悬浮石墨烯中氧吸附的异常随机电报信号
Anomalous Random Telegraphy Signal in Suspended Graphene with Oxygen Adsorption
AI总结：
本文研究了氧吸附对悬浮石墨烯低频噪声的影响，发现氧气会导致毫秒级随机电报信号（RTS），并揭示了吸附过程中的时间常数变化，为石墨烯传感器设计提供了重要参考。
摘要：
石墨烯因其大的比表面积和低噪声而成为传感应用中极具前景的材料。在许多应用中，石墨烯不可避免地会与氧气接触，因为氧气是大气中第二丰富的气体。因此，了解这种气体如何影响传感器特性具有重要意义。在这项工作中，展示了氧气对悬浮石墨烯低频噪声的影响。我们制备了宽度（W）和长度（L）均为200 nm的悬浮石墨烯纳米带器件。通过交流锁相方法，在真空和纯氧气氛下测量了电阻随时间的变化。经过小波去噪与分析的信号处理后，结果表明氧气导致了毫秒级的随机电报信号（RTS），在高阻态下的平均停留时间为2.9毫秒，在低阻态下为2毫秒。研究还表明，这种RTS仅在某些时段出现，这表明分子在吸附后需要一些时间才能找到能量上最有利的吸附态。此外，还观察到RTS时间常数的减慢，这表明随着时间的推移，由于氧吸附，可用的活性位点变少。因此，为了确保在其使用寿命期间将暴露于氧气的石墨烯基传感器具有高灵敏度和高耐久性，考虑这些影响是非常重要的。
英文摘要：
Graphene is a promising material for sensing applications because of its large specific surface area and low noise. In many applications, graphene will inevitably be in contact with oxygen since it is the second most abundant gas in the atmosphere. Therefore, it is of interest to understand how this gas affects the sensor properties. In this work, the effect of oxygen on the low-frequency noise of suspended graphene is demonstrated. Devices with suspended graphene nanoribbons with a width (W) and length (L) of 200 nm were fabricated. The resistance as a function of time was measured in a vacuum and pure oxygen atmosphere through an ac lock-in method. After signal processing with wavelet denoising and analysis, it is demonstrated that oxygen causes random telegraphy signal (RTS) in the millisecond scale, with an average dwell time of 2.9 milliseconds in the high-resistance state, and 2 milliseconds in the low-resistance state. It is also shown that this RTS occurs only at some periods, which indicates that, upon adsorption, the molecules take some time until they find the most energetically favorable adsorption state. Also, a slow-down in the RTS time constants is observed, which infers that less active sites are available as time goes on because of oxygen adsorption. Therefore, it is very important to consider these effects to guarantee high sensitivity and high durability for graphene-based sensors that will be exposed to oxygen during their lifetime.
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