Single-crystal organic nanowires of copper-tetracyanoquinodimethane: synthesis, patterning, characterization, and device applications.-猫眼课题宝

DOI：

10.1002/anie.200604397

发表时间：

2007-04

期刊：

Angewandte Chemie

影响因子：

通讯作者：

中科院分区：

文献类型：

作者：

Kai Xiao;J. Tao;Z. Pan;A. Puretzky;I. Ivanov;S. Pennycook;D. Geohegan

单晶、一维半导体纳米结构是纳米级光学和电子器件非常重要的构建模块。目前，无机材料受到广泛关注，例如碳纳米管和无机氧化物纳米线，其特性赋予它们巨大的潜力。尽管有机半导体纳米线在廉价的有机薄膜光电器件中得到了广泛的发展，但对它们的研究却很少。由较小分子组成的有机半导体材料通常具有共轭结构。由于它们的多样性、可定制性、多功能性以及易于形成高度有序的晶体，因此非常需要从小分子化合物合成单晶有机半导体纳米线，它可以作为下一代轻型显示器和信息存储应用的低成本、高性能构建块。铜-四氰基醌二甲烷 (Cu-TCNQ) 是一种被广泛研究的有机半导体，因为它能够通过电场或光激发的感应，将电导率从高态切换到低态。块状和薄膜形式的 Cu-TCNQ 已被广泛研究，迄今为止，已经报道了各种制造 Cu-TCNQ 纳米结构的方法，例如真空气相沉积、有机溶剂中的溶液工艺，以及在金属 Cu 或 Cu 离子存在下 TCNQ 的化学和电化学还原。然而，使用这些技术来制造微米级和纳米级 Cu-TCNQ 结构在产量、尺寸、相、材料多样性、高密度阵列的生产以及实现图案化结构的能力方面存在显着的缺点。在此，我们报告了通过低温气固途径合成和图案化单晶半导体 Cu-TCNQ 纳米线。该合成路线的优点在于其简单且反应条件温和，以及阵列中生长的纳米线的高结晶度。为了展示该技术的潜力，我们报告了基于柔性聚对苯二甲酸乙二醇酯（PET）柔性基板上的有机单晶纳米线网络的交叉点非易失性存储器件的设计、制造和特性。 Cu-TCNQ 有机纳米线是通过 Cu 薄膜和 TCNQ 蒸气在低温下的反应以可控方式生长的（图 1）。纳米线的直径范围为20至100纳米，而通过调整铜膜的生长时间和厚度，长度可以在1毫米至20毫米之间变化。这些 Cu-TCNQ 纳米线有几个重要特征。首先，纳米线最初直接从基板表面上的图案化铜膜生长，并与未经处理的铜层形成良好的机械连接，这是与器件电极良好电连接的重要起点（图1a）。随着纳米线变长，它们会弯曲形成纳米线网络（图 1b）。其次，Cu-TCNQ纳米线可以通过使用简单的化学气相沉积（CVD）方法在低至120 8C的温度下合成。因此，Cu-TCNQ纳米线可以在一些温度敏感的基底上生长，例如玻璃和柔性塑料，这对于大面积、低成本的柔性电子应用具有广阔的前景。第三，由于气固反应生长，纳米线仅在铜薄膜图案化的区域生长，并且很容易产生图案化的纳米线。仔细暴露铜薄膜区域可以影响纳米线的方向。电子束光刻和光刻等各种技术可用于创建图案化的铜薄膜，以便随后生长 Cu-TCNQ 纳米线。 SEM 研究揭示了细长的大量生长，[*] K. Shaw 博士、Z. Pan 博士、A. A. Puretzky 博士、I. N. Ivanov 博士、D. B. Geohegan 纳米材料科学中心 Oak Ridge National Laboratory 1 Bethel Valley Road, Oak Ridge, TN 37831-6030 (USA) 传真：(+1)865-574-4143电子邮箱：xiaok@ornl.gov geohegandb@ornl.gov

Single-crystal, one-dimensional semiconductor nanostructures are very important building blocks for nanoscale optical and electronic devices. Currently, much attention is focused on inorganic materials, such as carbon nanotubes and inorganic oxide nanowires, whose properties endow them with considerable potential. Fewer studies have been performed on organic semiconductor nanowires, despite their widespread development for inexpensive organic thin-film optoelectronic devices. Organic semiconducting materials comprised of smaller molecules normally have conjugated structures. As a consequence of their diversity, tailorability, multifunctionality, and ease in forming very highly ordered crystals, it is highly desirable to synthesize single-crystal organic semiconducting nanowires from small molecular compounds, which could serve as low-cost, high-performance building blocks for the next-generation lightweight displays and for applications in information storage. Copper–tetracyanoquinodimethane (Cu–TCNQ) is a widely studied organic semiconductor because of its capability for reversible, bistable switching of conductivity from a high to a low state through induction by an electric field or optical excitation. Bulk and thin-film forms of Cu–TCNQ have been widely studied, and thus far various methods for the fabrication of Cu–TCNQ nanostructures have been reported, such as vacuum vapor deposition, solution processes in organic solvents, as well as chemical and electrochemical reduction of TCNQ in the presence of metallic Cu or Cu ions. However, the use of these techniques to fabricate microand nanoscale Cu–TCNQ structures have resulted in significant drawbacks with respect to the yield, size, phase, material multiplicity, production of high-density arrays, and ability to achieve patterned structures. Herein we report the synthesis and patterning of single-crystal semiconductor Cu–TCNQ nanowires by a low-temperature vapor–solid route. The advantage of this synthetic route lies in its simplicity and mild reaction conditions, as well as the high crystallinity of the nanowires grown in the arrays. To demonstrate the potential of the technique we report the design, fabrication, and characteristics of cross-point nonvolatile memory devices based on a network of organic singlecrystal nanowires on a flexible poly(ethylene terephthalate) (PET) flexible substrate. Cu–TCNQ organic nanowires were grown in a controllable manner from reactions of a Cu thin film and TCNQ vapor at low temperatures (Figure 1). The diameters of the nanowires range from 20 to 100 nm, while the lengths could be varied between 1 mm and 20 mm by adjusting the growth time and thickness of the Cu film. There are several important features of these Cu–TCNQ nanowires. First, the nanowires initially grow directly from the patterned Cu film on the substrate surface and make good mechanical connections to the untreated Cu layer, an essential starting point for good electrical connections to device electrodes (Figure 1a). As the nanowires grow longer, they curve to form a network of nanowires (Figure 1b). Second, Cu–TCNQ nanowires can be synthesized at temperatures as low as 120 8C by using a simple chemical vapor deposition (CVD) method. Therefore, Cu–TCNQ nanowires can be grown on some temperaturesensitive substrates, such as glass and flexible plastics, which is promising for large-area, low-cost flexible electronic applications. Third, as a result of the vapor–solid reaction growth, the nanowires grow only in areas patterned with Cu thin films and readily yield patterned nanowires. The direction of the nanowires can be influenced by carefully exposing regions of the Cu thin film. Various techniques, such as electron-beam lithography and photolithography, can be used to create patterned Cu films for subsequent growth of Cu–TCNQ nanowires. SEM studies reveal massive growth of fine, long, [*] Dr. K. Xiao, Dr. Z. Pan, Dr. A. A. Puretzky, Dr. I. N. Ivanov, Dr. D. B. Geohegan Center for Nanophase Materials Sciences Oak Ridge National Laboratory 1 Bethel Valley Road, Oak Ridge, TN 37831-6030 (USA) Fax: (+1)865-574-4143 E-mail: xiaok@ornl.gov geohegandb@ornl.gov

Single-crystal organic nanowires of copper-tetracyanoquinodimethane: synthesis, patterning, characterization, and device applications.

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