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Öğe Anomalous peak in the forward-bias C-V plot and temperature-dependent behavior of Au/PVA (Ni,Zn-doped)/n-Si(111) structures(Springer, 2011) Tunç, Tuncay; Altındal, Şemsettin; Dökme, İlbilge; Uslu, HabibeIn this study, the temperature-dependent mean density of interface states (N(SS)) and series resistance (R(S)) profiles of Au/PVA (Ni,Zn-doped)/n-Si(111) structures are determined using current-voltage (I-V) and admittance spectroscopy [capacitance-voltage (C-V) and conductance-voltage G/omega-V] methods. The other main electronic parameters such as zero-bias barrier height (Phi(B0)), ideality factor (n), and doping concentration (N(D)) are also obtained as a function of temperature. Experimental results show that the values of Phi(B0), n, R(S), and N(SS) are strongly temperature dependent. The values of Phi(B0) and R(S) increase with increasing temperature, while those of n and N(SS) decrease. The C-V plots of Au/PVA (Ni,Zn-doped)/n-Si(111) structures exhibit anomalous peaks in forward bias (depletion region) at each temperature, and peak positions shift towards negative bias with increasing temperature. The peak value of C has been found to be strongly dependent on N(SS), R(S), and temperature. The experimental data confirm that the values of N(SS), R(S), temperature, and the thickness and composition of the interfacial polymer layer are important factors that influence the main electrical parameters of the device.Öğe Frequency and temperature dependence of dielectric properties of au/polyvinyl alcohol (co, ni-doped)/n-si schottky diodes(Taylor & Francis As, 2010) Tunç, Tuncay; Uslu, İbrahim; Dökme, İlbilge; Altındal, Şemsettin; Uslu, HabibeThe dielectric properties and AC conductivity of Au/polyvinyl alcohol (Co, Ni-doped)/n-Si Schottky diodes (SDs) were investigated in the frequency range 1kHz-1MHz and in the temperature range 80-400K. The frequency and temperature dependence of dielectric constant (epsilon'), dielectric loss (epsilon''), loss tangent (tan ), AC electrical conductivity (sigma ac) and the real and imaginary parts of the electric modulus (M' and M'') were found to be a strong function of frequency and temperature. The values of epsilon', epsilon'' and tan decrease with increasing frequency, while they increase with increasing temperature, especially above 275K. The values of sigma ac increase with both increasing frequency and temperature. Such temperature-related behavior of sigma ac can be attributed to the high mobility of free charges at high temperature. Electric modulus formalism was also analyzed to obtain experimental dielectric data. The values of M' and M'' increase with increasing frequency, while they decrease with increasing temperature. The interfacial polarization, which more easily occurs at low frequencies and high temperatures, consequently contributes to the improvement of the dielectric properties of SDs.Öğe Illumination effect on admittance measurements of polyvinyl alcohol (Co, Zn-doped)/n-Si Schottky barrier diodes in wide frequency and applied bias voltage range(2011) Yerişkin, Seçkin Altındal; Uslu, Habibe; Tunç, Tuncay; Altındal, ŞemsettinIn order to have a good interpretation of the illumination effect on the capacitance-voltage (C-V) and conductance-voltage (G/?-V) profiles, C-V and G/?-V characteristics of the polyvinyl alcohol (Co, Zn-Doped)/n-Si Schottky barrier diodes (SBDs) were investigated in the wide frequency and applied bias voltage ranges at room temperature. Experimental results show that the values of both C and G/? are strong functions of frequency and applied bias voltage in dark and under illumination (200 W) conditions. It is clear that the dispersion in C and G/? is considerably high in the depletion and accumulation regions due to illumination induced electron-hole pairs and series resistance (R s) effect, respectively. The values of C and G/? exponentially decrease with the increasing frequency and at high frequencies (f>100kHz) the values of C and G/? become almost independent of frequency both in dark under illumination. © 2011 American Institute of Physics.Öğe Preparation and dielectric properties of polyvinyl alcohol (Co, Zn Acetate) Fiber/n-Si and polyvinyl alcohol (Ni, Zn Acetate)/n-Si Schottky diodes(Korean Fiber SOC, 2011) Tunç, Tuncay; Uslu, Habibe; Altındal, ŞemsettinDielectric properties and ac electrical conductivity (sigma(ac)) of Au/PVA(Co, Zn acetate)/n-Si and Au/PVA(Ni, Zn acetate)/n-Si Schottky diodes (SDs) have been investigated in dark and under illumination by using experimental capacitance-voltage (C-V) and conductance-voltage (G/omega-V) measurements at 1 MHz and room temperature. Experimental results indicate that the change in dielectric constant (e), dielectric loss (epsilon ''), loss tangent (tan delta), the real (M') and imaginary (M '') parts of electric modulus and ac electrical conductivity (sigma(ac)) with illumination were found to change linearly with illumination level (P). On the other hand, the epsilon', epsilon '', tan delta and sigma(ac) vs P have positive slope while the M' and M '' vs P have negative slope. Such behavior of dielectric properties and sigma(ac) can be attributed to illumination induced electron-hole pairs under illumination effect in the depletion region of SDs. The obtained results under illumination suggest that these devices can be used as a sensor in optical applications.Öğe Temperature dependent currentvoltage (IV) characteristics of Au/n-Si (1 1 1) Schottky barrier diodes with PVA(Ni,Zn-doped) interfacial layer(ELSEVIER SCI, 2011) Tunç, Tuncay; Altındal, Şemsettin; Uslu, İbrahim; Dökme, İlbilge; Uslu, HabibeCurrent-voltage (I-V) characteristics of Au/PVA/n-Si (1 1 1) Schottky barrier diodes (SBDs) have been investigated in the temperature range 80-400 K. Here, polyvinyl alcohol (PVA) has been used as interfacial layer between metal and semiconductor layers. The zero-bias barrier height (Phi(B0)) and ideality factor (n) determined from the forward bias I-V characteristics were found strongly dependent on temperature. The forward bias semi-logarithmic I-V curves for different temperatures have an almost common cross-point at a certain bias voltage. The values of Phi(B0) increase with the increasing temperature whereas those of n decrease. Therefore, we have attempted to draw Phi(B0) vs. q/2kT plot in order to obtain evidence of a Gaussian distribution (GD) of the barrier heights (BHs). The mean value of BH (Phi) over bar (B0) and standard deviation (sigma(0)) were found to be 0.974 eV and 0.101 V from this plot, respectively. Thus, the slope and intercept of modified In(I-0/T-2)-q(2)sigma(2)(0)/2(kT)(2) vs. q/kT plot give the values of (Phi) over bar (B0) and Richardson constant (A*) as 0.966 eV and 118.75 A/cm(2)K(2), respectively, without using the temperature coefficient of the BH. This value of A* 118.75 A/cm(2)K(2) is very close to the theoretical value of 120 A/cm(2)K(2) for n-type Si. Hence, it has been concluded that the temperature dependence of the forward I-V characteristics of Au/PVA/n-Si (1 1 1) SBDs can be successfully explained on the basis of the Thermionic Emission (TE) theory with a GD of the BHs at Au/n-Si interface.Öğe The illumination intensity and applied bias voltage on dielectric properties of au/polyvinyl alcohol (Co, Zn-doped)/n-Si Schottky barrier diodes(Wiley-Blackwell, 2011) Uslu, Habibe; Altındal, Şemsettin; Tunç, Tuncay; Uslu, İbrahim; Mammadov, Tofig S.The Au/polyvinyl alcohol (PVA) (Co, Zndoped)/ n-Si Schottky barrier diodes (SBDs) were exposed to various illumination intensities. Illumination effect on the dielectric properties has been investigated by using capacitance- voltage (C-V) and conductance-voltage (G/omega-V) characteristics at 1 MHz and room temperature. The values of dielectric constant (epsilon'), dielectric loss (epsilon ''), loss tangent (tan delta), electric modulus (M' and M ''), and AC electrical conductivity (sigma(AC)) were found strongly intensity dependent on both the illumination levels and applied bias voltage especially in depletion and accumulation regions. Such bias and illumination dependency of these parameters can be explained on the basis of Maxwell-Wagner interfacial polarization and restructuring and reordering of charges at interface states. In addition, the epsilon'-V plots also show an intersection feature at similar to 2.8 V and such behavior of the epsilon'-V plots appears as an abnormality compared with the conventional behavior of an ideal SBD. The obtained results revealed that illumination intensity enhances the conductivity of Au/PVA(Co, Zndoped)/ n-Si SBD. (C) 2010 Wiley Periodicals, Inc. J Appl Polym Sci 120: 322-328, 2011
