Physics / Fizik

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

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Author: search.filters.author.Tarhan, EnverPublisher: search.filters.publisher.Elsevier Ltd.

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  • Article
    Citation - WoS: 5
    Citation - Scopus: 5
    Effect of the Synthesis Conditions on the Properties of Co Embedded Porous Si Nanostructures
    (Elsevier Ltd., 2019) Çetinel, Alper; Artunç, Nurcan; Tarhan, Enver
    The electrodeposition of cobalt in the porous silicon (PSi) substrate was investigated in terms of the deposition times and current densities. The PSi/Co samples were characterized by SEM, XRD, Raman, and photoluminescence (PL) spectroscopies. The results indicated that for all current densities, the PL intensities of PSi/Co samples with shorter deposition times (t(s) <= 20 min) increased due to spherical Co nanoparticles (NPs) could be created the new recombination centers, compared to that of the undeposited PSi. On the other hand, the PL intensity of PSi/Co samples significantly decreased at longer deposition times (t(1) > 20 min) because of larger Co NP cluster promoted the formation of non-radiative centers. The increased PL intensities in samples with t(s) were attributed to both the quantum confinement effect and surface effects. PL analyses also suggested that after exposure to air for 60 days, PL characteristics of PSi/Co were stabilized depending on deposition time and current density.
  • Article
    Citation - WoS: 42
    Citation - Scopus: 44
    Growth of Cu2znsns4 Absorber Layer on Flexible Metallic Substrates for Thin Film Solar Cell Applications
    (Elsevier Ltd., 2015) Yazıcı, Şebnem; Olgar, Mehmet Ali; Akça, Fatime Gülşah; Cantaş, Ayten; Kurt, Metin; Aygün, Gülnur; Tarhan, Enver; Yanmaz, Ekrem; Özyüzer, Lütfi
    In this work, Cu2ZnSnS4 (CZTS) absorber layers were fabricated using a two-stage process. Sequentially deposited Cu-Zn-Sn thin film layers on metallic foils were annealed in an Ar + S2(g) atmosphere. We aimed to investigate the role of flexible titanium and molybdenum foil substrates in the growth mechanism of CZTS thin films. The Raman spectra and X-ray photoelectron spectroscopy analyses of the sulfurized thin films revealed that, except for the presence of Sn-based secondary phases, nearly pure CZTS thin films were obtained. Additionally, the intense and sharp X-ray diffraction peak from the (112) plane provided evidence of good crystallinity. Electron dispersive spectroscopy analysis indicated sufficient sulfur content but poor Zn atomic weight percentage in the films. Absorption and band-gap energy analyses were carried out to confirm the suitability of CZTS thin films as the absorber layer in solar cell applications. Hall effect measurements showed the p-type semiconductor behavior of the CZTS samples. Moreover, the back contact behavior of these metallic flexible substrates was investigated and compared. We detected formation of cracks in the CZTS layer on the molybdenum foils, which indicates the incompatibility of molybdenum's thermal expansion coefficient with the CZTS structure. We demonstrated the application of the magnetron sputtering technique for the fabrication of CZTS thin films on titanium foils having lightweight, flexible properties and suitable for roll-to-roll manufacturing for high throughput fabrication. Titanium foils are also cost competitive compared to molybdenum foils. © 2015 Elsevier B.V.
  • Article
    Citation - WoS: 29
    Citation - Scopus: 30
    The Structural, Optical and Morphological Properties of Caf2 Thin Films by Using Thermionic Vacuum Arc (tva)
    (Elsevier Ltd., 2013) Çetin, N. Emre; Korkmaz, Şadan; Elmas, Saliha; Ekem, Naci; Pat, Suat; Balbag, M. Zafer; Tarhan, Enver; Temel, Sinan; Özmumcu, Murat
    In this study, calcium fluoride (CaF2) thin films have been prepared by Thermionic Vacuum Arc (TVA) technique on glass substrates. In this technique CaF2 thin films are produced by condensing the plasma of anode material generated in the TVA setup under high vacuum conditions on glass substrates. Crystal structures as well as optical and surface properties of CaF2 antireflective (AR) coated thin films were investigated. X-ray diffraction (XRD) measurements showed that amorphous CaF2 thin films were formed. Optical and surface properties of CaF2 films have been studied based on optical transmittance, reflectance, refractive index and atomic force microscopy imaging (AFM). Our results also show that CaF2 coated samples exhibit lower reflectance (R). From our optical studies, we have observed that CaF2 thin films have high AR properties.