通过接触共振和超声扫描探针显微镜绘制悬浮和支撑多层石墨烯膜的纳米级动态特性
Mapping nanoscale dynamic properties of suspended and supported multi-layer graphene membranes via contact resonance and ultrasonic scanning probe microscopies
摘要：
石墨烯（GR）卓越的机械和电气性能-例如其杨氏模量，单位面积低质量，天然原子平坦度和电导-将使其成为微和纳米机电系统（MEMS和NEMS）的理想材料。然而，将GR附接至支撑件的困难加上在少层GR中自然发生的内部缺陷可显著地不利地影响此类装置的性能。在这里，我们已经使用了一个组合的接触共振原子力显微镜（CR-AFM）和超声波力显微镜（UFM）的方法来测量和地图与纳米级空间分辨率GR膜的性能无法访问最传统的扫描探针表征技术。使用多层GR板（膜）悬挂在一个圆孔，我们表明，这种组合的方法允许访问的机械性能，内部结构和附件的几何形状的膜提供有关的支持和悬挂区域的系统的信息。我们表明，UFM允许精确的几何位置的支持膜-基板接触被定位，并提供其质量的局部变化的指示在接触区域。同时，我们表明，通过映射的位置敏感的频率和相位响应的CR-AFM响应，可以可靠地量化膜的刚度，并在膜的悬浮区域的图像的缺陷。实验CR-AFM测量的相位和振幅显示出良好的协议与分析模型占组合CR-AFM探针膜系统的共振。UFM和CR-AFM的结合为基于二维材料的少层NEMS系统的研究提供了一个有益的组合。
英文摘要：
Graphene (GR) remarkable mechanical and electrical properties - such as its Young's modulus, low mass per unit area, natural atomic flatness and electrical conductance - would make it an ideal material for micro and nanoelectromechanical systems (MEMS and NEMS). However, the difficulty of attaching GR to supports coupled with naturally occurring internal defects in a few-layer GR can significantly adversely affect the performance of such devices. Here, we have used a combined contact resonance atomic force microscopy (CR-AFM) and ultrasonic force microscopy (UFM) approach to characterise and map with nanoscale spatial resolution GR membrane properties inaccessible to most conventional scanning probe characterisation techniques. Using a multi-layer GR plate (membrane) suspended over a round hole we show that this combined approach allows access to the mechanical properties, internal structure and attachment geometry of the membrane providing information about both the supported and suspended regions of the system. We show that UFM allows the precise geometrical position of the supported membrane-substrate contact to be located and provides indication of the local variation of its quality in the contact areas. At the same time, we show that by mapping the position sensitive frequency and phase response of CR-AFM response, one can reliably quantify the membrane stiffness, and image the defects in the suspended area of the membrane. The phase and amplitude of experimental CR-AFM measurements show excellent agreement with an analytical model accounting for the resonance of the combined CR-AFM probe-membrane system. The combination of UFM and CR-AFM provide a beneficial combination for investigation of few-layer NEMS systems based on two dimensional materials.
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