GIXRF–NEXAFS investigations on buried ZnO/Si interfaces: A first insight in changes of chemical states due to annealing of the specimen

Pagels, Marcel; Reinhardt, Falk; Pollakowski, B.; Roczen, Maurizio; Becker, Christiane; Lips, K.; Rech, Bernd; Kanngießer, Birgit; Beckhoff, Burkhard

doi:10.1016/j.nimb.2009.09.009

Cited by 16 publications

(8 citation statements)

References 8 publications

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“…Synchrotron based X-ray spectrometry is an emerging method for the non-destructive investigation of diffusion and the determination of the chemical species at buried interfaces of stacked thin layers, because of which it is particularly suited for the characterization of high-temperature processes in complex thin-film solar cell devices. [21][22][23] Here, we applied grazing incidence X-ray fluorescence combined with near edge X-ray absorption fine structure spectroscopy (GIXRF-NEXAFS) 24 at the Plane Grating Monochromator (PGM) beamline for undulator radiation 25 in the PTB laboratory at BESSY II for the analysis of buried ZnO:Al/poly-Si interfaces after high-temperature RTA processing.…”

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confidence: 99%

Chemical speciation at buried interfaces in high-temperature processed polycrystalline silicon thin-film solar cells on ZnO:Al

Becker

Pagels

Zachäus

et al. 2013

Journal of Applied Physics

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The combination of polycrystalline silicon (poly-Si) thin films with aluminum doped zinc oxide layers (ZnO:Al) as transparent conductive oxide enables the design of appealing optoelectronic devices at low costs, namely in the field of photovoltaics. The fabrication of both thin-film materials requires high-temperature treatments, which are highly desired for obtaining a high electrical material quality. Annealing procedures are typically applied during crystallization and defect-healing processes for silicon and can boost the carrier mobility and conductivity of ZnO:Al layers. In a combined poly-Si/ZnO:Al layer system, an in-depth knowledge of the interaction of both layers and the control of interface reactions upon thermal treatments is crucial. Therefore, we analyze the influence of rapid thermal treatments up to 1050 °C on solid phase crystallized poly-Si thin-film solar cells on ZnO:Al-coated glass, focusing on chemical interface reactions and modifications of the poly-Si absorber material quality. The presence of a ZnO:Al layer in the solar cell stack was found to limit the poly-Si solar cell performance with open circuit voltages only below 390 mV (compared to 435 mV without ZnO film), even if a silicon nitride (SiN) diffusion barrier was included. A considerable amount of diffused zinc inside the silicon was observed. By grazing-incidence X-ray fluorescence spectrometry, a depth-resolving analysis of the elemental composition close to the poly-Si/(SiN)/ZnO:Al interface was carried out. Temperatures above 1000 °C were found to promote the formation of new chemical compounds within about 10 nm of interface, such as zinc silicates (Zn2SiO4) and aluminium oxide (AlxOy). These results give valuable insights about the temperature-limitations of Si/ZnO thin-film solar cell fabrication and the formation of high-mobility ZnO-layers by thermal anneal.

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confidence: 99%

Chemical speciation at buried interfaces in high-temperature processed polycrystalline silicon thin-film solar cells on ZnO:Al

Becker

Pagels

Zachäus

et al. 2013

Journal of Applied Physics

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“…Nevertheless, it was observed that the electrical properties of the ZnO:Al improved due to the heat treatment. 4 First, x-ray spectroscopy experiments 6,7 indeed indicate that the SPC treatment has an impact on the chemical Si/ZnO interface structure, but could not completely clarify the underlying reaction mechanism. In this letter, we employ photoemission and its unique capability in chemical speciation combined with hard x-ray excitation allowing for the study of relevant buried Si/ZnO interfaces i.e., the Si top layer is sufficiently thick to form the same interface structure as present in a real-world Si thin-film solar cell layer stack.…”

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confidence: 99%

Hard x-ray photoelectron spectroscopy study of the buried Si/ZnO thin-film solar cell interface: Direct evidence for the formation of Si–O at the expense of Zn-O bonds

Wimmer

Bär

Gerlach

et al. 2011

Applied Physics Letters

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The chemical structure of the interface between silicon thin films and the transparent conductive oxide ZnO:Al has been investigated by hard x-ray photoelectron spectroscopy. By varying the excitation energy between 2010 and 8040 eV, we were able to probe the Si/ZnO interface buried below 12 nm Si. This allowed for the identification of changes induced by solid phase crystallization (SPC). Based on in-situ SPC annealing experiments, we find clear indications that the formation of Si–O bonds takes place at the expense of Zn–O bonds. Hence, the ZnO:Al acts as the oxygen source for the interfacial Si oxidation.

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“…Additionally, NEXAFS can be used to determine: presence of defects and amorphous content in carbon nanotubes, varying degrees of bond hybridization in mixed sp 2 /sp 3 -bonded carbon materials, degree of vertical alignment in nanotube samples, nature of oxygen-containing functional groups on nanotube surfaces (Hemraj-Benny et al, 2006). Applying grazing-incidence XRF-NEXAFS it will be possible to build up a profile of chemical bonding in multilayered samples (Pagels et al, 2010).…”

Section: Near-edge X-ray Absorption Fine Structure Spectroscopy (Nexafs)mentioning

confidence: 99%

Compilation on Synthesis, Characterization and Properties of Silicon and Boron Carbonitride Films

Hoffmann¹,

Файнер²,

Косинова³

et al. 2011

Silicon Carbide - Materials, Processing and Applications in Electronic Devices

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GIXRF–NEXAFS investigations on buried ZnO/Si interfaces: A first insight in changes of chemical states due to annealing of the specimen

Cited by 16 publications

References 8 publications

Chemical speciation at buried interfaces in high-temperature processed polycrystalline silicon thin-film solar cells on ZnO:Al

Chemical speciation at buried interfaces in high-temperature processed polycrystalline silicon thin-film solar cells on ZnO:Al

Hard x-ray photoelectron spectroscopy study of the buried Si/ZnO thin-film solar cell interface: Direct evidence for the formation of Si–O at the expense of Zn-O bonds

Compilation on Synthesis, Characterization and Properties of Silicon and Boron Carbonitride Films

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