Empa, Swiss Federal Laboratories for Materials Science and Technology , Überlandstrasse 129, Dübendorf CH-8600, Switzerland.
Department of Physics, Bernal Institute, University of Limerick , Limerick V94 T9PX, Ireland.
ACS Appl Mater Interfaces. 2017 Jul 26;9(29):25014-25022. doi: 10.1021/acsami.7b05143. Epub 2017 Jul 14.
Chemical vapor deposition (CVD) is a powerful technique to produce graphene for large-scale applications. Polymer-assisted wet transfer is commonly used to move the graphene onto silicon substrates, but the resulting devices tend to exhibit p-doping, which decreases the device quality and reproducibility. In an effort to better understand the origin of this effect, we coated graphene with n-methyl-2-pyrrolidone (NMP) and hexamethyldisilazane (HMDS) molecules that exhibit negligible charge transfer to graphene but bind more strongly to graphene than ambient adsorbents. Using Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), electrical transport measurements, and quantum mechanical computer simulations, we show that the molecules help in the removal of p-doping, and our data indicate that the molecules do this by replacing ambient adsorbents (typically O and water) on the graphene surface. This very simple method of improving the electronic properties of CVD graphene by passivating its surface with common solvent molecules will accelerate the development of CVD graphene-based devices.
化学气相沉积（CVD）是一种生产用于大规模应用的石墨烯的强大技术。聚合物辅助的湿法转移通常用于将石墨烯转移到硅衬底上，但得到的器件往往表现出 p 型掺杂，这降低了器件的质量和重现性。为了更好地理解这种效应的起源，我们用 n-甲基-2-吡咯烷酮（NMP）和六甲基二硅氮烷（HMDS）分子涂覆石墨烯，这些分子对石墨烯的电荷转移可以忽略不计，但与石墨烯的结合强度比环境吸附剂强。通过拉曼光谱、X 射线光电子能谱（XPS）、电输运测量和量子力学计算机模拟，我们表明这些分子有助于去除 p 型掺杂，并且我们的数据表明，这些分子通过取代石墨烯表面的环境吸附剂（通常是 O 和水）来实现这一点。通过用常见的溶剂分子对 CVD 石墨烯的表面进行钝化来改善其电子性质的这种非常简单的方法将加速基于 CVD 石墨烯的器件的发展。
