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From Cyclopentasilane to Thin-Film Transistors

: Gerwig, M.; Ali, A.S.; Neubert, D.; Polster, S.; Bohme, U.; Franze, G.; Rosenkranz, M.; Popov, A.; Ponomarev, I.; Jank, M.; Vieweger, C.; Brendler, E.; Frey, L.; Kroll, P.; Kroke, E.

Fulltext ()

Advanced electronic materials 7 (2021), No.2, Art. 2000422, 13 pp.
ISSN: 2199-160X
Journal Article, Electronic Publication
Fraunhofer IISB ()
ab initio calculations; photolysis; polymerization; semiconductors; silane; thin films

Cyclopentasilane (CPS) has been studied as an liquid precursor for the deposition of thin silicon films for printed electronics and related applications. The processing involves a UV-induced prepolymerization of CPS followed by liquid deposition and low-temperature thermolysis. An insight into the oligomer and polymer formation including crosslinking in solution using 29Si NMR spectroscopy and electron spin resonance spectroscopy is reported. Formation of SiH (T-units) and SiH3 (M-units) is observed as well as short-lived paramagnetic species. Additionally, the polymerization is followed by Raman spectroscopy. Reactive molecular dynamics simulations are applied to develop a theoretical model for the CPS-ring-opening and crosslinking steps. The experimental and computational data correspond well to each other and allow insight into the mechanism of polymer formation. The processing steps include spin-coating, thermal drying, and conversion to amorphous silicon, H-passivation, and fabrication of a CPS-derived thin-film transistor (TFT), without intermediate silicon crystallization. Further improvement is gained by using tetralene as a solvent, leading to a reduction of the time-consuming polymerization step by one order of magnitude compared to cyclooctane. The overall quality and characteristics of the CPS-derived spin-coated silicon thin films correspond to standard plasma enhanced chemical vapor deposition-derived devices with respect to performance levels.