Physics / Fizik

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

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Author: search.filters.author.Tarı, SüleymanPublisher: search.filters.publisher.Elsevier Ltd.

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Now showing 1 - 4 of 4
  • Article
    Citation - WoS: 35
    Citation - Scopus: 37
    Modification of Ito Surface Using Aromatic Small Molecules With Carboxylic Acid Groups for Oled Applications
    (Elsevier Ltd., 2011) Havare, Ali Kemal; Can, Mustafa; Demiç, Şerafettin; Okur, Salih; Kuş, Mahmut; Aydın, Hasan; Yağmurcukardeş, Nesli; Tarı, Süleyman
    4-[(3-Methylphenyl)(phenyl)amino]benzoic acid (MPPBA) was synthesized in order to facilitate the hole-injection in Organic Light Emitting Diodes (OLED). MPPBA was applied to form self-assembled monolayer (SAM) on indium tin oxide (ITO) anode to align energy-level at the interface between organic semiconductor material (TPD) and inorganic anode (ITO) in OLED devices. The modified surface was characterized by X-ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM) and Kelvin probe force microscopy (KPFM). KPFM was used to measure the surface potential and work function between the tip and the ITO surface modified by SAM technique using MPPBA. The OLED devices (ITO/MPPBA/TPD/Alq3/Al) fabricated with SAM-modified ITO substrates showed lower turn-on voltages and enhanced diode current compare to the OLED devices fabricated with bare ITO substrates.
  • Article
    Citation - WoS: 8
    Citation - Scopus: 8
    An Interface Study of Crystalline Fe/Ge Multilayers Grown by Molecular Beam Epitaxy
    (Elsevier Ltd., 2011) Tarı, Süleyman
    Fe/Ge multilayers were grown on single crystal Ge(0 0 1) substrates by molecular beam epitaxy. The structural, electronic and magnetic properties of Fe/Ge have been studied. The analysis shows that Fe grows in a layer-by-layer epitaxial growth mode on Ge(0 0 1) substrates at 150 ◦C and no intermixing has been observed. Growth of a crystalline Ge film at 150 ◦C on a single crystal Fe film has been observed. At this temperature Ge films grow by means of the island growth mode according to reflection of high energy electron diffraction patterns. Fe layers of 36nm thickness, deposited at 150 ◦C on Ge(0 0 1) substrates, show two magnetization reversal values indicating the growth of Fe in two different crystal orientations. 36nm thick Fe and Ge layers grown at 150 ◦C in Ge/Fe/Ge/Fe/Ge(0 0 1) sequence shows ferromagnetic behavior, however, the same structure grown at 200 ◦C shows paramagnetic behavior.
  • Article
    Citation - WoS: 2
    Citation - Scopus: 2
    Znte/Gaas(2 1 1)b Heterojunction Valence Band Discontinuity Measured by X-Ray Photoelectron Spectroscopy
    (Elsevier Ltd., 2011) Wang, X. J.; Tarı, Süleyman; Sporken, R.; Sivananthan, S.
    Thin ZnTe layers were grown by molecular beam epitaxy on single crystal GaAs(2 1 1)B substrates. Reflection high energy electron diffraction monitored the deoxidation of substrate and entire growth process. Valence band offset was calculated with X-ray photoelectron spectroscopy. Also interface formation of the ZnTe/GaAs was studied. Analysis shows that interface is abrupt and calculated valance band offset is 0.25±0.1 eV and indicates type I alignment. The experimental result agrees well with the theoretical predictions involving interface dipole effect as well as electron affinity rule.
  • Article
    Citation - WoS: 21
    Citation - Scopus: 22
    Structural and Electrical Characterization of the Nickel Silicide Films Formed at 850 °c by Rapid Thermal Annealing of the Ni/Si(1 0 0) Films
    (Elsevier Ltd., 2010) Utlu, G.; Artunç, N.; Budak, S.; Tarı, Süleyman
    Nickel di-silicide formation induced by RTA process at 850 °C for 60 s in the Ni/Si(1 0 0) systems are investigated as a function of the initial Ni film thickness of 7-89 nm using XRD, RBS, SEM, X-SEM and AFM. Based on the XRD and RBS data, in the silicide films of 400-105 nm, NiSi and NiSi2 silicide phases co-exist, indicating that Ni overlayer is completely transformed to NiSi and NiSi2 silicide phases. SEM reveals that these films consist of large grains for co-existence of NiSi2 and NiSi phases, separated from one another by holes, reflecting that NiSi2 grows as islands in NiSi matrix. These films have low sheet resistance, ranging from 1.89 to 5.44 Ω/□ and good thermal stability. For thicknesses ≤ 80 nm RBS yields more Si-rich silicide phases compared to thicker films, whereas SEM reveals that Si-enriched silicide islands with visible holes grow in Si matrix. As the film thickness decreases from 400 to 35 nm, AFM reveals a ridge-like structure showing a general trend of decreasing average diameter and mean roughness values, while sheet resistance measurements exhibit a dramatic increase ranging from 1.89 to 53.73 Ω/□. This dramatic sheet resistance increase is generated by substantial grain boundary grooving, followed by island formation, resulting in a significant phase transformation from NiSi2-rich to Si-rich silicide phases. © 2010 Elsevier B.V. All rights reserved.