The Urbach focus and optical properties of amorphous hydrogenated SiC thin films

Guerra, Jorge Andrés; Angulo, J R; Gomez, Sophia; Llamoza, J; Montañez, L; Tejada, Alvaro; Töfflinger, Jan Amaru; Winnacker, A.; Weingärtner, Roland

doi:10.1088/0022-3727/49/19/195102

Cited by 28 publications

(32 citation statements)

References 33 publications

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“…Thus, the band gap and bond angle distortions are enhanced in the amorphous network with the formation of Si—C bonds . Tauc gap is sensitive to Urbach energy, and there are some new models estimating the band gap more precisely than the Tauc model …”

Section: Resultsmentioning

confidence: 99%

“…While hydrogenated amorphous substoichiometric silicon carbide a‐Si 1− x C x :H is often prepared at temperatures below 300 °C, CH 4 suppresses polycrystalline Si growth in favor of H‐rich amorphous a‐Si 1− x C x :H at elevated deposition temperatures . The increasing carbon concentration in a‐Si 1− x C x :H broadens the band gap and introduces unwanted localized tail states near the band edge …”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Optoelectronic Properties of Hydrogenated Amorphous Substoichiometric Silicon Carbide with Low Carbon Content Deposited on Semi‐Transparent Boron‐Doped Diamond

Remeš

Stuchlı́k

Dragounová

et al. 2019

Physica Status Solidi (a)

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Hydrogenated amorphous substoichiometric silicon carbide (a-Si 1Àx C x :H, x < 0,1) thin films and diodes with low carbon content are prepared from a mixture of H 2 , SiH 4 , and CH 4 by plasma-enhanced chemical vapor deposition at a relatively high temperature of 400 C on semi-transparent boron-doped nanocrystalline diamond (B-NCD) electrodes with an underlying Ti grid. Vibration spectra indicate that CH 4 prevents Si crystallization at elevated deposition temperatures and confirm an increasing carbon content up to x ¼ 0.1 for samples grown with SiH 4 /CH 4 flows up to 1:3. Dark current-voltage characteristics of B-NCD/a-Si 1Àx C x :H diodes show a rectifying ratio of about four orders at AE1 V. However, under white light illumination, an energy conversion efficiency of 4% is limited by a high serial resistivity of the B-NCD electrode and S-shaped photocurrent near the open-circuit voltage.

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Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Optoelectronic Properties of Hydrogenated Amorphous Substoichiometric Silicon Carbide with Low Carbon Content Deposited on Semi‐Transparent Boron‐Doped Diamond

Remeš

Stuchlı́k

Dragounová

et al. 2019

Physica Status Solidi (a)

View full text Add to dashboard Cite

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“…This can be achieved by using a band fluctuations average, in the free electron approximation, which serves to describe the shape of disorder induced localized states and extended states in a single equation 18,19 . Here we use our approach 20,21 , modified for crystalline semiconductors with direct bandgap. It consists of using an average JDOS to calculate the electronic transition rate and is described as follows.…”

Section: Bandgap Determinationmentioning

confidence: 99%

Determination of the complex refractive index and optical bandgap of CH3NH3PbI3 thin films

Guerra

Tejada

Korte

et al. 2017

Journal of Applied Physics

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We report the complex refractive index of methylammonium lead iodide (CH 3 NH 3 PbI 3) perovskite thin films obtained by means of variable angle spectroscopic ellipsometry and transmittance/reflectance spectrophotometry in the wavelength range of 190 nm to 2500 nm. Film thickness and roughness layer thickness are determined by minimizing a global unbiased estimator in the region where the spectrophotometry and ellipsometry spectra overlap. We then determine the optical bandgap and Urbach energy from the absorption coefficient, by means of a fundamental absorption model based on band fluctuations in direct semiconductors. This model merges both the Urbach tail and the absorption edge regions in a single equation. In this way, we increase the fitting region and extend the conventional (α ω) 2-plot method to obtain accurate bandgap values.

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“…The optical bandgap has been further evaluated by means of other two models. With respect to the Tauc's model, the Ulrich's empirical model for the direct bandgap or the band fluctuation models [59,60] allow distinguishing between the absorption edge and absorption tails [61]. The resulting optical bandgaps are summarized in Table 1.…”

Section: Chemical and Structural Characterizationmentioning

confidence: 99%

Sub-gap defect density characterization of molybdenum oxide: An annealing study for solar cell applications

et al. 2020

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The application of molybdenum oxide in the photovoltaic field is gaining traction as this material can be deployed in doping-free heterojunction solar cells in the role of hole selective contact. For modeling-based optimization of such contact, knowledge of the molybdenum oxide defect density of states (DOS) is crucial. In this paper, we report a method to extract the defect density through nondestructive optical measures, including the contribution given by small polaron optical transitions. The presence of defects related to oxygen-vacancy and of polaron is supported by the results of our opto-electrical characterizations along with the evaluation of previous observations. As part of the study, molybdenum oxide samples have been evaluated after post-deposition thermal treatments. Quantitative results are in agreement with the result of density functional theory showing the presence of a defect band fixed at 1.1 eV below the conduction band edge of the oxide. Moreover, the distribution of defects is affected by post-deposition treatment.

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The Urbach focus and optical properties of amorphous hydrogenated SiC thin films

Cited by 28 publications

References 33 publications

Optoelectronic Properties of Hydrogenated Amorphous Substoichiometric Silicon Carbide with Low Carbon Content Deposited on Semi‐Transparent Boron‐Doped Diamond

Optoelectronic Properties of Hydrogenated Amorphous Substoichiometric Silicon Carbide with Low Carbon Content Deposited on Semi‐Transparent Boron‐Doped Diamond

Determination of the complex refractive index and optical bandgap of CH3NH3PbI3 thin films

Sub-gap defect density characterization of molybdenum oxide: An annealing study for solar cell applications

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