Effective low energy Hamiltonians and unconventional Landau level spectrum of monolayer C3_3N

We derive a low-energy effective $\mathbf{k}\cdot\mathbf{p}$ Hamiltonians for monolayer C$_{3}$N at the $\Gamma$ and $M$ points of the Brillouin zone where the band edge in the conduction and valence band can be found. Our analysis of the electronic band symmetries helps to better understand several results of recent ab-initio calculations[1,2] for the optical properties of this material. We also calculate the Landau level spectrum. We find that the Landau level spectrum in the degenerate conduction bands at the $\Gamma$ point acquires properties that are reminiscent of the corresponding results in bilayer graphene, but there are important differences as well. Moreover, because of the heavy effective mass, $n$-doped samples may host interesting electron-electron interaction effects.Comment: 10 pages, 5 figure

Comparing half-metallic, MOKE, and thermoelectric behavior of the CrTiZ (Z = As, P) half-Heuslers: a DFT study

Structural, half-metallic, magneto-optic, and thermoelectric properties of CrTiZ (Z = As, P) half-Heusleres compounds are investigated based on density functional theory. These compounds have mechanical stability in the ferromagnetic state with a high bulk modulus. They are often half-metallic with a large and integer magnetic moment and are very attractive in spintronics, magneto-optics applications. The magnetic moments of CrTiAs and CrTiP were 2.9865 mu (B) and 3.00 mu (B), respectively, which were attributed to their ferromagnetic phase. Additionally, the positive sign of the phonon branches indicates the dynamic stability of these compounds. Applying both GGA and mBJ approximations, CrTiAs and CrTiP compounds exhibited a half-metallic nature by 100% spin polarization. The Kerr angle obtained from magneto-optic results demonstrated a high-intense peak for these compounds in the visible edge with a negative sign. Eventually, a figure of merit with a value above the room temperature was found for both compounds in which the holes are charge carriers

Surface Effect on Electronic, Magnetic and Optical Properties of PtCoBi Half-Heusler: A DFT Study

The electronic, magnetic, and optical properties of PtCoBi half-Heusler compound [001] surfaces and its bulk state have been investigated in the framework of density functional theory using GGA approximation. The half-metallic behaviors of CoBiterm, CoPt-term and PtBi-term decrease with respect to its bulk state. The spin polarization at the Fermi level is 73.2% for the bulk state, and it is -64.4% and -64.1% for the CoBi-term and PtBi-term, respectively while less polarization has been observed for the CoPt-term. All terminations have given almost similar optical responses to light. Plasmon oscillations for the terminations occur in the range of 12.5 to 14.5 eV (21 to 22 eV) along xx (zz), and it occurs at 23 eV for the bulk state. The refractive index for the bulk and all three terminations is very high in the infrared and visible areas, meaning a very strong metallic trend in these compounds. The phenomenon of super-luminance occurs for the incident light with energy exceeding 5.5 eV for all three terminations, and it occurs in the range of 10 eV for the bulk mode. These terminations show transparent behavior after the energy of 10 eV

Ab-initio study of mechanical, half-metallic and optical properties of Mn2ZrX (X = Ge, Si) compounds

The structural, elastic, electronic, magnetic and optical properties of Mn2 based full-Heusler alloys, Mn2ZrGe and Mn2ZrSi, were investigated by the first-principles full-potential linearized augmented plane wave (FP-LAPW) method in the framework of the Density Functional Theory. The AlCu2Mn-type structure was considered for both compounds. Based on E-V calculation, the ferromagnetic (FM) state was more stable than paramagnetic (PM) state. So, in the FM state the equilibrium lattice parameter was calculated as 5.995 Å and 6.079 Å for Mn2ZrSi and Mn2ZrGe respectively. The integer value 2.000 µB is obtained for total magnetic moments of both compounds that is perfectly consistent with Slater-Pauling rule. These alloys in the minority spin channel have metallic property while in the majority spin channel, they have band gap that confirms their semiconductor properties. Elastic properties of the alloys such as bulk modulus B, shear modulus G, Young’s modulus E and Poisson's modulus ν were obtained. Also, optical properties like dielectric function, reflectivity, energy loss function, absorption coefficient and optical conductivity were calculated. Keywords: Mn2ZrGe, Mn2ZrSi, DFT, Half-metal, Minority-majority spi

Tuning the electronic and optical properties of Co2TiGe Heuslerene by selecting Ge- or Ti- termination structure

In this work, the Ge- and Ti-termination monolayers of Co2TiGe were investigated by density functional theory. The phonon dispersion curves of these monolayers revealed their dynamical stability. The calculated spin-resolved density of states and band structure of the monolayers confirmed the asymmetrical pattern of spin-up and spin-down showing the magnetic as well as the half-metallic characters of these monolayers. The calculated optical properties of the Ge- and Ti-termination monolayers of Co2TiGe by the Bethe-Salpeter equation showed the absorption of Ge-termination in the visible region of the electromagnetic spectrum which was extended to the UV region in the Ti-termination monolayer

Synthesis of multiwalled carbon nanotubes on Cu-Fe nano-catalyst substrate

Considering the importance of metal nano catalysts, this research tries to apply sputtered nanoparticles as catalyst for growing carbon nanotubes and studies the effect of metals in modifying the catalytic property. One and bilayer Cu and Fe thin films were placed inside a quartz tube reactor to synthesis carbon nanotubes using acetylene gas as carbon source and argon gas for cooling down the reactor from 850 °C to room temperature. By scanning electron microscope images distribution of diameter of multi walled carbon nanotubes has recorded. The amounts of ID/IG obtained from Raman spectroscopy analysis showed the best quality of carbon nanotubes for Cu-Fe bilayer. Both analyses indicate the improve of catalytic effect of one transition metal by another one. On the other hand, multi walled carbon nanotubes are confirmed by both Raman spectroscopy and transmission electron microscopy images. Keywords: Transition metal nano catalyst, TCVD, MWCNT, Raman spectroscop

The Vanadium effect on the electronic and optical properties of Ti3C2 graphene like: Based DFT

A first principles study of the electronic and optical properties of the Vanadium impurity on the Ti3C2 graphene like has been done in the framework of density functional theory to calculate the density of states, Bandstructure and optical coefficients spectra. Results inferred to the metallic behavior for Ti3C2:V graphene like. Adding the V impurity caused the energy loss has a red shift and the dielectric function show lower metallic behavior and the reflection index is shifted to one in the lower energy. Also, for the two cases we have anisotropy for the x and z direction. Keywords: Ti3C2:V graphene like, Electronic property, Optical property, DF

Vanadium impurity effects on optical properties of Ti3N2 mono-layer: An ab-initio study

The present work is investigated the effect of vanadium impurity on electronic and optical properties of Ti3N2 monolayer by using density function theory (DFT) implemented in Wien2k code. In order to study optical properties in two polarization directions of photons, namely E||x and E||z, dielectric function, absorption coefficient, optical conductivity, refraction index, extinction index, reflectivity, and energy loss function of Ti3N2 and Ti3N2-V monolayer have been evaluated within GGA (PBE) approximation. Although, Ti3N2 monolayer is a good infrared reflector and can be used as an infrared mirror, introducing V atom in the infrared area will decrease optical conductivity because optical conductivity of a pure form of a material is higher than its doped form. Keywords: Dielectric function, Optical conductivity, DFT, Ti3N2: V mono-laye

Surface micromorphology analysis of Cu/Ni nanocomposite thin films by power spectra density and fractal geometry

Copper (Cu) and nickel (Ni) nanoparticles have been grown simultaneously on glass and silicon substrates by RF sputtering method to form three Cu/Ni nanocomposites at different deposition times. The existence of Cu and Ni peaks in the X-ray diffraction (XRD) profiles confirms the crystalline structure of samples with Cu and Ni atomic content which have also been characterized by Rutherford backscattering (RBS) method. Moreover, the structural and morphological properties of the prepared nanocomposites have been compared with respect to their morphologies by means of atomic force microscopy (AFM) analysis. In order to compare the surface roughness over different spatial frequency ranges and evaluate surface quality, power spectral density (PSD) of each sample has been extracted from AFM data and also, the experimental and theoretical results have been compared. The fractal nature of these nanocomposites has been finally discussed

The Ru Impurity Effect on Electronic, Optical and Thermoelectric Properties of MoS2 Nano-Sheet: a DFT Study

The electronic, optical and thermoelectric properties of MoS2 nano-sheet in presence of the ru impurity have been calculated by density functional theory framework with generalized gradient approximation. The MoRuS2 nano-sheet electronic structure was changed to the n-type semiconductor by 1.3 eV energy gap. The optical coefficients were shown that the loosing optical energy occurred in the higher ultraviolet region, so this compound is a promising candidate for optical sensing in the infrared and visible range. The thermoelectric behaviors were implied to the good merit parameter in the 100K range and room temperatures and also has high amount of power factor in 600K which made it for power generators applications