Size Dependence of Excitons in Silicon Nanocrystals

Na, Hill; Kb, Whaley

doi:10.1103/physrevlett.75.1130

Cited by 232 publications

(158 citation statements)

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“…10 Such an emission has been deeply studied in Si-SiO 2 materials and ascribed to the confinement of the photogenerated carriers in Si grains whose size is smaller than 8 nm. [11][12][13][14] Besides the QC effect for explaining the new optical properties of nanometer-scaled Si films, some studies also pointed out the important role played by the Si/ SiO 2 interface in the PL. 13,[15][16][17] Thus, the PL of Si nanocluster ͑Si-ncl͒ is governed by key parameters such as grain size and the Si/ SiO 2 phase separation.…”

Section: Introductionmentioning

confidence: 99%

Silicon-rich SiO2/SiO2 multilayers: A promising material for the third generation of solar cell

Gourbilleau

Ternon

Maestre

et al. 2009

Journal of Applied Physics

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Method for fabricating third generation photovoltaic cells based on Si quantum dots using ion implantation into SiO2 J. Appl. Phys. 109, 084337 (2011) Si-rich-SiO 2 ͑SRSO͒ / SiO 2 multilayers ͑MLs͒ have been grown by reactive magnetron sputtering. The presence of silicon nanoclusters ͑Si-ncls͒ within the SRSO sublayer and annealing temperature influence optical absorption as well as photoluminescence. The optimized annealing temperature has been found to be 1100°C, which allows the recovery of defects and thus enhances photoluminescence. Four MLs with Si-ncl size ranging from 1.5 to 8 nm have been annealed using the optimized conditions and then studied by transmission measurements. Optical absorption has been modeled so that a size effect in the linear absorption coefficient ␣ ͑in cm −1 ͒ has been evidenced and correlated with TEM observations. It is demonstrated that amorphous Si-ncl absorption is fourfold higher than that of crystalline Si-ncls.

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Section: Introductionmentioning

confidence: 99%

Silicon-rich SiO2/SiO2 multilayers: A promising material for the third generation of solar cell

Gourbilleau

Ternon

Maestre

et al. 2009

Journal of Applied Physics

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“…11,12 In spherical NCs, however, owing to the strong quantum confinement, Coulomb interactions are usually a first-order perturbation effect for the low-lying states. 13 Furthermore, a strong spatial confinement leads to compensations between electron and hole charge distributions, 14,15 so that the optical properties are barely affected by the dielectric environment.…”

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confidence: 99%

Strong configuration mixing due to dielectric confinement in semiconductor nanorods

et al. 2009

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The interaction between electron-electron and electron-hole pairs in semiconductor nanorods embedded in dielectric media is investigated using a configuration-interaction method. Contrary to spherical quantum dots of similar volume, the dielectric confinement is shown to bring nanorods into a regime of strong configuration mixing. The wave functions are particularly sensitive to such mixing, which leads to qualitative changes in the electronic and optical properties of the rods. DOI: 10.1103/PhysRevB.79.161301 PACS number͑s͒: 73.21.La, 77.22.Ej, 78.67.Hc, 71.27.ϩa Semiconductor quantum rods or nanorods ͑NRs͒ are colloidal quantum dots with strong radial confinement and variable length.1,2 Even though NRs were first synthesized long after spherical nanocrystals ͑NCs͒, it was soon realized that their anisotropic shape posed many benefits for optical and transport applications.3 This prompted a large number of studies, often revealing characteristic physical phenomena which stem from the weak longitudinal confinement, for NRs bridge the gap between zero-dimensional and onedimensional quantum-confined systems. [4][5][6][7][8][9][10] Similar to NCs, NRs are usually embedded in insulating media, whose dielectric constant is much lower than that of the semiconductor structure. This dielectric mismatch gives rise to a so-called dielectric confinement, which greatly enhances the Coulomb interactions inside the semiconductor. 11,12 In spherical NCs, however, owing to the strong quantum confinement, Coulomb interactions are usually a first-order perturbation effect for the low-lying states. 13Furthermore, a strong spatial confinement leads to compensations between electron and hole charge distributions, 14,15 so that the optical properties are barely affected by the dielectric environment.None of these restrictions apply to NRs, where the longitudinal confinement may be fairly weak. Indeed, the dielectric confinement has been held responsible for the large variation in the optical gap of CdSe NRs as compared to the transport one. 7,16 What is more, NRs are the zerodimensional counterpart of quantum wires, where variations in the dielectric confinement have been shown to induce drastic changes in the binding energy and oscillator strength of excitons, thus enabling Coulomb interaction engineering. [17][18][19] One may then wonder to which extent the single-particle and perturbational treatments of Coulomb interactions that dominate the literature of NRs ͑Refs. 6-10͒ provide a valid description of the optoelectronic properties.In this work, we perform a theoretical study of the effect of the dielectric confinement on interacting particles ͑two electrons or one electron and one hole͒ confined in a semiconductor NR. A numerical procedure is used which allows us to estimate the effect of the dielectric environment for arbitrary three-dimensional potentials, thus addressing realistic geometries. Electron correlations are then accounted for exactly using an effective mass-configuration-interaction ͑CI͒ scheme. We go beyond en...

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“…This is evidence that by hightemperature annealing Si clusters are formed in crystalline phase and with sizes, being in nano-scale range. It has been established (11,12) that the electron structure of Si nanocrystallites is modified by quantum confinement, which is reflected in shift of characteristic peaks in ε 2 , 25 (3) 379-384 (2009) spectra of Si. Most probably because of that we could not observe directly another feature in the ε 2 spectra around 4.2 eV, where the other characteristic peak E 2 of c-Si (9) is situated.…”

Section: Resultsmentioning

confidence: 99%

Effect of High-temperature Annealing on Evaporated Silicon Oxide Films: A Spectroscopic Ellipsometry Study

et al. 2009

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Silicon oxide films, vacuum evaporated and annealed in Ar atmosphere at a temperature of 1000 and 1100ºC have been studied by multiple-angle spectroscopic ellipsometry (SE) in the spectral range of 280-820 nm. The thickness, complex refractive index and composition of the films have been determined from the SE data analysis, performed with multiple-layer optical models and applying the Bruggeman effective medium approximation theory. The SE results have revealed that during annealing at 1000 o C the Si clusters with volume fraction of ~ 14 % crystallize in the substoichiometric SiO 1.61 matrix, while annealing at 1100 o C transforms the oxide structure to a fully stoichiometric SiO 2 with embedded nc-Si clusters with enhanced volume fraction of 22%. The TEM micrographs visualized the Si crystallites, which have random distribution in the amorphous oxide matrix and an average size of 3 nm.

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Size Dependence of Excitons in Silicon Nanocrystals

Cited by 232 publications

References 14 publications

Silicon-rich SiO2/SiO2 multilayers: A promising material for the third generation of solar cell

Silicon-rich SiO2/SiO2 multilayers: A promising material for the third generation of solar cell

Strong configuration mixing due to dielectric confinement in semiconductor nanorods

Effect of High-temperature Annealing on Evaporated Silicon Oxide Films: A Spectroscopic Ellipsometry Study

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