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een determined and quantitatively compared to that in InP quantum dots[46]. Preliminary results indicate that II–VI quantum wires can be grownsimilarly [48]. A similar approach was applied to growth of insoluble, but sizemonodispersedin diameter (4–5 nm), silicon nanowires. Here, reactions wereconducted at elevated temperature and pressure (500jC and 200–270 bar,respectively) using alkanethiol-coated gold nanoclusters (2.5 F 0.5 nmdiameter) as the nucleation and growth ‘‘seeds’’ [49].V. PHASE TRANSITIONS AND PHASE CONTROLNanocrystal quantum dots have been used as model systems to study solid–solid phase transitions [50–53]. The transitions, studied in CdSe, CdS, InP andSi nanocrystals [52], were induced by pressure applied to the nanoparticles in adiamond anvil cell by way of a pressure-transmitting solvent medium, ethylcyclohexane.Such transitions in bulk solids are typically complex anddominated by multiple nucleation events, the kinetics of which are controlledby crystalline defects that lower the barrier height to nucleation [50,53]. Innearly defect-free nanoparticles, the transitions can exhibit single-structuraldomainbehavior and are characterized by large kinetic barriers (Fig. 21). Incontrast to original interpretations which described the phase transition innanocrystals as ‘‘coherent’’ over the entire nanocrystal [50], the nucleation ofthe phase transition process was recently shown to be localized to specificcrystallographic planes [53]. The simple unimolecular kinetics of the transitionstill support a single nucleation process; however, the transition is nowthought to result from plane sliding as opposed to a coherent deformationprocess. Specifically, the sliding-plane mechanism involves shearing motionalong the (001) crystallographic planes, as supported by detailed analyses oftransformation times as a function of pressure and temperature.Because of the large kinetic barriers in nanocrystal systems, their phasetransformations are characterized by hysteresis loops (Fig. 21) [50,51,53]. Thepresence of a strong hysteresis signifies that the phase transition does notoccur at the thermodynamic transition pressure and that time is required forthe system to reach an equilibrium state. This delay is fortunate in that itpermits detailed analysis of the transition kinetics even though the system ischaracterized by single-domain (finite-size) behavior. As alluded to, theseanalyses were used to determine the structural mechanism for transformation.Specifically, kinetics studies of transformation times as a function of temperatureand pressure were used to determine relaxation times, or average timesto overcome the kinetic barrier, and, thereby, rate constants. The temperaturedependence of the rate constants led to the determination of activationenergies for the forward and reverse transitions, and the pressure dependenceCopyright 2004 by Marcel Dekker, Inc. All Rights Reserved.
Figure 21 Two complete hysteresis cycles for 4.5-nm CdSe NQDs presented asunit cell volumes for the wurtzite sixfold-coordinated phase (triangles) and the rocksaltfourfold-coordinated phase (squares) versus pressure. Solid arrows indicate thedirection of pressure change, and dotted boxes indicate the mixed-phase regions.Unlike bulk-phase transitions, the wurtzite to rock-salt transformation in nanocrystalsis reversible and occurs without the formation of new high-energy defects, asindicated by overlapping hysteresis loops. The shape change that a sliding-planetransformation mechanism (see text) would induce is shown schematically on theright. (From Ref. 51; reprinted with permission.)of the rate constants led to the determination of activation volumes for theprocess [53]. The latter represents the volume change between the startingstructure and an intermediate transitional structure. Activation volumes forthe two directions, wurtzite to rock salt and rock salt to wurtzite, respectively,were unequal and smaller for the latter, implying that the intermediatestructure more closely resembles the four-coordinate structure. The activa-Copyright 2004 by Marcel Dekker, Inc. All Rights Reserved.
Page 1:
Copyright 2004 by Marcel Dekker, In
Page 4 and 5: Copyright 2004 by Marcel Dekker, In
Page 6 and 7: Copyright 2004 by Marcel Dekker, In
Page 8 and 9: This book covers several topics of
Page 10 and 11: esult, some exciting topics were no
Page 12 and 13: 3. Fine Structure and Polarization
Page 14 and 15: 9. III-V Quantum Dots and Quantum D
Page 16 and 17: ContributorsUri BaninThe Hebrew Uni
Page 18 and 19: 1‘‘Soft’’ Chemical Synthesi
Page 20 and 21: structure of energy states leads to
Page 22 and 23: growth can proceed by Ostwald ripen
Page 24 and 25: Figure 3 Transmission electron micr
Page 26 and 27: Figure 4 Temporal evolution of the
Page 28 and 29: No. 26, are f85% (Fig. 6) [21]. Alt
Page 30 and 31: tion spectra and broad PL spectra.
Page 32 and 33: ing surface-to-volume ratio with di
Page 34 and 35: Figure 8 Photoluminescence spectra
Page 36 and 37: lattice mismatch. Such a large latt
Page 38 and 39: match between InAs and ZnS of f11%.
Page 40 and 41: successfully repeated for up to thr
Page 42 and 43: Under a different growth regime, on
Page 44 and 45: Figure 14 Atomic model of the CdSe
Page 46 and 47: ‘‘Teardrop-shaped’’ particl
Page 48 and 49: Figure 17 High-resolution TEMs of C
Page 50 and 51: allows isolation of tetrapods in f8
Page 52 and 53: ligand concentrations yield a reduc
Page 56 and 57: tion volumes were also shown to be
Page 58 and 59: synthesis temperatures of z400jC ar
Page 60 and 61: Figure 23 (a) Photoluminescence spe
Page 62 and 63: levels (fV1 Mn per NQD). Despite in
Page 64 and 65: Figure 25 X-ray diffraction pattern
Page 66 and 67: Figure 27 Transmission electron mic
Page 68 and 69: An additional factor that strongly
Page 70 and 71: Figure 30 (a,b) Schematics illustra
Page 72 and 73: Slow, controlled precipitation of h
Page 74 and 75: Figure 34 Schematic illustrating th
Page 76 and 77: Figure 36 Transmission electron mic
Page 78 and 79: achieving biological compatibility
Page 80 and 81: 47. Yu H.; Gibbons P.C.; Kelton K.F
Page 82 and 83: 2Electronic Structure inSemiconduct
Page 84 and 85: Figure 2 (a) Simple model of a nano
Page 88 and 89: electron and hole to be treated as
Page 90 and 91: independently, Eq. (13) is commonly
Page 92: a better description of the bulk ba
Page 95 and 96: investigated. For optical experimen
Page 97 and 98: Figure 4 (a) Absorption (solid line
Page 99 and 100: Figure 6 Normalized PLE scans for s
Page 101 and 102: Figure 8 A simplistic model for des
Page 103 and 104: Figure 10 Theoretically predicted p
Page 105 and 106:
Figure 12 Schematics depicting the
Page 107 and 108:
Figure 14 Calculated band-edge exci
Page 109 and 110:
Figure 15 Absorption (solid line) a
Page 111 and 112:
Figure 18 (a) Calculated band-edge
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IV.BEYOND CdSeA. Indium Arsenide Na
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the six-band Luttinger Hamiltonian.
Page 117 and 118:
11. Norris, D.J.; Efros, Al.L.; Ros
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69. Gaponenko, S.V.; Woggon, U.; Sa
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formation of a long-lived dark exci
Page 123 and 124:
where the constant A is determined
Page 125 and 126:
In crystals for which the function
Page 127 and 128:
The respective wave functions areC
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passive, as was shown in Ref. 12. T
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square of the matrix element of the
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where e F = e F ieV and e F F = e x
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see that for all nanocrystal shapes
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optical recombination of the excito
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B. Recombination of the Dark Excito
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where x = cos h and f = l B g e H/3
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The theory of the polarization memo
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Figure 7 The size dependence of the
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state would have an infinite lifeti
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crystal axis [see Eq. (40)]. As a r
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time of the exciton momentum relaxa
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One must also account for the influ
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observed in one of the first studie
Page 157 and 158:
REFERENCES1. Bawendi, M.G.; Wilson,
Page 159 and 160:
4Intraband Spectroscopyand Dynamics
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The solid line in Fig. 1 shows the
Page 163 and 164:
Figure 2 FTIR spectra of n-type CdS
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of the center frequency. The experi
Page 167 and 168:
limit given by radiative relaxation
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from a long lifetime due to the pho
Page 171 and 172:
are two natural approaches to study
Page 173 and 174:
32. Inoshita, T.; Sakaki, H. Physic
Page 175 and 176:
continuous spectral tunability over
Page 177 and 178:
function and envelope function mome
Page 179 and 180:
ottleneck’’ [14,28]. Further re
Page 181 and 182:
in NQDs is dominated by nonphonon e
Page 183 and 184:
Figure 4 Dynamics of the IR postpum
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Figure 5 (a) Time-resolved PL spect
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Figure 6 (a) The time delay of the
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and due to Auger-type e-h interacti
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Figure 9 Dynamics of the 1S bleachi
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significantly greater than the fast
Page 195 and 196:
Figure 11 (a) Pump-intensity-depend
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NQD size. For small NQD sizes (R =
Page 199 and 200:
Figure 14 Nonlinear absorption/gain
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sorption change associated with a s
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where n h em is the hole ‘‘emit
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ultrafast (subpicosecond to picosec
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Figure 18 Schematic of transitions
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Figure 19 Dynamics of pump-induced
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where n i (i=1, 2 . . . , N ) is th
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Figure 21 (a) Two-e-h-pair (biexcit
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the volume fraction (filling factor
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intensity dependence of this peak (
Page 219 and 220:
Page 221 and 222:
can contribute to the saturation of
Page 223 and 224:
Page 225 and 226:
coupling between ‘‘volume’’
Page 227 and 228:
numerous discussions on the photoph
Page 229 and 230:
53. Kang, K.; Kepner, A.; Gaponenko
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the ‘‘on-off ’’ emission in
Page 233 and 234:
parallel form of data acquisition i
Page 235 and 236:
Figure 3 (a) Spectral time trace of
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transition energies. In fact, these
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distribution (dark line) does not d
Page 241 and 242:
exposure to only room light. In our
Page 243 and 244:
statistics for the off times are in
Page 245 and 246:
230Shimizu and BawendiCopyright 200
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Figure 10 (a) Time trace of a CdSe(
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and excited QD core states to fluct
Page 251 and 252:
arrows indicate the on-time truncat
Page 253 and 254:
W. K. Woo and V. C. Sundar for assi
Page 255 and 256:
size allows the electron affinity a
Page 257 and 258:
II.THEORY OF ELECTRON TRANSFER BETW
Page 259 and 260:
For the specific case of charge tra
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dominates, the mobility is often fi
Page 263 and 264:
where the constant A and the temper
Page 265 and 266:
components of modulation which are
Page 267 and 268:
nanocrystals [41], understanding ph
Page 269 and 270:
and ionization potential through tw
Page 271 and 272:
quantum dots. Furthermore, because
Page 273 and 274:
For many applications, a host mater
Page 275 and 276:
form blends with morphologies that
Page 277 and 278:
Figure 11 Photoluminescence efficie
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Figure 12 (a) Room-temperature PIA
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discussed briefly in Section IV. Ch
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dithiolates to thiol-terminated DNA
Page 285 and 286:
Films of passivated CdSe nanocrysta
Page 287 and 288:
Figure 16 Photocurrent action spect
Page 289 and 290:
decay with stretched exponential ki
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siderably larger than might be esti
Page 293 and 294:
dispersing CdSe nanocrystal chromop
Page 295 and 296:
memory and charge storage effects [
Page 297 and 298:
all) of the optically excited elect
Page 299 and 300:
composites of nanocrystals and conj
Page 301 and 302:
55. Asbury, J.B.; Hao, E.C.; Wang,
Page 303 and 304:
108. Morgan, N.Y.; Leatherdale, C.A
Page 305 and 306:
The approaches to fabrication of se
Page 307 and 308:
Figure 1 Experimental realization o
Page 309 and 310:
Due to this voltage division, the m
Page 311 and 312:
Figure 3 Simulated tunneling spectr
Page 313 and 314:
electron charging. In both positive
Page 315 and 316:
Figure 5 shows the typical features
Page 317 and 318:
Figure 7 Map of levels for InAs nan
Page 319 and 320:
Figure 8 Scanning electron microsco
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D CB = 0.31 eV is thus obtained. On
Page 323 and 324:
Figure 11 Correlation of optical an
Page 325 and 326:
atomistic approach based on pseudop
Page 327 and 328:
charging indicated that the tunneli
Page 329 and 330:
capacitance values were also kept t
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could not be detected in the QD/DT/
Page 333 and 334:
Figure 18 Tunneling conductanceF sp
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data in the inset of Fig. 19 repres
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corresponding to the s-like wave fu
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7. Grabert, H.; Devoret, M.H., Eds.
Page 341 and 342:
66. Su, B.; Goldman, V.J.; Cunningh
Page 343 and 344:
dimensional confinement are created
Page 345 and 346:
Figure 1 Transmission electron micr
Page 347 and 348:
The room-temperature absorption and
Page 349 and 350:
narrower in samples with larger mea
Page 351 and 352:
GaInP 2 QDs from a plot of the squa
Page 353 and 354:
crystal, indicating lattice-matched
Page 355 and 356:
Figure 5 Evolution of Stranski-Kras
Page 357 and 358:
Figure 7 Photoluminescence spectra
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Figure 8 Photoluminescence spectra
Page 361 and 362:
C. Efficient Anti-Stokes Photolumin
Page 363 and 364:
Because HF treatment has been shown
Page 365 and 366:
Page 367 and 368:
intensity of the PL when it is on a
Page 369 and 370:
eV stems from recombining carriers
Page 371 and 372:
Figure 16 Model to explain two-colo
Page 373 and 374:
although this term is not rigorousl
Page 375 and 376:
10 ps (about an order of magnitude
Page 377 and 378:
electron relaxation is inhibited an
Page 379 and 380:
Figure 18 Transmission electron mic
Page 381 and 382:
QDs, the nature of the QD capping s
Page 383 and 384:
QD solution. For an interdot distan
Page 385 and 386:
emission spectra of the two individ
Page 387 and 388:
Figure 23 Change of the PL intensit
Page 389 and 390:
(viz. the absorbed light intensity)
Page 391 and 392:
Figure 25Impact ionization in QDs.m
Page 393 and 394:
prevent electron-hole recombination
Page 395 and 396:
36. Miller, R.D.J.; McLendon, G.; N
Page 397 and 398:
91. Vurgaftman, I.; Singh, J. Appl.
Page 399 and 400:
139. Mićić, O.I.; Ahrenkiel, S.P.
Page 401 and 402:
10Synthesis and Fabrication of Meta
Page 403 and 404:
Figure 2 (A-C) Progression of HR-TE
Page 405 and 406:
Figure 3 Schematic for gold nanocry
Page 407 and 408:
Nanocrystal growth can occur by two
Page 409 and 410:
on the other hand, provide an ensem
Page 411 and 412:
Figure 6 (a) SAXS patterns for disp
Page 413 and 414:
Figure 8 The gold nanocrystal film
Page 415 and 416:
of the stabilizing ligand, and the
Page 417 and 418:
successfully modeled the 2D island
Page 419 and 420:
2. Steric Stabilization and a Soft
Page 421 and 422:
are fully extended. Moving away fro
Page 423 and 424:
Figure 11 High-resolution SEM image
Page 425 and 426:
Figure 13 (A) Transmission electron
Page 427 and 428:
function of the density of localize
Page 429 and 430:
Figure 15 High-resolution SEM image
Page 431 and 432:
thiol-capped nanocrystals [2]. The
Page 433 and 434:
41. Ackerson, B.J. Nature 1993, 365
Page 435 and 436:
with the effect of the particle com
Page 437 and 438:
Figure 1a shows the surface plasmon
Page 439 and 440:
Figure 2 (a) Ultraviolet-visible ab
Page 441 and 442:
agents [34]. The short-wavelength b
Page 443 and 444:
Figure 4 (a) Plot of the plasmon ab
Page 445 and 446:
the framework of traditional Mie’
Page 447 and 448:
show that effects due to the surrou
Page 449 and 450:
is located at the position of the g
Page 451 and 452:
Page 453 and 454:
Figure 8 Ultraviolet-visible absorp
Page 455 and 456:
laser pulses while being mixed in t
Page 457 and 458:
Figure 10 shows HR-TEM images of go
Page 459 and 460:
Figure 11 Transmission electron mic
Page 461 and 462:
final irradiation product. At the s
Page 463 and 464:
following the laser excitation appe
Page 465 and 466:
36. Papavassiliou, G.C. Prog. Solid
Page 467 and 468:
particles to expand. Because the he
Page 469 and 470:
was frequency doubled in a 1-mm B-
Page 471 and 472:
Figure 2 Frequency of the acoustic
Page 473 and 474:
Figure 3 Change in radius (DR/R) ve
Page 475 and 476:
In this model, the electrons couple
Page 477 and 478:
Figure 5 Transient bleach data for
Page 479 and 480:
Figure 7 (a) Transient bleach data
Page 481 and 482:
that the particles with >80% Au hav
Page 483 and 484:
3. Del Fatti, N.; Valle´e, F.; Fly
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