Abstract The work function of graphene is known to be tuned by gate voltage on SiO2 substrates. For a graphene field-effect transistor (FET), chemical species such as oxygen and water molecules induce electrostatic interactions between the graphene and SiO2 substrate, and consequently, the conductance of graphene can be shifted with respect to the applied field effect. Furthermore, these shifts cause an inevitable hysteresis in the I–V characteristics of the graphene device, which degrades its performance. Herein, we study the work-function of graphene devices on SiO2 substrates with chemical vapor deposition-grown graphene using Kelvin probe force microscopy and report the gate voltage-dependent work-function hysteresis, which is analogous to the hysteresis in the electronic transport of graphene FETs. The degree of work-function hysteresis is inhomogeneous depending on the positions on the graphene, and it originates from the inhomogeneous distribution of the chemical species such as H2O and O2 molecules at the interface of a graphene/SiO2 substrate. This inhomogeneity of chemical species seems to be moderated by the gate voltage sweeping during the gate-voltage-dependent work-function measurements. The proposed study provides an advanced understanding of hysteresis phenomena in graphene devices and the guidance for developing controlled graphene devices with minimal influence from ambient conditions.

中文翻译：

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化学气相沉积生长的石墨烯场效应器件中的非均匀功函数滞后

摘要 石墨烯的功函数可以通过 SiO2 衬底上的栅极电压来调节。对于石墨烯场效应晶体管 (FET)，氧和水分子等化学物质会在石墨烯和 SiO2 衬底之间引起静电相互作用，因此，石墨烯的电导可以相对于施加的场效应而发生变化。此外，这些变化会导致石墨烯器件的 I-V 特性不可避免地出现滞后，从而降低其性能。在此，我们使用开尔文探针力显微镜研究了具有化学气相沉积生长的石墨烯的 SiO2 衬底上石墨烯器件的功函数，并报告了与栅极电压相关的功函数滞后，这类似于石墨烯电子传输中的滞后场效应管。功函数滞后的程度是不均匀的，取决于石墨烯上的位置，它源于石墨烯/SiO2 衬底界面处化学物质（如 H2O 和 O2 分子）的不均匀分布。在栅极电压相关功函数测量期间，这种化学物质的不均匀性似乎被栅极电压扫描所缓和。拟议的研究提供了对石墨烯器件中滞后现象的高级理解，并为开发受环境条件影响最小的受控石墨烯器件提供了指导。在栅极电压相关功函数测量期间，这种化学物质的不均匀性似乎被栅极电压扫描所缓和。拟议的研究提供了对石墨烯器件中滞后现象的高级理解，并为开发受环境条件影响最小的受控石墨烯器件提供了指导。在栅极电压相关功函数测量期间，这种化学物质的不均匀性似乎被栅极电压扫描所缓和。拟议的研究提供了对石墨烯器件中滞后现象的高级理解，并为开发受环境条件影响最小的受控石墨烯器件提供了指导。