Spectroscopic ellipsometry studies on microstructure evolution of a-Si:H to nc-Si:H films by H2 plasma exposure

Kanneboina, Venkanna; Madaka, Ramakrishna; Agarwal, Pramod

doi:10.1016/j.mtcomm.2018.02.023

Cited by 20 publications

(10 citation statements)

References 60 publications

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“…As can be seen in Table , the HWHM of the band at 480 cm −1 for the deposited and treated sample for 20 minutes is identical within the margin of error (27 and 29 cm −1 , respectively, ±2 cm −1 ). This means that there was no improvement in the distortion of the bond angle, and thus indicating that the compressive stress introduced by the hydrogen molecules is of no relevance to the bond angle deviation, which is in line with the results reported by Sekimoto et al Δθ can be calculated using the following relationship:

HWHM ((), in {cm}^{‐ 1}) = 7.5 + 3 normalΔ θ ((), ^{°}) .

For the deposited film, Δθ is around 6.5°, which is a low value compared with the values that are found in the literature for films with similar structures in terms of nanocrystallite density . For a‐Si films, meaning nonhydrogenated silicon, 6.6° is a theoretical minimum value for Δθ characterizing a “relaxed state” of the structure .…”

Section: Discussionsupporting

confidence: 88%

“…It was also shown that the after deposition treatment of a‐Si:H films with a hydrogen plasma can lead to a complete crystallization of the amorphous film . A layer by layer deposition of a‐Si:H films, where each layer was exposed to a hydrogen plasma, can also produce crystalline structures . The exact mechanism of this hydrogen induced postdeposition crystallization is not well understood.…”

Section: Introductionmentioning

confidence: 99%

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Molecular hydrogen‐induced nucleation of hydrogenated silicon nanocrystals at low temperature

Filali

Brahmi

Sib

et al. 2019

Surface & Interface Analysis

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Highly crystallized hydrogenated silicon layers were obtained via the treatment of hydrogenated polymorphous silicon films in a molecular hydrogen ambient. This contrasts other postdeposition studies that obtained nanocrystalline silicon films but necessitated either a plasma activation or high-temperature annealing. The structure of the samples was analyzed by Raman spectroscopy to determine the crystallite volume fraction, which was found to increase up to 80% within 1 hour of treatment.Atomic force microscopy (AFM) showed that the roughness of the surfaces was found to increase after the H 2 treatment. Optical transmission and spectroscopic ellipsometry revealed the pronounced porosity of the films characterized by a static refractive index that is below three, which is a low value for hydrogenated silicon films and a void fraction that is around 15% in the bulk of the films. The effect of the hydrogen molecules on the structure of the films was discussed in terms of the compressive stress exerted by the molecules, trapped in structural inhomogeneities, on the amorphous tissue. It is suggested that for this process to take effect, the films need to be porous and that the amorphous network needs to be in a "relaxed" state.

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HWHM ((), in {cm}^{‐ 1}) = 7.5 + 3 normalΔ θ ((), ^{°}) .

Section: Discussionsupporting

confidence: 88%

Section: Introductionmentioning

confidence: 99%

Molecular hydrogen‐induced nucleation of hydrogenated silicon nanocrystals at low temperature

Filali

Brahmi

Sib

et al. 2019

Surface & Interface Analysis

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“…The dielectric function consists of two components, namely real (ε 1 ) and imaginary (ε 2 ). The real component ε 1 represents the polarization of the material due to the electric dipole which contributes to the atomic and electric polarization, while the imaginary component ε 2 represents the amount of light absorption in the material (Kanneboina et al, 2018). The real component ε 1 shows the value of E 0 in the p-i-n sample of 2.86 eV and the sample p-i 1 -i 2 -n of 2.66 eV.…”

Section: About Here]mentioning

confidence: 99%

Analysis increase in the efficiency of a-Si: H solar cell due to the addition of an intrinsic layer to the p-i-n structure by ellipsometric spectroscopy

Prayogi

Cahyono

Darminto

2021

Preprint

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Backround: In this study, we report for the first time that the addition of an intrinsic layer to the a-Si: H p-i-n solar cell structure greatly enhances the conversion efficiency. The a-Si: H p-i-n solar cells were grown using Plasma Enhanced Chemical Vapor Deposition (PECVD) techniques on the Indium Tin Oxide (ITO) substrate and added an intrinsic layer with the p-i1-i2-n structure in order to prevent sunlight energy from being absorbed the first intrinsic layer can be absorbed by the second intrinsic layer. Result The a-Si: H p-i-n and p-i1-i2-n solar cells were characterized including optical properties, electrical properties, surface morphology, thickness, band-gap using Ellipsometric Spectroscopy (ES). Furthermore, from the optical constant and thin film thickness, the reflectance and transmittance of each sample were obtained. The p-i-n and p-i1-i2-n samples show good transparency in the infrared region and this transparency decreases in the visible light region shows an interference pattern with a sharp decrease in transmission at the absorption edge and the performance of solar cells (curve I-V) measured by use sun simulator and sunshine. Conclussion: Our results show that there is a very good increase in the efficiency of the a-Si: H p-i1-i2-n solar cells by 58.6% of the original p-i-n structure.

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“…About 1 eV of decrease in work function value is reported when thin films of MoO 3-x are air exposed for long times. 12,15 It is mainly due to surface contaminations and the adsorption of oxygen present in the atmosphere on the surface. Work function reduction degrades the hole selectivity and deteriorates the overall performance of a photovoltaic device.…”

Section: Introductionmentioning

confidence: 99%

“…In this article, oxygen plasma treatment (OPT) is chosen as an approach to tune the work function of MoO 3‑ x deposited by thermal evaporation. The plasma-enhanced chemical vapor deposition (PECVD) technique is used to carry out this treatment that is a well-established technique for improving the interface defects of c-Si through hydrogen plasma treatment . After treatment, all the measurements are done in an ambient atmosphere to check its effect on work function.…”

Section: Introductionmentioning

confidence: 99%

Oxygen Plasma Treatment of Thermally Evaporated MoO_3-x Films: An Approach to Tune the Work Function

Kumari

Bhardwaj

Rahul

et al. 2023

ACS Appl. Electron. Mater.

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The hole selectivity of molybdenum oxide (MoO3‑x ) in organic and inorganic heterojunction solar cells depends on its work function value. MoO3‑x with a higher work function value has superior selectivity and facilitates the flow of holes through it. The oxidation state of the Mo atoms and the oxygen vacancy affect the work function of MoO3‑x . Here, for the first time, thermally evaporated MoO3‑x films are subjected to oxygen (O2) plasma treatment using a plasma-enhanced chemical vapor deposition method to tune the work function. The effect of O2 plasma treatment on work function is studied using Kelvin probe force microscopy. The work function of thick MoO3‑x films increased from 4.91 ± 0.01 eV for as-deposited films to 5.22 ± 0.02 eV by proper tuning of rf power, oxygen flow rate, and O2 plasma treatment time. This increase in work function is accompanied with the increase in O/Mo ratio in these films as confirmed by EDX. Oxygen plasma treatment has also resulted in the enhancement of work function, transmittance, and band gap of thin (23 and 14 nm) MoO3‑x films. An optimum increase in work function for thin films by ∼0.40 eV is observed for 5 min plasma treatment at 80 W rf power with a 30 SCCM oxygen flow rate. The studies suggest oxygen plasma treatment as an effective approach to recover or tune the work function of molybdenum oxide films.

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Spectroscopic ellipsometry studies on microstructure evolution of a-Si:H to nc-Si:H films by H2 plasma exposure

Cited by 20 publications

References 60 publications

Molecular hydrogen‐induced nucleation of hydrogenated silicon nanocrystals at low temperature

Molecular hydrogen‐induced nucleation of hydrogenated silicon nanocrystals at low temperature

Analysis increase in the efficiency of a-Si: H solar cell due to the addition of an intrinsic layer to the p-i-n structure by ellipsometric spectroscopy

Oxygen Plasma Treatment of Thermally Evaporated MoO_3-x Films: An Approach to Tune the Work Function

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Spectroscopic ellipsometry studies on microstructure evolution of a-Si:H to nc-Si:H films by H2 plasma exposure

Cited by 20 publications

References 60 publications

Molecular hydrogen‐induced nucleation of hydrogenated silicon nanocrystals at low temperature

Molecular hydrogen‐induced nucleation of hydrogenated silicon nanocrystals at low temperature

Analysis increase in the efficiency of a-Si: H solar cell due to the addition of an intrinsic layer to the p-i-n structure by ellipsometric spectroscopy

Oxygen Plasma Treatment of Thermally Evaporated MoO3-x Films: An Approach to Tune the Work Function

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Oxygen Plasma Treatment of Thermally Evaporated MoO_3-x Films: An Approach to Tune the Work Function