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KFM: Fachverband Kristalline Festkörper und deren Mikrostruktur

KFM 7: Microstructure of thin films / TEM-based Nanoanalysis

KFM 7.5: Vortrag

Montag, 12. März 2018, 16:20–16:40, E 124

A study on Amorphous Silicon Films using SAXS and SANS to distinguish nano-crystals from voids. — •Eike Gericke¹, Armin Hoell², Jimmy Melskens³, Dragomir Tatchev⁴, Uwe Keiderling², Robert Wendt^{1, 2}, Simone Raoux^{1, 2}, Klaus Rademann¹, and Klaus Lips^{1, 5} — ¹Humboldt-Universität Berlin — ²Helmholtz-Zentrum Berlin — ³Technische Universiteit Eindhoven — ⁴Bulgarian Academy of Sciences — ⁵Freie Universität Berlin

Albeit amorphous silicon (a-Si:H) is used since the 70th as thin-film material for opto-electronic applications, its structural properties are still under discussion. a-Si:H contains up to 16 at% of hydrogen in a complex micro- and nano-structured Si-network. Generally, it is described as a continuous random network (CRN), but also models involving nanocrystalls are discussed. TEM hints at nano-voids. It was shown that even reduced-density-functions can be described by a pure CRN but also by a model including nanocrystals. Resolving the complex structure of a-Si:H is essential to correlate light-induced degradation to local inhomogeneities of the material. We revisit the structure of a-Si:H by SAXS and SANS, to distinguish density fluctuations from voids. We have studied differently prepared a-Si:H samples with morphologies from dense to porous. We will review the structure of a-Si:H and present our results, indicating nano-sized grains with enlarged mass density inside dense- and hydrogen decorated voids inside porous-aSi:H samples. We will present a new model for the a-Si:H structure which correlates the nanostructure with light-induced degradation.