Direct Gravure Printing of Silicon Nanowires Using Entropic Attraction Forces

1. Jungmok Seo¹, 
2. Hyonik Lee¹, 
3. Seulah Lee¹,
4. Tae Il Lee², 
5. Jae-Min Myoung², 
6. Taeyoon Lee^1,*

Article first published online: 19 MAR 2012

DOI: 10.1002/smll.201102367The development of a method for large-scale printing of nanowire (NW) arrays onto a desired substrate is crucial for fabricating high-performance NW-based electronics. Here, the alignment of highly ordered and dense silicon (Si) NW arrays at anisotropically etched micro-engraved structures is demonstrated 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, and the assembly characteristics of the NWs were highly dependent on the polarity of the NW solutions. After complete evaporation, the aligned NW arrays are subsequently transferred onto a flexible substrate with 95% selectivity using a direct gravure printing technique. As a proof-of-concept, flexible back-gated NW field-effect transistors (FETs) are fabricated. The fabricated FETs have an effective hole mobility of 17.1 cm²·V⁻¹·s⁻¹ and an on/off ratio of ∼2.6 × 10⁵.