• Korean Journal of Materials Research
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• v.23 no.10
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• pp.586-591
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• 2013

The printing of nanomaterials onto certain substrates is one of the key technologies behind high-speed interconnection and high-performance electronic devices. For the printing of next-generation electronic devices, a printing process which can be applied to a flexible substrate is needed. A printing process on a flexible substrate requires a lowtemperature, non-vacuum process due to the physical properties of the substrate. In this study, we obtained well-ordered Ag nanowires using modified gravure printing techniques. Ag nanowires are synthesized by a silver nitrate ($AgNO_3$) reduction process in an ethylene glycol solution. Ag nanowires were well aligned by hydrodynamic force on a micro-engraved Si substrate. With the three-dimensional structure of polydimethylsiloxane (PDMS), which has an inverse morphology relative to the micro-engraved Si substrate, the sub-micron alignment of Ag nanowires is possible. This technique can solve the performance problems associated with conventional organic materials. Also, given that this technique enables large-area printing, it has great applicability not only as a next-generation printing technology but also in a range of other fields.

• Proceedings of the Materials Research Society of Korea Conference
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• 2011.05a
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• pp.3.1-3.1
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• 2011

Over the past decade, the major efforts for lowering the cost of electronics has been devoted to increasing the packaging efficiency of the integrated circuits (ICs), which is defined by the ratio of all devices on system-level board compared to the area of the board, and to working on a larger but cheaper substrates. Especially, in flexible electronics, the latter has been the favorable way along with using novel nanomaterials that have excellent mechanical flexibility and electrical properties as active channel materials and conductive films. Here, the tool for achieving large area patterning is by printing methods. Although diverse printing methods have been investigated to produce highly-aligned structures of the nanomaterials with desired patterns, many require laborious processes that need to be further optimized for practical applications, showing a clear limit to the design of the nanomaterial patterns in a large scale assembly. Here, we demonstrate the alignment of highly ordered and dense silicon (Si) NW arrays to anisotropically etched micro-engraved structures using a simple evaporation process. During evaporation, entropic attraction combined with the internal flow of the NW solution induced the alignment of NWs at the corners of pre-defined structures. The assembly characteristics of the NWs were highly dependent on the polarity of the NW solutions. After complete evaporation, the aligned NW arrays were subsequently transferred onto a flexible substrate with 95% selectivity using a direct gravure printing technique. As proof-of-concept, flexible back-gated NW field effect transistors (FETs) were fabricated. The fabricated FETs had an effective hole mobility of 0.17 $cm2/V{\cdot}s$ and an on/off ratio of ${\sim}1.4{\times}104$. These results demonstrate that our NW gravure printing technique is a simple and effective method that can be used to fabricate high-performance flexible electronics based on inorganic materials.