Redox-Inactive CO2 Determines Atmospheric Stability of Electrical Properties of ZnO Nanowire Devices through a Room-Temperature Surface Reaction
Redox-Inactive CO2 Determines Atmospheric Stability of Electrical Properties of ZnO Nanowire Devices through a Room-Temperature Surface Reaction
复制标题
DOI：
10.1021/acsami.9b13231
复制
发表时间：
2019-10-30
影响因子：
9.5
通讯作者：
Yanagida, Takeshi
中科院分区：
文献类型：
--
作者：
Nakamura, Kentaro;Takahashi, Tsunaki;Yanagida, Takeshi
物联网时代新兴的交互式电子产品本质上要求暴露在空气中的半导体器件的长期稳定性。纳米结构的金属氧化物由于其在空气中的固有稳定性，是这种大气稳定半导体器件的有希望的选择。在各种氧化物纳米结构中，ZnO纳米线在光电器件方面的应用研究最为深入。在这里，我们展示了一种实现ZnO纳米线器件大气电稳定性的策略。虽然空气中的化学活性氧和水是影响纳米级金属氧化物电稳定性的重要因素，但我们发现空气中ppm水平的氧化还原活性CO2对水热生长单晶ZnO纳米线的大气电稳定性起着关键的决定作用。利用大气控制的单纳米线器件的电学特性、傅里叶变换红外光谱、扫描透射电子显微镜和x射线光电子能谱进行的一系列分析一致表明，即使在室温下，大气中的CO2也会与ZnO纳米线表面发生大量反应，形成电绝缘的碳酸锌薄层。该层的形成基本上限制了ZnO纳米线器件的大气电稳定性。基于这种表面碳化机理，我们提出了一种抑制有害表面反应的策略，即：(1)降低表面羟基的密度；(2)通过热预处理提高纳米线的结晶度。这种方法将大气中的电稳定性提高到至少40天。
Emerging interactive electronics for the Internet of Things era inherently require the long-term stability of semiconductor devices exposed to air. Nanostructured metal oxides are promising options for such atmospherically stable semiconductor devices owing to their inherent stability in air. Among various oxide nanostructures, ZnO nanowires have been the most intensively studied for electrical and optical device applications. Here, we demonstrate a strategy for achieving the atmospheric electrical stability of ZnO nanowire devices. Although the chemically active oxygen and water in air are strong candidates for affecting the electrical stability of nanoscale metal oxides, we found that the ppm-level redox-inactive CO2 in air critically determines the atmospheric electrical stability of hydrothermally grown single-crystalline ZnO nanowires. A series of analyses using atmosphere-controlled electrical characterization of single nanowire devices, Fourier transform infrared spectroscopy, scanning transmission electron microscopy, and X-ray photoelectron spectroscopy consistently revealed that atmospheric CO2 reacts substantially with the ZnO nanowire surfaces, even at room temperature, to form an electrically insulative zinc carbonate thin layer. The formation of this layer essentially limits the atmospheric electrical stability of the ZnO nanowire devices. Based on this surface carbonation mechanism, we propose a strategy to suppress the detrimental surface reaction, which is based on (1) reducing the density of surface hydroxyl groups and (2) improving the nanowire crystallinity by thermal pretreatment. This approach improves the atmospheric electrical stability to at least 40 days in air.