Atomistic study of electrostatics and carrier transport properties of CNT@MS2 (M = Mo, W) and CNT@BN core–shell nanotubes

Abstract

In this work we present an ab-initio study of electronic properties of 1 dimensional (1D) core-shell nanostructures made of MS2 (MoS2, WS2) or BN armchair nanotube encapsulated carbon nanotubes (CNT). With local density approximation (LDA) in density functional theory (DFT) we calculate the bandstructure, carrier effective masses, various fundamental electrostatic features and optical absorption in such core-shell tubes. The carrier transport in these structures are important for nanoelectronics applications and are studied with the Greens function formalism. Simulations show a moderate indirect band gap in the core-shell CNT@MS2 tubes while the CNT@BN shows metallic nature. The varying chirality of CNT strongly affects the carrier effective masses of the CNT@MS2 structure. Electron density is found to be much more localized near the atom cores and stronger in magnitude for the CNT@BN while the W atoms show a more prominent electron-gas presence around them than Mo atoms as found in the electron localization functions. In the CNT@MS2 systems the electrostatic difference potential indicates a drive to transfer charge from the metal to the S atoms in the shell. In terms of optical absorption a strong and sharper peak is observed around 6 eV for the CNT@BN compared to a more broad absorption spectra of the CNT@MS2. Metallic transmission spectra is seen for CNT@BN while CNT@MS2 shows non-metallic transport but with a larger number of transmission states near fermi level. The electronic and optical properties and its possible tuning in the core-shell structures can be useful in various applications such as shielded interconnects, logic switches and optoelectronics.