Effect of the Nanoparticles on the Structure and Crystallization of Amorphous Silicon Thin Films Produced by rf Glow Discharge

Bertrán, E.; Sharma, S.N.; Viera, G.; Costa, J.; Šťahel, Pavel; Cabarrocas, Pere Roca i

doi:10.1557/jmr.1998.0347

Cited by 33 publications

(25 citation statements)

References 18 publications

(22 reference statements)

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“…The lattice constant deduced from this diffraction pattern is 3.7 Å. A similar crystalline structure was found in nanostructured Si thin films deposited under continuous SiH 4 -H 2 rf plasma 12 and in Si nanometric powder, 22 where nanocrystalline clusters with fcc structure were found to be embedded in an amorphous matrix. It is assumed that polymorphous Si films are formed by the incorporation of Si nanocrystallites ͑grown in the plasma gas phase͒ in an amorphous Si film.…”

Section: A Tem Characterizationsupporting

confidence: 74%

“…5 Recently, silicon films deposited under conditions close to those for powder-particle formation have revealed interesting new optoelectronic properties, in particular better transport and stability properties as compared to a-Si:H. [6][7][8][9] This new class of silicon thin films has been fabricated using a wide range of plasma conditions. [10][11][12][13][14] They are referred to as polymorphous silicon ͑pm-Si:H͒.…”

Section: Introductionmentioning

confidence: 99%

“…12,13 Polymorphous silicon is now considered as a good candidate in possible future applications particularly in the photovoltaic domain.…”

Section: Introductionmentioning

confidence: 99%

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Polymorphous Si thin films from radio frequency plasmas of SiH4 diluted in Ar: A study by transmission electron microscopy and Raman spectroscopy

Viera

Huet

Bertrán

et al. 2001

Journal of Applied Physics

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In this study, we present a detailed structural characterization by means of transmission electron microscopy and Raman spectroscopy of polymorphous silicon ͑pm-Si:H͒ thin films deposited using radio-frequency dust-forming plasmas of SiH 4 diluted in Ar. Square-wave modulation of the plasma and gas temperature was varied to obtain films with different nanostructures. Transmission electron microscopy and electron diffraction have shown the presence of Si crystallites of around 2 nm in the pm-Si:H films, which are related to the nanoparticles formed in the plasma gas phase coming from their different growth stages, named particle nucleation and coagulation. Raman scattering has proved the role of the film nanostructure in the crystallization process induced ''in situ'' by laser heating.

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Section: A Tem Characterizationsupporting

confidence: 74%

Section: Introductionmentioning

confidence: 99%

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Polymorphous Si thin films from radio frequency plasmas of SiH4 diluted in Ar: A study by transmission electron microscopy and Raman spectroscopy

Viera

Huet

Bertrán

et al. 2001

Journal of Applied Physics

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“…This is in contrast to previous crystallization experiments carried out at a lower temperature (590°C) during isothermal treatments, where pm-Si:H crystallized faster than a-Si:H did. 16 In that case, nucleation was heterogeneous, and the grain size after crystallization was correlated with the density of nanoparticles revealed by transmission electron microscopy. This apparent contradiction could be understood if we take into account the pronounced dependence of the homogeneous nucleation rate r n on temperature.…”

Section: Crystallizationmentioning

confidence: 92%

Thermally Induced Structural Transformations on Polymorphous Silicon

et al. 2005

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Polymorphous Si is a nanostructured form of hydrogenated amorphous Si that contains a small fraction of Si nanocrystals or clusters. Its thermally induced transformations such as relaxation, dehydrogenation, and crystallization have been studied by calorimetry and evolved gas analysis as a complementary technique. The observed behavior has been compared to that of conventional hydrogenated amorphous Si and amorphous Si nanoparticles. In the temperature range of our experiments (650-700°C), crystallization takes place at almost the same temperature in polymorphous and in amorphous Si. In contrast, dehydrogenation processes reflect the presence of different hydrogen states. The calorimetry and evolved gas analysis thermograms clearly show that polymorphous Si shares hydrogen states of both amorphous Si and Si nanoparticles. Finally, the total energy of the main Si-H group present in polymorphous Si has been quantified.

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“…A number of structural analyses have revealed that polymorphous silicon has a higher degree of medium-range order than the conventional amorphous material. 9,10 Both samples have been deposited onto the walls of the reaction chamber, which was maintained at 250°C during 10 h. This long deposition time results in thick layers of around 10 m. The third sample consists of hydrogenated silicon nanoparticles (np-Si:H). They were grown in a pure silane plasma at room temperature (for details see Ref.…”

Section: Lpicm (Umr 7647 Cnrs) Ecole Polytechnique 91128 Palaiseau Cmentioning

confidence: 99%

Anomalous crystallization of hydrogenated amorphous silicon during fast heating ramps

et al. 2005

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Thermal crystallization experiments carried out using calorimetry on several a-Si:H materials with different microstructures are reported. The samples were crystallized during heating ramps at constant heating rates up to 100 K/min. Under these conditions, crystallization takes place above 700°C and progressively deviates from the standard kinetics. In particular, two crystallization processes were detected in conventional a-Si:H, which reveal an enhancement of the crystallization rate. At 100 K/min, such enhancement is consistent with a diminution of the crystallization time by a factor of 7. In contrast, no systematic variation of the resulting grain size was observed. Similar behavior was also detected in polymorphous silicon and silicon nanoparticles, thus showing that it is characteristic of a variety of hydrogenated amorphous silicon materials.Crystallization of amorphous silicon (a-Si) is a subject that has been studied extensively during the last three decades. It improves the electrical conductivity substantially, 1 making the resulting polycrystalline silicon useful for a number of applications, such as thin film transistors (TFT), liquid crystal displays (LCD), and image sensors.2 The kinetics of this process follows the nucleation and growth steps with rate constants characterized by transmission electron microscopy. [3][4][5][6] The relative values of nucleation and growth rates determine the final grain size that can be controlled through the crystallization temperature or by ion irradiation during crystallization. 4 The temperature range in the published results seldom extends above 700°C because of the difficulty in reaching the isothermal conditions without any incipient crystallization taking place during the heating ramp. This difficulty is partially overcome by calorimetric experiments where the material is heated at a constant rate.From the heat that evolves the crystallization rate can be obtained. Kinetic studies using calorimetry have only been performed during the epitaxial crystallization of thin a-Si films obtained from rapid solidification.7 With the exception of our preliminary work, 8 no systematic studies on hydrogenated a-Si (a-Si:H) have been published. In this paper we extend the temperature range during the heating ramps above 700°C up to 100 K/min. Under these conditions, an unexpected and substantial enhancement of the crystallization rate was observed. Besides the intrinsic interest of characterizing a new phenomenon, our study can be useful to understand the crystallization that occurs during rapid thermal annealing (RTA) processes.

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Effect of the Nanoparticles on the Structure and Crystallization of Amorphous Silicon Thin Films Produced by rf Glow Discharge

Cited by 33 publications

References 18 publications

Polymorphous Si thin films from radio frequency plasmas of SiH4 diluted in Ar: A study by transmission electron microscopy and Raman spectroscopy

Polymorphous Si thin films from radio frequency plasmas of SiH4 diluted in Ar: A study by transmission electron microscopy and Raman spectroscopy

Thermally Induced Structural Transformations on Polymorphous Silicon

Anomalous crystallization of hydrogenated amorphous silicon during fast heating ramps

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