Magnetic property of porous black phosphorene layer

Arqum Hashmi,M. Umar Farooq Umar,Jisang Hong 한국자기학회 2016 한국자기학회 학술연구발표회 논문개요집 Vol.2016 No.05

Band gap and effective mass of multilayer BN/graphene/BN: van der Waals density functional approach

Hashmi, Arqum,Hong, Jisang American Institute of Physics 2014 Journal of Applied Physics Vol.115 No.19

Using the van der Waals density functional theory method (DFT-D2), we have investigated thickness dependent energy band gaps and effective masses of multilayer BN/graphene/BN structures by changing the stacking order. The band gap is substantially dependent on the stacking order. For instance, the calculated band gap in ABA stacking is about 150 meV, whereas it becomes 31 meV in ABC stacking. No significant thickness dependent band gap is observed in both ABA and ABC stackings although the band gap is gradually increasing with the BN thickness in ABA stacking. In addition, the effective mass is found to be strongly dependent on the stacking order. The effective mass in ABA stacking is much larger than that found in ABC stacking. On the other hand, the effective mass along K-M direction is smaller than that along K-Gamma direction in ABA stacking. However, it is independent on the band direction in ABC stacking. We have found that the inclusion of van der Waals interaction alters thickness dependent band gap and effective mass of BN/graphene/BN multilayer systems compared with those found with standard density functional theory. (C) 2014 AIP Publishing LLC.

Spin-Dependent Transport and Optical Properties of Transparent Half-Metallic g-C₄N₃ Films

Hashmi, Arqum,Farooq, M. Umar,Hu, Tao,Hong, Jisang American Chemical Society 2015 The Journal of Physical Chemistry Part C Vol.119 No.4

<P>Half-metallic materials play an essential role in the spin-dependent transport study, and so far it is believed that the 3d transitional metal elements are necessary to obtain a ferromagnetic state. Herein, we demonstrate that the metal free two-dimensional graphitic carbon nitride (g-C<SUB>4</SUB>N<SUB>3</SUB>) film show half metallic state and this is independent of the film thickness and stacking order. We find that the half-metallicity results in a very large magnetoresistance even at finite bias. Moreover, we have also investigated various optical properties. The g-C<SUB>4</SUB>N<SUB>3</SUB> thin films have a very high refractive index for parallel polarization and extremely weak reflectivity for perpendicular polarization. Additionally, the g-C<SUB>4</SUB>N<SUB>3</SUB> thin films are optically transparent because of very weak absorption coefficients. Overall, our findings suggest that the transparent half-metallic g-C<SUB>4</SUB>N<SUB>3</SUB> thin films can be used for both spintronics and optical applications because of potential multifunctionality.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/jpccck/2015/jpccck.2015.119.issue-4/jp510179p/production/images/medium/jp-2014-10179p_0007.gif'></P>

Transition Metal Doped Phosphorene: First-Principles Study

Hashmi, Arqum,Hong, Jisang American Chemical Society 2015 The Journal of Physical Chemistry Part C Vol.119 No.17

<P>Recently, a newly fabricated two-dimensional layer structured material so-called phosphorene is receiving great research interests due to its peculiar physical properties. So far, mostly electrical properties are explored because it has a direct band gap and its nonmagnetic behavior in pristine layer. In this report, we propose that the transition metal doped phosphorene layer can have dilute magnetic semiconductor properties. Here, we investigated the structural property, binding energy, and magnetic property by changing the TM impurity dopants in the substitutional site. Our results demonstrate that spin polarized semiconducting state is realized in phosphorene by substitutional doping of Ti, Cr, and Mn, while a half-metallic state is obtained by V and Fe doping. In particular, we suggest that the most promising dopants are Cr and Mn because the spin polarized state is achieved with a band gap larger than 0.5 eV. The magnetic interaction between two same types of TM atoms is also checked. Magnetic ground state was obtained with GGA and GGA+U approaches are quite consistent, except for Mn- and Fe-doped systems. These findings indicate that the TM-doped phosphorene can be used as a potential next-generation spintronics material.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/jpccck/2015/jpccck.2015.119.issue-17/jp511574n/production/images/medium/jp-2014-11574n_0007.gif'></P>

Metallic Behavior and Enhanced Adsorption Energy of Graphene on BN Layer Induced by Cu(111) Substrate

Arqum Hashmi,Jisang Hong 한국물리학회 2014 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.64 No.6

We have investigated the adsorption properties and the electronic structure of graphene/BN andgraphene/BN/Cu(111) systems by using van der Waals density functional theory. The ground-stateadsorption site of graphene on BN/Cu(111) is found to be the same as that of graphene/BN. TheCu(111) substrate did not induce a significant change in the geometrical feature of graphene/BN. However, the adsorption energy of graphene on BN/Cu(111) is observed to be enhanced due to theCu(111) substrate. In addition, we have found that the graphene layer displays a weak metalliccharacter in graphene/BN/Cu(111) whereas an energy band gap is observed in the graphene in thegraphene/BN bilayer system. Therefore, we have found that the metallic Cu(111) substrate affectsthe electronic structure and adsorption properties of graphene on BN/Cu(111), although it has nosignificant effect on the geometrical features

Magnetic Properties of graphene/BN/Co

Arqum Hashmi,Jisang Hong 한국자기학회 2013 한국자기학회 학술연구발표회 논문개요집 Vol.2013 No.5

Half metallic g-C₄N₃ on BN layer

Hashmi Arqum,Jicheol Son,Jisang Hong 한국자기학회 2014 한국자기학회 학술연구발표회 논문개요집 Vol.2014 No.5

First-principles Study of Bilayer Graphene on BN/Co(111): van der Waals Density Functional Approach

Arqum Hashmi,홍지상 한국물리학회 2014 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.64 No.9

We have investigated the magnetic property of bilayer graphene adsorbed on BN/Co(111) byusing the van der Waals density functional method. We found that the BN layer adjacent tothe Co(111) substrate showed a buckling geometry while the BN layer next to the graphenelayer became flat. According to previous results, a one-monolayer (ML) thickness of grapheneon BN/Co(111) displayed a spin polarized state, but we observed that the half metallic state disappearedin bilayer graphene on BN/Co(111) while Co(111) was still half metallic as found ingraphene(1ML)/BN/Co(111). We found that the surface graphene layer had a gap whereas thefirst interface graphene on BN/Co(111) showed an ordinary metallic state. Thus, we realized thatthe electronic structure of bilayer graphene grown on BN/Co(111) had been significantly alteredcompared with that of graphene(1ML)/BN/Co(111) system.

Graphene/phosphorene bilayer: High electron speed, optical property and semiconductor-metal transition with electric field

Arqum Hashmi,Umar Farooq,Jisang Hong 한국물리학회 2016 Current Applied Physics Vol.16 No.3

We investigated the electric field dependent band structures and optical properties of graphene/phosphorene bilayer. Remarkably, the effective electron Fermi velocity in graphene/phosphorene was comparable to that of pure graphene monolayer. Moreover, this feature was not disrupted even in the presence of a finite external electric field. The electronic band structure changed from a semiconductor to a metallic state with an external electric field strength of 0.5 V/Å. In addition, the electric field enhanced the structural stability of a bilayer system because the binding energy was increased approximately 20 e30% as compared with that at zero electric field. We found that the optical anisotropy regarding the electric polarization along armchair and zigzag directions disappeared, but the anisotropic optical properties still survived regarding the electric polarization for in-plane and perpendicular directions. The small effective mass, high speed of electrons, and optical property in graphene/phosphorene bilayer may provide a promising way for graphene based device applications.

Two-dimensional honeycomb hafnene monolayer: stability and magnetism by structural transition

Hashmi, Arqum,Umar Farooq, M.,Khan, Imran,Hong, Jisang Royal Society of Chemistry 2017 Nanoscale Vol.9 No.28

<P>A few years ago, it was claimed that the two-dimensional ferromagnetic planar Hf monolayer could be synthesized on Ir(111). However, several questions remained unanswered. Herein, we unravel the structural stability of the HF monolayer and its influence on magnetism using first principles calculations. Despite the ferromagnetic state in the planar free-standing Hf layer, extensive systematic calculations with phonon spectra reveal that the planar free-standing Hf layer is unstable and it has a non-magnetic high-buckled structure in the ground state. We also find a structural transition from buckled to flat honeycomb geometry on the Ir(111) substrate. Nonetheless, 2D hafnene has no magnetic state due to strong hybridization with the Ir(111) surface. The evolution from the non-magnetic to the ferromagnetic state combined with structural transition is observed by adding BN as a spacer layer on the Ir(111) substrate (BN/Ir(111)). In addition, we find that 2D Hf on BN/Ir(111) has a giant perpendicular magnetic anisotropy of 3.41 meV.</P>