Department of Physics, Faculty of Science, Tokyo Metropolitan University, 1-1 Minami-osawa, Hachioji, Tokyo 192-0397, Japan.
ACS Nano. 2009 May 26;3(5):1279-87. doi: 10.1021/nn900221t.
In this paper, we report novel ferroelectric properties of a new form of ice inside single-walled carbon nanotubes (SWCNTs). These are called "ice nanotubes" (ice NTs) and they consist of polygonal water rings stacked one-dimensionally along the SWCNT axis. We performed molecular dynamics (MD) calculations for the ice NTs under an external electric field and in a temperature range between 100 and 350 K. It is revealed that ice NTs show stepwise polarization with a significant hysteresis loop as a function of the external field strength. In particular, pentagonal and heptagonal ice NTs are found to be the world's smallest ferroelectrics with spontaneous polarization of around 1 microC/cm(2). The n-gonal ice NT, where n = 5, 6, or 7, has (n + 1)-polarized structures with different polarizations. These findings suggest potential applications of SWCNTs encapsulating dielectric materials for the fabrication of the smallest ferroelectric devices. Experimental evidence for the presence of ice NTs inside SWCNTs is also discussed in great detail.
本文报道了一种新型冰的铁电特性，这种冰存在于单壁碳纳米管（SWCNTs）内部。这种冰被称为“冰纳米管”（ice NTs），它们由沿 SWCNT 轴一维堆积的多边形水环组成。我们在外部电场和 100 到 350 K 的温度范围内对 ice NTs 进行了分子动力学（MD）计算。结果表明，ice NTs 在外电场作用下表现出阶跃式极化，具有显著的滞后回线。特别是五边形和七边形 ice NTs 被发现是世界上最小的铁电体，具有约 1 微 C/cm(2) 的自发极化。n-边形 ice NT（其中 n = 5、6 或 7）具有不同极化的（n + 1）-极化结构。这些发现表明，SWCNTs 封装介电材料在制造最小铁电器件方面具有潜在的应用前景。还详细讨论了 SWCNTs 内部存在 ice NTs 的实验证据。
