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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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    On the Anomalous Peak in the Forward Bias Capacitance and Dielectric Properties of the Al/Co-Doped (PVC plus TCNQ)/p-Si structures as Function of Temperature
    (Amer Scientific Publishers, 2015) Yucedag, I.; Kaya, A.; Altindal, S.
    The temperature and voltage dependence of electric and dielectric characteristics and ac electrical conductivity (sigma(ac)) of Al/Co-doped (PVC + TCNQ)/p-Si structure in the temperature range of 200-360 K and voltage range of (-4 V)-(9 V) have been investigated in detail by using experimental C-V and G/omega -V measurements at 500 kHz. The value of dielectric constant (epsilon'), dielectric loss (epsilon ''), dielectric loss tangent (tan delta), the real and imaginary parts of electric modulus (M' and M ''), and the sigma(ac) were strongly dependent applied bias voltage and temperature, especially in the depletion and accumulation regions. Such a behavior in these parameters can be explained on restructuring and reordering of charges at interface traps/states. The forward C-V plots exhibit an anomalous peak for each temperature and the peak position shift towards lower voltages with increasing temperature due to the particular density distribution of interface traps (D-it) and series resistance (Rs) of structure. Therefore the plots of dielectric properties and also sigma(ac) indicate two different behaviors before and after intersection point. Before this intersection point, while the values of the epsilon', epsilon '', and sigma(ac) increase, the tan delta decreases, after this intersection point, while the value of the epsilon', epsilon '', and sigma(ac) decrease, the tan delta increases. The ln (sigma(ac))-q/kT plot shows two linear regions both for the 2 V and 9 V which are corresponding to below room temperature (200-300 K) and above room temperature (320-360 K) and the corresponding activation energy (E-a) values were called as Ea((I)) and Ea((II)), respectively. Thus the E-a values were obtained from the slope of these Arrhenius plot as 182 meV and 4.7 meV for 2 V and 22 meV and 0.6 meV for 9 V, respectively.
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    On the frequency dependent negative dielectric constant behavior in Al/Co-doped (PVC plus TCNQ)/p-Si structures
    (World Scientific Publ Co Pte Ltd, 2014) Yucedag, I.; Kaya, A.; Altindal, S.
    The dielectric properties, electric modulus and ac electrical conductivity (sigma(ac)) of Al/Co-doped (PVC + TCNQ)/p-Si structures have been investigated in the wide frequency and voltage range of 0.5 kHz-3 MHz and (-4 V)-( 9 V), respectively, using the capacitance-voltage (C-V) and conductance-voltage (G/omega-V) measurements at room temperature. The real and imaginary parts of dielectric constant (epsilon ', epsilon ''), loss tangent (tan delta), sigma(ac) and the real and imaginary parts of electric modulus (M ', M '') were found strongly function of frequency and applied voltage especially at low frequencies. The epsilon '-V plot shows an anomalous peak in the forward bias region due to the series resistance (R-s), surface states (N-ss) and interfacial layer (PVC + TCNQ) effects for each frequency and then it goes to negative values known as negative dielectric constant (NDC) at low frequencies (f <= 70 kHz). Such observation of NDC is important result because it implies that an increment of bias voltage produces a decrease in the charge on the electrodes. The amount of negativity epsilon ' value increases with decreasing frequency and this decrement in the NDC corresponds to the increment in the epsilon ''.
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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.