Temperature dependent Raman scattering of directly grown twisted bilayer graphene film using LPCVD method

Abstract

To get insight into the thermal management of twisted bilayer graphene based devices, the interpretation of temperature variation on twisting properties becomes crucial. In this aspect, we report the temperature dependent Raman scattering of twisted bilayer graphene (tBLG) on the Si substrate having SiO2 thickness 300 nm. The tBLG samples have been directly grown on the copper foil substrate using a home-built low pressure chemical vapor deposition (LPCVD) setup. The temperature dependent Raman scattering has been studied on two samples of tBLG named as tB1 and tB2. The twisting nature of bilayer graphene film has been analyzed using R, G, and 2D peak characteristics in Raman spectra. The Raman mapping with respect to different peak parameters of G and 2D peak (intensity, width, and position), intensity ratio (I2D/IG) has been employed to probe the uniformity of tBLG film. In tB1, the R peak has been found at 1395.82 cm−1 and not observed in sample tB2 at room temperature. The temperature dependence of G and 2D peak frequency in Raman spectra has been investigated in the temperature range from 80 to 450 K. In tB1 and tB2, the temperature coefficient of G peak has been found to be - (0.97 ± 0.34) × 10−2 cm−1/K, and - (1.08 ± 0.15) × 10−2 cm−1/K, respectively. Further, the extracted value of temperature coefficient of 2D peak in tB1, and tB2 are - (2.92 ± 0.80) × 10−2 cm−1/K, and - (3.01 ± 0.29) × 10−2 cm−1/K respectively. Additionally, the twist angle has been estimated as ∼23°-27° for T ≤ 300 K and 3°-8° for T > 300 K in tB1. In tB2, it has been found to be ∼13°-16° for the temperature range of 80–200 K and 5°-9° for 250–450 K. These findings shed light on the twisting behavior of bilayer graphene film and its anharmonic properties.