Scopus İndeksli Yayınlar Koleksiyonu / Scopus Indexed Publications Collection

Permanent URI for this collectionhttps://hdl.handle.net/11147/7148

Browse

Filters

2018 - 201912020 - 20211

Settings

Author: search.filters.author.Özbay, Ekmel

Search Results

Now showing 1 - 2 of 2
  • Article
    Citation - WoS: 1
    Citation - Scopus: 1
    Substrate Effects on Electrical Parameters of Dirac Fermions in Graphene
    (Elsevier, 2021) Tıraş, Engin; Ardalı, Şükrü; Fırat, Hakan Asaf; Arslan, Engin; Özbay, Ekmel; 01. Izmir Institute of Technology
    The substrate effects on the electronic transport properties of single-layer graphene on TiO2/Si substrate have been studied. The Hall mobility, sheet carrier density, and transport lifetime were obtained from the temperature-dependent Hall measurements, while the in-plane effective mass, quantum lifetime was obtained from the temperature-dependent variation of the Shubnikov de Haas (SdH) oscillations that were made at 1.8 to 45 K temperature range and up to the magnetic field of 11 T. The measurement results showed that in SLG/TiO2/ Si sample, there were 2.36 +/- 0.12x1016 m-3 amounts of 3D carriers coming from the substrate. In our previous studies, 3D carrier densities were measured as 6.07x1016 m-3 and zero for SLG/SiO2/Si and SLG/SiC sample, respectively. This result shows that the 3D carriers formed in the structure are significantly changed by a substrate. The scattering mechanisms were determined using the zt/zq ratio. The ratio values obtained as 3.66. This value obtained was compared with the values we found for SLG/SiC (zt/zq=1.36) sample and SLG/TiO2/Si (zt/zq=3.08) sample our previous study. The results show that small-angle scattering is dominant in SLG/SiC sample, but large-angle scattering is dominant in SLG/SiO2/Si and SLG/TiO2/Si samples. The charged impurity scattering is the dominant scattering mechanism in SLG/TiO2/Si and SLG/SiO2/Si samples, whereas in SLG/SiC samples, a short-range scattering mechanism such as lattice defects can be said to affect the electronic transport.
  • Article
    Citation - WoS: 134
    Citation - Scopus: 136
    Electrically Switchable Metadevices Via Graphene
    (American Association for the Advancement of Science, 2018) Balcı, Osman; Balcı, Sinan; Karademir, Ertuğrul; Balcı, Sinan; Çakmakyapan, Semih; Polat, Emre O.; Çağlayan, Hümeyra; Özbay, Ekmel; Kocabaş, Çoşkun; 04.04. Department of Photonics; 04. Faculty of Science; 01. Izmir Institute of Technology
    Metamaterials bring subwavelength resonating structures together to overcome the limitations of conventional materials. The realization of active metadevices has been an outstanding challenge that requires electrically reconfigurable components operating over a broad spectrum with a wide dynamic range. However, the existing capability of metamaterials is not sufficient to realize this goal. By integrating passive metamaterials with active graphene devices, we demonstrate a new class of electrically controlled active metadevices working in microwave frequencies. The fabricated active metadevices enable efficient control of both amplitude (>50 dB) and phase (>90°) of electromagnetic waves. In this hybrid system, graphene operates as a tunable Drude metal that controls the radiation of the passive metamaterials. Furthermore, by integrating individually addressable arrays of metadevices, we demonstrate a new class of spatially varying digital metasurfaces where the local dielectric constant can be reconfigured with applied bias voltages. In addition, we reconfigure resonance frequency of split-ring resonators without changing its amplitude by damping one of the two coupled metasurfaces via graphene. Our approach is general enough to implement various metamaterial systems that could yield new applications ranging from electrically switchable cloaking devices to adaptive camouflage systems.