Electronic And Transport Properties Of CNT And BNNT Nanopeapods Embedded With Fe_n（Cp）_n+1 And C₆₀-V

With the rapid development of micro-electronics and continuous minimizationof electronic devices, using single molecule or molecular cluster, such as singleorganic molecule, single-or multiple-walled carbon nanotubes, some biomoleculesand so on, to construct functional electronic devices has become one recognizeddeveloping trend. As new techniques for the atomic-scale manipulation andmodification of materials progressed, electron transport properties of nanostructureshave attracted considerable interest. We investigate electronic and transportproperties of a novel form of nanopeapod structure, where the “pod” component iseither CNT or BNNT while the “pea” component is a chain of Fen(Cp)n+1cluster orC60-V dimers.Characteristics of computed electric conductivities are qualitatively consistentwith the computed electronic structures of the corresponding infinite nanopeapodsystems. Because the transport channels can be changed by the applied bias voltage,however, the transport properties cannot be solely predicted from the electronicstructures of infinite systems alone. Encapsulating either Fe(Cp)2or Fe2(Cp)3intoCNT has little effect on the conductivity owing to the strong metallic character of theCNT sheath. Encapsulating Fe(Cp)2into BNNT can notably enhance electronconducting due to electron hopping from the core Fe(Cp)2to the sheath BNNT.However, encapsulating Fe2(Cp)3has little effect to the electron conducting of BNNTnanopeapods due to the trap effect of the longer guest molecules. Hence, the lengthof guest molecules can effectively tune electronic and transport properties of theBNNT nanopeapods.Compared to the conventional carbon peapod where the “pea” is a chain of C60fullerenes, marked changes in the electronic structures are found due to the formationof coordination bonds between V and two neighboring C60molecules. The local spinsin the (η6-C60-V)@CNT or (η6-C60-V)@BNNT peapod are coupled via AFMexchange interaction. In particular, the C60-V chain in BNNT yields a well-definedspin qubit. Density-functional theory calculation suggests that the (η6-C60-V)@CNT peapod is metallic with characteristics of multiple carriers contributed from CNT, C60,and V. The (η6-C60-V)@BNNT peapod is predicted to be semiconducting with anarrow band gap, and its charge carriers are contributed by the C60-Vchain. Evidently,the insertion of a V atom between every two C60fullerenescan enhance theconductivity of the peapod. Binding H atoms on the all α positions of the pentagonsin C60can further strengthen the V-C60interaction. Both AFM and FM states of theH-containing peapod are nearly degenerate in energy. The FM state gives rise to amagnetic moment of3.0μBper unit cell, three times greater than that of the V-C6H6or V-C5H5multidecker complexes. The binding of H atoms to the C60howevercannot enhance electron transport due to the removal of the π channel of C60.