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tion volumes were also shown to be of opposite sign, indicating that themechanism by which the phase transformation takes place involves a structurewhose volume is in between that of the two end phases. Most significantly,the magnitude of the activation volume is small compared to the totalvolume change that is characteristic of the system (f0.2% versus 18%). Theactivation volume is equal to the critical nucleus size responsible for initiatingthe phase transformation—defining the volume change associated with thenucleation event.The small size of the activation volume suggests that the structuralmechanism for transformation cannot be a coherent one involving the entirenanocrystal [53]. Spread out over the entire volume of the nanocrystal, theactivation volume would amount to a volume change smaller than that inducedby thermal vibrations in the lattice. Therefore, a mechanism involvingsome fraction of a nanocrystal was considered. The nucleus was determinednot to be three dimensional, as a sphere the size of the activation volumewould be less than a single unit cell. Also, activation volumes were observed toincrease with increasing particle size (in the direction of increasing pressure).There is no obvious mechanistic reason for a spherically shaped nucleus toincrease in size with an increase in particle size. Further, additional observationshave been made: (1) particle shape changes from cylindrical or ellipticalto slablike upon transformation from the four-coordinate phase to the sixcoordinatephase [51], (2) the stacking-fault density increases following a fullpressure cycle from the four-coordinate through the six-coordinate and backto the four-coordinate structure [51], and (3) the entropic contribution to thefree-energy barrier to transformation increases with increasing size (indicatingthe nucleation event can initiate from multiple sites) [53]. Together, thevarious experimental observations suggest that the mechanism involves adirectionally dependent nucleation process that is not coherent over the wholenanocrystal. The specific proposed mechanism entails shearing of the (001)planes, with precedent found in martensitic phase transitions (Fig. 22) [51,53].Further, the early observation that activation energy increases with size [50]likely results from the increased number of chemical bonds that must bebroken for plane sliding to occur in large nanocrystals, compared to that insmall nanocrystals. Such a mechanistic-level understanding of the phasetransformation processes in nanocrystals is important because nanocrystalbasedstudies, due to their simple kinetics, may ultimately provide a betterunderstanding of the hard-to-study, complex transformations that occur inbulk materials and geologic solids [53].Phase control, much like shape control (Sect. IV), can be achieved innanocrystal systems by operating in kinetic growth regimes. Materials synthesisstrategies have typically relied upon the use of reaction conditions farfrom standard temperature and pressure (STP) to obtain nonmolecularCopyright 2004 by Marcel Dekker, Inc. All Rights Reserved.
Figure 22 Schematic illustrating the sliding-plane transformation mechanism: (a)zinc-blende structure, where brackets denote (111) planes, dashed boxes show planesthat slide together, and arrows indicate the directions of movement; (b) structure of(a) after successive sliding has occurred; (c) rock-salt structure, where dashed linesdenote (111) planes. Structures are oriented the same in (parts a–c). (From Ref. 51,reprinted with permission.)materials such as ceramics and semiconductors. The crystal-growth barriersto covalent nonmolecular solids are high and have historically been surmountedby employing relatively extreme conditions, comprising a directassault on the thermodynamic barriers to solid-state growth. The interfacialprocesses of adsorption–desorption and surface migration permit atomsinitially located at nonlattice sites on the surface of a growing crystal torelocate to a regular crystal lattice position. When these processes areinefficient or not functioning, amorphous material can result. Commonly,Copyright 2004 by Marcel Dekker, Inc. All Rights Reserved.
Page 1:
Copyright 2004 by Marcel Dekker, In
Page 4 and 5:
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 54 and 55: een determined and quantitatively c
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
Page 113 and 114:
IV.BEYOND CdSeA. Indium Arsenide Na
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the six-band Luttinger Hamiltonian.
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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
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where the constant A is determined
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In crystals for which the function
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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
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REFERENCES1. Bawendi, M.G.; Wilson,
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4Intraband Spectroscopyand Dynamics
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The solid line in Fig. 1 shows the
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Figure 2 FTIR spectra of n-type CdS
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of the center frequency. The experi
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limit given by radiative relaxation
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from a long lifetime due to the pho
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are two natural approaches to study
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32. Inoshita, T.; Sakaki, H. Physic
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continuous spectral tunability over
Page 177 and 178:
function and envelope function mome
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ottleneck’’ [14,28]. Further re
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in NQDs is dominated by nonphonon e
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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
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Figure 11 (a) Pump-intensity-depend
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NQD size. For small NQD sizes (R =
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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:
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can contribute to the saturation of
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Page 225 and 226:
coupling between ‘‘volume’’
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numerous discussions on the photoph
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53. Kang, K.; Kepner, A.; Gaponenko
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the ‘‘on-off ’’ emission in
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parallel form of data acquisition i
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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
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exposure to only room light. In our
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statistics for the off times are in
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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
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arrows indicate the on-time truncat
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W. K. Woo and V. C. Sundar for assi
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size allows the electron affinity a
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II.THEORY OF ELECTRON TRANSFER BETW
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For the specific case of charge tra
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dominates, the mobility is often fi
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where the constant A and the temper
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components of modulation which are
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nanocrystals [41], understanding ph
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and ionization potential through tw
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quantum dots. Furthermore, because
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For many applications, a host mater
Page 275 and 276:
form blends with morphologies that
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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
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Films of passivated CdSe nanocrysta
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Figure 16 Photocurrent action spect
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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 [
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all) of the optically excited elect
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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
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Figure 3 Simulated tunneling spectr
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electron charging. In both positive
Page 315 and 316:
Figure 5 shows the typical features
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Figure 7 Map of levels for InAs nan
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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
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atomistic approach based on pseudop
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charging indicated that the tunneli
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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
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dimensional confinement are created
Page 345 and 346:
Figure 1 Transmission electron micr
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The room-temperature absorption and
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narrower in samples with larger mea
Page 351 and 352:
GaInP 2 QDs from a plot of the squa
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crystal, indicating lattice-matched
Page 355 and 356:
Figure 5 Evolution of Stranski-Kras
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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:
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intensity of the PL when it is on a
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eV stems from recombining carriers
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Figure 16 Model to explain two-colo
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although this term is not rigorousl
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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
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Figure 2 (A-C) Progression of HR-TE
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Figure 3 Schematic for gold nanocry
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Nanocrystal growth can occur by two
Page 409 and 410:
on the other hand, provide an ensem
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Figure 6 (a) SAXS patterns for disp
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Figure 8 The gold nanocrystal film
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of the stabilizing ligand, and the
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successfully modeled the 2D island
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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
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Figure 13 (A) Transmission electron
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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
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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
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is located at the position of the g
Page 451 and 452:
Page 453 and 454:
Figure 8 Ultraviolet-visible absorp
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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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