Science and Application of Nanotubes (eBook)

SERIES PREFACE 6
PREFACE 8
CONTENTS 11
FILLING CARBON NANOTUBES USING AN ARC DISCHARGE 15
ABSTRACT 15
INTRODUCTION 15
EXPERIMENTAL PROCEDURES 17
STRUCTURAL AND CHEMICAL ANALYSIS 17
ANALYSIS OF THE ROLE OF SULFUR 24
DISCUSSION: GROWTH MECHANISM 24
CONCLUSION 29
SIMULATION OF STM IMAGES AND STS SPECTRA OF CARBON NANOTUBES 31
INTRODUCTION 31
STM THEORY 32
GRAPHITE 34
PERFECT NANOTUBES 36
STM images 38
MULTI-WALL NANOTUBES AND ROPES 41
DEFECTS IN NANOTUBES 42
CONCLUSIONS 45
ACKNOWLEDGMENT 45
REFERENCES 45
APPLICATIONS RESEARCH ON VAPOR-GROWN CARBON FIBERS 48
VAPOR-GROWN CARBON FIBERS 48
INFILTRATION 51
COMPARATIVE FIBER PROPERTIES 54
COMPOSITE THEORY 54
SURFACE TREATMENTS 57
PROPERTIES IMPROVEMENTS 61
ELECTRICAL CONDUCTIVITY 62
ACKNOWLEDGMENTS 63
REFERENCES 63
THE GROWTH OF CARBON AND BORON NITRIDE NANOTUBES: A QUANTUM MOLECULAR DYNAMICS STUDY 65
INTRODUCTION 65
1. MICROSCOPIC GROWTH MECHANISMS FOR CARBON NANOTUBES 66
2. FRUSTRATION EFFECTS AND GROWTH MECHANISMS FOR BORONNITRIDE NANOTUBES 70
CONCLUSION 75
ACKNOWLEDGEMENTS 76
REFERENCES 76
NANOSCOPIC HYBRID MATERIALS: THE SYNTHESIS, STRUCTURE AND PROPERTIES OF PEAPODS, CATS AND KIN 78
INTRODUCTION 78
EXPERIMENTAL METHOD 78
EXPERIMENTAL RESULTS AND DISCUSSION 79
SUMMARY 85
ACKNOWLEDGEMENTS. 86
REFERENCES 86
LINEAR AUGMENTED CYLINDRICAL WAVE METHOD FOR NANOTUBES: BAND STRUCTURE OF 88
INTRODUCTION 88
FORMALISM 88
APPLICATIONS 92
ACKNOWLEDGEMENT 93
REFERENCES 93
COMPARATIVE STUDY OF A COILED CARBON NANOTUBE BY ATOMIC FORCE MICROSCOPY AND SCANNING ELECTRON MICROSCOPY 94
ABSTRACT 94
INTRODUCTION 94
EXPERIMENTAL 96
RESULTS 96
CONCLUSION 101
ACKNOWLEDGMENTS 102
REFERENCES 102
INVESTIGATION OF THE DEFORMATION OF CARBON NANOTUBE COMPOSITES THROUGH THE USE OF RAMAN SPECTROSCOPY 103
ABSTRACT 103
INTRODUCTION 103
EXPERIMENTAL 104
RESULTS AND DISCUSSION 105
Deformation of SWNT Nanocomposites 108
Multi-Walled Nanotubes 110
Reinforcement of Epoxy Resin with Carbon Nanotubes 110
CONCLUSIONS 111
ACKNOWLEDGEMENTS 112
REFERENCES 112
ELECTRONIC STATES, CONDUCTANCE AND LOCALIZATION IN CARBON NANOTUBES WITH DEFECTS 113
INTRODUCTION 113
SCATTERING THEORY APPROACH TO CONDUCTANCE 114
SCATTERING FROM A SIMPLE BARRIER IN A NANOTUBE 119
QUASIPARTICLE LIFETIME AND DENSITY OF STATES 123
LOCALIZATION LENGTH 126
CONCLUDING REMARKS 128
ACKNOWLEDGMENT 129
REFERENCES 129
PHYSICS OF THE METAL-CARBON NANOTUBE INTERFACES: CHARGE TRANSFERS, FERMI-LEVEL “PINNING” AND APPLICATION TO THE SCANNING TUNNELING SPECTROSCOPY 131
INTRODUCTION 131
METHODS 132
RESULTS 137
DISCUSSIONS AND CONCLUSIONS 141
ACKNOWLEDGMENT 143
REFERENCES 143
SINGLE PARTICLE TRANSPORT THROUGH CARBON NANOTUBE WIRES: EFFECT OF DEFECTS AND POLYHEDRAL CAP 146
INTRODUCTION 146
METHOD 147
DEFECTS 149
TRANSPORT THROUGH A POLYHEDRAL CAP 151
CONCLUSIONS 155
REFERENCES 157
CARBON NANOTUBES FROM OXIDE SOLID SOLUTION : A WAY TO COMPOSITE POWDERS, COMPOSITE MATERIALS AND ISOLATED NANOTUBES 159
INTRODUCTION 159
EXPERIMENTAL 160
RESULTS AND DISCUSSION 162
CONCLUSIONS 174
REFERENCES 175
IMPULSE HEATING AN INTERCALATED COMPOUND USING A 27.12 MHz ATMOSPHERIC INDUCTIVELY COUPLED ARGON PLASMA TO PRODUCE NANOTUBULAR STRUCTURES 177
INTRODUCTION 177
DISCUSSION AND RESULTS 181
THE FUTURE? 186
CONCLUSIONS 186
ACKNOWLEDGEMENTS 187
REFERENCES 187
THE SYNTHESIS OF SINGLE-WALLED CARBON NANOTUBES BY CVD CATALYZED WITH MESOPOROUS MCM-41 POWDER 189
INTRODUCTION 189
EXPERIMENTAL 190
RESULTS 191
CONCLUSIONS 200
ACKNOWLEDGEMENT 200
REFERENCE 200
MECHANICAL PROPERTIES AND ELECTRONIC TRANSPORT IN CARBON NANOTUBES 202
INTRODUCTION 202
MECHANICAL PROPERTIES 202
TRANSPORT PROPERTIES 206
SUMMARY AND CONCLUSIONS 207
REFERENCES 210
ELECTROCHEMICAL STORAGE OF HYDROGEN IN CARBON SINGLE WALL NANOTUBES 211
ABSTRACT 211
EXPERIMENTAL 211
CYCLIC STABILITY 213
CHARGE/DISCHARGE CURVES 215
CHEMICAL TREATMENT TO IMPROVE THE KINETIC PROPERTIES 215
CONCLUSIONS 219
REFERENCES 219
DIRECT MEASUREMENT OF BINDING ENERGY VIA ADSORPTION OF METHANE ON SWNT 220
ABSTRACT 220
INTRODUCTION 220
Experimental 221
BIBLIOGRAPHY 226
ELECTRICAL PROPERTIES OF CARBON NANOTUBES: SPECTROSCOPY, LOCALIZATION AND ELECTRICAL BREAKDOWN 227
INTRODUCTION 227
ELECTRICAL PROPERTIES OF SINGLE-WALLED NANOTUBES: NANOTUBE RINGS 228
ELECTRICAL TRANSPORT AND BREAKDOWN IN MULTI-WALLED TUBES 233
ELECTRICAL PROPERTIES OF SEMICONDUCTING NANOTUBES 235
REFERENCES 240
FIELD EMISSION OF CARBON NANOTUBES FROM VARIOUS TIP STRUCTURES 242
INTRODUCTION 242
MODEL SYSTEM AND COMPUTATIONAL METHOD 242
ELECTRONIC STRUCTURE OF MODEL SYSTEMS 243
EFFECT OF EXTERNAL FIELDS 244
LOCAL FIELD ENHANCEMENT 249
DISCUSSION 253
REFERENCES 254
FIRST AND SECOND-ORDER RESONANT RAMAN SPECTRA OF SINGLE-WALLED CARBON NANOTUBES 255
INTRODUCTION 255
1D DENSITY OF ELECTRONIC STATES 258
FIRST-ORDER STOKES SPECTRA 260
THE D-BAND AND G´ BAND FEATURES 263
OVERTONES AND COMBINATION MODES 268
SUMMARY 273
ACKNOWLEDGMENTS 275
REFERENCES 275
ON THE OVERLAP ENERGY IN CARBON NANOTUBES 277
INTRODUCTION 277
THEORETICAL ISSUES 277
RELEVANT EXPERIMENTAL RESULTS 287
STS/STM Measurements 288
Optical Measurements 288
Resonant Raman Scattering Experiments 289
Anti-Stokes Resonant Raman Spectra 291
THE ‘D-BAND’ DISPERSION EFFECTS 294
SUMMARY AND CONCLUSIONS 295
REFERENCES 296
ELECTRONIC AND MECHANICAL PROPERTIES OF CARBON NANOTUBES 298
INTRODUCTION 298
SAMPLES 298
MECHANICAL PROPERTIES 301
TRANSPORT PROPERTIES 305
ELECTRON SPIN RESONANCE 312
ELECTRON AND LIGHT EMISSION 315
ACKNOWLEDGEMENT 320
REFERENCES 320
LOW ENERGY THEORY FOR STM IMAGING OF CARBON NANOTUBES 322
ABSTRACT 322
INTRODUCTION 322
STM IMAGES: GENERAL THEORY 323
RESULTS FOR STM IMAGES OF CONDUCTING TUBES 326
IMAGE SWITCHING FOR SEMICONDUCTING TUBES 328
SUMMARY 330
ACKNOWLEDGMENTS 331
REFERENCES 331
QUANTUM TRANSPORT IN INHOMOGENEOUS MULTI-WALL NANOTUBES 333
INTRODUCTION 333
GENERAL SCATTERING TECHNIQUE 335
CONDUCTANCE IN MULTI-WALL NANOTUBES 338
TRANSPORT IN INHOMOGENEOUS MULTI-WALL NANOTUBES 342
CONCLUSIONS 346
ACKNOWLEDGEMENTS 346
REFERENCES 346
CONDUCTIVITY MEASUREMENTS OF CATALYTICALLY SYNTHESIZED CARBON NANOTUBES 348
ABSTRACT 348
INTRODUCTION 348
NANOTUBE SYNTHESIS 349
RESULTS AND DISCUSSION 349
CONCLUSIONS 352
ACKNOWLEDGEMENTS 352
REFERENCES 352
FABRICATION OF FULL-COLOR CARBON-NANOTUBES FIELD-EMISSION DISPLAYS: LARGE AREA, HIGH BRIGHTNESS, AND HIGH STABILITY 354
I. Introduction 354
II.Field Emission Display 354
III. Fabrication process of CNT-FED 356
IV. Emission properties of CNT-FED A. Imaging of emission site 358
C. Emission current-voltage characteristics 359
FREE SPACE CONSTRUCTION WITH CARBON NANOTUBES 364
ABSTRACT 364
INTRODUCTION 364
EXPERIMENTAL APPARATUS 365
EXPERIMENT 369
RESULTANT GEOMETRIES 373
CONCLUSIONS 374
ACKNOWLEDGEMENTS 376
REFERENCES 376
PARTICIPANTS 377
GLOSSARY OF COMMON ABBREVIATIONS 391
INDEX 392

PHYSICS OF THE METAL-CARBON NANOTUBE INTERFACES: CHARGE TRANSFERS, FERMI-LEVEL "PINNING" AND APPLICATION TO THE SCANNING TUNNELING SPECTROSCOPY (p. 121-122)

Yongqiang Xue1 and Supriyo Datta2
1 School of Electrical and Computer Engineering, Purdue University,
West Lafayette, IN 47907, USA
Email: yxue@ecn.purdue.edu
2 School of Electrical and Computer Engineering, Purdue University,
West Lafayette, IN 47907, USA
Email: datta@ecn.purdue.edu

INTRODUCTION

After its discovery in 1991,1 carbon nanotube has rapidly emerged as the most promis-- ing candidate for molecular electronics due to its quasi-one dimensional structure and the unique characterization of its electronic structure in terms of two simple geometric indices.2 Besides its huge technological potential, carbon nanotube also serves as the artificial laboratory in which one-dimensional transport can be investigated,3 sim-- ilar to the semiconductor quantum wire.4 However, unlike its semiconductor cousin where transport is mostly ballistic, the study of transport in carbon nanotube has been distressed by the difficulty of making low resistance contact to the measuring electrodes. The high resistances reported in various two- and three-terminal measurements5 have led Tersoff6 (and also independently by one of the authors7) to suggest that wavevector conservation at the metal-carbon nanotube contact may play an important role in explaining the high contact resistance.8 The complexity and importance of the metal-carbon nanotube interface makes it an immediate challenge to both theorists and experimentalists.

The single most important property of the metal-carbon nanotube interface (and in general, of any interface involving metal) is the position of the energy bands (or energy levels) of the nanotube relative to the Fermi-level of the metal which manifests itself in the electronic transport property of the interface. Depending on the contact geometry, transport can occur in the direction parallel to the nanotube axis, in the case of the nanotube field-effect-transistor (FET),5,9 or perpendicular to it, in the case of the STS measurement.10,11 In the STS measurement, the Fermi-level is found to have shifted to the valence band edge of the semiconducting nanotube.10 Such observed Fermi-level "pinning" has been used to explain the operation of the nanotube FETs with highresistance contacts,5 where the measured two-terminal resistance for metallic nanotube is Recently low resistance contacts with two-terminal resistance as low as have been obtained.9 However, low temperature transport measurements using these low resistance contacts show that the Fermi-level is located between the valence and the conductance band of the semiconducting nanotube, instead of being "pinned" at the valence band edge. This conflict raises the important question of whether the Fermi-level positioning may depend on the contact geometry and the interface coupling. In this paper we present a theory of the scanning tunneling spectroscopy of a singlewall carbon nanotube (SWNT) supported on the Au(111) substrate.

The central idea is that the work function difference between the gold substrate and the nanotube leads to charge transfers across the interface, which induce a local electrostatic potential perturbation on the nanotube side. This atomic-scale interfacial potential perturbation shifts the energy level of the nanotube relative to the gold Fermi-level, and gives rise to the observed Fermi-level shift in the STS current-voltage characteristics. However, for transport in the direction parallel to the nanotube axis, as in the case of nanotube transistors, such local potential perturbation at the interface is not important in determining the Fermi-level position if the coupling between the metal and the nanotube is strong (i. e. , low resistance contact). In this case, the metal-induced gap states (MIGS) model provides a good starting point for determining the Fermi-level position. Based on this model, we expect that any discrepancy between the metal Fermi-level and the nanotube "charge-neutrality level" should be rapidly screened out by the metal-induced gap states in the nanotube side,12–14 leading to the "pinning" of the Fermi-level. Another important feature in our theory is that we have taken into account the localized 5d orbitals of the platinum tip in our treatment of the STS which can have significant effects on the interpretation of the STS data.15 Our discussion is restricted to the low temperature regime, in correspondence with the experimental works.

METHODS

A convenient way of characterizing the band lineup problem at any interface is to find a reference level, the role of which is to put all materials forming the interface on a common absolute energy scale.13,14 If the position of the reference level depends only on the bulk property, then the relative position of the energy bands at the interface can be determined trivially by merely lining up the reference levels. This is the elegant idea of "charge-neutrality level",12 which has been applied with impressive success by Tersoff13,14 to various metal-semiconductor junctions and semiconductor heterojunctions. For metal, the reference level is the Fermi-level while for semiconductor, it is the so called "charge-neutrality level" which can be taken as the energy where the gap states cross over from valence- to conduction-band character.

This approach greatly simplifies the band lineup problem and gives quantitatively accurate prediction of the Schottky barrier height when applied to the metalsemiconductor interface.13 The success of this model relies on the fact that there exists a continuum of gap states around at the semiconductor side of the metalsemiconductor interface due to the tails of the metal wavefunction decaying into the semiconductor, which can have significant amplitude a few atomic layers away from the interface.12 Any deviation from the local charge neutrality condition in the interface region will be screened out rapidly by these metal-induced gap states (MIGS). In this way, the local charge and potential perturbations right at the interface are not important in determining the barrier height observed in the transport characteristics since the range of this local perturbation is only a few atomic layers, and the charge carriers can easily tunnel through this region.