Search results

1

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

100%

Lorenc M., Humlíček J.

Acta Physica Polonica A

|

1998

|

vol. 94

|

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}.

2

Micro-Raman Investigation of Hydrogen Localized in Cone-Shaped Defects Formed on the Silicon Wafer Surface

100%

Frantskevich N., Fedotov A., Frantskevich A., Mazanik N.

Acta Physica Polonica A

|

2014

|

vol. 125

|

issue 6

1332-1334

EN

The goal of this work is the micro-Raman study of molecular hydrogen localized in cone-shaped defects, which are formed on the surface of previously helium implanted and annealed Czochralski Si wafers as a result of hydrogen plasma treatment. The line at ≈ 4158 cm^{-1} corresponding to molecular hydrogen is observed in the Raman spectra when the laser beam is focused both on cone-shaped defects or defect-free regions of the surface. The laser irradiation of cone-shaped defects during micro-Raman experiments leads to intensity increase of this line when the irradiation time is increasing, with subsequent appearance of lines at ≈ 3621 and ≈ 3698 cm^{-1} and simultaneous disappearance of 4158 cm^{-1} line. No such effect was observed when the laser beam was focused on defect-free regions. The experiments have shown that heat treatment of the samples studied causes the appearance in the Raman spectra of lines at ≈ 3468, ≈ 3621, and ≈ 3812 cm^{-1}, which can be associated with molecular hydrogen.

3

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

100%

Lorenc M., Humlíček J.

Acta Physica Polonica A

|

1997

|

vol. 92

|

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.

4

Solar Cell Emitters Fabricated by Flash Lamp Millisecond Annealing

80%

Prucnal S., Shumann T., Skorupa W., Abendroth B., Krockert K., Möller H.

Acta Physica Polonica A

|

2011

|

vol. 120

|

issue 1

30-34

EN

Phosphorus ion implantation was used for the emitter formation in mono- and multicrystalline silicon solar cells. After ion implantation the silicon is strongly disordered or amorphous within the ion range. Therefore subsequent annealing is required to remove the implantation damage and activate the doping element. Flash-lamp annealing offers here an alternative route for the emitter formation at overall low thermal budget. During flash-lamp annealing, only the wafer surface is heated homogeneously to very high temperatures at ms time scales, resulting in annealing of the implantation damage and electrical activation of phosphorus. However, variation of the pulse time also allows to modify the degree of annealing of the bulk region to some extent as well, which can have an influence on the gettering behaviour of metallic bulk impurities. The μ-Raman spectroscopy showed that the silicon surface is amorphous after ion implantation. It could be demonstrated that flash-lamp annealing at 800°C for 20 ms even without preheating is sufficient to recrystallize implanted silicon. The highest carrier concentration and efficiency as well as the lowest resistivity were obtained after annealing at 1200°C for 20 ms both for mono- and multicrystalline silicon wafers. Photoluminescence results point towards P-cluster formation at high annealing temperatures which affects metal impurity gettering within the emitter.

5

Raman Spectra of Bismuth Oxyhalide Single Crystals

80%

Bunda S., Bunda V.

Acta Physica Polonica A

|

2014

|

vol. 126

|

issue 1

272-273

EN

Oxyhalogenides of bismuth BiOX (X=Cl, Br and I) are very interesting materials which find various applications as X-ray luminescent screens, anti-Stokes (frequency upshift) converters, luminophors, and photoconducting analyzers of linear polarized radiation. Since each primitive cell consist of six monoatomic sites, the structure of the reduced representation of the 15 normal modes of vibration is: Γ= 2A_{1g}(Ra.)+B_{1g}(Ra.)+ 3E_{g}(Ra.)+ 2A_{2u}(i.r.)+ 2E_{u}(i.r.), in which the vibrations of A_{1g}, B_{1g} and E_{g} species are active in the Raman spectrum and those of A_{2u} and E_{u} species are active in the infrared (i.r.) spectrum. The Raman active modes are observed in frequency range 55 - 225 cm^{-1}, 50 - 185 cm^{-1 }, and 45 - 175 cm^{-1} for the BiOCl, BiOBr and BiOI single crystals respectively.

6

Residual Strain and Electrical Activity of Defects in Multicrystalline Silicon Solar Cells

80%

Martínez O., Mass J., Tejero A., Moralejo B., Hortelano V., González M., Jiménez J., Parra V.

Acta Physica Polonica A

|

2014

|

vol. 125

|

issue 4

1013-1016

EN

The growth process by casting methods of multi-crystalline Si results in a crystalline material with, among other defects, a high density of dislocations and grain boundaries. Impurity incorporation and their gathering around grain boundaries and dislocations seem to be the main factor determining the electrical activity of those defects, which limit the minority carrier lifetime. In this work, we analyze multi-crystalline Si samples by combining etching processes to reveal the defects, Raman spectroscopy for strain measurements, and light beam induced current measurements for the localization of electrically active defects. In particular, we have explored the etching routes capable to reveal the main defects (grain boundaries and dislocation lines), while their electrical activity is studied by the light beam induced current technique. We further analyze the strain levels around these defects by Raman micro-spectroscopy, aiming to obtain a more general picture of the correlation between residual stress and electrical activity of the extended defects. The higher stress levels are observed around intra-grain defects associated with dislocation lines, rather than around the grain boundaries. On the other hand, the intra-grain defects are also observed to give dark light beam induced current contrast associated with a higher electrical activity of these defects as compared to the grain boundaries.

7

Raman Study of Multicrystalline Silicon Wafers Produced by the RST Process

80%

Tejero A., Tupin E., González M., Martínez O., Jiménez J., Belouet C., Baillis C.

Acta Physica Polonica A

|

2014

|

vol. 125

|

issue 4

1006-1009

EN

In the silicon ribbon on a sacrificial template process silicon is deposited on both sides of a carbon ribbon, thus forming a Si/carbon/Si trilayer. The fast cooling of the ribbon in large temperature gradients generates stresses that are detrimental to both the electrical performance and the mechanical behaviour of the wafers. The assessment of the stresses is crucial for the setting-up of thermal treatments allowing for the stress relaxation of the wafers, prior to the cell fabrication. We present an analysis of the stress in the as-grown trilayer by a simulation of the thermomechanical behaviour of the cooling ribbon. Experimental measurements of the stress in as-grown and annealed trilayers are also presented. The results permit to establish the conditions for optimized growth and annealing.

8

Structural and Optoelectronic Properties of In-Zn-S sprayed Layers

80%

Lazzez S., Boubaker K., Ben Nasrallah T., Amlouk M., Belgacem S., Mnari M., Chtourou R.

Acta Physica Polonica A

|

2008

|

vol. 114

|

issue 4

869-880

EN

In this work, In-Zn-S thin layers were prepared using the spray pyrolysis technique on glass substrates at 320°C. The molar ratio between zinc and indium x=[Zn^{2+}]/[In^{3+}] was varied in 0-0.4 domain whereas [S^{2-}]/[In^{3+}] one was taken constant equal to 2. The atomic composition was carried out with the atomic absorption. The structural study of all layers via X-ray diffraction and atomic force microscopy shows that the layer, obtained using x=0 is formed by binary material In_2S_3 with a principal orientation along (400). When the composition increases the same study depicts the presence of other materials such as ZnO, ZnS, and ZnIn_2S_4. On the contrary, for x=0.4, the film is mainly formed by the ternary compound ZnIn_2S_4 which crystallizes in cubic phase. Moreover, the optical analysis via the transmittance, reflectance as well as the photocurrent reveals that the band gap energy E_g increases slightly as a function of the x composition (E_g varies from 2.6 to 2.9 eV).

Refine search results

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

Micro-Raman Investigation of Hydrogen Localized in Cone-Shaped Defects Formed on the Silicon Wafer Surface

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

Solar Cell Emitters Fabricated by Flash Lamp Millisecond Annealing

Raman Spectra of Bismuth Oxyhalide Single Crystals

Residual Strain and Electrical Activity of Defects in Multicrystalline Silicon Solar Cells

Raman Study of Multicrystalline Silicon Wafers Produced by the RST Process

Structural and Optoelectronic Properties of In-Zn-S sprayed Layers