Structural characterization of nc-Si films grown by low-energy PECVD on different substrates

Donne, A. Le; Binetti, S.; Isella, Giovanni; Pichaud, B.; Texier, M.; Acciarri, M.; Pizzini, S.

doi:10.1016/j.apsusc.2007.10.025

Cited by 27 publications

(20 citation statements)

References 21 publications

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“…Furthermore, X-ray diffraction analyses carried out according to the experimental setup, as well as the elaboration methods reported in Ref. 9, confirmed that the mean crystallite sizes in the present samples ranged between 5 and 12 nm, thus leading to the observed redshift of the nc-Si Raman peak position. 16 As nc-Si is a mixed phase material in which small crystallites are surrounded by an amorphous tissue, 17 the film growth was often explained by vapor phase models similar to those used for amorphous silicon films.…”

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confidence: 74%

“…A problem arising in the region of growth parameters used to obtain such a crystallinity is that the microstructure of the resulting intrinsic layer was shown to be inhomogeneous along the growth direction. 8,9 Conversely, from the aspects of photovoltaic application, it is very important to obtain the smallest differences in the texture along the growth direction, as a uniform microstructure must yield a uniform electric field in the intrinsic layer, resulting in high fill factors and open-circuit voltages. 10 In the present work, nc-Si samples were grown by LEPECVD 11 using different SiH 4 and H 2 fluxes, all yielding the same dilution factor.…”

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confidence: 99%

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Structural Homogeneity of nc-Si Films Grown by Low-Energy PECVD

Donne

Binetti

Isella

et al. 2008

Electrochem. Solid-State Lett.

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Nanocrystalline silicon is considered one of the most promising materials for thin-film solar cells. For such an application, one of the critical issues yet unsolved is to obtain a good structural uniformity along the film growth direction to yield high fill factors and open-circuit voltages. In this article, Raman spectroscopy was used to obtain crystallinity in-depth profiles of samples grown at a high growth rate by low-energy plasma-enhanced chemical vapor deposition ͑PECVD͒ using different SiH 4 and H 2 fluxes, all yielding the same dilution factor. The results showed that the total flow rate strongly affects the structural uniformity of nanocrystalline silicon films.Nanocrystalline silicon ͑nc-Si͒, a biphasic material consisting of a dispersion of silicon nanocrystals embedded in an amorphous silicon matrix, is considered a challenging opportunity for thin-film solar cells. 1,2 Nowadays, the design and fabrication of nc-Si-based solar cells is still in the initial stage, having however reached cell efficiencies around 11% in laboratory tests. 3 Notwithstanding its potentialities, the industrial applications of nc-Si have been limited, at first, by the relatively low growth rate typical of most deposition techniques. Recently, however, it has been shown that in the case of both the very high-frequency chemical vapor deposition 4 and the low-energy plasma-enhanced chemical vapor deposition 5 ͑LEPECVD͒, growth rates of 3-5 nm/s can be obtained, compatible with industrial applications.Nanocrystalline silicon deposited by variants of plasmaenhanced chemical vapor deposition is commonly obtained from a gas mixture of silane and hydrogen; the resulting crystalline volume fraction strongly depends on the silane dilution in the hydrogensilane feed gas mixture d% = ⌽ SiH 4 /͑⌽ SiH 4 + ⌽ H 2 ͒. 6 As already reported in Ref. 7, nc-Si solar cells with the highest open-circuit voltage are obtained in the case of a crystalline volume fraction near the nc-Si/a-Si transition. A problem arising in the region of growth parameters used to obtain such a crystallinity is that the microstructure of the resulting intrinsic layer was shown to be inhomogeneous along the growth direction. 8,9 Conversely, from the aspects of photovoltaic application, it is very important to obtain the smallest differences in the texture along the growth direction, as a uniform microstructure must yield a uniform electric field in the intrinsic layer, resulting in high fill factors and open-circuit voltages. 10 In the present work, nc-Si samples were grown by LEPECVD 11 using different SiH 4 and H 2 fluxes, all yielding the same dilution factor. A detailed characterization of these samples by Raman spectroscopy in-depth profiles was carried out in order to show the difference obtained in the morphological uniformity along the growth direction.Three series of nc-Si samples about 1 m thick were grown with high deposition rates ͑between 1.5 and 4 nm/s͒ by LEPECVD 11 on ITO ͑indium tin oxide͒-coated glass, on ZnO-coated glass, and on Corning 7059 glass. Th...

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confidence: 74%

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confidence: 99%

Structural Homogeneity of nc-Si Films Grown by Low-Energy PECVD

Donne

Binetti

Isella

et al. 2008

Electrochem. Solid-State Lett.

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“…Several nc-Si:H films, grown on different substrates (silicon, oxidized silicon, Corning glass, ITO and ZnO on Corning glass) by LEPECVD (low energy plasma enhanced chemical vapour deposition) were examined. Further details on the deposition conditions and structural properties of the films can be found in [11,12]. Among the CVD variant growth methods used for producing nc-Si:H (such as hot wire CVD and the standard plasma enhanced CVD), LEPECVD is of major interest due to the low ion energy, which causes only limited surface damage.…”

Section: Methodsmentioning

confidence: 99%

The electrical conductivity of hydrogenated nanocrystalline silicon investigated at the nanoscale

Cavalcoli

Detto

Rossi³

et al. 2009

Nanotechnology

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Hydrogenated nanocrystalline silicon (nc-Si:H) is a multiphase, heterogeneous material, composed of Si nanocrystals embedded in an amorphous matrix. It has been intensively studied in the last few years due to its great promise for photovoltaic and optoelectronics applications. The present paper aims to study the current transport mechanisms in nc-Si:H by mapping the local conductivity at the nanoscale. The role of B doping in nc-Si:H is also investigated. Conductivity maps are obtained by atomic force microscopy using a conductive tip. Differences and similarities between intrinsic and doped nc-Si:H conductivity maps were observed and these are also explained on the basis of recently published computational studies.

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“…The LEPECVD process [17,18] allows deposition of nc-Si films with Raman crystallinity v = 50% at fast growth rates (1-3.5 nm/s) and low substrate temperatures (250°C) at low pressures p * 2.5 Pa for relatively low dilutions (d = 0.3 ± 0.05) at constant discharge parameters [19,20] ensuring efficient gas utilization.…”

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confidence: 99%

Plasma Composition by Mass Spectrometry in a Ar-SiH4-H2 LEPECVD Process During nc-Si Deposition

Moiseev

Chrastina

Isella

2011

Plasma Chem Plasma Process

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Mass spectrometry has been used to assess plasma composition during a lowenergy plasma-enhanced chemical vapor deposition (LEPECVD) process using argonsilane-hydrogen (Ar-SiH 4 -H 2 ) gas mixtures with input flows of 50 sccm Ar, 2-20 sccm SiH 4 and 0-50 sccm H 2 at total pressures of 1-4 Pa. Energy-integrated ion densities, residual gas analysis and threshold ionization mass spectrometry have been used to characterize the transition from amorphous (a-Si) to nano-crystalline silicon (nc-Si) deposition at constant LEPECVD operating parameters. While relative ion densities have a marked decrease with H 2 input, the densities of SiH x (x \ 4) radicals show evolution trends depending on the SiH 4 and H 2 input. For conditions leading to nc-Si growth a turning point is reached above which SiH is the main radical. Observed SiH x density trends with H 2 input are explained based on kinetic reaction rates calculated from previously obtained Langmuir probe data.

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Structural characterization of nc-Si films grown by low-energy PECVD on different substrates

Cited by 27 publications

References 21 publications

Structural Homogeneity of nc-Si Films Grown by Low-Energy PECVD

Structural Homogeneity of nc-Si Films Grown by Low-Energy PECVD

The electrical conductivity of hydrogenated nanocrystalline silicon investigated at the nanoscale

Plasma Composition by Mass Spectrometry in a Ar-SiH4-H2 LEPECVD Process During nc-Si Deposition

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