AbstractsPhysics

This thesis discusses deposition, self-assembly, polymerisation and covalent bonding of bromine functionalised molecules on Au(111), Ag(111), Cu(111) and Cu(110) metal substrates are investigated. The debromination and subsequent covalent bonding is found to depend heavily on the reactivity of the substrate, the molecular coverage and anneal temperatures. Characterisation was performed using scanning tunnelling microscopy (STM), x-ray photoelectron spectroscopy (XPS) and synchrotron based photoelectron spectroscopy (PES) as well as x-ray absorption spectroscopy (XAS). Deposition of hexabromotriphenylene (HBTP) on the Au(111), Ag(111) and Cu(111) surfaces resulted in the formation of disordered, covalently bonded nano-networks which remained stable up to a temperature of 300˚C. C-Br bonds of HBTP can cleave at room temperature (RT) on Ag and Cu due to the substrate reactivity allowing new covalent C-C bonds to form. In the case of Cu, disordered networks are observed at RT while in contrast, more ordered networks develop on the Ag and Au substrates after annealing to 150˚C and 200˚C respectively. On the Au(111) surface bromine desorption begins at 250˚C whereas on the Ag(111) and Cu(111) surfaces the atomic bromine remains on the surface and forms a (√3×√3)R30˚ structure. The formation of atomically precise graphene nanoribbons (GNR) from a 10,10’-dibromo-9,9’-bianthryl (DBBA) precursor molecule was investigated on the Au(111), Ag(111), Cu(111) and Cu(110) surfaces. After deposition, the DBBA molecules undergo two thermally induced chemical changes; (i) a debromination reaction to produce covalently bonded polymerised chains and (ii) a cyclodehydrogenation reaction at higher temperatures to form GNRs. The threshold for the debromination reaction, polymerisation and final cyclodehydrogenation reaction decreases proportionally with the reactivity of the substrate. Ni(II) 5,15-dibromo-10,20-diphenyl (DBrDPP) was studied on the Cu(110) surface to investigate its suitability for integration into GNRs. Thermally induced covalent bonding of DBrDPP was observed via a C-Cu-C organo-metallic bond while a Ni-Cu ion exchange reaction occurs in the porphyrin macrocycle. At higher anneal temperatures domains of graphene emerge which exhibit a moiré pattern with varying periodicities indicating a lattice mismatch between the graphene layer and the underlying copper substrate.