Influence of surface chemistry on photoluminescence from deuterium-passivated silicon nanocrystals

Salivati, Navneethakrishnan; Shuall, Nimrod; Baskin, E.; Garber, V.; McCrate, Joseph M.; Ekerdt, John G.

doi:10.1063/1.3224952

Cited by 9 publications

(22 citation statements)

References 28 publications

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“…The XPS and TPD data (Figures and ) indicate that N atoms are being inserted into the Si−Si bonds without an appreciable increase in deuterides. A similar result was observed in our earlier work with Si NCs passivated using atomic deuterium generated from D 2 on the hot tungsten filament; at extremely high atomic deuterium doses, the surface saturated with trideuteride species and the D 2 + area did not increase any further. Once the NC surface is covered with substantial amounts of trideuteride species, atomic D can attack the Si backbonds, resulting in the formation of an amorphous layer on the NC surface, and this amorphous layer was shown to quench the PL signal .…”

supporting

confidence: 89%

“…Reducing the HWCVD growth time reduces the particle size, and PL peak position should shift to a lower wavelength in accordance with quantum confinement. Such a quantum shift has been observed in our earlier work with deuterium-passivated particles . However, with the ND 3 -passivated NCs, no quantum shift is discernible.…”

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confidence: 79%

“…Silicon (Si) nanocrystals (NCs) less than 5 nm in diameter exhibit size-dependent light emission and such materials can potentially be used to fabricate low-cost, light-emitting devices (LEDs). − However, the ratio of surface atoms to the total number of atoms in nanostructured materials is very large, and surface effects play an important role in determining the optoelectronic properties. − Dangling bonds and surface reconstructions create defect states in the bandgap, which can result in nonradiative recombination of excitons. − Defect states can also be introduced by surface passivants such as oxygen, sulfur, or nitrogen when present in the bridged or double-bond configurations. − A complete understanding of the influence of surface chemistry in determining the optoelectronic properties is still not available. In this paper, we describe in detail the effect of the various ND x and deuteride species on the photoluminescence (PL) emitted from Si NCs subjected to hot wire doses of ND 3 .…”

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confidence: 99%

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Effect of Surface Chemistry on Quantum Confinement and Photoluminescence of Ammonia-Passivated Silicon Nanocrystals

Salivati

Shuall²,

McCrate

et al. 2010

J. Phys. Chem. Lett.

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Silicon (Si) nanocrystals (NCs) less than 5 nm in diameter are grown on SiO 2 surfaces using hot wire chemical vapor deposition, and the dangling bonds and the reconstructed bonds at the NC surface are passivated and transformed with D and ND x by using deuterated ammonia (ND 3 ), which is predissociated over a hot filament. At low hot wire ND 3 doses, photoluminescence (PL) emission is observed from a defect state at 1000 nm corresponding to reconstructed surface bonds capped by predominantly monodeuteride and Si-ND 2 species. As the hot wire ND 3 dose is increased, di-and trideuteride species form, and intense PL is observed around 800 nm, which does not shift with NC size and is associated with defect levels resulting from ND x insertion into the strained Si-Si bonds forming Si 2 dND. A clean bandgap can be realized with fully relaxed and fully terminated NC surfaces consisting of di-and trideuterides and SiND 2 . SECTION Nanoparticles and Nanostructures

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confidence: 89%

supporting

confidence: 79%

mentioning

confidence: 99%

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Effect of Surface Chemistry on Quantum Confinement and Photoluminescence of Ammonia-Passivated Silicon Nanocrystals

Salivati

Shuall²,

McCrate

et al. 2010

J. Phys. Chem. Lett.

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“…12(b) but it is shifted with respect to the bulk band gap (shown by dashed lines) and more importantly, the wavefunctions of the states at the anticipated top of the VB (and bottom of the CB) are localized at the QD surface rather than extending through the volume of the QD. Since surface passivation is known to be important both from the perspective of enhancing measured optical properties 62,63 and calculated positions of energies in VB and CB, 50,64 we have added an extra atomic layer to the clusters which we investigated, making sure that there remains no dangling bond of the QD core. The passivation layer atoms are assumed to have the same hopping to the QD core atoms as the core atoms between each other and to keep the model simple, we assign a single on-site energy E pass to their s-and porbitals.…”

Section: Appendix B: Tight-binding Model For Simple Cubic Face Centementioning

confidence: 99%

Nodal ground states and orbital textures in semiconductor quantum dots

et al. 2014

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Conventional understanding implies that the ground state of a nonmagnetic quantum mechanical system should be nodeless. While this notion also provides a valuable guidance in understanding the ordering of energy levels in semiconductor nanostructures, there are reports that nodal ground states for holes are possible. However, the existence of such nodal states has been debated and even viewed merely as an artifact of a k·p model. Using complementary approaches of both k·p and tight-binding models, further supported by an effective Hamiltonian for a continuum model, we reveal that nodal ground states in quantum dots are not limited to a specific approach. Remarkably, the emergence of nodal hole states at the top of the valence band can be attributed to the formation of orbital vortex textures through competition between the hole kinetic energy and the coupling to the conduction band states. We suggest an experimental test for our predictions of the reversed energy ordering and the existence of nodal ground states. We discuss how our findings and the studies of orbital textures could be also relevant for other materials systems.

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“…Alternative preparation methods produces NCs with different surface terminations (D, F, C, and others) that earned some interest in the last years. [14][15][16][17][18] Moreover, also the role of nitrogen has been recently explored 19 .…”

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confidence: 99%

Size, oxidation, and strain in smallSi/SiO2nanocrystals

2009

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The structural, electronic and optical properties of Si nanocrystals of different size and shape, passivated with hydrogens, OH groups, or embedded in a SiO2 matrix are studied. The comparison between the embedded and free, suspended nanocrystals shows that the silica matrix produces a strain on the embedded NCs, that contributes to determine the band gap value. By including the strain on the hydroxided nanocrystals we are able to reproduce the electronic and optical properties of the full Si/SiO2 systems. Moreover we found that, while the quantum confinement dominates in the hydrogenated nanocrystals of all sizes, the behaviour of hydroxided and embedded nanocrystals strongly depends on the interface oxidation degree, in particular for diameters below 2 nm. Here, the proportion of NC atoms at the Si/SiO2 interface becomes relevant, producing surface-related states that may affect the quantum confinement appearing as inner band gap states and then drastically changing the optical response of the system.

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Influence of surface chemistry on photoluminescence from deuterium-passivated silicon nanocrystals

Abstract: Stability of Se passivation layers on Si(001) surfaces characterized by time-of-flight positron annihilation inducedAuger electron spectroscopy

Cited by 9 publications

References 28 publications

Effect of Surface Chemistry on Quantum Confinement and Photoluminescence of Ammonia-Passivated Silicon Nanocrystals

Effect of Surface Chemistry on Quantum Confinement and Photoluminescence of Ammonia-Passivated Silicon Nanocrystals

Nodal ground states and orbital textures in semiconductor quantum dots

Size, oxidation, and strain in smallSi/SiO2nanocrystals

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