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Solution-processed silicon films and transistors

Abstract

The use of solution processes—as opposed to conventional vacuum processes and vapour-phase deposition—for the fabrication of electronic devices has received considerable attention for a wide range of applications1,2,3,4,5,6,7, with a view to reducing processing costs. In particular, the ability to print semiconductor devices using liquid-phase materials could prove essential for some envisaged applications, such as large-area flexible displays. Recent research in this area has largely been focused on organic semiconductors8,9,10,11, some of which have mobilities comparable to that of amorphous silicon11 (a-Si); but issues of reliability remain. Solution processing of metal chalcogenide semiconductors to fabricate stable and high-performance transistors has also been reported12,13. This class of materials is being explored as a possible substitute for silicon, given the complex and expensive manufacturing processes required to fabricate devices from the latter. However, if high-quality silicon films could be prepared by a solution process, this situation might change drastically. Here we demonstrate the solution processing of silicon thin-film transistors (TFTs) using a silane-based liquid precursor. Using this precursor, we have prepared polycrystalline silicon (poly-Si) films by both spin-coating and ink-jet printing, from which we fabricate TFTs with mobilities of 108 cm2 V-1 s-1 and 6.5 cm2 V-1 s-1, respectively. Although the processing conditions have yet to be optimized, these mobilities are already greater than those that have been achieved in solution-processed organic TFTs, and they exceed those of a-Si TFTs (≤ 1 cm2 V-1 s-1).

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Acknowledgements

We thank the members of Seiko Epson Corporation's pilot line and ink-jet industrial application project, for fabricating TFTs and ink-jet experiments in this research. This work is partially supported by a grant from the New Energy and Industrial Technology Development Organization (NEDO).

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Correspondence to Masahiro Furusawa.

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Further reading

Figure 1: Gel permeation chromatogram (GPC) of liquid precursor for Si film.
Figure 2: Thermal desorption spectrum (TDS) of solution-processed a-Si film.
Figure 3: A TEM image of a solution-processed poly-Si film.
Figure 4: The structure and characteristics of solution-processed LTPS TFTs.

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