The nanostructural analysis of hydrogenated silicon films based on positron annihilation studies

Melskens, Jimmy; Smets, Arno H. M.; Eijt, S.W.H.; Schüt, H.; Brück, E.; Zeman, Miro

doi:10.1016/j.jnoncrysol.2012.01.037

Cited by 23 publications

(34 citation statements)

References 14 publications

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“…The curve in the range of 1995-2005 cm −1 is known as the low-stretching mode (LSM) while the curve with a peak in the range of 2080-2090 cm −1 is known as the high stretching mode (HSM). [27] Responses in the LSM correspond to hydrogen which is incorporated into small volume deficiencies such as divacancies and is therefore assigned to monohydrides. [28].…”

Section: Fourier Transform Infrared Spectroscopymentioning

confidence: 99%

Light-Induced Effects on the a-Si:H/c-Si Heterointerface

Vasudevan

Poli

Deligiannis

et al. 2017

IEEE J. Photovoltaics

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Section: Fourier Transform Infrared Spectroscopymentioning

confidence: 99%

Light-Induced Effects on the a-Si:H/c-Si Heterointerface

Vasudevan

Poli

Deligiannis

et al. 2017

IEEE J. Photovoltaics

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“…Often, the nanostructure is modeled as a continuous random network where isolated dbs form the dominant defects [30]. Although the simplicity of the continuous random network is appealing, many experimental results have explicitly questioned its correctness as a description of the a-Si:H nanostructure [15,17,19,31,32]. Additionally, recent electron-paramagnetic resonance (EPR) studies indicate that isolated dbs are not the only defects in the nanostructure.…”

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confidence: 99%

“…Instead, at least two distinct types of defects are involved in the SWE [33,34]. This suggests that an alternative view on the nanostructure is needed, like the so-called disordered network with hydrogenated vacancies [35,36], also termed the anisotropic disordered network [31,32]. Note that the disordered network with hydrogenated vacancies consists of regions dominated by various types of open volume deficiencies, i.e., divacancies, multivacancies, and nanosized voids, which are embedded in disordered regions similar to the continuous random network.…”

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confidence: 99%

“…Furthermore, a porous R = 0 film was deposited by increasing the rf power density, P rf , which in turn increases the deposition rate, r d . This a-Si:H material serves as an interesting reference, since it is known to have a poor light-soaking stability due to the presence of nanosized voids [37], which is indicated by a relatively large high stretching mode (HSM) intensity as indicated by Fourier transform infrared (FTIR) spectroscopy [31]. This film is indeed porous, while all others are dense, as illustrated in Table I by the much larger nanostructure parameter R * , which is defined as the relative contribution of the HSM to the total infrared absorption induced by the Si-H stretching modes.…”

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confidence: 99%

“…To study the nature of the defects in the different a-Si:H nanostructures and pave the way towards SWE mitigation we employ a powerful combination of Doppler broadening positron annihilation spectroscopy (DBPAS) [31,32], quantitative continuous wave electron-paramagnetic resonance (cw-EPR) spectroscopy, and electron spin echo (ESE) decay measurements [34]. DBPAS is utilized to determine the dominant type of open volume deficiency in the material, as more valence electrons are probed by the implanted positron when the average open volume increases in size.…”

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Structural and electrical properties of metastable defects in hydrogenated amorphous silicon

et al. 2015

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The structural and electrical properties of metastable defects in various types of hydrogenated amorphous silicon have been studied using a powerful combination of continuous wave electron-paramagnetic resonance spectroscopy, electron spin echo (ESE) decay measurements, and Doppler broadening positron annihilation spectroscopy. The observed dependence of the paramagnetic defect density on the Doppler S parameter indicates that porous, nanosized void-rich materials exhibit higher spin densities, while dense, divacancy-dominated materials show smaller spin densities. However, after light soaking more similar spin densities are observed, indicating a long-term defect creation process in the Staebler-Wronski effect that does not depend on the a-Si:H nanostructure. From ESE decays it appears that there are fast and slowly relaxing defect types, which are linked to various defect configurations in small and large open volume deficiencies. A nanoscopic model for the creation of light-induced defects in the a-Si:H nanostructure is proposed. The light-induced degradation (LID) of hydrogenated amorphous silicon (a-Si:H), also known as the StaeblerWronski effect (SWE) [1,2], has been extremely thoroughly investigated in the past decades [3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20][21]. Although the origin of the SWE and the nature of native and metastable defects is still poorly understood, impressive progress has been made in, for instance, the development of thin-film silicon (TF Si) solar cells. Record initial and stable conversion efficiencies of 16.3%[22] and 13.4%-13.6% [23,24], respectively, have been reported for small area (∼1 cm 2 ) solar cells, all in triple-junction configuration. However, the amorphous junction produces most of the power in such solar cells, which means that fundamentally understanding the SWE is still important when aiming to increase the conversion efficiency of TF Si solar cells. Successfully applied LID-reduction methods include hydrogen (H 2 ) dilution of the silane gas (SiH 4 ) used during the plasma-enhanced chemical vapor deposition (PECVD) [25,26] and the use of a triode PECVD reactor [27,28]. However, the film growth follows such a complex interplay of deposition, etching, and hydrogen (H) effusion that the precise role of H in the a-Si:H nanostructure and the SWE remains obscured, although various growth models have been proposed [29].

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Metastable Refractive Index Manipulation in Hydrogenated Amorphous Silicon for Reconfigurable Photonics

Mohammed

Melskens

Pagliano

et al. 2020

Advanced Optical Materials

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Hydrogenated amorphous silicon (a‐Si:H) is known for exhibiting light‐induced metastable properties that are reversible upon annealing. While these are commonly associated with the well‐known deleterious Staebler–Wronski effect in the field of thin‐film silicon solar cells, the associated changes in optical properties have not been well studied. Emerging reconfigurable photonic devices and applications can benefit from metastable optical properties where two states of the material are reversibly accessible without the need for continuous stimulation. The study demonstrates a light‐induced 0.3% increase of the metastable refractive index of a‐Si:H that is reversed upon annealing over several cycles using a highly sensitive Fabry–Pérot interferometric technique. Utilizing this technique, a metastable optical switch based on a micro‐ring resonator is demonstrated with reversible distinct switching states separated by 0.3 nm between the light‐soaked and annealed states, a switching extinction exceeding 20 dB and an unchanged Q‐factor, suggesting no excess discernible optical loss. Furthermore, metastable strain changes in a‐Si:H‐based freestanding membrane structures are linked to the observed metastable optical properties and present a possible route to stable photonic devices. Our proof‐of‐concept demonstration showcases a‐Si:H‐based reconfigurable photonics that support multiple purpose photonic integrated circuits, reconfigurable metamaterials, and advanced optomechanical devices.

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The nanostructural analysis of hydrogenated silicon films based on positron annihilation studies

Cited by 23 publications

References 14 publications

Light-Induced Effects on the a-Si:H/c-Si Heterointerface

Light-Induced Effects on the a-Si:H/c-Si Heterointerface

Structural and electrical properties of metastable defects in hydrogenated amorphous silicon

Metastable Refractive Index Manipulation in Hydrogenated Amorphous Silicon for Reconfigurable Photonics

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