Gowthami Thavasiappan, Tamilselvi Gopal, Jacob George, Raina Gargi
Center for Nanotechnology Research, VIT University, Vellore 632014, India.
Phys Chem Chem Phys. 2015 Jun 7;17(21):13964-72. doi: 10.1039/c5cp01703c. Epub 2015 May 7.
In this work, we report the role of ice-like water adlayers (IWLs) formed under ambient conditions in between mechanically exfoliated as-prepared and patterned few layer graphene (FLG) and multi-layer graphene (MLG) on hydrophobic Si and hydrophilic SiO2/Si substrates. The growth of the IWL is probed by measuring the height changes in graphene using intermittent contact atomic force microscopy (IC-AFM) and their electrostatic effect is studied using electrostatic force microscopy (EFM) over time. It is found that more IWLs are formed within a shorter period of time, when both as-prepared graphene and underlying substrates are either hydrophobic or hydrophilic in nature. In contrast, AFM voltage nanolithographically patterned trenches on FLG and MLG on the Si substrate show quick formation of IWLs. The effect of IWL formed, on the dimensions of trenches, is correlated with the variation of the measured EFM phase shift over time. This study demonstrates the dependence of the formation of IWLs under ambient conditions on the affinity towards water, at the interface of graphene on hydrophobic and hydrophilic substrates, which has important implications for the performance of graphene-based nanoelectronic devices.
在这项工作中，我们报告了在环境条件下形成于机械剥离的初始制备且图案化的少层石墨烯（FLG）和多层石墨烯（MLG）与疏水Si和亲水SiO₂/Si衬底之间的类冰水吸附层（IWLs）的作用。通过使用间歇接触原子力显微镜（IC-AFM）测量石墨烯中的高度变化来探测IWL的生长，并随着时间的推移使用静电力显微镜（EFM）研究其静电效应。结果发现，当初始制备的石墨烯和下层衬底在性质上均为疏水或亲水时，会在更短的时间内形成更多的IWL。相比之下，在Si衬底上的FLG和MLG上通过原子力显微镜电压纳米光刻图案化的沟槽显示出IWL的快速形成。所形成的IWL对沟槽尺寸的影响与随时间测量的EFM相移变化相关。这项研究表明，环境条件下IWL的形成取决于石墨烯在疏水和亲水衬底界面处对水的亲和力，这对基于石墨烯的纳米电子器件的性能具有重要意义。
