Hydrogen-modulated Spin Interference In Graphene

Graphene is a novel carbon material, whose lattice structure is composed ofa monolayer two-dimensional structure with carbon atoms arranged intohexagon. In recent years, by investigating, scientists have discovered graphenehas many special excellent performances as followings:1, Highercarrier-mobility rate at room temperature,2×105cm2/Vs, about100times of thatof silicon.2, Low resistivity, around10-8Ω cm, even lower than that of silver(1.65×10-8Ω cm).3, Superior mechanical performance.4, Very high thermalconductivity, reaching up to5300W/mK, about12times of that of silver (420W/mK). These excellent properties make graphene have very widelyapplications in many areas, including electronic components, sensors, capacitors,solar cells, etc. However, there are certain difficulties to prepare graphenewithout impurity and defect, which indicates there is a long distance to putgraphene into practical applications in large quantities. Hence, it is urgent tocontinue to optimize the preparation process of graphene for achieving andfurther broadening the applications of graphene.Graphene is a semiconductor without bandgap, but it can adsorb variouskinds of atoms (e.g hydrogen atoms, fluorine atoms, oxygen atoms). The interplay between carbon atoms and adatoms as well as external electronicintroduced by adatoms causes the splitting up of graphene’s bands and grapheneshould exhibit magnetism, which provides a route to employ graphene into thefield of spintronic devices. In this paper, based on density functional theory,through the process of “probe” hydrogen and “raster” hydrogen adsorbed ongraphene, we observe that spin density generates regular interference effects dueto its redistribution. The rule can be utilized in spin signal generators and spinmemories. The major conclusions are as follows.1. Spin interference in graphene modulated by hydrogen. Through theoptimision of graphene with “raster” hydrogen by CASTEP, we find that:(1) Graphene adsorbed by hydrogen grid oscillates in its spatial structure.Simultaneously, the band of graphene alters and the bandgap varies from zero to0.214eV. By analyzing the spin density, we can judge graphene exhibitsferromagnetic properties.(2) By adsorbing “probe” hydrogen in the vicinity of hydrogen grid, spindensity in graphene redistributes, moreover, spin interference patterns nearbyhydrogen grid are witnessed clearly. Meanwhile, the spin interference patternsindicate difference in case of “probe” hydrogen locating at four non-equivalentpositions of A1, A2, B1and B2relative to hydrogen grid.2. Based on density functional theory, we investigate the electrical transportproperties of graphene nanoribbons and graphene nanoribbons adsorbed byatoms via utilizing DFTB. One can conclude graphene nanoribbon absorbed by various atoms can lead to different transmission spectra and electron densities,which can contribute to distinguish the different atoms adsorbed.3. Ring opening by breaking the C-O bond in β-glucose: halogenbombardment. Based on the first principle molecular dynamics, our work reportsthe study of ring opening in β-glucose molecule resulting from bombardment ofhalogen atoms.