Quantum Confinement Effects on the Dielectric Constant of Porous Silicon

Tsu, Raphael; Ioriatti, L.; Harvey, James; Shen, Haibo; Lux, R. A.

doi:10.1557/proc-283-437

Cited by 29 publications

(16 citation statements)

References 9 publications

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“…Up to now, this problem has been studied only theoretically. By generalizing the well-known two-band semiconductor model (Penn model [1]), Tsu et al [2] have demonstrated that the static dielectric constant´͑0͒ is significantly reduced for nanometer-sized particles compared to the bulk value. Wang and Zunger [3] have calculated the reduction in the dielectric constant from global blueshifts in the clusters absorption spectra.…”

Section: Polarizabilities Of Isolated Semiconductor Clustersmentioning

confidence: 99%

“…(3)], this observation indicates that for these silicon clusters either r or´͑0͒ is smaller than for bulk silicon. Since the quantum size effects on´͑0͒ have been recently investigated theoretically [2,3], we will focus our discussion on the size dependence of the dielectric constant by assuming r r bulk . The observed polarizabilities then correspond to an average static dielectric constant of´͑0͒ 7.4 for N 60 120.…”

Section: Polarizabilities Of Isolated Semiconductor Clustersmentioning

confidence: 99%

“…Therefore, it may be possible that the clusters behave already for T nozzle 300 K similar to a molten salt where the ions can be easily separated by the applied field. (2) The increase in polarizability for several Ge N Te M clusters with temperature reflects a kind of ionic instability that is analogous to the occurrence of soft (TO phonon) modes in bulk ferroelectric crystals when the temperature approaches T C [24].…”

Section: Polarizabilities Of Isolated Semiconductor Clustersmentioning

confidence: 99%

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Polarizabilities of Isolated Semiconductor Clusters

et al. 1996

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The static polarizabilities a c of the isolated semiconductor clusters Si N , Ga N As M , and Ge N Te M have been investigated in dependence of cluster size and temperature. The results for the Si N clusters are discussed within a two-band semiconductor model that includes a widening of the band gap due to quantum size effects. Additionally, the importance of defectlike electronic states is discussed for Si N and Ga N As M clusters. The temperature dependence of the polarizability values for several Ga N As M and Ge N Te M species gives evidence for vibronic (ionic) contributions to a c . PACS numbers: 36.40.CgThe aim of this Letter is to investigate the question of how the static dielectric constant, or the polarizability, of a small semiconductor particle depends on its size. Up to now, this problem has been studied only theoretically. By generalizing the well-known two-band semiconductor model (Penn model [1]), Tsu et al. [2] have demonstrated that the static dielectric constant´͑0͒ is significantly reduced for nanometer-sized particles compared to the bulk value. Wang and Zunger [3] have calculated the reduction in the dielectric constant from global blueshifts in the clusters absorption spectra. Absorption spectra have been already investigated for semiconductor colloids [4], oxidized nanospheres [5], and isolated clusters [6]. Experimental information on cluster polarizabilities are only available for the metal clusters Na N 2 , K N 2 , and Al N [7]. Theoretical a c values of isolated semiconductor clusters are only available for Si 7 2 , Si 10 2 , and Si 13 [8,9].We have measured the polarizabilities of three types of isolated semiconductor clusters with 4-120 atoms in order to throw light upon their dielectric properties. Moreover, the results will allow us to discuss the important role of defect states for the polarizability of semiconductor clusters by means of simple models. Such defects, like, e.g., dangling bonds, are expected especially at the surfaces of the clusters [10,11].The experimental apparatus has been already described in detail elsewhere [12,13]. The clusters are produced by a pulsed laser vaporization cluster source [13]. The clusters leave the source through a nozzle with adjustable nozzle temperature and form a molecular beam. The beam is collimated and then deflected by an inhomogeneous electric field. The deflections are measured for each cluster size by means of a collimated ionization laser beam which scans the cluster beam. Thereby, we obtain size selective cluster beam profiles by detecting the ionized clusters with a time-of-flight mass spectrometer for each scanning position. The velocities y of the clusters in the beam are measured size selective by means of a chopper. Figure 1(a) shows a typical beam profile for Ga N As M clusters ͑N 1 M 14͒ with and without deflecting field ͑E ഠ 20 kV͞mm͒. In principle, the profiles correspond to a distribution of the clusters with all possible N͞M compositions, since all the corresponding masses can hardly be resolved by simultaneously obta...

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Section: Polarizabilities Of Isolated Semiconductor Clustersmentioning

confidence: 99%

Section: Polarizabilities Of Isolated Semiconductor Clustersmentioning

confidence: 99%

Section: Polarizabilities Of Isolated Semiconductor Clustersmentioning

confidence: 99%

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Polarizabilities of Isolated Semiconductor Clusters

et al. 1996

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“…The size-dependent dielectric constant e(a) was first derived using a modified Penn model taking into account the eigenstates of a sphere instead of the usual free electron energy-momentum relation. 19,20 The effects of the reduction of the dielectric constant in nanoscale silicon are presented by Tsu and Babic. 21 Since then similar results were obtained by using far more sophisticated calculations.…”

Section: Dielectric Constant Of Nanoscale Silicon Particlementioning

confidence: 99%

Room Temperature Silicon Quantum Devices

Tsu

1998

Int. J. Hi. Spe. Ele. Syst.

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Quantum mechanical devices utilize the wave nature of electrons for their operations whenever the electron mean-free-path exceeds the appropriate dimensions of the device structure. Some of the issues such as the tunneling time, the reduction of the dielectric constant and the drastic increase in the binding energy of dopants are discussed. Lacking an appropriate barrier for silicon, the majority of quantum devices are fabricated with compound semiconductors. In the past several years, certain schemes appeared, such as the resonant tunneling via nanoscale silicon particles imbedded in an oxide matrix, and the superlattice barrier for silicon consisting of several periods of Si/O. There appears some doubt about the tunneling nature of the former, and the possibility of dielectric breakdowns. This article aims to show that dielectric breakdowns can occur under fabrication conditions without using a controlled forming process. The latter results in epitaxially grown silicon beyond the superlattice barrier region, free of stacking fault defects, and thus is potentially important for silicon based quantum devices as well as serving as an SOI (silicon on insulator), without ion-implantation damage and oxygen inclusion. The replacement of SOI by the epitaxially grown Si/O superlattice barrier should promote the effort in high speed and low power MOSPET devices. 157 Int. J. Hi. Spe. Ele. Syst. 1998.09:145-163. Downloaded from www.worldscientific.com by FLINDERS UNIVERSITY LIBRARY on 02/06/15. For personal use only.

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“…For Si NCs, we have to take into account the NC sizedependent Coulomb screening governing the hydrogenic dopant state, which results in a size-dependent donor electron wave function localization [26]. This is done with a size-dependent dielectric screening constant NC parameterized by using a generalization of the Penn model NC ðdÞ ¼ 1 þ ð bulk À 1Þ=½1 þ ð=dÞ l [29][30][31][32], with ¼ 1:94 nm and l ¼ 1:3 as considered previously in describing the confinement of single donors in NCs [26,32]. In Eq.…”

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confidence: 99%

Exchange-Coupled Donor Dimers in Nanocrystal Quantum Dots

et al. 2012

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Doping of semiconductor nanocrystals (NCs) is expected to enable the control of key NC properties, yet its practical exploitation requires an understanding of exchange interactions when multiple dopants are incorporated in a single NC. Here, we experimentally probe the exchange of donor dimers in NCs via a deviation of their triplet-state magnetic resonance from Curie paramagnetism. We show that the exchange coupling of the closely spaced donors can be well described by effective mass theory, which allows the consideration of statistical effects crucial in NC ensembles. While a dimer induces discrete states in a NC, their energy splitting differs by up to 3 orders of magnitude for randomly placed dimers in a NC ensemble, due to an enormous dependence of the exchange energy on the dimer configuration.

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Quantum Confinement Effects on the Dielectric Constant of Porous Silicon

Cited by 29 publications

References 9 publications

Polarizabilities of Isolated Semiconductor Clusters

Polarizabilities of Isolated Semiconductor Clusters

Room Temperature Silicon Quantum Devices

Exchange-Coupled Donor Dimers in Nanocrystal Quantum Dots

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