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    A comparative electric and dielectric properties of Al/p-Si structures with undoped and Co-doped interfacial PVA layer
    (Elsevier Sci Ltd, 2014) Kaya, A.; Yucedag, I.; Tecimer, H.; Altindal, S.
    In this study, Al/p-Si structures with undoped and Co-doped PVA interfacial layer called S-1 and S-2 were fabricated and their both electrical and dielectric properties were compared by using 300 kHz capacitance voltage (C-V) and conductance voltage (G/omega-V) measurements at room temperature. Experimental results show that both C and G or dielectric constant (epsilon'), dielectric loss (epsilon '') values were found as strongly function of applied bias voltage especially at inverse and accumulation bias regions. It was found that the value of R-5 considerably decreases with doping Co metal contrary to conductivity especially in the forward bias region. Such behavior can be attributed to the lack of free charges in pure PVA. The imaginary parr of dielectric modulus (M '') gives Two peaks for S-1 corresponding To enough reverse and forward biases and passes from a minimum at about zero bias. Also, it is clear That the minimum of The M '' for S-2 coincides with The maximum of The for S-1 at zero bias. As a result, Co-doped PVA considerable improved The performance of structure. In addition, loss Tangent. (tan delta), ac conductivity (sigma(ac)) and real part. of The electric modulus (M') were obtained and compared each other. (C) 2014 Elsevier Ltd. All rights reserved,
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    Current-transport mechanism in Au/V-doped PVC plus TCNQ/p-Si structures
    (World Scientific Publ Co Pte Ltd, 2015) Tecimer, H.; Vural, O.; Kaya, A.; Altindal, S.
    The forward and reverse bias current-voltage (I-V) characteristics of Au/V-doped polyvinyl chloride+Tetracyanoquino dimethane/porous silicon (PVC+TCNQ/p-Si) structures have been investigated in the temperature range of 160-340 K. The zero bias or apparent barrier height (BH) (Phi(ap) = Phi(Bo)) and ideality factor (n(ap) = n) were found strongly temperature dependent and the value of nap decreases, while the n(ap) increases with the increasing temperature. Also, the Phi(ap) versus T plot shows almost a straight line which has positive temperature coefficient and it is not in agreement with the negative temperature coefficient of ideal diode or forbidden bandgap of Si (alpha(Si) = -4.73x10(-4) eV/K). The high value of n cannot be explained only with respect to interfacial insulator layer and interface traps. In order to explain such behavior of Phi(ap) and nap with temperature, Phi(ap) Versus q/2kT plot was drawn and the mean value of ((Phi) over bar (Bo)) and standard deviation (sigma(s)) values found from the slope and intercept of this plot as 1.176 eV and 0.152 V, respectively. Thus, the modified (ln(I-o/T-2) - (q sigma(s))(2)/2(kT)(2) versus (q/kT) plot gives the (Phi) over bar (Bo) and effective Richardson constant A* as 1.115 eV and 31.94 A.(cm.K)(-2), respectively. This value of A* (= 31.94 A.(cm.K)(-2)) is very close to the theoretical value of 32 A.(cm.K)(-2) for p-Si. Therefore, the forward bias I-V-T characteristics confirmed that the current-transport mechanism (CTM) in Au/V-doped PVC+TCNQ/p-Si structures can be successfully explained in terms of the thermionic emission (TE) mechanism with a Gaussian distribution (GD) of BHs at around mean BH.
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    Frequency and voltage dependence of dielectric properties and electric modulus in Au/PVC + TCNQ/p-Si structure at room temperature
    (Elsevier, 2014) Kaya, A.; Vural, O.; Tecimer, H.; Demirezen, S.; Altindal, S.
    Au/PVC + TCNQ/p-Si structure was fabricated and real and imaginary parts of the dielectric constant (epsilon', epsilon ''), loss tangent (tan delta), and the real and imaginary parts of the electric modulus (M', M '') and ac conductivity (sigma(ac)) of this structure have been investigated in wide frequency a range of 1 kHz-5 MHz at room temperature. All of these parameters were found strong function of frequency and voltage especially in the inversion and depletion regions at low frequencies due to interfacial polarization and charges at interface states (N-ss). The decrease in epsilon' and epsilon '' with increasing frequency indicated that the interfacial dipoles have less time to orient themselves in the direction of the alternate field. While the value of M' increase with increasing frequency and reach a maximum, M '' shows a peak and the peak position shifts to higher frequency with increasing applied voltage. The ln(sigma(ac)) vs ln(omega) plot of the structure for 0.5 V has three linear regions (I, II and III) with different slopes which correspond to low, intermediate and high frequency ranges, respectively. Such behavior of ln(sigma(ac)) vs ln(omega) plot indicated that there are three different conduction mechanisms in the Au/PVC + TCNQ/p-Si structure at room temperature. (C) 2013 Elsevier B. V. All rights reserved.
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    Temperature and voltage dependences of dielectric properties and ac electrical conductivity in Au/PVC plus TCNQ/p-Si structures
    (Elsevier Sci Ltd, 2014) Yucedag, I.; Kaya, A.; Tecimer, H.; Altindal, S.
    Dielectric properties and ac conductivity (sigma(ac)) of Au/PVC+TCNQ/p-Si structures have been investigated in the wide temperature range of 80-420 K using capacitance-voltage (C-V) and conductance-voltage (G/omega-V) measurements at 1 MlHz. It has been found that the forward bias C-V plots exhibit a distinct peak especially at a high temperature. Effects of the series resistance (R-s), interfacial PVC+TCNQ layer and the density distribution of interfaces'traps (D-it) on the electrical peak and the dielectric properties were investigated in detail. All of the dielectric properties such as the real and imaginary parts of dielectric constants (epsilon', epsilon''), electric moduli (M' and M), loss tangent (tan delta), and sigma(ac), values were found to be strong functions of temperature and applied bias voltage. These changes become considerably high especially in the depletion region. In addition, the voltage dependent Rs values were obtained and they increased with decreasing temperature C-V-T and G/omega-V-T measurements confirmed that R-s, D-it, and PVC+TCNQ layers are very important parameters that strongly influence both dielectric properties and sigma(ac) of structures. (C) 2014 Elsevier Ltd. All rights reserved.
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    Temperature and Voltage Effect on Barrier Height and Ideality Factor in Au/PVC plus TCNQ/p-Si Structures
    (Wiley-Hindawi, 2014) Kaya, A.; Demirezen, S.; Tecimer, H.; Altindal, S.
    The forward bias current conduction mechanisms of Au/PVC + TCNQ/p-Si structures have been investigated in a wide temperature range of 120-420K for various applied bias voltage. The analysis of the main electrical parameters such as zero-bias barrier height (BH) (phi(Bo)), ideality factor (n), and interface states (N-ss) was found strongly dependent on temperature and voltage. The obtained results show that, while phi(Bo) increases, n decreases with increasing temperature. The plot of phi(app) versus q/2kT was drawn to show a Gaussian distribution (GD) of the BHs, and this plot shows two distinct linear regions. The phi(Bo) and standard deviation (sigma(s)) values were found from the slope and intercept of these plots for two regions as 1.16 eV and 0.161V for the first region and 0.71 eV and 0.093V for the second region, respectively. Such behavior is typical of a double GD (DGD) of the BHs due to the BH inhomogeneities at the metal-semiconductor interface. The slope and intercept of the modified (ln(I-0/T-2) - q(2)sigma(2)(0)/2k(2)T(2)) versus q/kT plot gives the and phi(Bo) and effective Richardson constant (A*) as 1.16 and 0.76 eV and 36.7 and 83.8 A/cm(2)K(2), respectively. The value of the A* (36.7 A/cm(2) K-2) is very close to the theoretical value of 32 A/cm(2) K-2 for p-Si. In addition, to interrupt the voltage-dependent activation energy, the ln(I-s/T-2) versus q/kT plot was drawn in the voltage range of 0-0.3V in 0.05V steps. All of experimental results confirmed that the BH or E-a values depend on the temperature as well as bias voltages.