Department of Chemical and Biomolecular Engineering, University of Notre Dame , Notre Dame, Indiana 46556, United States.
Department of Chemical and Petroleum Engineering, University of Pittsburgh , Pittsburgh, Pennsylvania 15213, United States.
ACS Nano. 2017 May 23;11(5):4976-4984. doi: 10.1021/acsnano.7b01657. Epub 2017 May 4.
Nanoscale conductive filaments, usually associated with resistive memory or memristor technology, may also be used for chemical sensing and nanophotonic applications; however, realistic implementation of the technology requires precise knowledge of the conditions that control the formation and dissolution of filaments. Here we describe and characterize an addressable direct-write nanoelectrochemical approach to achieve repeatable formation/dissolution of Ag filaments across a ∼100 nm poly(ethylene oxide) (PEO) film containing either Ag alone or Ag together with 50 nm Ag-nanoparticles acting as bipolar electrodes. Using a conductive AFM tip, formation occurs when the PEO film is subjected to a forward bias, and dissolution occurs under reverse bias. Formation-dissolution kinetics were studied for three film compositions: Ag|PEO-Ag, Ag|poly(ethylene glycol) monolayer-PEO-Ag, and Ag|poly(ethylene glycol) monolayer-PEO-Ag/Ag-nanoparticle. Statistical analysis shows that the distribution of formation times exhibits Gaussian behavior, and the fastest average initial formation time occurs for the Ag|PEO-Ag system. In contrast, formation in the presence of Ag nanoparticles likely proceeds by a noncontact bipolar electrochemical mechanism, exhibiting the slowest initial filament formation. Dissolution times are log-normal for all three systems, and repeated reformation of filaments from previously formed structures is characterized by rapid regrowth. The direct-write bipolar electrochemical deposition/dissolution strategy developed here presents an approach to reconfigurable, noncontact in situ wiring of nanoparticle arrays-thereby enabling applications where actively controlled connectivity of nanoparticle arrays is used to manipulate nanoelectronic and nanophotonic behavior. The system further allows for facile manipulation of experimental conditions while simultaneously characterizing surface conditions and filament formation/dissolution kinetics.
纳米级导电丝通常与阻变存储器或忆阻器技术相关，也可用于化学传感和纳米光子学应用；然而，该技术的实际应用需要精确了解控制丝形成和溶解的条件。在这里，我们描述并表征了一种可寻址的直接写入纳米电化学方法，以实现横跨约 100nm 聚环氧乙烷（PEO）膜的 Ag 丝的重复形成/溶解，该膜中仅含有 Ag 或 Ag 与作为双极电极的 50nm Ag 纳米颗粒。使用导电 AFM 尖端，当 PEO 膜受到正向偏压时会发生形成，而在反向偏压下会发生溶解。研究了三种膜组成的形成-溶解动力学：Ag|PEO-Ag、Ag|聚乙二醇单层-PEO-Ag 和 Ag|聚乙二醇单层-PEO-Ag/Ag 纳米颗粒。统计分析表明，形成时间的分布呈高斯分布，Ag|PEO-Ag 体系的平均初始形成时间最快。相比之下，Ag 纳米颗粒存在下的形成可能通过非接触双极电化学机制进行，表现出最慢的初始丝形成。对于所有三种体系，溶解时间呈对数正态分布，并且从先前形成的结构中重新形成丝的过程表现出快速的再生长。这里开发的直接写入双极电化学沉积/溶解策略提供了一种可重构的、非接触式的原位纳米颗粒阵列布线方法-从而实现了主动控制纳米颗粒阵列的连接性用于操纵纳米电子和纳米光子行为的应用。该系统还允许轻松地操纵实验条件，同时同时表征表面条件和丝的形成/溶解动力学。
