Study On Electronic Transport Properties Of Monolayer Hexagonal Boron And Carbon-Based Nanostructures

Recent years,with the development of science and technology,and the deepening understanding of nanomaterials,a series of nanostructures,such as graphene,nanowires and nanotubes,have been discovered,and nanoelectronic device models suitable for various functional applications have been proposed and constructed.Among all kinds of nanomaterials,carbon-based nanostructures,especially graphene,are the most prominent,showing prospective structural and electronic properties,which are suitable for the construction of new nano-electronic devices.At the same time,one has not stopped exploring and studying the non-carbon-based nanostructures,such as single-layer hexagonal boron nitride with graphene-like honeycomb configuration,showing peculiar electronic properties.Moreover,recently,researchers have realized the fabrication of controllable defects in the single-layer hexagonal boron nitride structure,which provides an effective way for the regulation of electronic properties and provides a basis for the construction of new nanoelectronic devices.Based on density functional theory and non-equilibrium Green's function,the electronic structures and transport properties of several typical single-layer boron and carbon-based nanostructures are studied.The physical mechanism behind the phenomena is studied,and the relevant regulatory mechanisms are revealed.The main contents of this paper are as follows.Firstly,the electron transport properties of hexagonal boron nitride nanoribbons are studied,and single-layer hexagonal boron nitride nanoribbons with edge defects are constructed.It is found that the system exhibits double spin filtering effect,and the spin polarization direction can be controlled by the defect location.The analysis shows that the separation of the transmission eigenchannels with opposite spins in space is the mechanism of this effect,and the effect is robust to nanoribbons'width and defects'length.Secondly,the spin transport properties of SiC₇ nanoribbons are studied.It is found that the transmission spectra of SiC₇ nanoribbons exhibit three different states,i.e.,spin unpolarized,fully polarized and partially polarized?-33%?ones at the Fermi level,determined by both the position of the outermost silicon atoms in the nanoribbons and the combinations of the two edges'morphologies.For the latter two states,they are robust to the width of the nanoribbon,suitable for the application of practical devices.Through further analysis on the energy band,the transmission spectra can be understood.Finally,the electronic transport properties of hexagonal borophene nanoribbons are studied.It is found that both zigzag and armchair borophene nanoribbons exhibit metallic properties.With the increase of the nanoribbon's width,the transmission coefficient of the former one increases in an integer step at the Fermi level,and does not vary with the change of symmetry,while the latter one shows an odd-even effect in the symmetric configuration.Further analysis shows that this is due to the change in the number of bands passing through the Fermi level caused by the increase of the nanoribbon's width.