Tuning the plasmon resonance and work function of laser-scribed chemically doped graphene

Here, we present terahertz spectroscopy study on laser scribed graphene (LSG) doped with monovalent Na+ cations (LSG/MNCs), silver nanoparticles (LSG/SNPs), and silver nanowires (LSG/SNWs), in the frequency range from 0.06 to 3 THz. The terahertz absorption peaks observed at ≈ 1.98, 2.06, 2.73, and 3.06 THz are attributed to the collective oscillations of free carriers in LSG, LSG/MNCs, LSG/SNPs, and LSG/SNWs, respectively. The plasmon peak position and Fermi energy Ef of LSG doped samples are shifted to higher energy compared to undoped LSG indicating the n-doping of graphene. The σdc and the charges concentration n show higher values in case of LSG/SNWs compared to other doped samples. This is mainly because silver nanowires create conducting paths between the neighboring graphene sheets. The charge density n of the LSG and LSG doped samples versus Ef, scales as n1/4, illustrates power-law behavior which is the signature of the two-dimensional massless Dirac electrons.