As the importance of material surfaces and interfaces for industrial applications is ever increasing, a need for accurate measurement of their properties and functionalities with traceability and reproducibility through unbroken chain of measurements and their reference materials for proficiency testing has become very important. Carbon and its allotropes have several industrial applications and recently graphene which is a two dimensional layered material of carbon has proven to have great potential, and its characterization for layer number has become very important. A need for quantitative measurement apart from existing qualitative techniques is very much required for accurate determination of layer number. Under the aegis of Versailles Project on Advanced Materials and Standards (VAMAS), technical working area (TWA-2) an international round robin test is conducted among 13 laboratories for establishing a protocol for accurate measurement of graphene layer number and generating reference material. CSIR-NPL being NMI of India participated and contributed to the project which got recognition from VAMAS for its participation. Scanning Kelvin Probe Force Microscopy (SKPFM) of graphene layers on Au/SiO₂/Si and SiO₂/Si substrates is performed and their CPD data is compared. Graphene on Au/SiO₂/Si has shown consistent CPD data for different modulation voltages with least uncertainty. From the comparative analysis it is found that SKPFM has potential to be an international standard technique to determine graphene layer number and can generate certified reference material.

中文翻译：

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使用扫描开尔文探针力显微镜表征石墨烯层​​数

随着材料表面和界面在工业应用中的重要性不断提高，通过不间断的测量链及其参考材料进行准确度测试以精确地测量其特性和功能以及可追溯性和可重复性的需求变得非常重要。碳及其同素异形体在工业上有许多应用，最近，作为碳的二维层状材料的石墨烯已被证明具有巨大的潜力，并且其层数的表征变得非常重要。为了精确确定层数，非常需要除现有定性技术外的定量测量。在凡尔赛先进材料和标准项目（VAMAS）的主持下，技术工作区域（TWA-2）在13个实验室中进行了国际循环测试，以建立准确测量石墨烯层数并生成参考材料的协议。作为印度NMI的CSIR-NPL参与了该项目，并为该项目做出了贡献，得到了VAMAS的认可。Au / SiO上石墨烯层的扫描开尔文探针力显微镜（SKPFM）_进行2 / Si和SiO ₂ / Si基板，并比较其CPD数据。Au / SiO ₂ / Si上的石墨烯对于不同的调制电压显示出一致的CPD数据，不确定性最小。从比较分析中发现，SKPFM有可能成为确定石墨烯层数的国际标准技术，并且可以生成经过认证的参考材料。