Correlation between structural and opto-electronic properties of a-Si1−xCx:H films deposited by plasma enhanced chemical vapour deposition

Ambrosone, G.; Basa, D. K.; Coscia, U.; Rava, P.

doi:10.1016/j.tsf.2010.05.089

Cited by 10 publications

(7 citation statements)

References 39 publications

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“…range as for the films characterized here. The Tauc slope parameter for a-B x C:H y is further comparable to those found in a-Si:H, 86,89,90 a-Ge:H, 86,91 and a-SiC:H, 92,93 which range anywhere from 100 to 1200 cm À1/2 eV À1/2 . The authors are not aware of any reports of E U values for B x C or a-B x C:H y films.…”

Section: B Electronic and Optical Propertiessupporting

confidence: 73%

“…101 In a-SiC:H, hydrogen content has also been shown to correlate with density, albeit often indirectly. 92,[102][103][104] Similarly to a-Si:H, a-SiC:H exhibits micropores, which are associated with both SiH 2 and SiCH 3 groups to varying degrees depending on growth conditions and stoichiometric regime. 105 Because the hydrogen can be tied up in many ways including as SiH, SiH 2 , CH 2 bridging groups, and CH 3 terminal groups, even more refinements are introduced into the density/hydrogen relationship.…”

Section: A Atomic Composition Physical Structure and Mechanical Prmentioning

confidence: 99%

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The influence of hydrogen on the chemical, mechanical, optical/electronic, and electrical transport properties of amorphous hydrogenated boron carbide

Nordell

Karki

Nguyen

et al. 2015

Journal of Applied Physics

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Because of its high electrical resistivity, low dielectric constant (j), high thermal neutron capture cross section, and robust chemical, thermal, and mechanical properties, amorphous hydrogenated boron carbide (a-B x C:H y) has garnered interest as a material for low-j dielectric and solid-state neutron detection applications. Herein, we investigate the relationships between chemical structure (atomic concentration B, C, H, and O), physical/mechanical properties (density, porosity, hardness, and Young's modulus), electronic structure [band gap, Urbach energy (E U), and Tauc parameter (B 1/2)], optical/dielectric properties (frequency-dependent dielectric constant), and electrical transport properties (resistivity and leakage current) through the analysis of a large series of a-B x C:H y thin films grown by plasma-enhanced chemical vapor deposition from ortho-carborane. The resulting films exhibit a wide range of properties including H concentration from 10% to 45%, density from 0.9 to 2.3 g/cm 3 , Young's modulus from 10 to 340 GPa, band gap from 1.7 to 3.8 eV, Urbach energy from 0.1 to 0.7 eV, dielectric constant from 3.1 to 7.6, and electrical resistivity from 10 10 to 10 15 X cm. Hydrogen concentration is found to correlate directly with thin-film density, and both are used to map and explain the other material properties. Hardness and Young's modulus exhibit a direct power law relationship with density above $1.3 g/cm 3 (or below $35% H), below which they plateau, providing evidence for a rigidity percolation threshold. An increase in band gap and decrease in dielectric constant with increasing H concentration are explained by a decrease in network connectivity as well as mass/electron density. An increase in disorder, as measured by the parameters E U and B 1/2 , with increasing H concentration is explained by the release of strain in the network and associated decrease in structural disorder. All of these correlations in a-B x C:H y are found to be very similar to those observed in amorphous hydrogenated silicon (a-Si:H), which suggests parallels between the influence of hydrogenation on their material properties and possible avenues for optimization. Finally, an increase in electrical resistivity with increasing H at <35 at. % H concentration is explained, not by disorder as in a-Si:H, but rather by a lower rate of hopping associated with a lower density of sites, assuming a variable range hopping mechanism interpreted in the framework of percolation theory. V

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Section: B Electronic and Optical Propertiessupporting

confidence: 73%

Section: A Atomic Composition Physical Structure and Mechanical Prmentioning

confidence: 99%

The influence of hydrogen on the chemical, mechanical, optical/electronic, and electrical transport properties of amorphous hydrogenated boron carbide

Nordell

Karki

Nguyen

et al. 2015

Journal of Applied Physics

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“…Otherwise it is difficult to make out a clear relationship between the Tauc slope parameter and the Urbach energy. Ambrosone et al [17] observe how the Tauc slope parameter decreases from 788 to 663 (eV cm) −1/2 with rising Urbach energy in a range from 72 to 170 meV. This trend is not clearly demonstrated by our results since the variation in Urbach energy is quite small.…”

Section: Single Layer Resultscontrasting

confidence: 84%

Comparison of silicon oxide and silicon carbide absorber materials in silicon thin-film solar cells

et al. 2015

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Since solar energy conversion by photovoltaics is most efficient for photon energies at the bandgap of the absorbing material the idea of combining absorber layers with different bandgaps in a multijunction cell has become popular. In silicon thin-film photovoltaics a multijunction stack with more than two subcells requires a high bandgap amorphous silicon alloy top cell absorber to achieve an optimal bandgap combination. We address the question whether amorphous silicon carbide (a-SiC:H) or amorphous silicon oxide (a-SiO:H) is more suited for this type of top cell absorber. Our single cell results show a better performance of amorphous silicon carbide with respect to fill factor and especially open circuit voltage at equivalent Tauc bandgaps. The microstructure factor of single layers indicates less void structure in amorphous silicon carbide than in amorphous silicon oxide. Yet photoconductivity of silicon oxide films seems to be higher which could be explained by the material being not truly intrinsic. On the other hand better cell performance of amorphous silicon carbide absorber layers might be connected to better hole transport in the cell.

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“…As the CH3 symmetric ("umbrella") deformation is strongly dependent on the electronegativity of Considering the FTIR spectra of the as-deposited films, four main absorption bands can be observed: at 780 cm −1 , the Si-C stretching mode is located [1,13,14]. The absorption band centered at 1015 cm −1 is related to the rocking/wagging vibration modes of CH 2 radicals bonded to a silicon atom (Si-CH 2 ) [15]; however, this band absorption can also be related to OH radicals bonded to silicon (Si-OH) [16]. The strong and narrow peak at 1104 cm −1 is associated with Si-O-Si stretching vibration.…”

Section: Results and Analysismentioning

confidence: 99%

Enhanced Photoluminescence of Hydrogenated Amorphous Silicon Carbide Thin Films by Means of a Fast Thermal Annealing Process

Vivaldo

Ambrosio

López³

et al. 2020

Materials

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In this paper, the photoluminescence (PL) of hydrogenated amorphous silicon carbide (a-Si1−xCx:H) thin films obtained by Plasma Enhancement Chemical Vapor Deposition (PECVD) is reported. Strong PL is obtained after a fast annealing process for 60 s at temperatures of 200, 400, 600, and 800 °C. The thin films are characterized using Fourier Transform Infrared spectroscopy (FTIR), PL spectroscopy, and Energy-Dispersive X-ray Spectroscopy (EDS). According to the results of the structural characterization, it is deduced that a structural rearrangement of the amorphous matrix is carried out during the fast annealing process, which results in different degrees of oxidation on the a-Si1−xCx:H films. The PL peak position shifts towards higher energies as the temperature increases. The sample deposited with a silane/methane flux ratio of 37.5 at an Radio Frequency (RF) power of 6 W experiences an increase in PL intensity of more than nine times, with a displacement in the peak position from 2.5 eV to 2.87 eV, at 800 °C. From the PL analysis, we observe two emission bands: one centered in the near infrared and other in the visible range (with a blue peak). This study opens the possibility to use such thin films in the development of optoelectronics devices, with potential for application in solar cells.

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Correlation between structural and opto-electronic properties of a-Si1−xCx:H films deposited by plasma enhanced chemical vapour deposition

Cited by 10 publications

References 39 publications

The influence of hydrogen on the chemical, mechanical, optical/electronic, and electrical transport properties of amorphous hydrogenated boron carbide

The influence of hydrogen on the chemical, mechanical, optical/electronic, and electrical transport properties of amorphous hydrogenated boron carbide

Comparison of silicon oxide and silicon carbide absorber materials in silicon thin-film solar cells

Enhanced Photoluminescence of Hydrogenated Amorphous Silicon Carbide Thin Films by Means of a Fast Thermal Annealing Process

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