. 145 References . . . . . . . . . . . . . . . . . . . . . . . . . . 146

Contents of Scanning Tunneling Microscopy II

5. Magnetic Force Microscopy (MFM) By P. Grittter, H.J. Mamin and D. Rugar (With 38 Figures) . 5.1 Basic Principles of MFM ............ . 5.2 Measurement Techniques . . . . . . . . . . . ..

5.2.1 Force Detection ......... . 5.2.2 Force Gradient Detection ... . 5.2.3 Deflection Sensors . . . . 5.2.4 Servo Considerations ..

5.3 Force Sensors. . . . . . . . . . . . . . .. . ...... . 5.3.1 Basic Properties ................. . 5.3.2 Electrochemically Etched Tips. . . . . . . . . . . . 5.3.3 Tips Coated with Magnetic Thin Films . . . . . .

5.4 Theory of MFM Response . . . . . . . 5.4.1 Magnetic Interaction ................ . 5.4.2 Image Simulation . . . . . . . . . . . . . . .. 5.4.3 Mutual Disturbance of Tip and Sample ...

5.5 Imaging Data Storage Media. . . . . . . . . . . .. 5.5.1 Longitudinal Magnetic Recording Media .. 5.5.2 Modeling Longitudinal Media. . . . . . . .. 5.5.3 Magnetic Recording Studies . . . . . . . . . . . . . 5.5.4 Magneto-Optic Recording Media . . . . . .

5.6 Imaging Soft Magnetic Materials . . . . . . . . . . . . . . .. 5.6.1 Iron Whiskers ................ . 5.6.2 NiFe (Permalloy). . . . .. ...... . 5.6.3 Tip-Sample Interactions. ...... .

5.7 Resolution............. . ..... . 5.7.1 Experimental Results .......... . 5.7.2 Theoretical Considerations ............... .

5.8 Separation of Magnetic and Topographic Signals ..... . 5.9 Comparison with Other Magnetic Imaging Techniques 5.10 Conclusions and Outlook. . . . ...... . References . . . . . . . . . . .

6. Related Scanning Techniques By H.K. Wickramasinghe (With 18 Figures) 6.1 Historical Background ........ . 6.2 STM and Electrical Measurements

6.2.1 Basic Principle of STM . . . . . 6.2.2 Scanning Noise Microscopy

and Scanning Tunneling Potentiometry 6.3 STM and Optical Effects . . . . . . . . . . . .

6.3.1 Optical Rectification and Scanning Photon Microscope 6.3.2 STM and Inverse Photoemission Microscopy. .

6.4 Near-Field Thermal Microscopy. . . . . . . . . . . 6.5 Scanning Force Microscopy and Extensions ..... .

373

151 152 154 154 154 158 159 160 160 161 163 165 165 168 170 171 171 174 175 178 181 183 185 187 190 191 192 198 200 202 205

209 209 210 210

211 212 212 213 214 219

374 Contents of Scanning Tunneling Microscopy II

6.6 Conclusion. References . . . .

7. Nano-optics and Scanning Near-Field Optical Microscopy By D. W. Pohl (With 23 Figures) ............. . 7.1 Nano-optics: Optics of Nanometer-Size Structures

7.1.1 General Considerations ... . 7.1.2 Theoretical Approach ............ . 7.1.3 Gap Fields and Tip Plasmons ....... . 7.1.4 Pointed Tips as Near-Field Optical Probes 7.1.5 Spherical Particle Above Substrate .... 7.1.6 Nano-Apertures ..... 7.1.7 Dipole Above Ground.

7.2 Experimental Work ..... . 7.2.1 SNOM Designs .... . 7.2.2 Aperture/Transmission . 7.2.3 Aperture/Reflection ........ . 7.2.4 Protrusion/Reflection ....... . 7.2.5 Pointed Transparent Fiber/Transmission 7.2.6 The Photon-Emitting STM . 7.2.7 Basic NFO Experiments .. 7.2.8 Aperture/Transmission .. 7.2.9 Aperture/Reflection . . .. 7.2.10 Protrusion/Reflection ... 7.2.11 Pointed Optical Fiber (PSTM, STOM) . 7.2.12 Pointed Metal Tip ............ .

7.3 Plasmons and Spectroscopic Effects . . . . . . . 7.3.1 Protrusions: Influence of Particle Size. 7.3.2 Apertures: Enhanced Spectroscopy.

7.4 Imaging by SNOM ..... 7.4.1 Transmission.... .. . 7.4.2 Reflection/Aperture .. . 7.4.3 Reflection/Protrusion .. 7.4.4 Optical Fiber (PSTM, STOM) . 7.4.5 SNOM-Type Imaging with the STM

7.5 Discussion, Outlook, Conclusions . . . . . . 7.5.1 Problems Solved ............ . 7.5.2 Open Questions, Comparison of Different Methods 7.5.3 Outlook ..

References

8. Surface Modification with a Scanning Proximity Probe Microscope By U. Staufer (With 13 Figures) 8.1 Overview...............................

229 230

233 234 234 235 235 236 238 242 245 247 247 247 250 250 250 252 252 253 254 254 254 256 256 256 258 258 258 262 263 265 266 267 267 268 269 270

273 273

Contents of Scanning Tunneling Microscopy II 375

8.2 Microfabrication with a Scanning Probe Microscope. . 276 8.2.1 A Universal Approach . . . . . . . . 276 8.2.2 Discussion of the Basic Parameters . 277

8.3 Investigation of the Fabrication Process 285 8.3.1 Indirect Investigations. . . . . . . . . 285 8.3.2 Direct Investigations ... . . . . . . 286 8.3.3 Response of Different Samples and Environments 289

8.4 Review of SXM Lithography . . . . . . . . . . . 290 8.4.1 Exposure of an Electron or Photo-Resist 290 8.4.2 Mechanical Machining 291 8.4.3 Deposition . . . . . . . . . . . . . . . . . . 292 8.4.4 Thermal Treatment . . . . . . . . . . . . . 294 8.4.5 Decomposition of Organometallic Gases 295 8.4.6 Manipulation of Molecules and Atoms . 296 8.4.7 Electrochemical and Photo electrochemical Processes 297 8.4.8 Ion and Electron Etching. . . . . . . . . 298 8.4.9 Modifications of Indeterminate Origin . 299

References 300

Subject Index .. /. 303