The unique characteristics of graphene make it an optimal material for crucial studies; likewise, its potential applications are numerous. Graphene’s characteristics change with the number of total layers, and thus the rapid and accurate estimation of the number of graphene layers is essential. In this work, we review the methods till date used to identify the number of layers but they incorporate certain drawbacks and limitations. To overcome the limitations, a combination of these methods will provide a direct approach to identify the number of layers. Here we correlate the data obtained from Raman spectroscopy, optical microscopy images, and atomic force microscopy to identify the number of graphene layers. Among these methods, correlation of optical microscopy images with Raman spectroscopy data is proposed as a more direct approach to reliably determine the number of graphene layers.

• Rakesh Sadanand Sharbidre(Department of Material Science Engineering, Paichai University Division of Industrial Metrology, Korea Research Institute of Standards and Science)
• Chang Jun Lee(Division of Industrial Metrology, Korea Research Institute of Standards and Science School of Mechanical Engineering, Chonnam National University)
• Seong-Gu Hong(Division of Industrial Metrology, Korea Research Institute of Standards and Science)
• Jae-Kyung Ryu(Department of Dental Technology and Science)
• Taik Nam Kim(Department of Material Science Engineering, Paichai University) Corresponding author