Study on temperature-dependent carrier transport for bilayer graphene

Abstract

In order to investigate the temperature-dependent carrier transport property of the bilayer graphene, graphene films were synthesized on Cu foils by a home-built chemical vapor deposition (CVD) with C2H2. Samples regularity, transmittance (T) and layer number were analyzed by transmission electron microscope (TEM) images, transmittance spectra and Raman spectra. Van Der Pauw method was used for resistivity measurements and Hall measurements at different temperatures. The results indicated that the sheet resistance (Rs), carrier density (n), and mobility (μ) were 1096.20Ω/sq, 0.75×1012cm−2, and 7579.66cm2V−1s−1 at room temperature, respectively. When the temperature increased from 0°C to 240°C, carrier density (n) increased from 0.66×1012cm−2 to 1.55×1012cm−2, sheet resistance (Rs) decreased from 1215.55Ω/sq to 560.77Ω/sq, and mobility (μ) oscillated around a constant value 7773.99cm2V−1s−1. The decrease of the sheet resistance (Rs) indicated that the conductive capability of the bilayer graphene film increased with the temperature. The significant cause of the increase of carrier density (n) was the thermal activation of carriers from defects and unconscious doping states. Because the main influence on the carrier mobility (μ) was the lattice defect scattering and a small amount of impurity scattering, the carrier mobility (μ) was temperature-independent for the bilayer graphene.