Physics / Fizik

Permanent URI for this collectionhttps://hdl.handle.net/11147/6

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Institution Author: search.filters.institutionAuthor.Çelebi, CemPublisher: search.filters.publisher.AVS Science and Technology Society

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  • Article
    Citation - WoS: 2
    Citation - Scopus: 2
    Impact of Encapsulation Method on the Adsorbate Induced Electrical Instability of Monolayer Graphene
    (AVS Science and Technology Society, 2019) Kalkan, Sırrı Batuhan; Yanılmaz, Alper; Çelebi, Cem
    Monolayer graphene transferred onto a set of silicon carbide (SiC) substrates was encapsulated with a thin SiO2 film in order to prevent its interaction with atmospheric adsorbates. The encapsulation of graphene samples was realized by using two different thin film growth methods such as thermal evaporation (TE) and state-of-the-art pulsed electron deposition (PED). The encapsulation efficiency of these two techniques on the structural and electrical characteristics of graphene was compared with each other. Scanning electron microscopy (SEM) analysis showed that unlike the SiO2 thin film grown with PED, structural defects like cracks were readily formed on TE grown films due to the lack of surface wettability. The electronic transport measurements revealed that the electrical resistivity of graphene has been increased by two orders of magnitude, and the carrier mobility has been subsequently decreased upon the encapsulation process with the PED method. However, in-vacuum transient photocurrent spectroscopy (TPS) measurements conducted for short periods and a few cycles showed that the graphene layer encapsulated with the PED grown SiO2 film is electrically far more stable than the one encapsulated with TE grown SiO2 film. The results of TPS measurements were related to the SEM images to unravel the mechanism behind the improved electrical stability of graphene samples encapsulated with the PED grown SiO2 film.
  • Article
    Citation - WoS: 1
    Citation - Scopus: 2
    Electron Field Emission From Sic Nanopillars Produced by Using Nanosphere Lithography
    (AVS Science and Technology Society, 2017) Yeşilpınar, Damla; Çelebi, Cem
    Field emitter arrays of silicon carbide based nanopillars with high emitter density were fabricated by using a combination of nanosphere lithography and inductively coupled plasma reactive ion etching techniques. The electron field emission characteristics of the produced nanopillars with two different aspect ratios and geometries were investigated, and the obtained results were compared with each other. The authors found that unlike the samples containing low aspect ratio SiC nanopillars with blunt tip apex, the samples comprising high aspect ratio nanopillars with sharp tip apex generate greater emission currents under lower electric fields. The nanopillars with sharp tip apex produced field emission currents up to 240 μA/cm2 under 17.4 V/μm applied electric field, while the nanopillars with blunt tip apex produced an emission current of 70 μA/cm2. The electric fields required to obtain 10 μA/cm2 current density are found to be 9.1 and 7.2 V/μm for the nanopillars with blunt and sharp tip apex, respectively. Time dependent stability measurements yielded stable electron emission without any abrupt change in the respective current levels of both samples.