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1

Vibrational Modes in Si_{x}Ge_{1-x} Alloys: Temperature and Compositional Dependence

100%

Lorenc M., Humlíček J.

Acta Physica Polonica A

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1997

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vol. 92

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issue 5

899-902

EN

We report infrared absorption spectra of crystalline Si_{x}Ge_{1-x} alloys with silicon content 0 ≤ x ≤ 1 at room and liquid nitrogen temperature. We covered the spectral range from 375 to 1200 cm^{-1} that includes the "Si-Ge" and "Si-Si" single-phonon transitions, the continuum of two-phonon processes, and the localized mode of interstitial oxygen. We study the change of vibrational structure and correlation between reference (pure Si and Ge) and alloy spectra. We observed shifts to lower wave numbers by about 1 cm^{-1} of the two-phonon absorption bands per 1% increase in germanium concentration. Pronounced changes of the vibrational spectra upon lowering the temperature were detected.

2

Localized Vibrational Modes of Interstitial Oxygen in Si_{x}Ge_{1-x} Alloys

100%

Lorenc M., Humlíček J.

Acta Physica Polonica A

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1998

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vol. 94

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issue 3

436-440

EN

We study infrared-active vibrations of interstitial oxygen in Czochralski-grown samples of Si_{x}Ge_{1-x} alloys with the silicon content from 0 to 1 between room and liquid nitrogen temperature. The measurements were performed on a large series of samples including single crystals of Si and Si-rich alloys, and polycrystalline samples of alloys with a higher Ge content. We focus on quantitative data on the compositional and temperature evolution of the strongest absorption band above 1100 cm^{-1}, related to the asymmetric stretching of the Si_{2}O pseudomolecule. We have also observed a pronounced Fano-like resonance centered at 520 cm^{-1}.

3

Type-II InAs/GaAsSb/GaAs Quantum Dots as Artificial Quantum Dot Molecules

81%

Klenovský P., Křápek V., Humlíček J.

Acta Physica Polonica A

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2016

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vol. 129

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issue 1a

A-62-A-65

EN

We have studied theoretically the type-II GaAsSb capped InAs quantum dots for two structures differing in the composition of the capping layer, being either (i) constant or (ii) with Sb accumulation above the apex of the dot. We have found that the hole states are segmented and resemble the states in the quantum dot molecules. The two-hole states form singlet and triplet with the splitting energy of 4 μeV/325 μeV for the case (i)/(ii). We have also tested the possibility to tune the splitting by vertically applied magnetic field. Because the predicted tunability range was limited, we propose an approach for its enhancement.

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3 Acta Physica Polonica A

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1 Křápek V.

Vibrational Modes in Si_{x}Ge_{1-x} Alloys: Temperature and Compositional Dependence

Localized Vibrational Modes of Interstitial Oxygen in Si_{x}Ge_{1-x} Alloys

Type-II InAs/GaAsSb/GaAs Quantum Dots as Artificial Quantum Dot Molecules