Index. 2DACH, see two dimensional auto-correlation histogram

Index 2DACH, see two dimensional auto-correlation histogram acceptor 102 103, 131 133, 289, 296 297, 310, 332 action spectroscopy 230 233, 244 adiabatic 160 161, 165, 168, 185, 251 252, 255, 303, 362, 384 adsorbates, molecular 195, 330 AFM 46, 52 53, 56, 68, 86 87, 89, 91, 104, 106, 309, 331, 334, 336 see atomic force microscopy alkane 56 57, 110 112, 122, 125, 288 alkanedithiols 420 alkanedithol 119 anchoring groups 109, 111, 126, 132 asymmetric bias profile 422 asymmetric molecule electrode contacts 133 asymmetric molecule electrode interface 131 asymmetric potential profile 414 atomic force microscopy (AFM) 46, 52, 68, 104, 309, 331, 336 Au electrodes 104, 111, 113, 115, 122, 244, 298, 300, 304 Au nanoelectrodes 237 Au(111) 297, 303, 305, 329, 336 337, 340, 346 auto-correlation histogram 136 azobenzene 67 69, 82 85, 87 88, 91 azobenzene derivatives 68, 85 azobenzene molecules 68, 91 azurin 296 304, 325, 327, 332 333, 335 345 barrier height 15 19, 90, 138, 288, 299, 398 399 barrier model 404 405, 407, 409 411 barrier-shape conjecture 402, 404, 417, 424 BDA 126 127 BDT, see benzenedithiol benzene 126 127, 334, 394 benzenedithiol (BDT) 114 116, 129 130, 229, 234, 242 244 bi-potentiostat 329, 344 bias asymmetry factor 416 417 bioelectronics 282 biomolecules 67, 70 71, 294, 304 307, 313, 331, 333 biosensors 70 71, 345 biphenyl 124 Born-Oppenheimer approximation 362, 382 Bose Einstein distribution function 379, 392 break junction technique 224, 237 break junctions 101, 106, 139, 410, 419 4,4 -bypiridine 107, 114

440 Index C-AFM 52 53, 68, 87, 89, 91 C8DA, see octanediamine C8DT, see octanedithiol C60 126, 227, 286, 376 377 CAFM, see conducting atomic force microscopy CAFMBJ, see conducting-afm break junction carbon nanotube (CNT) 126, 251, 309, 313 cation-binding switchable molecular junction 77 81 charge transport (CT) 51, 57, 106, 133, 140, 255, 281, 284, 286 288, 294, 296, 298, 313 314 chemical linkers 110 111 chemical potential 5, 180, 183, 194, 199, 254, 258, 263, 265, 267 269, 356, 363, 374 376, 380, 387 CMOS see complementary metal oxide semiconductor see complementary metal-oxide semiconductor CNT, see carbon nanotube co-factors 325 328, 330, 332, 334, 336, 338, 340, 342, 344 348 co-tunneling processes 180, 183, 188 coherent tunneling 14 15, 18, 288 complementary metal oxide semiconductor (CMOS) 66, 398 complementary metal-oxide semiconductor (CMOS) 66 67, 92, 398 complexation 71, 77 82, 91 92 conductance contact 90, 106 cytochrome 302 higher 26, 68 ohmic 397, 405 single-azurin 301 zero bias 228, 241 conductance attenuation factor 409 conductance histogram 107, 119 120, 124, 126 128, 300 301, 312, 419 conductance of DNA duplexes 306 311 conductance traces 105, 107, 110, 116, 118, 120 122, 137 conducting-afm break junction (CAFMBJ) 106, 119 conducting atomic force microscopy (CAFM) 117 conducting probe AFM 52, 56 conductor 6 7, 252, 256, 265, 268, 270, 307 308, 366, 399 conjugation 124, 287 contact angle 73, 77 79, 84 85 contact geometries 24, 112, 119, 287 contacts metal molecule 51 molecular-electrode 110 molecule electrode 124, 421 physisorbed 15 single-molecule 171 continuous-stretch mode 118, 120 121 corrected Simmons (model, prefactor) 408 coupling asymmetric metal molecule 239 electrode molecule 413 coupling between the molecule and the electrode 241 cross-correlation 136 137, 139 CT, see charge transport current-induced force 373

Index 441 current-voltage 1, 302, 374, 387, 394 current-voltage spectroscopy 421 CV, see cyclic voltammetry cytochrome b562 327 cytochrome c551 332 data analysis 102, 110, 116, 122, 136 137, 139 decay constant 125, 138, 288 degree of coupling 138 density functional theory (DFT) 240, 353, 355 356, 362, 372, 382, 394 density-functional theory (DFT) 158 159, 358 359, 361, 385, 394, 400, 411, 415, 417 density functional theory, time-dependent 362 DFT, see density-functional theory DFT calculations 411 diarylethene 68 69 dihedral angle 114, 123 124, 287 direct tunneling 26, 56, 138, 368, 399, 402 403, 424 DNA 70 71, 129, 140, 293, 295, 306 314 electronic properties of 307 308 DNA-based molecular junctions 129 DNA conductance 129, 307, 310, 314 DNA duplexes 306 307, 309, 311 donor 102 103, 131 133, 289, 296 297, 310, 332 double-barrier 133 dynamic molecular junction 65 68, 70 72, 74, 76, 78, 80, 82, 84, 86, 88, 90 92 Dyson equation 170 171, 175, 177 EC-STM 305, 325 326, 328 330, 332, 334, 336, 338, 340, 342, 344, 346 348 ECSTM, see electrochemical STM ECSTM/STS 327, 335, 343, 345, 347 ECSTS 327, 339, 344 EDLs, see electrochemical double layer egain 80, 87 88, 91 electrical characterization 55, 65 electrochemical double layer (EDLs) 292 electrochemical etching and deposition 109 electrochemical scanning tunneling microscope 328 329 electrochemical STM (ECSTM) 298 300, 304, 327, 335 336, 339, 343, 345, 347 electrodes asymmetric 51, 132 macroscopic 2, 20, 67, 281 nanogap 224, 233 234 electromigration 56, 109 electromigration nanogap junctions 56 electron-phonon interactions 134 electron transfer metalloproteins 331 332 electron transport 50 52, 101 102, 104, 106, 108 112, 114 116, 118, 122 126, 128 130, 138 140, 156 202, 204, 327, 353 366, 394 non-equilibrium 394 resonant 179 electron tunneling, coherent 287, 342, 398 electron electron interactions 160, 166, 169, 171 172, 190, 192 193, 201

442 Index electronic devices hybrid molecular 104 molecular 58, 92, 281, 314, 399 electronic-vibrational coupling 161, 166, 171, 181, 183 184, 186 187, 196, 202 203 ellipsometry 73, 77 78 energetic alignment (of the HOMO or LUMO) 397, 399 energy gap 102, 138 environment 9, 38, 54, 66, 101, 129, 292 293, 298, 303 304, 308, 310, 328, 330, 344, 347 exchange-correlation 357 358, 361, 363 energy 361 kernel 361 local-density approximation 363 potential 357 358, 363 fabrication approaches 42, 46 47, 49, 51, 53 FC-2DCCH, see force-conductance two dimensional cross-correlation histogram Fermi level 5 6, 16, 19, 56, 133, 181, 190, 195, 202, 239, 241 242, 399, 401, 409, 412 Fermi wavelength 6, 354, 356, 359 Fermi Dirac distribution function 375, 378, 387 FET, see field-effect transistor field-effect transistor (FET) 290 field-effect transistor, single-molecule 291 field emission 18 20, 56, 138, 424 field-emission tunneling 402, 403, 424 Floquet theory 252 force-conductance trace 122 force-conductance two dimensional cross-correlation histogram (FC-2DCCH) 136 Fowler Nordheim diagram 401 Fowler Nordheim tunneling 14, 18, 26 Franck Condon blockade 188 Franck Condon contribution 242 Friedel oscillation 356 frontier molecular orbitals 111, 288, 292, 397, 399 graphene 47, 54, 68 69, 71, 290, 344 graphene electrode 68 Green 157, 165 168, 170 178, 252, 258, 260 262, 265, 361, 363 364 Green operator, molecular 260, 262 Green s functions 168, 173, 175, 252, 364 vibrational 172, 174 175, 177 178 Hamiltonian 158 163, 166 168, 253 256, 258, 260 265, 355, 362 363, 365, 381, 383 384, 392 Heisenberg equation of motion 168, 173 174 Hellmann-Feynman theory 372 Herzberg Teller contributions 242 highest occupied molecular orbital (HOMO) 15 16, 19, 56, 102, 133, 241, 243, 288, 399 400, 415 416

Index 443 HOMO, see highest occupied molecular orbital hydroquinone 345, 347 Kirchhoff s laws 127 Kondo effects 109, 140, 156 I(s) technique 108 IETS, see inelastic electron tunneling spectroscopy image charge 16 17, 134, 404, 406, 408, 410 image charge effect 16, 134, 406 image effects 410 inelastic electron tunneling spectroscopy (IETS) 131, 204, 224 227, 229, 231, 244, 387 inelastic tunneling spectroscopy 42 infrared spectroscopy 43, 45 interfacial electron transport 327 ion scattering spectroscopy (ISS) 57 ions 54, 71, 92, 129, 292, 330 331, 334, 371 372, 381 384 irradiation 84 89, 249, 251 isomerization 67, 69, 82, 84 86, 88 89 isotope effect 227, 232, 244 ISS, see ion scattering spectroscopy jellium model 355, 357, 371 junction conformations 110, 113, 119 junction lifetime 129 131 Keldysh equations 170 171, 175, 177 Labview program 119 Landauer 7, 138 139, 253, 258 259, 264, 367, 406, 412 Landauer formula 138 139, 259, 412 Landauer theory 7 lateral confinement 406, 425 leads 249 280 Lippmann Schwinger equation 361 362, 364 366, 372, 385, 394 liquid metal contacts 48 local heating 130 131, 156, 193, 195, 200 201, 251, 385, 390, 394 Lorentzian transmission 411 lowest unoccupied molecular orbital (LUMO) 15 16, 19, 26, 102, 133, 241 288, 399 400 LUMO, see lowest unoccupied molecular orbital MCBJ, see mechanically controlled break-junction mechanically controllable break junction 224 mechanically controlled break junction 106 mechanically controlled break-junction (MCBJ) 107, 123, 126, 237 memory 66 67, 69 71, 91 92 mercury drops 48, 68, 103

444 Index metal-molecule interactions 42, 241 metallization 43 45 metalloprotein electrochemical behavior 302 micropore 68 (MO) energy offset 410, 416, 421, 424 molecular bridge 71, 156, 158, 160 162, 164, 168, 170 171, 179 180, 183, 187 190, 193 194, 196, 296 non-interacting 164, 175 molecular conformations 105, 115 molecular-electrode contact 110 molecule-electrode interfaces 101, 113, 115, 118 119, 123, 131 132, 134 135 molecular electronic junctions 38, 45 46, 50, 55 56 molecular junction 19 20, 65 68, 71 72, 77 83, 113 120, 129 132, 162, 179 182, 185 187, 189 193, 195 197, 199 202, 224 225, 227 228, 235 244 molecular junctions 41 42, 44, 46 47, 51 54, 57 59, 65 66, 70 72, 106 108, 122 124, 131 136, 223 234, 236 240, 242 244, 249 254, 270 271 molecular monolayers 46 48, 284 molecular orbitals 2, 15, 26, 56, 81, 89 90, 102, 111, 133 134, 159, 288, 292, 397 400 molecular orientations 115 molecular rectifier 102 103, 133, 285 molecular rectifiers 102 103, 133, 284 285 molecular structures 68, 101, 104, 123, 125, 128, 139, 282 molecular transistors 290, 343 molecular transport junctions 165 molecular wires 70, 137, 249 250, 327 molecule electrode coupling 115, 135, 413 molecule electrode interface 101, 113, 115, 118 119, 123, 131 132, 134 135 molecule lead coupling 166, 169, 172, 174 moments of current counting statistics 370 shot noise 370 Moore s prediction 102 nanoelectronic devices 155, 398 nanoparticles 38, 68, 71, 109, 233 nanopore 42, 103 NDR, see negative differential resistance negative differential resistance (NDR) 131, 134, 156, 202 203 NEGF, see non-equilibrium Green s function Newns Anderson model 343, 397, 400, 411 412, 414, 420, 426 426 nitrite reductase 332 non-adiabatic 161, 252 non-equilibrium Green s function (NEGF) 157, 165, 177, 252, 361 non-monotonic 134 nonresonant tunneling 56, 90

Index 445 octanediamine (C8DA) 120 122 octanedithiol (C8DT) 111 112, 114, 119 122, 131, 288, 409, 420 421 octanethiol 20 21, 23, 27 oligophenylene vinylene (OPV) 236, 335, 346 347 optical switch molecular junction 82 89 OPV, see oligophenylene vinylene OPV-derivatized quinone 346 347 organic molecules 4, 125, 131, 300 organic monolayers 42 44, 58 pulses 249, 251 254, 257, 271 PVS, see peak voltage spectroscopy PZT, see piezoelectric transducer quantum dot 10 13 quantum scattering theory 250, 252 quantum transport 354 355 quaterthiophene 73 74, 77 78 quinones 327, 334 335, 345 346 PCS, see point-contact spectroscopy peak voltage spectroscopy (PVS) 426 phononic heat 378 380 conductance 379 380 current 378 380 photo-assisted 250 251, 253 photo-inert 253 photo-suppressed 253 photoisomerisable 83 photoisomerization 67 68, 88, 90, 92 piezoelectric transducer (PZT) 117 122 planar electrodes 16 point-contact spectroscopy (PCS) 225 227, 229, 231, 244 Poisson equation 162, 357 358, 362, 364 Poisson Schrödinger equation 357 358 preformed metal contacts 53 54 Pt electrodes 227 Pt nanowires 20 21, 23 pulse 3, 23, 249 250, 252 254, 256, 258, 260, 262, 264, 266, 268 270, 296 Raman scattering 233, 236, 242, 331 surface-enhanced 223 Raman spectrum 224, 233, 235 237 rectification 50, 131 134, 138, 202 203, 285 rectification ratio (RR) 133, 138, 368 370, 388 389, 391 rectifying effect 131 redox co-factor 327, 334 redox metalloprotein 288, 293, 325 328, 330 336, 338 340, 342, 344, 346, 348 resonant tunneling 90, 188, 193, 267 268, 300, 422 room temperature 20, 26, 50, 123, 130 131, 233, 243, 344 rotaxane 70 rotaxane molecules 70 RR, see rectification ratio SAMs, see self-assembled monolayers pristine 83, 86 88

446 Index saw-tooth 119 122 scanning probe microscopy (SPM) 109, 117 119, 305 scanning probe microscopy break junction (SPMBJ) 107, 109, 111, 117 119, 121 123 scanning tunneling microscope break junction (STMBJ) 70, 224, 286, 300, 302 scanning tunneling microscopy (STM) 3 4, 21 24, 68 69, 104 105, 108, 224 225, 239, 285 286, 298 300, 302, 325 332, 336, 338, 346 348, 376 377 scanning tunneling microscopy break junction (STMBJ) 70, 105 106, 114, 120, 126, 301 scattering 6 9, 157, 163 164, 233, 236 237, 242, 249 250, 252 257, 259, 267 268, 353 358, 361 365, 381 382, 385 387, 389 electron phonon 392 inelastic electron vibration 389 scattering theory 157, 164, 250, 252 253, 255 257 Schrödinger equation 362, 382 Seebeck coefficient 373 377, 379, 393 394, 426 self-assembled monolayers (SAMs) 46 49, 52, 57, 73 76, 78, 83, 85 88, 91, 304 305 self-breaking 238 sensors 38, 71, 314 SERS, see surface-enhanced Raman scattering silicon 39, 43 45, 58 Simmons approach 404 405, 407, 409 Simmons model 138 139, 398, 404, 411, 419, 425 simulation 114 115, 140, 240, 363 single-level tunneling model 241 single-molecule break junction (SMBJ) 101 102, 106, 111, 113, 115 119, 121 123, 125 127, 129, 131, 133, 135, 137, 139 140 single-molecule circuits 102, 127 single-molecule conductance 27, 101 102, 106 107, 109, 111, 113, 124, 126, 136, 286, 307, 314 single-molecule device 1 2, 4, 6, 8, 10, 12, 14, 16, 18, 20, 22, 24, 26, 28 29, 102 single molecule dynamics 224, 239 single-walled carbon nanotube (SWNT) 68, 70 71 SMBJ, see single-molecule break junction SMBJs, see single-molecule break junction spectroscopic characterization 57 SPM, see scanning probe microscopy SPMBJ, see scanning probe microscopy break junction statistical analysis 106, 109, 308, 419 stimulus 27, 65 67, 69 71, 92 STM, see scanning tunneling microscopy STMBJ, see scanning tunneling microscope break junction stochastic fluctuations 397, 419 421 Stokes components 236 stretch-hold 118 122 sulfur 20, 75, 79, 83 superexchange 15, 289, 310, 399 surface-enhanced Raman scattering (SERS) 224, 233 240, 242, 244

Index 447 SWNT, see single-walled carbon nanotube template 39, 53 terahertz 249, 251 theory of electron transport 354 355, 357, 359, 361, 363 thermal fluctuations 105, 238 thermoelectric nanojunctions 374 thermoelectricity 242 inelastic Seebeck coefficient 390 nano-refrigerator 395 self-powered transistor 395 thermoelectric figure of merit ZT 374, 379 380, 390, 392 393 thermopower 373, 376, 427 thioacetate 335, 345 Tien Gordon 250 251, 253, 259, 263 264, 271 time-dependent fields 249 time-periodic 250, 252, 257 time series analysis 136 trace 1, 21 22, 25, 107, 120 122, 259 260, 388 transient 38, 129 130, 164 165, 249 252, 254 255, 257, 271, 301 transient dynamics 249, 252 transistors single-molecule 2, 20, 27 single-particle 343 344 transition voltage 19, 56, 81 82, 89 90, 138 139, 224, 291, 302 304, 397 404, 406 408, 410, 412, 414 418, 420 422, 424 426 transition voltage spectroscopy (TVS) 89, 303 304, 397, 404 405, 409 411, 413, 415, 417 trapezoidal barrier 402 triangular barrier 402, 410 tunneling direct 138, 368, 399, 402 403 incoherent 17 off-resonant 267 268 sequential 187 188, 192, 288, 312 tunneling barrier 17, 26, 48, 90, 138, 299, 303, 402, 404, 409 411, 414, 424 tunneling current 21, 23 24, 108, 267 268, 298, 329 330, 336, 339 341, 344 347 TVS, see transition voltage spectroscopy two dimensional auto-correlation histogram (2DACH) 136 137 two-step coherent electron transfer 338 uncorrected Simmons 425 universality class 423 UV irradiation 86 88 UV light 69, 84 85, 88 89 vacuum 15, 19, 22, 28, 114, 123, 305, 307 308, 355 356, 359 360, 398, 404, 410, 425, 427 vacuum break junctions 410 vibration spectroscopy 223 224, 233, 244 vibrational excitation 179, 188 189, 192 193, 195 199, 201, 203

448 Index current-induced 157, 189, 192 193 vibrational spectroscopy 42 43, 58, 88 vibronic coupling 183, 271, 382, 384 vibronic effects 157, 186, 202, 380 381, 383, 385, 387, 389, 391, 393 vibronic interactions 255 electron-vibration interactions 381 inelastic electron tunneling spectroscopy 387 local heating 385 vibronic transport 181, 186, 189, 191 193 viologen 327 vitamins 334 voltage division factor 162, 412 414, 416 wide band 261 262, 264, 270 wide-band approximation 412 wide-band limit 264 265, 400 WKB approximation 407 408 WKB method 407 408 work function 15, 26, 52, 57, 404 working electrode 298, 328, 330 X-ray photoelectron spectroscopy 42, 57 XPS 57, 73, 75 79, 83 84, 331, 333

Prof. Mark A. Reed Yale University, USA Molecular electronics, an emerging research field at the border of physics, chemistry, and material sciences, has attracted great interest in the past decade. It aims at fabricating devices with sizes of nanometers under atomic control, by developing novel bottom-up approaches, as opposed to the classical top-bottom approaches. To achieve the ultimate goal of designing molecular electronic devices with desired functionality and experimental manipulation at the singlemolecule level, the microscopic understanding of electron transport at the nanoscale is an important prerequisite. This book, a multi-authored volume comprising reviews written by leading scientists, discusses recent advances in the field. To make the book useful for scientists of various disciplines interested in learning by doing, each chapter is written in a scientific/tutorial hybrid style, with its own introduction, presenting fundamental concepts and frameworks. Adopting a pedagogical, self-contained manner of presentation, the chapters provide guidelines for young scientists (physicists, chemists, and engineers) planning to actively contribute, as experimentalists or theorists, to molecular electronics. Still, a series of results are new and can certainly be inspiring and of interest to specialists in the field. The content reflects the strong transdisciplinary efforts needed for substantial progress. V471 ISBN 978-981-4613-90-3 Bâldea Ioan Bâldea is principal investigator at the Chair of Theoretical Chemistry, University of Heidelberg (Germany), and full research professor of theoretical physics at the Institute of Space Sciences, National Institute for Lasers, Plasma, and Radiation Physics, Bucharest (Romania). His research work comprises general theory of condensed matter physics, materials science, and quantum chemistry. In recent years, he has mainly focused on molecular electronics and nanotransport, with emphasis on quantum dots, quantum dots nanoarrays, transition voltage spectroscopy, solvent effects and reorganization effects in molecules with floppy degrees of freedom. Molecular Electronics This book contains state-of-the-art reviews of some of the most important experimental and theoretical aspects of electronic transport at the molecular level. The blend of tutorial aspects with cutting-edge results and approaches makes it an important reference for those interested in working in the field. Molecular Electronics An Experimental and Theoretical Approach edited by Ioan Bâldea