Determining the number of layers in graphene films synthesized by filtered cathodic vacuum arc technique

ABSTRACT

We have synthesized graphene film by the filtered cathodic vacuum arc (FCVA) technique and determined the number of layers in graphene films by various techniques. Amorphous carbon (a-C) films of different thicknesses (1, 2, 3, 6, 10 and 18 nm) were synthesized by the FCVA technique on Si/SiO₂/Ni substrate and then annealed in vacuum at 800°C and cooled down to room temperature naturally to obtain graphene. Prepared graphene films were transferred on different substrates and characterized by the Raman spectroscopy, UV-VIS-NIR spectroscopy, high-resolution transmission electron microscopy (HRTEM), optical microscopy, atomic force microscopy (AFM) and sheet resistance to determine the number of layers present in the graphene films. Raman spectra of the prepared graphene films exhibit that there is red shift in the position of D, G and 2 D peak. The value of I_2D/I_G varied from 0.18 to 0.51, I_D/I_G varied from 0.82 to 1.02 and full width at half maximum of 2 D peak varied from 101.2 to 128.0 cm⁻¹, for different thicknesses of graphene films, respectively. The value of transmittance decreases from 97 to 63.7% and that of sheet resistance increases from 460 to 1400 Ω/square with the increase in the thickness of the prepared graphene film. The HRTEM and AFM study revealed that the graphene synthesis from 1 nm thick a-C film possesses a single layer structure.

KEYWORDS:

• Number of layers
• Graphene
• Filtered cathodic vacuum arc
• Raman
• Transmittance
• HRTEM

Acknowledgments

The authors are grateful to the Director, CSIR-National Physical Laboratory, New Delhi (India), for his kind permission to publish this paper. They wish to thank Dr. Kamal Jeet and Dr. Anil Kumar of CSIR-CEERI, Pilani for growing SiO₂ layer on Si wafer and Mr. Sandeep Singh for providing the AFM image. Mr. A. K. Kesarwani and Mr. Atul Bisht are grateful to the Council of Scientific Industrial Research (CSIR) and the University Grant Commission (UGC), Government of India, New Delhi, respectively, for the financial assistance during the course of this work. Mr. Ashish Kumar is grateful to the Science Engineering Research Board (SERB), the Ministry of Science and Technology, Government of India for the financial assistance during the course of this work.