1. Introduction.- 1.1 Theoretical Concepts for Scanning Tunneling Microscopy.- 1.2 Theoretical Concepts for Force Microscopy.- References.- 2. STM Imaging of Single-Atom Adsorbates on Metals.- 2.1 Tunneling Hamiltonian Approach.- 2.2 Adsorbates on Metal Surfaces.- 2.2.1 Topography.- 2.2.2 Spectroscopy.- 2.2.3 Voltage Dependence of Images - Apparent Size of an Adatom.- 2.3 Close Approach of the Tip: The Strong-Coupling Regime.- 2.3.1 From Tunneling to Point Contact.- 2.3.2 Measuring the Tunneling Barrier.- References.- 3. The Scattering Theoretical Approach to the Scanning Tunneling Microscope.- 3.1 The Theoretical Formalism.- 3.1.1 The Limits of Perturbation Theory.- 3.1.2 Tunneling as a Scattering Process.- 3.1.3 Current Density and Generalized Ehrenfest Theorem.- 3.1.4 Local Charge Density at the Fermi Level and Tunnel Current.- 3.1.5 Resonance Tunneling.- 3.2 Tunneling Through Thick Organic Layers.- 3.2.1 The Experimental Situation.- 3.2.2 A Simple Soluble Model.- 3.3 Scanning Tunneling Microscopy at Metal Surface.- 3.3.1 A Method Based on the Korringa-Kohn-Rostocker (KKR) Band Theory.- 3.3.2 Including the Atomic Structure of the Tip: Model Hamiltonian Approach.- 3.3.3 Close Packed Metal Surface.- 3.3.4 Open Metal Surfaces.- 3.3.5 Imaging Adsorbed Alkali Atoms: K/Cu(110).- 3.4 Summary and Conclusions.- References.- 4. Spectroscopic Information in Scanning Tunneling Microscopy.- 4.1 Green's Function Method.- 4.1.1 Matching at a Single Surface.- 4.1.2 Matching at Two Surfaces.- 4.2 Derivation of the Transfer Hamiltonian Approach.- 4.2.1 The Transfer Hamiltonian Approach.- 4.2.2 Tersoff and Hamann's Theory.- 4.2.3 New Derivation of the Transfer Hamiltonian Approach.- 4.2.4 Validity of the Transfer Hamiltonian Approach.- 4.3 One-Dimensional Models.- 4.3.1 Free Electron Model with a Square Barrier.- 4.3.2 One-Dimensional Array of Square Well Potentials.- 4.3.3 The Question of the Surface States.- 4.3.4 Resonant States in the Barrier.- 4.4 Three-Dimensional Models.- 4.4.1 Formalism for a Spherical Tip.- 4.4.2 Application to an Adsorbate on a Surface.- 4.5 Conclusion.- References.- 5. The Role of Tip Atomic and Electronic Structure in Scanning Tunneling Microscopy and Spectroscopy.- 5.1 Background.- 5.2 Formalism of Theoretical Simulation of STM/STS.- 5.3 Simulation of STM/STS of the Graphite Surface.- 5.3.1 Normal Images.- 5.3.2 Abnormal Images.- 5.3.3 Effect of the Atom Kind of the Tip and the Tunnel Current Distribution.- 5.4 STM/STS of Si(100) Reconstructed Surfaces.- 5.5 The Negative-Differential Resistance Observed on the Si(111)$$ \sqrt {3} $$ × $$ \sqrt {3} $$-B Surface.- 5.6 The STM Image of the Si(111)$$ \sqrt {3} $$ × $$ \sqrt {3} $$-Ag Surface and the Effect of the Tip.- 5.7 Light Emission from a Scanning Tunneling Microscope.- 5.8 Summary and Future Problems.- Note Added in Proof.- References.- 6. Bohm Trajectories and the Tunneling Time Problem.- 6.1 Background.- 6.1.1 Motivation.- 6.1.2 Defining the Problem.- 6.2 A Brief Discussion of Previous Approaches.- 6.3 Bohm's Trajectory Interpretation of Quantum Mechanics.- 6.3.1 A Brief Introduction.- 6.3.2 Transmission and Reflection Times Within Bohm's Interpretation.- 6.4 Application to Simple Systems.- 6.4.1 Some Numerical Details.- 6.4.2 Reflection Times for an Infinite Barrier.- 6.4.3 Transmission and Reflection Times for Rectangular Barriers.- 6.4.4 Coherent Two-Component Incident Wave Packet.- 6.4.5 Transmission Times for Time-Modulated Barriers.- 6.4.6 Transmission Times for Symmetric Double Rectangular Barriers.- 6.5 Discussion.- 6.5.1 'Measurement' of Particle Momentum.- 6.5.2 'Measurement' of Mean Transmission and Reflection Times.- 6.5.3 Concluding Remarks.- References.- Additional References with Titles.- 7. Unified Perturbation Theory for STM and SFM.- 7.1 Background.- 7.1.1 A Brief Summary of Experimental Facts.- 7.1.2 The Bardeen Approach for Tunneling Phenomena.- 7.1.3 Perturbation Approach for STM and SFM.- 7.2 The Modified Bardeen Approach.- 7. sakriti opis