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- 저자 : I. Uslu (검색결과 3 건)
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Fabrication and characterization of boron doped BaZrO3 nanofibers via an electrospinning technique
T. Tunç,I. Uslu,S. Keskin 한양대학교 세라믹연구소 2011 Journal of Ceramic Processing Research Vol.12 No.5
In this study, boron doped and undoped poly(vinyl) alcohol/zirconium-barium acetate (PVA/Zr-Ba) nanofibers were prepared using an electrospinning technique then calcinated at three different temperatures; 250 oC, 500 oC, 800 oC for 2 h. The originality of this study is the addition of boron to metal acetates. The fibers were characterized by FT-IR, DSC, XRD and SEM. The addition of boron did not only increase the thermal stability of the fibers, but also increased their diameters, which gave stronger fibers. The FT-IR spectra of the fibers were in good accordance with literature data. The DSC results indicate that the glass transition (Tg) and melting temperatures (Tm) showed a change with the addition of boron. Also, boron doped fibers were observed to degrade at higher temperatures. XRD analyses showed that after further heat treatment at 800 oC,zirconia exists in two phases of tetragonal and monoclinic modifications. The systematic evolution of morphological features in the spun and the processed fibers were studied by scanning electron microscopy. The SEM appearance of the fibers showed that the addition of boron resulted in the formation of cross linked bright surfaced fibers.
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S. Demirezen,S. Altındal,I. Uslu 한국물리학회 2013 Current Applied Physics Vol.13 No.1
The forward and reverse bias currentevoltage (IeV), capacitance/conductanceevoltage (C/GeV) characteristics of the fabricated Au/PVA (Bi-doped)/n-Si photodiode have been investigated both in dark and under 250 W illumination intensity at room temperature. The energy density distribution profile of Nss was extracted from the forward bias IeV measurements by taking the voltage dependence of effective barrier height (Fe) and Rs for photodiode both in dark and under 250 W illumination cases. The exponential growth of the Nss from midgap toward the bottom of the conductance band is very apparent for two cases. The obtained high value of n and Rs were attributed to the particular distribution of Nss at metal/PVA interface, surface and fabrication processes, barrier inhomogeneity of interfacial polymer layer and the form of barrier height at M/S interface. While the values of C and G/w increase Rs and Rsh decrease under illumination, due to the illumination induced electronehole pairs in depletion region. The voltage dependent Nss profile was also obtained from the dark and illumination capacitance at 1 MHz and these values of Nss are in good agreement. In addition, the fill factor (FF) under 250 W illumination level was found as 28.5% and this value of FF may be accepted sufficiently high. Thus, the fabricated Au/ PVA (Bi-doped)/n-Si structures are more sensitive to light, proposing them as a good candidate as a photodiode or capacitance sensor for optoelectronic applications in modern electronic industry.
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M. Gökçen,T. Tunç,Ş. Altındal,İ. Uslu 한국물리학회 2012 Current Applied Physics Vol.12 No.2
Two types of Schottky Barrier Diodes (SBDs) with and without PVA (Bi2O3-doped) polymeric interfacial layer, were fabricated and measured at room temperature in order to investigate the effects of the PVA (Bi2O3-doped) interfacial layer on the main electrical parameters such as the ideality factor (n), zero-bias barrier height (FB0), series resistance (Rs) and interface-state density (Nss). Electrical parameters of these two diodes were calculated from the currentevoltage (IeV) characteristics and compared with each other. The values of FB0, n and Rs for SBDs without polymeric interfacial layer are 0.71 eV, 1.44 and 4775 U, respectively. The values of FB0, n and Rs for SBDs with PVA (Bi2O3-doped) polymeric interfacial layer are 0.74 eV, 3.49 and 10,030 U, respectively. For two SBDs, the energy density distribution profiles of interface states (Nss) were obtained from forward-bias IeV measurements by taking the bias dependence of Rs of these devices into account. The values of Nss obtained for the SBD with PVA (Bi2O3-doped)polymeric interfacial layer are smaller than those of the SBD without polymeric interfacial layer.
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