Engineering electronic structure of a fullerene C20 bowl with germanium impurities

Fullerene C20 represents one of the most active classes of nanostructures, and it has been used as an active material for important applications. In this study, we have carried out first principles calculations of the structural and electronic properties of a germanium-doped fullerenes C20 bowl using density functional theory (DFT) at the B3LYP/3-21G level through the Gaussian 09W program packages. The doping effect has been investigated by varying the number of Ge dopants and by considering many doping positions for the same number. By Ge doping, N-type doping is induced in the fullerene C20 bowl. While the planar structure of the fullerene C20 bowl remains unaffected by Ge doping, and the electronic properties change from those of a semiconductor to a conductor with an increasing number of dopants. The electronic properties include the optimized structures, density of states (DOS) analysis, total energies, dipole moment, HOMO energies, Fermi level energies, LUMO energies, energy gaps, and work functions. It has been noted that isomers molded by choosing different doping positions differ significantly in the bond length, band gap and stability introduced. The band gap is found to be at a maximum when the Ge dopants are placed in the same ring points of the fullerene, due to the combined influence of symmetry breaking of the ring, and the band gaps are closed when Ge dopants are placed in opposite positions. These interesting results provide for the possibility of designing the band gap of a fullerene C20 bowl as required, and for its application in nanoelectronic and solar cell devices.