Investigation of electronic transport properties of monolayer graphene by Monte Carlo method

Graphene, synthesized for the first time in 2004, consists of a single layer of car- bon atoms arranged in a honeycomb lattice. In monolayer graphene, near the so called Dirac points in the reciprocal space the electron energy linearly depends on wave vec- tor for low values of electron energy. Because of this, the effective mass of electrons is zero and moreover no forbidden energy gap exists. Because of linear energy dispersion relation, the motion of electrons in graphene is governed by Dirac equation where the particles mimic relativistic particles moving with Fermi velocity (≈ c/300) with zero rest mass. In this thesis, the electronic transport properties of monolayer graphene is inves- tigated in detail by using an ensemble Monte Carlo (EMC) method. For this purpose, the scattering rates due to acoustic, non-polar optic, surface polar optic, ionized impu- rity and interface roughness mecahnisms are taken into account. For the ionized impurity and surface polar phonon scattering cases, the effect of screening is also considered. The velocity-time curves under an applied field are obtained, and for specific material and ap- plied field values overshoot and undershoot effects are observed. Furthermore, velocity- applied field curves are obtained, and for the case of intrinsic graphene, negative differ- ential phenomenon is observed for specific material parameters. This effect decreased with the increase of acoustic phonon scattering rates and disappeared completely. Both interface roughness and impurity scattering decreases the mobility of electrons consider- ably. The mobility values are calculated both from conductivity and EMC calculations. The dependence of mobility on temperature is found and it is observed that it decreases with temperature monotonically. The dependence of mobility on electron concentration is also investigated. The dependence on electron concentration basicly comes from the depencence of Fermi energy on electron concentration. Key Words: Monolayer graphene, Monte Carlo, Scattering, Drift velocity, Mobility.