Vacuum ultraviolet absorption cross sections of SiH4, GeH4, Si2H6, and Si3H8

We present a systematic study of the photo-absorption spectra of various Si n H m clusters (n=1-10, m=1-14) using the time-dependent density functional theory (TDDFT). The method uses a real-time, real-space implementation of TDDFT involving full propagation of the time dependent Kohn-Sham equations. Our results for SiH 4 and Si 2 H 6 show good agreement with the earlier calculations and experimental data. We find that for small clusters (n<7) the photo-absorption spectrum is atomic-like while for the larger clusters it shows bulk-like behaviour. We study the photo-absorption spectra of silicon clusters as a function of hydrogenation. For single hydrogenation, we find that in general, the absorption optical gap decreases and as the number of silicon atoms increase the effect of a single hydrogen atom on the optical gap diminishes. For further hydrogenation the optical gap increases and for the fully hydrogenated clusters the optical gap is larger compared to corresponding pure silicon clusters. PACS number(s): 78.67. -n, 73.22.-f, 71.15 Pd PACS numbers:

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“…al. 6 and Suto and Lee 5 and other theoretical calculations. In particular, we get very good agreement with the results of Marques et.…”

Section: Resultsmentioning

confidence: 99%

Photo-absorption spectra of small hydrogenated silicon clusters using the time-dependent density functional theory

Thingna¹,

Prasad²,

Auluck³

2011

Journal of Physics and Chemistry of Solids

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“…Previous BSE calculations have predicted 9.0 eV 76 and 9.16 eV 8 for the same quantity. The experimental value has been reported to be around 8.8 eV 71 . For bigger clusters, the differences between TDLDA and BSE tend to disappear.…”

Section: A Benzene and Naphthalenementioning

confidence: 99%

“…There has been a very limited number of cases where such quantities were calculated within the framework of the GW approximation 4,8,9,17,18,19 , and the present results provide the first benchmarks for ionization potentials in oligoacenes. Small semiconductor clusters containing a few tens of atoms and with various chemical compositions have been mass produced and characterized in terms of their optical properties and structural configuration, although the synthesis of small silicon clusters remains a challenging task 14,71,72 . From a theoretical point of view, optical properties of small silicon clusters are interesting for one aspect: the linear optical spectrum of bulk silicon is known to be extremely well predicted by a first-principles approach based on the BSE 7,8 , whereas TDLDA fails to predict both the optical gap and excitonic effects 21,7396 .…”

Section: A Benzene and Naphthalenementioning

confidence: 99%

Optical excitations in organic molecules, clusters, and defects studied by first-principles Green’s function methods

Tiago¹,

2006

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Spectroscopic and optical properties of nanosystems and point defects are discussed within the framework of Green's function methods. We use an approach based on evaluating the self-energy in the so-called GW approximation and solving the Bethe-Salpeter equation in the space of singleparticle transitions. Plasmon-pole models or numerical energy integration, which have been used in most of the previous GW calculations, are not used. Fourier transforms of the dielectric function are also avoided. This approach is applied to benzene, naphthalene, passivated silicon clusters (containing more than one hundred atoms), and the F center in LiCl. In the latter, excitonic effects and the 1s → 2p defect line are identified in the energy-resolved dielectric function. We also compare optical spectra obtained by solving the Bethe-Salpeter equation and by using time-dependent density functional theory in the local, adiabatic approximation. From this comparison, we conclude that both methods give similar predictions for optical excitations in benzene and naphthalene, but they differ in the spectra of small silicon clusters. As cluster size increases, both methods predict very low cross section for photoabsorption in the optical and near ultra-violet ranges. For the larger clusters, the computed cross section shows a slow increase as function of photon frequency. Ionization potentials and electron affinities of molecules and clusters are also calculated.

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“…Despite the availability of a large body of experimental data for silicon dots, little is known about the actual structures of clusters studied in experiments. At present, spectroscopic data linked to specific cluster structures are only available for a few small Si n H m clusters [3,4]. Essentially all experimental data for larger clusters and quantum dots are obtained by studying the properties of macroscopic samples [1].…”

Section: Introductionmentioning

confidence: 99%

Optical excitations in small hydrogenated silicon clusters: comparison of theory and experiment

Vasiliev

2003

Physica Status Solidi (b)

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PACS 78.67.Bf Excitation energies and absorption spectra of small hydrogenated silicon clusters are calculated within the framework of time-dependent density-functional response theory. The calculations employ several different approximations for the exchange-correlation kernel, including the local density approximation as well as asymptotically correct Leeuwen-Baerends and Casida-Salahub potentials. The structures of the theoretical spectra are analyzed in detail and the positions of the absorption peaks obtained with different exchange-correlation kernels are matched to the available experimental data based on the oscillator strength and symmetry of electronic transitions. The calculated absorption gaps are compared to the experimental values and discussed in terms of the applicability of common theoretical and experimental definitions for optical gaps to small clusters.

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Vacuum ultraviolet absorption cross sections of SiH4, GeH4, Si2H6, and Si3H8

Cited by 307 publications

References 21 publications

Photo-absorption spectra of small hydrogenated silicon clusters using the time-dependent density functional theory

Photo-absorption spectra of small hydrogenated silicon clusters using the time-dependent density functional theory

Optical excitations in organic molecules, clusters, and defects studied by first-principles Green’s function methods

Optical excitations in small hydrogenated silicon clusters: comparison of theory and experiment

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