Showing papers by "Ashraful G. Bhuiyan published in 2014"
27 Mar 2014
TL;DR: In this paper, the authors reported the DC characteristics of dual gated large area graphene metal oxide semiconductor field effect transistor (MOSFET) and calculated the potential profile as well as sheet charge density of graphene channel.
Abstract: This work reports the DC characteristics of dual gated large area graphene metal oxide semiconductor field effect transistor (MOSFET). The sheet charge density dependent quantum capacitance is obtained self-consistently with considering the impurities concentration of the gate oxide layer. The potential profile as well as sheet charge density of graphene channel is calculated. The C-V and I-V characteristics are illustrated here. Finally, the velocity-field relation is shown.
5 citations
TL;DR: In this paper, the intensity ratio between the parallel and perpendicular polarized D band is evolved, providing a spectroscopy-based technique to probe the atomic-scale edge structures in graphene.
Abstract: This letter performed polarized microscopic laser Raman scattering spectroscopy on the curved edges of transferred epitaxial graphene on SiO2/Si. The intensity ratio between the parallel and perpendicular polarized D band is evolved, providing a spectroscopy-based technique to probe the atomic-scale edge structures in graphene. A detailed analysis procedure for non-ideal disordered curved edges of graphene is developed combining the atomic-scale zigzag and armchair edge structures along with some point defects. These results could provide valuable information of the realistic edges of graphene at the atomic-scale that can strongly influence the performance of graphene-based nanodevices.
4 citations
27 Mar 2014
TL;DR: In this article, the phonon properties of hydrogen passivated graphene with vacancy defects are studied using the forced vibrational method, and the authors find that the typical mode pattern for K point in-plane TO modes phonon shows the spatial localized vibrations persuaded by vacancy defects, which are in conceptually good agreement with the experimental results of the large D band peak of the Raman spectra comes from the imperfections of crystal.
Abstract: The phonon properties of hydrogen passivated graphene with vacancy defects are studied using the forced vibrational method. The phonon density of states (PDOS) and typical mode patterns are calculated over a broad range of vacancies. We find that phonon properties of graphene strongly depend on the system size. We observe a broadening and softening of the PDOS peaks with the increase of vacancy concentrations. We find an increasing C-H stretching mode with the increase of defect density. Our numerical experiments reveal that the typical mode pattern for K point in-plane TO modes phonon show the spatial localized vibrations persuaded by vacancy defects, which are in conceptually good agreement with the experimental results of the large D band peak of the Raman spectra comes from the imperfections of crystal. The typical displacement pattern for C-H stretching mode shows a random displacement of H atoms in contrast to C atoms. Our simulation results show the significant impact of vacancy defects on the vibrational properties of graphene.
3 citations
27 Mar 2014
TL;DR: In this paper, the influence of interdot distance, quantum dot size and indium content on the position and width of the intermediate bands is investigated by solving Schrodinger equation using Kronig-Penney model, which reveals that the InxGa1-xN/GaN quantum dot intermediate band solar cell manifests much larger power conversion efficiency than that of conventional solar cells.
Abstract: InxGa1-xN/GaN quantum dot intermediate band solar cell (QD-IBSC) is a promising candidate for the purpose of efficiency improvement of solar cells. In this work, the influences of interdot distance, quantum dot size and indium content of InxGa1-xN/GaN QD-IBSC on the position and width of the intermediate bands are investigated by solving Schrodinger equation using Kronig-Penney model. Finally the effects of intermediate band position and width on energy conversion efficiency are analyzed. The results reveal that the InxGa1-xN/GaN quantum dot intermediate band solar cell manifests much larger power conversion efficiency than that of conventional solar cells. The maximum efficiency occurs when the intermediate band is at the middle position of barrier material bandgap and bandwidth is wide enough to increase absorption of photons keeping carrier recombination negligible by tuning interdot distance, quantum dot size and indium content.
2 citations
27 Mar 2014
TL;DR: In this paper, a detailed theoretical analysis of how QD size variation and band offset affects the confinement energy of InN QD is presented, which allows us to tune dot size and band-offset to obtain required bandgap for InN based low dimensional device design.
Abstract: Detailed theoretical analysis of how QD size variation and band-offset affects the confinement energy of InN QD is presented. Low dimensional structures show a strong quantum confinement effect, which results in shifting the ground state away from the band edge and discrete eigen-states. Graphically solving 1D Schrodinger ground quantized energy levels of electrons were computed and using Luttinger-Khon 4×4 Hamiltonian matrix ground quantized energy level of holes were determined. Our results allow us to tune dot size and band-offset to obtain required bandgap for InN based low dimensional device design.