Browsing by Subject "Two-dimensional material"

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    An all-dielectric metasurface coupled with two-dimensional semiconductors for thermally tunable ultra-narrowband light absorption
    (Springer, 2020) Buhara, Ebru; Ghobadi, Amir; Özbay, Ekmel
    Two-dimensional (2D) transition metal dichalcogenides (TMDCs) have attracted tremendous attention over the past decades. Due to their unique features such as high mobility and direct bandgap, they are suitable candidate for the optoelectronic devices. However, due to their ultrathin thickness, their optical absorption is quite weak, and therefore, a trapping scheme for strong light- matter interaction is essential to overcome this deficiency. To accomplish strong light absorption, loss-less dielectric-based metasurfaces with ideally no parasitic absorption are excellent choices. Herein, we report an ultra-narrowband thermally tunable all-dielectric metasurface coupled absorber with TMD monolayer. In this proposed structure, high absorption with ultra-narrow full-width-at-half-maximum (FWHM) is achieved. Different design configurations are studied to find the most suitable structure. In the optimized design, an absorptance as high as 0.85 with a FWHM of 3.1 nm is achieved. This structure also shows thermal sensitivity of 0.0096 nm/°C, without the use of any phase change material component. This architecture can be used as a 2D and highly efficient tunable single-color photodetector. The proposed dielectric metasurface can be adopted for other types of 2D and ultrathin semiconductor-based optoelectronics.
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    Structural parameters and electronic properties of 2D carbon allotrope: graphene with a kagome lattice structure
    (Elsevier, 2020) Sarıkavak-Lisesivdin, B.; Lisesivdin, S. B.; Özbay, Ekmel; Jelezko, F.
    In this paper, the electronic properties of a carbon allotrope, graphene with a kagome lattice structure, are investigated. Spin-polarized density functional theory (DFT) calculations with Grimme dispersion corrections were done. Bond lengths, electronic band structure, and projected density of states were calculated. Electronic band structure calculations show kagome flat-band formation with higher d-orbital contributed bonding behavior than the pristine graphene structure. The structural parameters and electronic band results of this 2D carbon allotrope show wider possible usage in many applications from desalination membranes to possible high- temperature superconductor.