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 applications, 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 semiconductors, some of which have mobilities comparable to that of amorphous silicon (a-Si); but issues of reliability remain. Solution processing of metal chalcogenide semiconductors to fabricate stable and high-performance transistors has also been reported. 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 (< or = 1 cm2 V(-1) s(-1)).

Very thin (25–50-nm-thick) amorphous silicon (a-Si) films were crystallized into polycrystalline silicon (polysilicon) films by the combination of low temperature solid phase crystallization (SPC) and subsequent excimer laser annealing (ELA). These films are, then, subjected to a standard low temperature process (&lt;600 °C) of thin film transistor (TFT) fabrication. The performance of resultant TFTs was compared to those fabricated on polysilicon films obtained by simple excimer laser annealing of amorphous silicon films. The electrical characteristics of the TFTs were correlated with the structural characteristics of the polysilicon films, using transmission electron microscopy and x-ray diffraction as analytical tools. The polysilicon films obtained by the SPC process consist of large and heavily defected crystalline grains. These defects, however, could be eliminated by melting and solidifying the polysilicon films during the ELA process. As a result, the electrical properties of the 50-nm-thick polysilicon film subjected to SPC+ELA process improved dramatically when the laser energy density was between 280 and 360 mJ cm−2. The SPC+ELA method did not work successfully for the 25-nm-thick films due to the instability of the laser energy density. Hillock formation at the grain boundaries during the ELA process is also discussed in this article.

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