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interband term e B (x) and a Drude free-electron term e D (x) describing theintraband conduction-band contribution: e(x) = e B (x) + e D (x). The latteris given within the free-electron model [40] bye D ðxÞ ¼ 1x 2 px 2 þ icxwhere x p 2 = (ne 2 /e 0 m eff ) is the bulk plasmon frequency expressed in terms ofthe free-electron density n, the electron charge e, the vacuum permittivity e 0 ,and the electron effective mass m eff . In Eq. (8), c is a phenomenologicaldamping constant which is equal to the plasmon band width C for the case of afree-electron gas in the limit of g
the framework of traditional Mie’s theory. For very small clusters, quantumchemical methods or a jellim model have also been used to calculate thedielectric function from first principles [45–47]. A comprehensive overview ofdifferent theories with references to the original work can be found in Ref. 8.Most of the theories predict the 1/r dependence of the plasmon bandwidth.However, there are discrepancies regarding the size dependence of theplasmon absorption maximum. Some theories predict a red shift, whereasothers predict a blue shift of the plasmon resonance with decreasing particlesize [8]. Certainly, the medium dielectric constant e m has a large effect on theresonance condition, as can be seen from Eq. (3). An increase in e m leads to ared shift of the surface plasmon absorption maximum. Comparison betweentheories and experiments are further complicated by the fact that both red andblue shifts are observed experimentally. Furthermore, it is difficult to preparenearly monodisperse metal nanoparticles over a large range of sizes using thesame capping agent. Because different capping agents have different values ofthe medium dielectric constant e m , it is difficult to distinguish betweencontributions to the plasmon shift due to the particle size and the surroundingmedium.III.DEPHASING OF THE SURFACE PLASMONRESONANCEAlthough the plasmon absorption is well understood in terms of the electromagneticinteraction between the metal particles and light, less is knownabout the decay mechanism of the coherent electron motion. Both thedephasing of the coherent electron motion and the energy relaxation haveto be considered as decay mechanism. The dephasing of the electron motionleads to the loss of coherence, which is usually described by the time constantT 2 . T 2 and the time constant for energy relaxation, T 1 , are related by the puredephasing time T 2* [41]:1¼ C T 2 2h ¼ 1 þ 12T 1 T * ð11Þ2where C is the homogeneous spectral linewidth. The time T 2* can originatefrom collisions that change the plasmon wave vector but not its energy.Relaxation pathways for the plasmon energy decay (T 1 time constant) includethe radiative decay of the plasmon and the nonradiative decay into singleelectron–hole excitation [8,14].For a homogeneously broadened line, the dephasing time T 2 can bedirectly obtained from the absorption spectrum using Eq. (11). Figure 4b/Copyright 2004 by Marcel Dekker, Inc. All Rights Reserved.
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Copyright 2004 by Marcel Dekker, In
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This book covers several topics of
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esult, some exciting topics were no
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3. Fine Structure and Polarization
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9. III-V Quantum Dots and Quantum D
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ContributorsUri BaninThe Hebrew Uni
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1‘‘Soft’’ Chemical Synthesi
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structure of energy states leads to
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growth can proceed by Ostwald ripen
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Figure 3 Transmission electron micr
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Figure 4 Temporal evolution of the
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No. 26, are f85% (Fig. 6) [21]. Alt
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tion spectra and broad PL spectra.
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ing surface-to-volume ratio with di
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Figure 8 Photoluminescence spectra
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lattice mismatch. Such a large latt
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match between InAs and ZnS of f11%.
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successfully repeated for up to thr
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Under a different growth regime, on
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Figure 14 Atomic model of the CdSe
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‘‘Teardrop-shaped’’ particl
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Figure 17 High-resolution TEMs of C
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allows isolation of tetrapods in f8
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ligand concentrations yield a reduc
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een determined and quantitatively c
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tion volumes were also shown to be
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synthesis temperatures of z400jC ar
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Figure 23 (a) Photoluminescence spe
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levels (fV1 Mn per NQD). Despite in
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Figure 25 X-ray diffraction pattern
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Figure 27 Transmission electron mic
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An additional factor that strongly
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Figure 30 (a,b) Schematics illustra
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Slow, controlled precipitation of h
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Figure 34 Schematic illustrating th
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achieving biological compatibility
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47. Yu H.; Gibbons P.C.; Kelton K.F
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2Electronic Structure inSemiconduct
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Figure 2 (a) Simple model of a nano
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electron and hole to be treated as
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independently, Eq. (13) is commonly
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a better description of the bulk ba
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investigated. For optical experimen
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Figure 4 (a) Absorption (solid line
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Figure 6 Normalized PLE scans for s
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Figure 8 A simplistic model for des
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Figure 10 Theoretically predicted p
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Figure 12 Schematics depicting the
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Figure 14 Calculated band-edge exci
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Figure 15 Absorption (solid line) a
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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.
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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
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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 (
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can contribute to the saturation of
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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
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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
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dispersing CdSe nanocrystal chromop
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memory and charge storage effects [
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all) of the optically excited elect
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composites of nanocrystals and conj
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55. Asbury, J.B.; Hao, E.C.; Wang,
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108. Morgan, N.Y.; Leatherdale, C.A
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The approaches to fabrication of se
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Figure 1 Experimental realization o
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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
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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
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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/
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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.
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66. Su, B.; Goldman, V.J.; Cunningh
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dimensional confinement are created
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Figure 1 Transmission electron micr
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The room-temperature absorption and
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narrower in samples with larger mea
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GaInP 2 QDs from a plot of the squa
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crystal, indicating lattice-matched
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Figure 5 Evolution of Stranski-Kras
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C. Efficient Anti-Stokes Photolumin
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Because HF treatment has been shown
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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
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electron relaxation is inhibited an
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QDs, the nature of the QD capping s
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QD solution. For an interdot distan
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emission spectra of the two individ
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Figure 23 Change of the PL intensit
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(viz. the absorbed light intensity)
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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: Figure 4 (a) Plot of the plasmon ab
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: Copyright 2004 by Marcel Dekker, In
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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