Raman scattering by tellurium films on CdTe single crystals

Artamonov, V. V.; Valakh, M. Ya.; Strelchuk, V. V.; Baidullaeva, A.; Mozol, P. E.

doi:10.1007/bf01133668

Cited by 11 publications

(10 citation statements)

References 9 publications

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“…3b as the evidence for the formation of elemental tellurium were previously reported for bulk CdTe [40,41] and other tellurides [42]. Moreover, Raman spectroscopy of glassembedded CdTe nanocrystals revealed, besides the clear CdTe LO phonon band at 159-163 cm À1 , two intense distinct bands at 120-123.5 and 139-141.5 cm À1 indicating the presence of tellurium precipitates in the sample [43].…”

Section: Methodsmentioning

confidence: 79%

Precipitates of selenium and tellurium in II–VI nanocrystal‐doped glass probed by Raman scattering

Azhniuk

Lopushansky

Hutych

et al. 2011

Physica Status Solidi (b)

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, Phone: þ380 312 643822, Fax: þ380 312 643650As follows from Raman studies, the formation of cadmium chalcogenide nanocrystals in borosilicate glass under thermal treatment at 625-700 8C can be accompanied by precipitation of elemental Se or Te in the form of molecular Se 2 or Te 2 clusters or larger aggregations. The clusters are in most cases formed when the thermal treatment temperature and/or duration values are beyond the range most suitable for the formation of the II-VI nanocrystals. Larger aggregations are formed at intense thermal treatment, precipitation of tellurium being achieved much easier than that of selenium.1 Introduction II-VI (mostly CdSe 1Àx S x ) semiconductor nanocrystal-doped glasses were extensively studied by Raman spectroscopy and the excellent applicability of this technique to determine the nanocrystal parameters was demonstrated. Low-wavenumber Raman scattering by acoustic phonons due to the confinement-related selection rules relaxation in CdSe 1Àx S x nanocrystals was used to estimate the average nanocrystal size [1][2][3][4][5]. Raman spectroscopy was also proven to be a very efficient tool to examine the chemical composition of ternary II-VI nanocrystals diluted in the glass matrix, based on the LO phonon frequencies taking into account the specific effects related to glass matrix pressure, phonon confinement, surface phonon scattering and compositional and size dispersion of nanocrystals within the ensemble [6][7][8][9][10][11][12][13][14][15][16][17][18].Fabrication of II-VI semiconductor nanocrystals in glass matrices is performed by a well-elaborated diffusion-limited growth technique [19][20][21]. Recently Raman scattering studies revealed that not only the nanocrystal size, but also their composition is affected by the growth conditions (thermal treatment temperature and duration) [16,18]. Moreover, it was reported that at certain thermal treatment conditions molecular clusters of selenium can be formed in CdSe and CdSe 1Àx S x nanocrystal-doped glasses [22].

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Section: Methodsmentioning

confidence: 79%

Precipitates of selenium and tellurium in II–VI nanocrystal‐doped glass probed by Raman scattering

Azhniuk

Lopushansky

Hutych

et al. 2011

Physica Status Solidi (b)

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“…For these samples, the laser was focused in two different spatial regions: on top of the film surface (a) and inside the ablated holes (b), to verify the presence of CdTe over the whole microstructured substrate. For both regions, Raman spectra show a peak at 167 cm −1 , which corresponds to the CdTe LO phonon [ 35 ]. Additionally, it can be observed that the first harmonic at 335 cm −1 and, subsequently, the second, third, and fourth harmonics at 501, 667, and 834 cm −1 , respectively.…”

Section: Resultsmentioning

confidence: 99%

Optical Absorption Enhancement in CdTe Thin Films by Microstructuration of the Silicon Substrate

Rangel-Cárdenas

Sobral

2017

Materials

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In this work, the reflectance, optical absorption, and band gap have been determined for CdTe thin films grown on planar and microstructured substrates. The treated surface was prepared by laser ablation of a silicon wafer, forming holes in a periodic arrangement. Thin films were grown by pulsed laser ablation on silicon samples kept at 200 °C inside a vacuum chamber. The presence of CdTe was verified with X-ray diffraction and Raman spectroscopy indicating a nanocrystalline zinc blended structure. The optical absorption of thin films was calculated by using the Fresnel laws and the experimental reflectance spectrum. Results show that reflectance of 245 nm films deposited on modified substrates is reduced by up to a factor of two than the obtained on unchanged silicon and the optical absorption is 16% higher at ~456 nm. Additionally, it was determined that the band gap energy for planar and microstructured films is about 1.44 eV for both cases.

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“…In particular, the effect of CdTe surface enrichment with Te, well-known for bulk CdTe crystals and thin films [ 49 ], can be even more probable for NC due to their large surface-to-volume ratio and surface curvature. Thus, the sample #641 can have some radial composition inhomogeneity, with Te enrichment towards surface and therefore a reduced volume of pure (stoichiometric) CdTe.…”

Section: Resultsmentioning

confidence: 99%

“…As the enhancement of the HFS after treatment in pyridine was observed for two samples, #641 and #642, with higher Te concentration during synthesis, this Raman feature may be related with the Te phase on the NC's surface. Note that Raman spectroscopy on phonons is an efficient tool to detect the surface Te on CdTe crystalline films [ 49 ] due to much larger scattering cross section for Te compared to CdTe [ 50 ]. The only reported Te-related Raman feature above CdTe LO phonon frequency is the bond-stretching vibration of the crown-like Te 8 ring at 182 cm -1 [ 50 ], which is also observed in a-Te.…”

Section: Resultsmentioning

confidence: 99%

Phonon Raman spectra of colloidal CdTe nanocrystals: effect of size, non-stoichiometry and ligand exchange

et al. 2011

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Resonant Raman study reveals the noticeable effect of the ligand exchange on the nanocrystal (NC) surface onto the phonon spectra of colloidal CdTe NC of different size and composition. The oleic acid ligand exchange for pyridine ones was found to change noticeably the position and width of the longitudinal optical (LO) phonon mode, as well as its intensity ratio to overtones. The broad shoulder above the LO peak frequency was enhanced and sharpened after pyridine treatment, as well as with decreasing NC size. The low-frequency mode around 100 cm-1 which is commonly related with the disorder-activated acoustical phonons appears in smaller NCs but is not enhanced after pyridine treatment. Surprisingly, the feature at low-frequency shoulder of the LO peak, commonly assigned to the surface optical phonon mode, was not sensitive to ligand exchange and concomitant close packing of the NCs. An increased structural disorder on the NC surface, strain and modified electron-phonon coupling is discussed as the possible reason of the observed changes in the phonon spectrum of ligand-exchanged CdTe NCs.PACS: 63.20.-e, 78.30.-j, 78.67.-n, 78.67.Bf

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Raman scattering by tellurium films on CdTe single crystals

Cited by 11 publications

References 9 publications

Precipitates of selenium and tellurium in II–VI nanocrystal‐doped glass probed by Raman scattering

Precipitates of selenium and tellurium in II–VI nanocrystal‐doped glass probed by Raman scattering

Optical Absorption Enhancement in CdTe Thin Films by Microstructuration of the Silicon Substrate

Phonon Raman spectra of colloidal CdTe nanocrystals: effect of size, non-stoichiometry and ligand exchange

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