Yazar "Yucedag, Ibrahim" seçeneğine göre listele

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  • Küçük Resim Yok
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    Comparative study of the temperature-dependent dielectric properties of Au/PPy/n-Si (MPS)-type Schottky barrier diodes
    (KOREAN PHYSICAL SOC, 2015) Gumus, Ahmet; Ersoz, Gulcin; Yucedag, Ibrahim; Bayrakdar, Sumeyye; Altindal, Semsettin
    The dielectric properties of Au/PPy/n-Si metal-polymer-semiconductor (MPS)-type Schottky barrier diodes (SBDs) were investigated by using capacitance-voltage (C-V) and conductancevoltage (G/omega-V) measurements at various temperatures and voltages at frequencies of 100 kHz and 500 kHz. Both the real and the imaginary parts of the complex dielectric constant and dielectric loss (epsilon', epsilon aEuro(3)) and of the electric modulus (M', MaEuro(3)), as well as the conductivity (sigma (ac) ), were found to depend strongly on the temperature and the voltage. Both the C and G/omega values increased with increasing applied voltage and had inversion, depletion, and accumulation regions as with a metal-insulator-semiconductor (MIS) type behavior. Both the dielectric constant (epsilon') and the dielectric loss (epsilon aEuro(3)) increased with increasing temperature and decreased with increasing frequency. The loss tangent (tan delta) vs. temperature curve had a peak at about 200 K for both frequencies. The M' and the MaEuro(3) values decreased with increasing temperature and became independent of the frequency at high temperatures. The series resistance (R (s) ) of the diode decreased with increasing temperature for the two frequencies while the sigma (ac) increased. Such behaviors of the dielectric properties with temperature were attributed to the restructuring and reordering of charges at interface states/traps due to the varying temperature, the interfacial polarization, and the interfacial polymer layer. ln(sigma (ac) ) vs. q/kT plots had two distinct linear regions with different slopes for the two frequencies. Such behaviors of these plots confirmed the existence of two different conduction mechanisms corresponding to low and high temperatures. The values of the activation energy (E (a) ) were obtained from the slopes of these plots, and its value at low temperatures was considerably lower than that at high temperatures.
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    Dielectric properties and electric modulus of Au/PPy/n-Si (MPS) type Schottky barrier diodes (SBDS) as a function of frequency and applied bias voltage
    (WORLD SCIENTIFIC PUBL CO PTE LTD, 2015) Yucedag, Ibrahim; Ersoz, Gulcin; Gumus, Ahmet; Altindal, Semsettin
    Au/PPy/n-Si Schottky barrier diodes (SBDs) were fabricated by forming polypyrrole (PPy) organic layer on n-Si using the spin coating technique. Frequency-dependent dielectric constant (epsilon'), dielectric loss (epsilon ''), loss tangent (tan delta), real and imaginary parts of electrical modulus (M' and M '') and AC electrical conductivity (sigma(ac)) parameters of the structure were investigated in the frequency range of 10-500 kHz. It was found that the values of the epsilon', epsilon '' and tan delta, in general, decrease with increasing frequency while an increase is observed in sigma(ac), M' and M ''. The tan delta and M '' also exhibit a peak at about zero-bias voltage, while peak intensity weakens with increasing frequency. The values of epsilon' and M' decrease with increasing voltage while an increase is observed in epsilon '', tan delta sigma(ac) and M ''. These changes in epsilon', epsilon '', tan delta, M', M '' and sigma(ac) values was attributed to surface charge polarization and the particular density distribution of surface states localized at PPy/n-Si interface.
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    Investigation of photo-induced effect on electrical properties of Au/PPy/n-Si (MPS) type schottky barrier diodes
    (SPRINGER, 2017) Ersoz, Gulcin; Yucedag, Ibrahim; Bayrakdar, Sumeyye; Altindal, Semsettin; Gumus, Ahmet
    Au/PPy/n-Si (MPS) type Schottky barrier diodes (SBDs) were produced and their current-voltage (I-V) characteristics were measured in the positive and negative bias regions at 300 K. The basic electronic quantities such as reverse-saturation current (I-o ), ideality factor (n), zero-bias barrier height (Phi(B0) ), series (R-s) and shunt resistances (R-sh) were obtained by using I-V data in total darkness and illumination (100 W/m(2)). The values of these parameters were found as 7.79 x 10(-9) A, 5.41, 0.75 eV, 1 k Omega and 130 M Omega in dark) and 4 x 10(-9) A, 4.89, 0.77 eV, 0.9 k Omega and 1.02 M Omega under illumination), respectively. Also the energy density distribution behaviors of surface states (N-ss ) have been acquired by calculation of effective barrier height (Phi(e) ) and ideality factor n (V) depending on voltage in total darkness and illumination. The values of N (ss) show an exponentially increase from the mid-gap of Si to the lower part of conduction band (E-c ) for two conditions. The possible current conduction mechanisms were determined by plotting of the double logarithmic I-V plots in the positive voltage zone and the value of current was found proportional to voltage (I similar to V (m) ). The high values of n and R-s were ascribed to the certain density distribution of N-ss localized at semiconductor /PPy interface, surface conditions, barrier inequality, the thickness of PPy interlayer and its roughness. The open-circuit voltage of the photodiode was found as 0.36 V under 100 W/m(2) illumination level. This is evidence that the fabricated sample is very sensitive to illumination. Therefore, it can be put into practice in optoelectronic industries as a photodiode or solar cells.