Electron transport in core-shell type fullerene nanojunction

Within the framework of the density functional theory combined with the method of non-equilibrium Green's functions (DFT + NEGF), the features of electron transport in fullerene nanojunctions, which are "core-shell" nanoobjects made of a combination of fullerenes of different diameters C20, C80, C180, placed between gold electrodes (in a nanogap), are studied. Their transmission spectra, the density of state, current-voltage characteristics and differential conductivity are determined. It was shown that in the energy range of -0.45–0.45 eV in the transmission spectrum of the "Au–C180–Au" nanojunction appears a HOMO–LUMO gap with a width of 0.9 eV; when small-sized fullerenes C20, C80 are intercalation into the cavity C180 the gap disappears, and a series of resonant structures are observed on their spectra. It has been established that distinct Coulomb steps appear on the current-voltage characteristics of the "Au–C180–Au" nanojunction, but on the current-voltage characteristics "Au–C80@C180–Au", "Au–(C20@C80)@C180–Au" these step structures are blurred due to a decrease in Coulomb energy. An increase in the number of Coulomb features on the dI/dV spectra of core-shell fullerene nanojunctions was revealed in comparison with nanojunctions based on fullerene C60, which makes it possible to create high-speed single-electron devices on their basis. Models of single–electron transistors (SET) based on fullerene nanojunctions "Au–C180–Au", "Au–C80@C180–Au" and "Au–(C20@C80)@C180-Au" are considered. Their charge stability diagrams are analyzed and it is shown that SET based on C80@C180, (C20@C80)@C180 nanojunctions is output from the Coulomb blockade mode with the lowest drain-to-source voltage.