Theoretical Study On The Physical Properties Of SiC/C Nanotube Heterojunctions

Recently, one-dimensional nano-materials have received much attention due totheir unique structures and properties, as well as their value in science. Theirinteresting electronic, optical, magnetic properties make them have widespreadapplication in many aspects, such as nanoelectronics, optoelectronics, plasma,medical diagnosis, separation, catalysis, drug delivery and therapy, and chemicalsensing. The one-dimensional nanotube heterojunction, formed by joining two kindsof nanotubes in its axial direction, has unique properties, and can realize the functions,which are not realized in single-component structures. Therefore, one-dimensionalnanotube heterojunctions have potential applications. In this paper, the physicalproperties of the SiC/C nanotube (NT) heterojunction are studied by using densityfunctional theory with pseudopotential plane wave method, combining with thegeneralized gradient approximation. The main contents are as following:1. The zigzag (n,0)(n=6-10) SiC/C nanotube superlattices (NSLs) areinvestigated. The (n,0)(n=7-10) SiC/C nanotube superlattices are semiconductingand nonspin-polarized. However, the (6,0) SiC/C nanotube superlattice isspin-polarized with2.0μB magnetic moments due to the curvature effect. The spindensities distribute periodically along the axial direction and mainly locate at the CNTsegment, thus forming the magnetic nanonodes.2. The mechanical and electronic properties of the heterojunction formed by (4,4)CNT and (4,4) SiCNT have been studied. It is found that the Young’s modulus of theheterojunction is mainly determined by that of SiCNT. The existence of interface doesnot lower the Young’s modulus of the heterojunction. The SiC/C nanotubeheterojunction is broken near the junction interface with applying a relative largeuniaxial strain along the axial direction, and then forming a SiC cage. Band structureshows that (4,4) SiC/C nanotube heterojunction is a semiconductor with direct bandgap. Both valence band maximum and conduction band minimum originate fromCNT segment. Furthermore, the effect of CNT and SiCNT length on the electronicstructures of the nanotube heterojunction is investigated. The Schottky barrier of thenano-tube heterojunction is also estimated.3. The adsorption of the magnetic atoms (Fe、Co、Ni) on the (4,4) SiC/Cnatotube heterojunction are studied. The results show that single magnetic atom tends to adsorb on the SiCNT segment. For the adsorption of two magnetic atoms, thesystem with two atoms being close to each other and locating on the SiCNT segmentis relatively stable. Moreover, the relationship between the electronic and magneticproperties of the (4,4) SiC/C nanotube heterojunction and the type, position and thenumber of magnetic atoms is studied.