Surface Analysis with STM and AFM

Transcription

1 Sergei N. Magonov, Myung-Hwan Whangbo Surface Analysis with STM and AFM Experimental and Theoretical Aspects of Image Analysis VCH Weinheim New York Basel Cambridge Tokyo

2 Preface V 1 Introduction Development of Scanning Probe Microscopy Key Problems of STM and AFM Applications Image Interpretation Tip-Sample Interactions Surface Relaxation and Local Hardness Surface Forces and AFM Objectives 7 References 7 2 Physical Phenomena Relevant to STM and AFM Electron Transport Processes Conventional Electron Tunneling Regime Electronic and Mechanical Contact Regimes STM in Different Environments Survey of Force Interactions Force-vs.-Distance Curves Short-Range Forces and Sample Deformation Long-Range and Other Forces Long-Range Forces Adhesion and Capillary Forces 18 References 18 3 Scanning Probe Microscopes Operating Principles and Main Components Scanner Tip-Sample Approach and Electronic Feedback Scanning Modes and Parameters Images and Filtering Isolation of Vibrational Noise Scanning Tunneling Microscope STM Tips and Current Detection Bias Voltage Scanning Tunneling Spectroscopy 30

3 3.3 Atomic Force Microscope Contact Mode and Force Detection AFM Probes Dynamic AFM Measurements AFM Operation in the Attractive Force Regime Tapping Mode Force-Modulation Techniques Magnetic Force Microscopy STM and AFM as Metrology Tools Resolution in STM and AFM Metrological Applications 43 References 44 4 Practical Aspects of STM and AFM Measurements Samples Optimization of Experiments Optimization of STM Experiments Optimization of Contact-Mode AFM Experiments Optimization of Tapping-Mode AFM Experiments STM and AFM Measurements Large-Scale Imaging Atomic-Scale Imaging Image Artifacts 58 References 62 5 Simulations of STM and AFM Images Electronic Structures of Solids Theoretical Aspects of STM Tunneling Between Metals Tunneling Between Metal and Semiconductor Tersoff-Hamman Theory and its Extension Other Theories Theoretical Aspects of AFM Image Simulation by Density Plot Calculations STM Image Simulation AFM Image Simulation STM and AFM Images of Graphite 77 References 80 6 STM and AFM Images of Layered Inorganic Compounds Layers from MX 6 Trigonal Prisms and Octahedra 83

4 IX 6.2 Images of Layered Compounds H-MoS MoOCl WTe NbTe ß-Nb 3 I lt-tase Charge Density Waves of MC g (M = K, Rb, Cs) Observations Origin of Nonuniform Charge Distribution Concluding Remarks 109 References STM Images Associated with Point Defects of Layered Inorganic Compounds Imperfections in Compounds with Metal Clusters Point Defects in Semiconductor 2H-MoS Cases Tractable by Electronic Band Structure Calculations Ligand-Atom Vacancy Metal-Atom Vacancy Donor Substitution at the Metal Site Cases Intractable by Electronic Band Structure Calculations Donor Substitution at the Ligand Site The Case of Negative Bias The Case of Positive Bias Acceptor Substitution at the Ligand Site The Case of Positive Bias The Case of Negative Bias Acceptor Substitution at the Metal Site Survey of Image Imperfections Observed for d 2 2H-MX 2 Systems Atomic-Scale Images Nanometer-Scale Images Concluding Remarks 133 References Tip-Sample Interactions Electronic Interactions in STM Tip Electronic States Tip-Induced Local States Force Interactions in STM Force Interactions in Ambient Conditions Force Interactions in Ultra High Vacuum (UHV) 140

5 X Contents 8.3 Tip-Sample Interactions in AFM Force Interactions on the Atomic Scale Surface Deformation Concluding Remarks 148 References Surface Relaxation in STM and AFM Images Tip Force Induced Deformation in HOPG Three-for-Hexagon Pattern of HOPG Hexagonal Moire Patterns in STM Images Wagon-Wheel Patterns of MoSe 2 Epilayers on MoS STM and AFM Images of a-rucl 3 and a-mocl Images of a-rucl 3 at Low Applied Force Images of a-rucl 3 at High Applied Force Tip Force Induced Surface Deformation in a-rucl AFM Images of a-mocl Layered Transition-Metal Tellurides MA^Te Atomic-Scale Deformation in the Commensurate Tellurides Structure of Incommensurate Telluride TaGe 0355 Te Tip Force Induced Changes in AFM Images of NbTe Nanoscale Ring Structure of MoS 2 and WSe Concluding Remarks 184 References Organic Conducting Salts Crystal and Electronic Structures Early STM Studies of Organic Conductors STM and AFM Imaging of Organic Conductors Surface Processes During Imaging Molecular-Scale Images Analysis of the Images of TCNQ Salts TTF-TCNQ Qn(TCNQ) EP(TCNQ) TEA(TCNQ) TCNQ Salts with Substituted Phenylpyridines Analysis of the Images of BEDT-TTF Salts Cation-Layer Images of a-phases HOMO Density of ß-(BEDT-TTF) 2 I Cation-Layer Images of K-Phases Anion-Layer Images of K-Phases 212

6 XI 10.6 Concluding Remarks 216 References Organic Adsorbates at Liquid/Solid Interfaces STM of Organic Adsorbates Organic Compounds and Substrates STM Imaging at Liquid/Solid Interfaces STM of Normal and Cyclic Alkane Layers Images of Normal Alkanes on HOPG Molecular Order of Cycloalkane Adsorbates on HOPG Influence of Substrate on Adsorbate Structure Molecular-Scale Images of Normal Alkanes on ß-Nb 3 I Alkyl-4'-cyanobiphenyls on HOPG Alkyl-4'-cyanobiphenyls on ß-Nb 3 I Concluding Remarks 241 References Self-Assembled Structures Scanning Probe Microscopy Studies of Thin Organic Films Morphology and Molecular Order Nanomechanical Properties Self-Organization of Amphiphiles Basic Principles Sample Preparation and AFM Imaging AFM Study of 7V-(n-AlkyI)-D-gluconamides Crystal Structures Layers with Crystal-Like Order Thin Overlayers Double Layers Supramolecular Assemblies Micellar Structures Fiber-Like Assemblies Rod-Like Assemblies Structural Models AFM Study of AHn-alkyO-A^'-D-maltosylsemicarbazones Self-Assembled Structures of 10MS Self-Assembled Structures of 16MS Structural Models Concluding Remarks 274 References 275

7 XII Contents 13 Polymers General Considerations Polymer Structure Analysis of Polymer Surfaces Applying STM and AFM STM of Polymer Samples Conducting Polymers Metal-Coated Polymer Surfaces Polymer Layers on Conducting Substrates AFM of Polymer Crystal Surfaces Polydiacetylene Single Crystal Polyethylene Single Crystal Polymer Spherulites AFM of Oriented Polymers Imaging of Molecular Chain Order Nanostructure of Polyethylene Tapes and Fibers Other Oriented Polymer Samples AFM of Di-Block Copolymers Poly(styrene-b-isoprene) Films Poly(styrene-b-methyl methacrylate) and Poly(styrene-b-2-vinylpyridine) Films Concluding Remarks 308 References Future Outlook 313 Acknowledgements 317 Index 319