Electronic and transport properties of carbon structures

Abstract

The electronic structure is determined for different carbon structures like carbon six chain, infinite graphene sheet, and different nanotubes. Electron transport properties of bare metallic carbon nanotubes (CNT) and a CNT with a single Barium atom are studied using the software Virtual NanoLab (VNL) and Atomistix ToolKit (ATK). The software combines advanced numerical methods, such as non-equilibrium Green's functions (NEGF) and density functional theory (DFT), to describe the detailed electronic structure of these carbon structures. Advanced numerical algorithms enable the application of a bias voltage across the structure, as well as the calculation and analysis of current-voltage characteristics of two-probe nanotubes.NanoLanguage scripts are written to generate and calculate the current for a two-probe bare CNT and a CNT with a single Barium atom. The currents thus obtained for different voltages are imported into Poly Software International (PSI) Plot spreadsheet and the current-voltage curves are plotted and compared for both the CNTs. The data is further analyzed and differential conductance is calculated and plotted for comparison. The current-voltage (IV) curves exhibit linearity for low voltages. Above a critical voltage, the IV curves flatten and exhibit features where sharp changes occur in the differential conductance. Adding a single Barium atom dramatically affects the conductance of the carbon nanotubes.