First-principles characterization and functionalization of graphene-like materials
29 April 2015
UAntwerp - Campus Groenenborger - Room U0.25 - Groenenborgerlaan 171 - 2020 Antwerp
Organization / co-organization:
Department of Physics
Prof. dr. Bart Partoens, Hasan Sahin
PhD defence Jozef Sivek - Faculty of Science, Department of Physics
The aim of this thesis is to explore, using first-principles calculations, the characteristics of chemically decorated graphene and other graphene-like quasi two dimensional materials including silicene and molybdenum disulfide. The body of the results starts with the investigation of the electronic properties of bilayer fluorographene following the previous works on bilayer graphane.
Fully fluorinated bilayer graphene, with a strength comparable with the elastic strength of graphene, shows an increased electronic bang gap over the one of graphane and monolayer fluorographene. Next the patterning of pristine graphene with titanium and its oxide, is discussed. Strong n-type doping of Ti covered graphene is proven by the calculation of changes to the work functions and electronic structure. In addition, titanium dioxide is found to induce lower and structure dependent charge doping.
Afterwards two chapters present results covering patterned silicene, a monolayer of silicon, its surface reactivity, characteristic changes in vibrational properties and the influence of the Stone-Wales defects on its chemical and electronic properties. The focus is on the atom adsorption and absorption with B, N, Al and P atoms on the functionalizable silicene surface. The formation of SW defects in free standing as well as in supported silicene is found to be easier compared to the graphitic surfaces and it reduces the number of favourable doping sites.
The work culminates in the final part where a directed decoration of fluorographene and molybdenum disulfide is used to engineer the magnetocrystalline anisotropy properties. The transition metal atoms W, Os, Ir, Pt, Ru, Rh and Co adsorbed in single fluorine (sulfur) vacancy form stable structures and induce giant magnetocrystalline anisotropy energies with an clear link between the easy magnetization axis and the orbital character of the electronic band states around the Fermi level.