16 research outputs found
Terahertz Rectennas on Flexible Substrates Based on One-Dimensional Metal–Insulator–Graphene Diodes
Flexible energy harvesting devices fabricated in scalable thin-film processes are crucial for wearable electronics and the Internet of Things. We present a flexible rectenna based on a one-dimensional junction metal–insulator–graphene diode, offering low-noise power detection at terahertz (THz) frequencies. The rectennas are fabricated on a flexible polyimide film in a scalable process by photolithography using graphene grown by chemical vapor deposition. A one-dimensional junction reduces the junction capacitance and enables operation up to 170 GHz. The rectenna shows a maximum responsivity of 80 V/W at 167 GHz in free space measurements and minimum noise equivalent power of 80 pW/√Hz
Variability and Reliability of Graphene Field-Effect Transistors with CaF2 Insulators
Graphene is a promising material for applications as a channel in graphene
field-effect transistors (GFETs) which may be used as a building block for
optoelectronics, high-frequency devices and sensors. However, these devices
require gate insulators which ideally should form atomically flat interfaces
with graphene and at the same time contain small densities of traps to maintain
high device stability. Previously used amorphous oxides, such as SiO2 and
Al2O3, however, typically suffer from oxide dangling bonds at the interface,
high surface roughness and numerous border oxide traps. In order to address
these challenges, here we use for the first time 2nm thick epitaxial CaF2 as a
gate insulator in GFETs. By analyzing device-to-device variability for over 200
devices fabricated in two batches, we find that tens of them show similar gate
transfer characteristics. Our statistical analysis of the hysteresis up to 175C
has revealed that while an ambient-sensitive counterclockwise hysteresis can be
present in some devices, the dominant mechanism is thermally activated charge
trapping by border defects in CaF2 which results in the conventional clockwise
hysteresis. We demonstrate that both the hysteresis and bias-temperature
instabilities in our GFETs with CaF2 are comparable to similar devices with
SiO2 and Al2O3. In particular, we achieve a small hysteresis below 0.01 V for
equivalent oxide thickness (EOT) of about 1 nm at the electric fields up to 15
MV/cm and sweep times in the kilosecond range. Thus, our results demonstrate
that crystalline CaF2 is a promising insulator for highly-stable GFETs
Zero Bias Power Detector Circuits based on MoS Field Effect Transistors on Wafer-Scale Flexible Substrates
We demonstrate the design, fabrication, and characterization of wafer-scale,
zero-bias power detectors based on two-dimensional MoS field effect
transistors (FETs). The MoS FETs are fabricated using a wafer-scale process
on 8 m thick polyimide film, which in principle serves as flexible
substrate. The performances of two CVD-MoS sheets, grown with different
processes and showing different thicknesses, are analyzed and compared from the
single device fabrication and characterization steps to the circuit level. The
power detector prototypes exploit the nonlinearity of the transistors above the
cut-off frequency of the devices. The proposed detectors are designed employing
a transistor model based on measurement results. The fabricated circuits
operate in Ku-band between 12 and 18 GHz, with a demonstrated voltage
responsivity of 45 V/W at 18 GHz in the case of monolayer MoS2 and 104 V/W at
16 GHz in the case of multilayer MoS, both achieved without applied DC
bias. They are the best performing power detectors fabricated on flexible
substrate reported to date. The measured dynamic range exceeds 30 dB
outperforming other semiconductor technologies like silicon complementary metal
oxide semiconductor (CMOS) circuits and GaAs Schottky diodes.Comment: 28 page
RETRATO EN EL PATIO [Material gráfico]
INCLUIDAS EN EL PEQUEÑO ÁLBUM FOTOGRÁFICO FAMILIAR DE LA COLECCIÓN LUIS SUÁREZ GALVÁNCopia digital. Madrid : Ministerio de Educación, Cultura y Deporte. Subdirección General de Coordinación Bibliotecaria, 201
Düzlemsel ve burulmalı iki boyutlu malzemelerin sürtünme özelliklerinin modellenmesi
Cataloged from PDF version of article.Thesis (M.S.): Bilkent University, Department of Physics, İhsan Doğramacı Bilkent University, 2018.Includes bibliographical references (leaves 43-45).The law of friction has been known since the 18th century but yet, the development on the tribology field was established in the last decades mainly by the invention of frictional force microscope (FFM), which enabled scientist to study friction on atomic levels. To describe the friction phenomena at nanoscale, molecular dynamics (MD) and density functional theory (DFT) models are commonly used, popular models and detailed information about friction can be obtained via those models. On the other hand, reduced-order simplified models such as Prandtl-Tomlinson (PT) model can also provide essential information about friction phenomena and understanding a phenomenon via a simplified model is always motivate.
In this thesis, Prandtl-Tomlinson model is generalized into three dimensions and the model is illustrated in both two and three dimensions on various quasi two dimensional crystal structures such as graphene, silicene, germanene and hexagonal boron nitride. By solving the equation of motion of the PT model numerically, friction curves and some parametric dependences of the friction such as anisotropy and friction dependence on external loading force is analyzed. We concluded that the PT model in three dimensions provides good results and can be used to analyze friction phenomena to save from computational cost in MD and DFT models.by Hasan Burkay Uzlu.M.S
Ankara Oyuncak Müzesi
Ankara : İhsan Doğramacı Bilkent Üniversitesi İktisadi, İdari ve Sosyal Bilimler Fakültesi, Tarih Bölümü, 2014This work is a student project of the The Department of History, Faculty of Economics, Administrative and Social Sciences, İhsan Doğramacı Bilkent University.by Emiroğlu, Kudret
Appel à communication : "Beyond Reproductive Printmaking: Prints and the Canon of European Painting, ca. 1500–1810"
Nicolas François Regnault d’après Jean-Honoré Fragonard, Le Baiser à la dérobée, XVIIIe siècle, estampe, 42,2 x 48,5 cm, Paris, musée du Louvre, collection Rothschild Type : Appel à communication. Date limite appel à candidature: 15 février 2017. Date de la manifestation : 18-19 septembre 2017. Lieu : Dresde. Conference for Ph.D. students, postgraduates and researchers at museums and universities in the Kupferstich-Kabinett (Museum of Prints, Drawings and Photographs) of the Staatliche Kunsts..