Photoluminescence of Ge nanocrystals self-assembled on SiO2

Rowell, N. L.; Lockwood, D. J.; Karmous, A.; Szkutnik, Pierre-David; Berbézier, Isabelle; Ronda, A.

doi:10.1016/j.spmi.2008.01.011

Cited by 18 publications

(32 citation statements)

References 26 publications

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“…For this reason it was thought that the TB model simulates more accurately the effect of NC size on bandgap in Ge NCs. From our earlier experimental work, 18 there was a more reasonable agreement between our results and the TB model calculation.…”

Section: Methodssupporting

confidence: 87%

“…1 were measured using a Bomem DA3 Fourier transform infrared spectrometer with samples at 5 K excited with 100 mW at 457.9 nm from an argon ion laser, which was above the bandgap energy for NCs larger than 3.3 ͓1.7͔ nm assuming a k · p ͓tight binding ͑TB͔͒ model bandgap. 18 Reference 12 argues that the k · p approximation overestimates the carrier confinement in Si NCs and that a similar overestimation occurs for Ge NCs. For this reason it was thought that the TB model simulates more accurately the effect of NC size on bandgap in Ge NCs.…”

Section: Methodsmentioning

confidence: 99%

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Photoluminescence Efficiency of Self-Assembled Ge Nanocrystals

Rowell

Lockwood

Berbézier

et al. 2009

J. Electrochem. Soc.

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For self-assembled Ge nanocrystals ͑NCs͒, the predicted nonlinear increase in the photoluminescence ͑PL͒ efficiency with decreasing NC diameter has been evaluated using the NC size distribution observed from transmission electron microscopy. The NCs were formed by thermal annealing of an amorphous Ge layer deposited by molecular beam epitaxy on a thin SiO 2 layer on Si͑001͒. For the present range of particle sizes ͑2.5-60 nm͒, the NC PL appeared primarily as a wide near-IR band near 800 meV. The peak energy of the PL band reflects the average NC size, and its shape depends on the NC size distribution. Using both the k · p and tight binding models, the PL energy spectrum was transformed into the PL variation with NC size. For smaller diameter NCs, the band shape contains significant bandgap enlargement due to quantum confinement. The present results show how NC size distributions can be obtained from the PL data.

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Section: Methodssupporting

confidence: 87%

Section: Methodsmentioning

confidence: 99%

Photoluminescence Efficiency of Self-Assembled Ge Nanocrystals

Rowell

Lockwood

Berbézier

et al. 2009

J. Electrochem. Soc.

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“…For the present samples [25], silicon (001) substrates supplied by STMicroelectronics covered by a homogeneous 5 nm thick layer of thermally grown amorphous SiO 2 were used. Ge atoms were deposited by electron beam evaporation at a rate of 0.05 nm/sec at a pressure of 1x10 −10 Torr on SiO 2 surfaces pre-cleaned chemically in sulfuric peroxide mixture (H 2 SO 4 :H 2 O 2 (3:1)) and in acidic peroxide mixture (HCl : H 2 O 2 : H 2 O (1 : 1 : 20)) solutions followed by rapid thermal annealing at 700 °C in ultrahigh vacuum.…”

Section: Methodsmentioning

confidence: 99%

“…For these experiments, the Ge NCs were then capped with a 15-nm thick layer of a-Si in situ, i.e., the Ge NCs were never exposed to air. In table I we provide the Ge layer thickness, h 0 , and mean NC diameter obtained for each of the structures grown by this process described in detail previously [25]. Using high resolution transmission electron microscopy (HRTEM) images, average NC diameters were obtained from the analysis of plan view micrographs [25].…”

Section: Methodsmentioning

confidence: 99%

Size distribution of self assembled Ge nanocrystals determined by photoluminescence

Rowell¹,

Lockwood²,

Berbézier

et al. 2008

MRS Proc.

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Germanium nanocrystals (NCs) were formed by in-situ thermal annealing of an amorphous Ge layer deposited by molecular beam epitaxy on a thin SiO 2 layer on Si(001). The Ge NCs were then capped in situ with a thin layer of amorphous Si to prevent oxidation. For the present range of particle sizes (2.5 to 60 nm), the NC photoluminescence (PL) appeared primarily as a wide near-infrared band peaked near 800 meV. The peak energy of the PL band reflects the average NC size and its shape depends on the NC size distribution. Using both the k⋅ ⋅ ⋅ ⋅p and tight binding theoretical models, we have analyzed the PL spectrum in terms of the NC size distribution required to reproduce the observed asymmetric band shape, which includes, for the smaller diameter NCs, a band gap enlargement due to quantum confinement. The observed size distribution determined from transmission electron microscopy analysis allowed the determination of the nonlinear increase in the PL quantum efficiency with decreasing NC diameter. This implies that, given a good theoretical description of the system, it is possible to evaluate the size distribution of semiconductor NCs from their PL energy dependence.

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“…The common structural characteristic is that the Ge QDs are randomly distributed in the SiO 2 matrix with non-uniform size. 13,16 To realize practical applications, the Ge QDs need to be accurately controlled with the position, size, and density. However, the difficulty in the realization of these goals has prevented the exploration with further progress despite intensive studies of Ge QDs embedded in the SiO 2 matrix.…”

Section: Thermally Oxidized Formation Of New Ge Dots Over As-grown Gementioning

confidence: 99%

Thermally oxidized formation of new Ge dots over as-grown Ge dots in the Si capping layer

Nie

Lin

Chen

et al. 2011

Journal of Applied Physics

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A Si-capped Ge quantum dot sample was self-assembly grown via Stranski-Krastanov mode in a molecular beam epitaxy system with the Si capping layer deposited at 300 C. After annealing the sample in an oxygen atmosphere at 1000 C, a structure, namely two layers of quantum dots, was formed with the newly formed Ge-rich quantum dots embedded in the oxidized matrix with the position accurately located upon the as-grown quantum dots. It has been found that the formation of such nanostructures strongly depends upon the growth temperature and oxygen atmosphere. A growth mechanism was proposed to explain the formation of the nanostructure based on the Ge diffusion from the as-grown quantum dots, Ge segregation from the growing oxide, and subsequent migration/agglomeration.

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Photoluminescence of Ge nanocrystals self-assembled on SiO2

Cited by 18 publications

References 26 publications

Photoluminescence Efficiency of Self-Assembled Ge Nanocrystals

Photoluminescence Efficiency of Self-Assembled Ge Nanocrystals

Size distribution of self assembled Ge nanocrystals determined by photoluminescence

Thermally oxidized formation of new Ge dots over as-grown Ge dots in the Si capping layer

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