Influence of the crystallization process on the luminescence of multilayers of SiGe nanocrystals embedded in SiO2

Avella, M.; Prieto, Á. C.; Jiménez, J.; Rodrı́guez, A.; Sangrador, J.; Rodrı́guez, T.; Ortiz, M. I.; Ballesteros, C.

doi:10.1016/j.mseb.2007.08.016

Cited by 13 publications

(8 citation statements)

References 11 publications

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“…8, indicating that the absence of the SiGe Raman signature in the spectra of the singlelayer samples is due to the small number of Ge-Ge bonds and not to reduced absorption due to an increase of the bandgap of the nanoparticles with decreasing diameter as has been previously suggested. 32 It should be noted that the UV-Raman setup used in this work is a commercial one (see the experimental paragraph); therefore, this sensitivity limit can be assumed as a true experimental limit for the observation of SiGe nanoparticles with a Raman microprobe under UV (325 nm) excitation. Note that, for conventional visible excitation (488 or 514 nm), one needs much higher areal density to detect the Raman signal arising from the nanoparticles.…”

Section: Tem Images Of the Four Single Layers (S-1 To S-4) And Two Mumentioning

confidence: 99%

Crystallization of Amorphous Si0.6Ge0.4 Nanoparticles Embedded in SiO2: Crystallinity Versus Compositional Stability

Rodrı́guez

Prieto

et al. 2010

Journal of Elec Materi

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Si 0.6 Ge 0.4 nanocrystals, of diameter <5 nm, embedded in SiO 2 in the form of single layers (2.1 9 10 12 nanoparticles cm -2 ) and five-period multilayers (above 10 13 nanoparticles cm -2 ) have been fabricated using a low-thermalbudget process consisting of deposition by low-pressure chemical vapor deposition and crystallization by rapid thermal annealing at several temperatures and for different times. The crystallization process was monitored by Raman spectroscopy and transmission electron microscopy. The loss of integrity and compositional changes of the nanoparticles during the annealing process were characterized by Rutherford backscattering spectrometry. During the annealing process, crystallization and Ge out-diffusion have been observed to compete with each other. Annealing of samples with nanoparticles of 4.6 nm diameter at low temperature (750°C) yields poor crystallization of the nanoparticles and causes the Ge to leave them by a pure diffusive mechanism, thus destroying their integrity. At higher temperatures ( ‡800°C), crystallization takes place in a short period of time (<30 s) and diffusion from the crystallized material is initially hindered. For samples with nanoparticles of 3.3 nm diameter, partial crystallization is detected at 800°C and 900°C and the crystalline quality is improved in both cases as the annealing time increases. Also, the detection capabilities of the Raman spectroscopy system for the detection of a certain density of SiGe nanocrystals of given diameter and composition have been explored and the lower limit estimated.

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Section: Tem Images Of the Four Single Layers (S-1 To S-4) And Two Mumentioning

confidence: 99%

Crystallization of Amorphous Si0.6Ge0.4 Nanoparticles Embedded in SiO2: Crystallinity Versus Compositional Stability

Rodrı́guez

Prieto

et al. 2010

Journal of Elec Materi

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“…In particular, the GLPC that are located at the interface layers between ncGe and SiO 2 produced during the preparation of the materials seem to be involved [6][7][8][9]. The control of the luminescence intensity of this type of material is an important argument [6,13], and many production methods were used to adjust the interface areas (GeOx layers) and to maximize the photoluminescence intensity at 3.2 eV [6,7,13].…”

Section: Introductionmentioning

confidence: 99%

Ge‐doping dependence of gamma‐ray induced germanium lone pair centers in Ge‐doped silica

Alessi

Agnello

Gelardi

et al. 2008

Physica Status Solidi (b)

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We report an experimental study on the γ irradiation effects in Ge‐doped sol‐gel silica samples doped with Ge from 102 up to 104 part per million molar. The samples were exposed to the radiation generated by a 60Co source up to an accumulated dose value of 10 MGy. Our data evidence that the γ irradiation significantly increases the number of Germanium Lone Pair Centers (GLPC). Such defects are induced with a concentration that depends on the Ge content of the employed material in those samples where no optical activity related to GLPC was detected before irradiation. Furthermore an increase of the GLPC concentration was detected also in a sample that already contains this defect after the production. These findings show that, in addition to the GLPC bleaching effect already reported in the literature, γ rays can generate such defects and a range of doses exists in which the generation processes overcome the bleaching processes. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

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“…It is worth noting that the calculated bandgap for such clusters would exhibit emission considerably higher in energy than those observed experimentally [13,17,18]. The bluegreen luminescence was experimentally observed from Ge nanostructures prepared by several methods, such as radiofrequency sputtering [19], stain etching [20], ion implantation/annealing [21], chemical vapour deposition (CVD) growth [11,22] and electrochemical deposition [23]. Ge nanodots can also be fabricated using a dewetting mechanism for thin Ge films on insulator layers [2,[24][25][26][27].…”

Section: Introductionmentioning

confidence: 89%

“…The potential applications of Ge quantum structures as light emitters are, thus, associated with the ability of yielding high emission efficiency due to radiative recombination in the Ge crystal. The origin of light emission from Ge nanostructures is, however, a subject of controversial interpretation of experimental evidence, which is attributed to quantum confinement effects [4,7,8] as well as to defects [9][10][11]. The evolution of the Ge electronic structure upon reducing the size was experimentally deduced from X-ray absorption spectra by Bostedt et al [12].…”

Section: Introductionmentioning

confidence: 99%

Role of surface passivation on visible and infrared emission of Ge quantum dots formed by dewetting

et al. 2019

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The dual action of oxide-related defects in the visible and infrared emission of germanium (Ge) self-assembled quantum dots (QDs) is discussed. The Ge particles were fabricated by solid-state dewetting on a thin layer of SiO 2. Subsequent surface passivation by amorphous silicon was carried out for several samples. All samples were encapsulated by SiO 2. Atomic force microscopy analysis indicates a linear relationship between the size of QDs and the initial thickness of the amorphous Ge films. The crystallization of the QDs was evidenced by transmission electron microscopy and Raman spectroscopy. Photoluminescence measurements show that the main visible emission is blue-green centred around 520 nm. The luminescence attributed to the radiative recombination of quantum-confined excitons is only observed when the surface is in-situ passivated prior to the deposition of the oxide matrix. The results of this work are helpful for optimizing the performance of the optoelectronic devices based on the infrared emission of Ge nanocrystals.

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Influence of the crystallization process on the luminescence of multilayers of SiGe nanocrystals embedded in SiO2

Cited by 13 publications

References 11 publications

Crystallization of Amorphous Si0.6Ge0.4 Nanoparticles Embedded in SiO2: Crystallinity Versus Compositional Stability

Crystallization of Amorphous Si0.6Ge0.4 Nanoparticles Embedded in SiO2: Crystallinity Versus Compositional Stability

Ge‐doping dependence of gamma‐ray induced germanium lone pair centers in Ge‐doped silica

Role of surface passivation on visible and infrared emission of Ge quantum dots formed by dewetting

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