Properties Of Germanene Research Articles

Effect of Al doping on the electronic structure and optical properties of germanene

The effects of different doping concentrations and hydrogenation on the electronic structure and optical properties of Al-doped germanene were studied based on a density generalised theory first-principles approach. It was found that the system with a doping concentration of 3.125% was more stable. The bandgap is lower than 0.1 eV for doping concentrations of 3.125% to 6.25%, which is consistent with the nature of semimetals. The bandgap transition from indirect-direct-indirect is achieved at doping concentrations of 11.11% to 25%. Both the s- and p-states of Al and Ge atoms contribute to the total density of states compared to the intrinsic germanene, and the doping of Al promotes the absorption and reflection of light from germanene and also undergoes different degrees of blue shift. Hydrogenation has a large effect on the electronic structure of Al-doped germanene, making the s and p state's electronic interactions of Al atoms weaker. The Al-doped germanene system can be converted from indirect bandgap to direct bandgap when fully hydrogenated.

Some properties of germanene when adsorption of NH3 in the external field

This work studies on germanene when adsorbing NH3 gas, the system is placed in an 0 external electric field of 0.3 V / AÅ. By using the density functional theory (DFT) and VASP software, the properties of the energy band structure, the density of the state, and the charge displacement have been studied. There are four locations in which NH3 doped research is hollow, bridge, valley, and top. At the bridge position for the minimum adsorption energy, this indicates that the bridge position is the most optimal position when doped with NH3. The state density energy region structure, the charge displacement will be studied for the most optimal position. Placing the system in an external electric field will change the energy band structure as well as other properties of the NH3 doped germanene. This study will be useful for all steps of research in sensor or biomedical.

Geometric analysis of the properties of germanene using Lifson–Wershel potential function

Numerous experiments on graphene, which is a 2D carbon material with excellent mechanical and electrical properties, have been carried out in recent years. By recognizing the properties of graphene, the researchers focused on other two-dimensional materials. Several studies have been done on graphene, but other two-dimensional structures have not yet been studied extensively. In this work, Germanene’s simulation of molecular dynamics was performed and Germanene’s stress–strain curve was obtained. The mechanical properties of Germanene have been investigated by practicing the proposed method of structural molecular mechanics. The two-step procedure was followed, where, in first step with the aid of the relations governing the force field and the Lifson–Wershel potential function and structural mechanics relations, the coefficients for the BEAM elements were found, and a structural mechanics model for Germanene was proposed. Then, a germanene sheet with [Formula: see text] Ȧ was modeled and Young’s modulus of Germanene was obtained by molecular dynamics and proposed molecular mechanics methods.

First-principles calculations of magnetic properties of germanene under strain

Magnetic properties of germanene with five different nonmetal atoms have been analyzed and discussed by the DFT calculations. Magnetic moments could be induced by C, N, and O adatoms in the germanene. We further study the effect of strain on the magnetism in O-adsorbed germanene, and a tunable magnetism shows. The analysis of the PDOS shows that the p–p hybridization between O and Ge atoms is responsible for such magnetic behavior. Our results indicate that the magnetism induced by the O adatom is switchable depending on the strength of strain, which might show some potential applications in the nanoscale devices.

Ab Initio Study of Electronic and Magnetic Properties of Germanene with Different Nonmagnetic Metal Adatoms

Electronic and magnetic properties of two-dimensional (2D) germanene (Ge) with five different adatoms have been analyzed and discussed by the DFT method. Different nonmagnetic metals adsorbed at different sites, on one hand, a magnetic moment is induced by Mg adatom in the germanene. On the other hand, the adsorptions of Al, Ga, Li, and Na show no magnetism. We further study the effect of strain on the magnetism in Mg-adsorbed germanene; we apply an isotropic tensile and compressive strain on the system. On the basis of our calculations, a tunable magnetism shows as the strain increases. The analysis of the PDOS shows that the s–p hybridization between Mg and Ge atoms results in such magnetic behavior. These magneticadsorbed germanene materials might show potential applications in the nanoscale devices.

Growth of uniform CaGe2 films by alternating layer molecular beam epitaxy

Layered Zintl phase van der Waals (vdW) materials are of interest due to their strong spin-orbit coupling and potential for high mobility. Here, we report the successful growth of large area CaGe2 films, as a model of layered Zintl phase materials, on atomically flat Ge(111) substrates by molecular beam epitaxy (MBE) using an alternating layer growth (ALG) protocol. Reflection high energy electron diffraction (RHEED) patterns of the Ge buffer layer and CaGe2 indicate high quality two dimensional surfaces, which is further confirmed by atomic force microscopy (AFM), showing atomically flat and uniform CaGe2 films. The appearance of Laue oscillations in X-ray diffraction (XRD) and Kiessig fringes in the X-ray reflectivity (XRR), which are absent in co-deposited CaGe2, confirms the uniformity of the CaGe2 film and the smoothness of the interface. These results demonstrate a novel method of deposition of CaGe2 that could be also applied to other layered Zintl phase vdW materials. Also, the high quality of the CaGe2 film is promising for the exploration of novel properties of germanane.

Optimized Tersoff empirical potential for germanene

In the current work, the issue of re-parameterization of Tersoff empirical potential model was addressed for 2D nanomaterial ‘germanene’ to be applied in molecular dynamics simulation based studies. The well-known chi-square minimization procedure was used to optimize the original Tersoff potential parameters. Many properties of germanene were extracted using both original and optimized Tersoff potentials and they compared with the corresponding density functional theory data. According to the results, the optimized Tersoff potential provides a significant improvement in many structural, thermodynamic, mechanical, and thermal properties of geramanene.

Mechanisms on the GeH/ interactions in germanene/germanane bilayer for tuning band structures

Germanene, one of the most important two-dimensional materials after graphene and silicone have been discovered, is attracting wide attentions due to its many excellent physical properties. Since a suitable band gap is needed for the electronics and optoelectronics, the lack of a band gap has essentially restricted the practical applications of germanene in macroelectronics. In this article, density functional theory calculations with van de Waals corrections is utilized to study the geometric and electronic properties of germanene (Ge), germanane (GeH) and germanene/germanane (Ge/GeH) bilayer. The band gaps for Ge and GeH are zero and 1.16 eV, respectively. For the Ge/GeH bilayer, a considerable binding energy of 273 meV/unit cell is obtained between Ge and GeH layers. This value is smaller than that of Ge bilayer (402 meV/unit cell), but larger than that of GeH bilayer (211 meV/unit cell), indicating a considerable GeH/ bonding. This means that Ge and GeH layers could be combined steadily by the interlayer weak interactions. Meanwhile, a band gap of 85 meV is opened, which is contributed to the breaking of the equivalence of the two sublattices in the Ge sheet, yielding a nonzero band gap at the K point. Charge density difference indicates that the electrons on the s orbital of H transfer to the Ge_p orbital, enhancing the interlayer interactions. It should be noted here that the van de Waals corrections are pretty important for the geometric and electronic properties of the Ge/GeH bilayer. Without the van de Waals corrections, the binding energy of the Ge/GeH bilayer is reduced from 273 meV/unit cell to only 187 meV/unit cell, severely underestimated the strength of the weak forces between Ge and GeH layers, resulting in a much smaller band gap of 50 meV. Interestingly, no band gap is obtained for the sandwich structure GeH/Ge/GeH, in which the equivalence of two sublattices in germanene is kept. Finally, all the results are confirmed by the high accurate hybrid functional calculations. At the Heyd-Scuseria-Ernzerhof level, the band gap of Ge/GeH bilayer is 117 meV, slightly larger than 85 meV at the Perder-Burke-Ernzerhof level. Our work would promote utilizing germanene in microelectronics and call for more efforts in using weak interactions for band structure engineering.