Computational Investigation of 2D monolayer and heterostructures materials' electronic and optical properties using First-Principles Density Functional Theorem (DFT)
Germanene/2D-GaP hetero-bilayer structure: scf and bands calculation (Quantum Espresso codes)”
Now, let’s see some of the outputs. First, the scf and band outputs for the considered gemranene/2D-AlP hetero-bilayer is provided below.
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Left - Four stacking arrangements of the germanene/2D-AlP heterostructure at equilibrium (a) pattern-I, (b) pattern-II, (c) pattern-III, and (d) pattern-IV. A typical side view of the heterobilayer is placed in the center. “h” denotes the interlayer separation, and “Δ” denotes the buckling height.
Middle - The variation of binding energy/Ge atom as a function of the interlayer separation for the four patterns of germanene/2D-AlP heterobilayers. Downward arrows indicate the optimized interlayer distances for the respective patterns.
Right - Band diagrams and associated density of states (DOS) for germanene/2D-AlP heterobilayers for (a) pattern-I, (b) pattern-II, (c) pattern-III, and (d) pattern-IV.
Left - Band structures of the germanene/2D-AlP heterobilayer with SOC (a) pattern-I, (b) pattern-II, (c) pattern-III, and (d) pattern-IV.
Middle - (a) Atom projected density of states (PDOS) and (b) orbital projected density of states (PDOS) for pattern-III of the germanene/2D-AlP heterobilayer. Fermi level is set at 0.
Right - (a) Space charge density and (b) charge density difference (CDD) for pattern-III of the germanene/2D-AlP heterobilayer. The isovalue is 0.00187 e/Å3. (VB - Valence Band and CB- Conduction Band).
Left - The variation of the bandgap and effective mass of the electron as a function of tensile strain (+ve) and compressive strain (−ve) for pattern-III of the germanene/2D-AlP heterobilayer.
Middle - The bandgap and electron mobility variation as a function of the applied electric field for pattern-III of the germanene/2D-AlP heterobilayer. The direction of the applied positive electric field is from the 2D-AlP monolayer toward the germanene monolayer.
Right - (a) Phonon dispersion relation and (b) vibrational density of states (VDOS) of pattern-III of the germanene/2D-AlP heterobilayer.
References
2022
Tunable electronic properties of germanene and two-dimensional group-III phosphides heterobilayers
In this research work, the 2D structure of the germanene layer is compounded with 2D group-III phosphides: AlP and GaP. The planar structure of AlP and low-buckled GaP have been taken to form the bilayer patterns. In each case, three stacking patterns are considered, and their relaxed interlayer distance and binding energy have been reported. The binding energy being around in the range between 150 to 210 meV shows the existence of weak van der Waals interactions between the layers. The heterostructures containing germanene and these two phosphides show an opening of a large indirect bandgap of magnitude range of 200 meV to 600 meV, which can be tuned by changing interlayer distance and by incorporating bi-axial compressive and tensile strain. Although their normal bandgap, which significantly changes with SOC, is an indirect one, whilst tunning the interlayer distance band gap jumps from unsymmetrical point to symmetrical Dirac cones and becomes direct on K points. The charge carrier mostly concentrates on the p-orbitals of the germanene in the conduction regions; thus, the electrical properties of germanene will be retained, and the carrier will provide a much faster device response property. The absence of the phosphides influence makes them the intended substrate for growing the germanene layer on top of that. Again, due to the bandgap at Dirac cones being opened and jumps between the Dirac cones and band gap changes with SOC tropological insulator can be formed, and Quantum Spin Hall effect may exist.
@article{mojumder2022tunable,title={Tunable electronic properties of germanene and two-dimensional group-III phosphides heterobilayers},author={Mojumder, Md Rayid Hasan},journal={arXiv preprint arXiv:2201.02676},year={2022},doi={10.48550/arXiv.2201.02676},url={https://arxiv.org/abs/2201.02676},dimensions={true},}
2021
Germanene/2D-SiC van der Waals heterobilayer: Structural features and tunable electronic properties
Md Sherajul Islam, Md Rayid Hasan Mojumder, Naim Ferdous, and 1 more author
Van der Waals heterobilayer, consisting of different two-dimensional (2D) materials, has recently drawn substantial research attention. We present a detailed investigation of the structure and electronic properties of germanene and 2D silicon carbide (Ge/2D-SiC) van der Waals heterobilayer by means of first-principles calculations under the framework of density functional theory. Three different stacking patterns are predicted for this Ge/2D-SiC heterostructure. All the representative structures offer a direct bandgap of approximately 80–100 meV. The breaking of the sub-lattice symmetry as well as the transfer of charges are perceived as the pivotal effects that open the bandgap for each structure. The compressive bi-axial strain is applied for the further tune of the bandgap, resulting in an alter in the bandgap from 85 to 118 meV. Upon varying the interlayer distance between germanene and 2D-SiC the bandgap can further be tuned. The distribution of space charges of the conduction and valence bands and projected density of states represent that germanene plays the main role in forming the heterobilayers electronic properties, thus suggesting the ability of 2D-SiC as a stable substrate. These outcomes expose that Ge/2D-SiC heterostructure would be an incredible resource for imminent Ge-based high-performance nanoelectronic devices such as quantum computing spintronic devices and nanoscale energy storage devices.
@article{islam2021germanene,title={Germanene/2D-SiC van der Waals heterobilayer: Structural features and tunable electronic properties},author={Islam, Md Sherajul and Mojumder, Md Rayid Hasan and Ferdous, Naim and Park, Jeongwon},journal={Materials Today Communications},volume={26},pages={101718},year={2021},publisher={Elsevier},doi={10.1016/j.mtcomm.2020.101718},url={https://www.sciencedirect.com/science/article/pii/S235249282032729X},dimensions={true},}
Germanene/2D-AlP van der Waals heterostructure: Tunable structural and electronic properties
Md Rayid Hasan Mojumder, Md Sherajul Islam, and Jeongwon Park
Developing van der Waals heterostructures (vdWHs) utilizing vertical mounting of diverse two-dimensional (2D) materials is an efficient way of achieving favorable characteristics. Using first-principles calculations, we demonstrated the geometric configurations and electronic properties of germanene/2D-AlP vdWHs. We considered four high symmetric patterns that show a bandgap opening in the heterostructures of 200 meV–460 meV. The incorporation of spin-orbital coupling reduces the bandgap by 20 meV–90 meV. Both direct and indirect bandgaps were found from these high symmetric patterns, depending on the structural patterns. The charge density distribution and the partial density of states confirmed that germanene was the property builder of the heterostructure, in which 2D-AlP could be a decent substrate. The heterostructure bandgap can be widely tuned in the range 0 meV–500 meV by changing the interlayer separation between the two monolayers. The application of strain and external electric fields also significantly tailored the electronic structures of the heterostructures. Intriguingly, an exceptionally high carrier mobility of more than 1.5 × 105 cm2 V−1 s−1 was observed, which outperforms compared to other studies on germanene heterostructures. All these promising properties make the germanene/2D-AlP heterostructure a viable candidate for FETs, strain sensors, nanoelectronics, and spintronic devices.
@article{mojumder2021germanene,title={Germanene/2D-AlP van der Waals heterostructure: Tunable structural and electronic properties},author={Mojumder, Md Rayid Hasan and Islam, Md Sherajul and Park, Jeongwon},journal={AIP Advances},volume={11},number={1},year={2021},publisher={AIP Publishing},doi={10.1063/5.0023448},url={https://pubs.aip.org/aip/adv/article/11/1/015126/1069922},dimensions={true},}
2020
Electronic properties of Ge/2D-GaP heterobilayer: A first-principles investigation
Md Rayid Hasan Mojumder, Md Sherajul Islam, Md Sakib Hassan, and 1 more author
In 2020 11th International Conference on Electrical and Computer Engineering (ICECE), 2020
ln this paper, we demonstrated geometric construction and electronic properties of Germanene/2D-GaP (Ge/2D-GaP) heterobilayer utilizing first-principles calculation. We found that the formation of Ge12D-GaP results in a directly opened band gap of 85.6, meV at the Γ-point. Our calculation of the charge density difference between the germanene and 2D-Gal layer and the partial density of states confirmed the germanene as the property builder of the heterostructure. The variation in interlaver distances between the bilayer demonstrated tunable bandgap property. We observed both direct and indirect band bandgap through the process and find very high electron mobility of 13.2x10 4 cm 2 V -1 s -1 . The electronic properties of the Ge/12D-GaP heterubilaver stood as a viable option to further investigate its application in the field of nanoelectranic storage devices and mino-piezoelectric generators.
@inproceedings{mojumder2020electronic,title={Electronic properties of Ge/2D-GaP heterobilayer: A first-principles investigation},author={Mojumder, Md Rayid Hasan and Islam, Md Sherajul and Hassan, Md Sakib and Hossain, Md Jikrul Sayeed},booktitle={2020 11th International Conference on Electrical and Computer Engineering (ICECE)},pages={141--144},year={2020},organization={IEEE},doi={10.1109/ICECE51571.2020.9393065},url={https://ieeexplore.ieee.org/abstract/document/9393065},dimensions={true},}
