Hydrogen Effusion Experiments

Beyer, W.; Einsele, Florian

doi:10.1002/9783527636280.ch17

Cited by 9 publications

(8 citation statements)

References 36 publications

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“…23 The effusing species is known to be always H 2 . The effusion rate may be limited by several effects like the primary rupture of Si-H bonds, the diffusion of atomic or molecular hydrogen to the film surface, and (in case of diffusion of hydrogen atoms) the recombination of H atoms to form H 2 molecules at the film surface.…”

Section: Hydrogen Effusion a Experimental Proceduresmentioning

confidence: 99%

“…23 Thus, if H effusion spectra show both types of effusion peaks, a reconstruction of Si-Si bonds must take place where void-rich material is transformed to a more compact one. As the material densifies, diffusion by atomic H becomes apparently the major hydrogen transport process, as in the case for initially dense material.…”

Section: B Influence Of Film Microstructure On the Effusion Of Hydrogenmentioning

confidence: 99%

“…These additional H diffusion processes result in a widening of the H effusion peak. Using the theoretical diffusion prefactor of hydrogen in silicon D 0 ¼ 10 À3 cm 2 /s for a-Si:H, 23 Eq. (5) yields the H diffusion energy E D from the HT effusion peak temperature T M in Fig.…”

Section: Diffusion-limited Release Of Hydrogenmentioning

confidence: 99%

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Analysis of sub-stoichiometric hydrogenated silicon oxide films for surface passivation of crystalline silicon solar cells

Einsele¹,

Beyer²,

Rau³

2012

Journal of Applied Physics

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Thermal stability of passivating layers in amorphous/crystalline silicon (a-Si/c-Si) heterojunction solar cells is crucial for industrial processing and long-term device stability. Hydrogenated amorphous silicon (a-Si:H) yields outstanding surface passivation as atomic hydrogen saturates silicon dangling bonds at the a-Si/c-Si interface. Yet, a-Si surface passivation typically starts to degrade already at annealing temperatures in the range of 200 to 250 °C depending on annealing time, and optical absorption in front layers of a-Si reduces the short circuit current density. We show that oxygen incorporation into a-Si:H films enhances the thermal stability of the passivation and reduces parasitic absorption. We further show that for good passivation of the a-Si/c-Si interface, a compact material structure of the a-Si:O:H films is required where atomic hydrogen is the dominating type of diffusing hydrogen species. For plasma deposited a-Si:O:H films, oxygen incorporation of up to 10 at. % leads to an increase of the optical band gap while the hydrogen concentration is almost constant at approximately 10 at. %. For oxygen concentrations below 3%, the films yield surface recombination velocities as low as 10 cm/s on p-type wafers, and the temperature stability improves by about 50 K compared to pure a-Si:H. For films with relatively low oxygen content, hydrogen effusion spectra and Fourier transform infrared spectroscopy (FTIR) indicate a compact microstructure where only atomic H diffuses. For oxygen concentrations above 3%, the passivation quality reduces and H effusion and FTIR suggest the formation of an open, void-rich material where molecular H2 diffuses. In this case, annealing above 400 °C results in improved interface passivation, presumably due to a densification of the material. Likely, this densification results in an increased density of atomic H, which saturates Si dangling bonds near the c-Si interface.

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Section: Hydrogen Effusion a Experimental Proceduresmentioning

confidence: 99%

Section: B Influence Of Film Microstructure On the Effusion Of Hydrogenmentioning

confidence: 99%

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Analysis of sub-stoichiometric hydrogenated silicon oxide films for surface passivation of crystalline silicon solar cells

Einsele¹,

Beyer²,

Rau³

2012

Journal of Applied Physics

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“…The effused species were detected by a quadrupole-mass spectrometer. The setup was described in detail elsewhere [42]. For effusion measurements, symmetrical samples were prepared using polished FZ silicon wafers as substrates.…”

Section: B Characterization Methodsmentioning

confidence: 99%

“…As the SIMS results show a loss in hydrogen content of NiO after high temperature annealing, we used effusion measurements to detect the effused gases from the layers upon high temperature annealing. Effusion measurements have proven useful to understand the hydrogenation of various systems reported in the literature, where the hydrogen effusion signal can indicate the temperature at which hydrogen atoms become mobile and also provide an insight into the hydrogen content of different layers [14], [21], [42], [54]. Similar to SIMS, effusion measurements were done with 20-nm NiO for a direct comparison.…”

Section: Role Of Hydrogen Retainment In the Layersmentioning

confidence: 99%

Effective Hydrogenation of Poly-Si Passivating Contacts by Atomic-Layer-Deposited Nickel Oxide

Phung

Helvoirt

Beyer³

et al. 2022

IEEE J. Photovoltaics

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In recent years, passivating contacts based on SiO 2 /poly-Si have proven to be an enabling technology for Si solar cells. Effective hydrogenation of the interfacial SiO 2 is vital for realizing efficient contacts. Hydrogen-rich dielectrics, such as SiN x and Al 2 O 3 , are commonly employed for hydrogenation, whereas also recently, n-type conductive oxides, such as In 2 O 3 :Sn and ZnO, have been demonstrated to yield excellent hydrogenation. This study presents the use of a p-type metal oxide, specifically NiO, as a suitable hydrogenation source. The p-type character of NiO makes it an interesting candidate for hydrogenation because of its potential use in selective contacting structures. Herein, we show that NiO, synthesized by atomic layer deposition (ALD), can be used to hydrogenate poly-Si/SiO 2 contacts effectively. Furthermore, we benchmark its hydrogenation performance to the established ALD ZnO/Al 2 O 3 stack and provide insights into the hydrogenation process. On planar surfaces, NiO yields almost as excellent results as ZnO/Al 2 O 3 stacks, whereas it lags behind on more challenging textured surfaces. Interestingly, even though elastic recoil detection analysis reveals that ALD NiO is rich in hydrogen, secondary ion mass spectrometry measurements show that, when NiO is compared to the ZnO/Al 2 O 3 stack, less hydrogen is present at the Si/SiO 2 interface after annealing. This is explained from effusion measurements, which show substantial effusion of hydrogen from NiO around 300 °C. Hence, Al 2 O 3 capping is further employed to prevent hydrogen loss and on textured wafers, the NiO/Al 2 O 3 stacks on poly-Si achieve an implied open-circuit voltage of 728 mV, confirming the excellent hydrogenation from ALD metal oxides.

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Hydrogen incorporation, stability, and release effects in thin film silicon

Beyer

2016

Physica Status Solidi (a)

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Thin film silicon (amorphous silicon, microcrystalline silicon) contains typically about 10 at.% of hydrogen. Several hydrogen effects in connection with hydrogen incorporation, hydrogen diffusion/stability, and hydrogen release have been observed and are reviewed with focus on the experimental techniques of infrared absorption, hydrogen diffusion, and effusion measurements. Hydrogen effects in hydrogen‐implanted amorphous, microcrystalline, and crystalline silicon materials are also discussed. The knowledge and the understanding of these effects may help for improved products and is, furthermore, a challenging scientific task.

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Hydrogen Effusion Experiments

Cited by 9 publications

References 36 publications

Analysis of sub-stoichiometric hydrogenated silicon oxide films for surface passivation of crystalline silicon solar cells

Analysis of sub-stoichiometric hydrogenated silicon oxide films for surface passivation of crystalline silicon solar cells

Effective Hydrogenation of Poly-Si Passivating Contacts by Atomic-Layer-Deposited Nickel Oxide

Hydrogen incorporation, stability, and release effects in thin film silicon

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