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Influence of post-hydrogenation upon electrical, optical and structural properties of hydrogen-less sputter-deposited amorphous silicon

Gerke, S. ; Becker, H.-W. ; Rogalla, D. ; Singer, F. ; Brinkmann, N. ; Fritz, S. ; Hammud, A. ; Keller, P. ; Skorka, D. ; Sommer, D. ; Weiß, C. ; Flege, S. ; Hahn, G. ; Job, R. ; Terheiden, B. (2016)
Influence of post-hydrogenation upon electrical, optical and structural properties of hydrogen-less sputter-deposited amorphous silicon.
In: Thin Solid Films, 598
doi: 10.1016/j.tsf.2015.11.063
Artikel, Bibliographie

Kurzbeschreibung (Abstract)

Amorphous silicon (a-Si) is common in the production of technical devices and can be deposited by several techniques. In this study intrinsic and doped, hydrogen-less amorphous silicon films are RF magnetron sputter deposited and post-hydrogenated in a remote hydrogen plasma reactor at a temperature of 370 degrees C. Secondary ion mass spectrometry of a boron doped (p) a-Si layer shows that the concentration of dopants in the sputtered layer becomes the same as present in the sputter-target. Improved surface passivation of phosphorous doped 5 Omega cm, FZ, (n) c-Si can be achieved by post-hydrogenation yielding a minority carrier lifetime of similar to 360 mu s finding an optimum for similar to 40 nm thin films, deposited at 325 degrees C. This relatively low minority carrier lifetime indicates high disorder of the hydrogen-less sputter deposited amorphous network. Post-hydrogenation leads to a decrease of the number of localized states within the band gap. Optical band gaps (Taucs gab as well as E-04) can be determined to similar to 1.88 eV after post-hydrogenation. High resolution transmission electron microscopy and optical Raman investigations show that the sputtered layers are amorphous and stay like this during post-hydrogenation. As a consequence of the missing hydrogen during deposition, sputtered a-Si forms a rough surface compared to CVD a-Si. Atomic force microscopy points out that the roughness decreases by up to 25% during post-hydrogenation. Nuclear resonant reaction analysis permits the investigation of hydrogen depth profiles and allows determining the diffusion coefficients of several post-hydrogenated samples from of a model developed within this work. A dependency of diffusion coefficients on the duration of post-hydrogenation indicates trapping diffusion as the main diffusion mechanism. Additional Fourier transform infrared spectroscopy measurements show that hardly any interstitial hydrogen exists in the post-hydrogenated a-Si layers. The results of this study open the way for further hydrogen diffusion experiments which require an initially unhydrogenated drain layer. (C) 2015 Elsevier B.V. All rights reserved.

Typ des Eintrags: Artikel
Erschienen: 2016
Autor(en): Gerke, S. ; Becker, H.-W. ; Rogalla, D. ; Singer, F. ; Brinkmann, N. ; Fritz, S. ; Hammud, A. ; Keller, P. ; Skorka, D. ; Sommer, D. ; Weiß, C. ; Flege, S. ; Hahn, G. ; Job, R. ; Terheiden, B.
Art des Eintrags: Bibliographie
Titel: Influence of post-hydrogenation upon electrical, optical and structural properties of hydrogen-less sputter-deposited amorphous silicon
Sprache: Englisch
Publikationsjahr: 1 Januar 2016
Titel der Zeitschrift, Zeitung oder Schriftenreihe: Thin Solid Films
Jahrgang/Volume einer Zeitschrift: 598
DOI: 10.1016/j.tsf.2015.11.063
Kurzbeschreibung (Abstract):

Amorphous silicon (a-Si) is common in the production of technical devices and can be deposited by several techniques. In this study intrinsic and doped, hydrogen-less amorphous silicon films are RF magnetron sputter deposited and post-hydrogenated in a remote hydrogen plasma reactor at a temperature of 370 degrees C. Secondary ion mass spectrometry of a boron doped (p) a-Si layer shows that the concentration of dopants in the sputtered layer becomes the same as present in the sputter-target. Improved surface passivation of phosphorous doped 5 Omega cm, FZ, (n) c-Si can be achieved by post-hydrogenation yielding a minority carrier lifetime of similar to 360 mu s finding an optimum for similar to 40 nm thin films, deposited at 325 degrees C. This relatively low minority carrier lifetime indicates high disorder of the hydrogen-less sputter deposited amorphous network. Post-hydrogenation leads to a decrease of the number of localized states within the band gap. Optical band gaps (Taucs gab as well as E-04) can be determined to similar to 1.88 eV after post-hydrogenation. High resolution transmission electron microscopy and optical Raman investigations show that the sputtered layers are amorphous and stay like this during post-hydrogenation. As a consequence of the missing hydrogen during deposition, sputtered a-Si forms a rough surface compared to CVD a-Si. Atomic force microscopy points out that the roughness decreases by up to 25% during post-hydrogenation. Nuclear resonant reaction analysis permits the investigation of hydrogen depth profiles and allows determining the diffusion coefficients of several post-hydrogenated samples from of a model developed within this work. A dependency of diffusion coefficients on the duration of post-hydrogenation indicates trapping diffusion as the main diffusion mechanism. Additional Fourier transform infrared spectroscopy measurements show that hardly any interstitial hydrogen exists in the post-hydrogenated a-Si layers. The results of this study open the way for further hydrogen diffusion experiments which require an initially unhydrogenated drain layer. (C) 2015 Elsevier B.V. All rights reserved.

Freie Schlagworte: AFM, Amorphous silicon, Hydrogen depth profiling, NRRA, Post-hydrogenation, Raman, RF sputter-deposition
Fachbereich(e)/-gebiet(e): 11 Fachbereich Material- und Geowissenschaften
11 Fachbereich Material- und Geowissenschaften > Materialwissenschaft
11 Fachbereich Material- und Geowissenschaften > Materialwissenschaft > Fachgebiet Materialanalytik
Zentrale Einrichtungen
Hinterlegungsdatum: 06 Jun 2016 11:34
Letzte Änderung: 11 Jul 2016 06:30
PPN:
Sponsoren: Part of this work was supported by the German Federal Ministry for the Environment, Nature Conservation and Nuclear Safety (FKZ 0325581).
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