Current conduction in Schottky barrier diodes with poly(propylene glycol)-b-polystyrene block copolymer interfacial layer

Polymeric materials have gained great importance in electron devices. There has been considerable number of studies on block copolymers due to enhanced features that appear after co-polymerization. In this study, poly (propylene glycol)-b-polystyrene block copolymer has been synthesized and Schottky barrier diodes (SBDs) have been fabricated with this block copolymer. Current-voltage (I-V) measurements have been conducted at room temperature in order to investigate electrical characteristics and current conductions governing in these SBDs. Series resistance and shunt resistance of the SBDs have been calculated using Ohm’s law. Ideality factor, reverse saturation current and zero-bias barrier height of the SBDs have been extracted from the forward-bias I-V data. Fabricated SBDs exhibited high rectifying ratio of the order 104. Also, current conduction mechanisms and the density of interface states in the SBDs have been investigated. Calculated values of density of interface states in the SBDs are on the order of 1013 which is acceptable for this kind of SBDs having polymeric interfacial layer

Illumination Effects on Electrical Characteristics of Au/Bi4Ti3O12/n-Si Structures

Gokcen, Muharrem/0000-0001-9063-3028WOS: 000358931600004The effects of illumination on electrical and photocurrent properties of Au/n-Si structures with and without Bi4Ti3O12 interfacial ferroelectric layer were investigated using current-voltage (I-V) and admittance measurements (C-V, G/omega-V). For this purpose, Au/n-Si metal-semiconductor (MS) and Au/Bi4Ti3O12/n-Si metal-ferroelectric-semiconductor (MFS) structures were fabricated and measured at dark and under various illumination intensity levels at room temperature. It was found that the ferroelectric interfacial layer increased the rectifying ratio by decreasing the leakage current and passivated the interface states. Furthermore, the photocurrent of MFS structure is more sensitive to illumination compared with that of MS structure, whereas the situation is opposite for interface states

Dielectric Properties of Au/PVA (Cobalt-Doped)/n-Si Photoconductive Diodes

Gokcen, Muharrem/0000-0001-9063-3028;WOS: 000312660100014The voltage (V) and frequency (f) dependence of dielectric parameters such as the dielectric constant (epsilon'), dielectric loss (epsilon aEuro(3)), dielectric loss tangent (tan delta), real and imaginary parts of electrical modulus (M' and MaEuro(3)), and alternating-current (AC) electrical conductivity (sigma (AC)) of Au/PVA (cobalt-doped)/n-Si structures have been investigated by using experimental admittance measurements conducted at room temperature. The values of epsilon', epsilon aEuro(3), and tan delta were found to be strong functions of voltage and frequency, especially at low frequencies in the positive voltage region. It was observed that the values of epsilon' and epsilon aEuro(3) increase as the frequency decreases. The M' values increase with increasing frequency due to increasing dielectric relaxation, while MaEuro(3) values, in general, remain stable as frequency is changed. The sigma (AC) values at each bias voltage increase with increasing frequency.Duzce University Scientific Research ProjectDuzce University [2012.05.02.110]This work is supported by Duzce University Scientific Research Project (project no. 2012.05.02.110). Also, the author would like to thank Dr. Ibrahim Uslu (Department of Chemistry Education, Gazi University, Turkey), Dr. Tuncay Tunc (Department of Science Education, Aksaray University, Turkey), and Dr. Semsettin Altindal (Department of Physics, Gazi University, Turkey) for providing the material and its spinning

THE INVESTIGETION OF FREQUENCY AND TEMPERATURE DEPENDENCE OF ELECTRICAL AND DIELECTRIC PROPERTIES OF Au/SiO2/n-GaAs (MOS) STRUCTURES

u/SiO2/n-GaAs (MOS) yapıların; seri direnç (Rs), arayüzey durumları (Nss) ve ac elektrik iletkenlik (sac) gibi elektriksel karakteristikleri ile dielektrik sabiti (e\'), dielektrik kayıp (e\"), dielektrik kayıp tanjantı (tand), reel ve imajiner elektrik modülü (M\' and M\") gibi dielektrik özelliklerinin frekans, sıcaklık ve oksit tabaka kalınlığına bağımlılığı, 80-350 K sıcaklık aralığında değisik frekans ve oksit tabaka kalınlıkları için deneysel kapasitans-voltaj (C-V) ve kondüktans-voltaj (G/w-V) ölçümleri kullanılarak arastırıldı. Deneysel sonuçlar göstermistir ki; özellikle yüksek sıcaklık ve düsük frekanslarda, arayüzey durum yoğunluğunun (Nss) dağılımı ile gevseme zamanı t ve arayüzeyin termal olarak yeniden yapılanmasına bağlı olarak C ve G/w değerleri frekans, sıcaklık ve oksit tabaka kalınlığına oldukça bağımlıdır. Au/SiO2/n-GaAs (MOS) yapısının Rs ve Nss değerleri sırasıyla Nicollian ve Hill-Coleman metotları kullanılarak hesaplanmıs olup bu değerler artan frekansla azalmaktadır. Artan sıcaklıkla azalan seri direnç, artan oksit kalınlığına bağlı olarak lineer olarak artmaktadır. Dielektrik sabiti, dielektrik kayıp, kayıp tanjant ve elektrik modülünün frekans, sıcaklık ve oksit tabaka kalınlığının kuvvetli bir fonksiyonu olduğu bulundu. ε\', ε\'\' ve tanδ değerleri artan frekansla azalırken reel ve imajiner elektrik modülü artan frekansla artmaktadır. Ayrıca, ε\' ve ε\'\' artan v sıcaklıkla artarken, reel ve imajiner elektrik modülü artan sıcaklıkla azalmaktadır. Artan oksit kalınlığına bağlı olarak dielektrik sabiti e\' değerleri azalırken, tand ve elektrik modülünün imajiner bileseni olan M\" değerleri artmaktadır.The frequency, temperature and oxide thickness dependence of electrical characteristics such as series resistance (Rs), interface states (Nss) and ac electrical conductivity (sac) and dielectric properties such as dielectric constant (e\'), dielectric loss (e\"), dielectric loss tangent (tand), real and imaginary part of electric modulus (M\' and M\") of the Au/SiO2/n-GaAs (MOS) structures have been investigated in the temperature range of 80-350 K at various frequencies by using experimental capacitance-voltage (C-V) and conductance-voltage (G/w- V) measurements. Experimental results show that both the values of C and G/w were quite sensitive to frequency, temperature and oxide layer thickness at relatively high temperatures and low frequencies due to a continuous density distribution of Nss and their relaxation time (t), and thermal restructuring and reordering of the interface. The values Rs and Nss of the Au/SiO2/n-GaAs (MOS) structure were obtained from Nicollian and Hill-Coleman methods, respectively, and their values decrease with increasing frequency. While the series resistance decreases with increasing temperature, it increases linearly with increasing oxide layer thickness. The dielectric constant, dielectric loss, loss tangent and the electric modulus were found a strong function of frequency, temperature and oxide layer thickness. While the values of the ε\', ε\'\' and tanδ decrease with increasing frequencies, the electric modulus (real and imaginary part) increase vii with increasing frequency. Also, while the dielectric constant and dielectric loss increase with increasing temperature, electric modulus (real and imaginary part) decrease with increasing temperature. While the ε\' decreases with increasing oxide layer thickness tand and imaginary electric modulus increase with increasing oxide layer thickness

On the profile of temperature dependent electrical and dielectric properties of Au/SiO2/n-GaAs (MOS) structures at various frequencies

Gokcen, Muharrem/0000-0001-9063-3028;WOS: 000271908100071The temperature (T) dependence of electrical and dielectric characteristics such as series resistance (R-s), dielectric constant (epsilon'), dielectric loss (epsilon ''), dielectric loss tangent (tan delta), and real and imaginary pan of electrical modulus (M' and M '') of the Au/SiO2/n-GaAs (MOS) structures have been investigated in the temperature range of 80-350 K at various frequencies by using experimental capacitance (C) and conductance (G/w) measurements. Experimental results show that both C and G/w characteristics were quite sensitive to frequency and temperature at especially high temperatures and low frequencies due to a continuous density distribution of interface states and their relaxation time, and thermal restructuring and reordering of the inter-face. Series resistance values of this device obtained from Nicollian method decrease with increasing frequency and temperature. The epsilon', epsilon '', tan delta, and M' and M '' were found a strong function of frequency and temperature. While the values of epsilon', epsilon '', and tan delta decrease, M' and M '' increase with increasing frequency. Also, while epsilon' and epsilon '' increase, M' and M '' decrease with increasing temperature. The tan delta and M' values are almost independent temperature especially at high frequencies (f >= 500 kHz). (C) 2009 Elsevier B.V. All rights reserved.Turkish Prime Ministry state Planning Agency [2001K120590]; European Transnational Access Program [RITA-CT-2003-506095-WISSMC]This study is supported by the Turkish Prime Ministry state Planning Agency under project no: 2001K120590. We acknowledge the support of European Transnational Access Program no. RITA-CT-2003-506095-WISSMC. Last but not least we thank Dr. Hadas Shtrikman from the Braun Center for Submicron Research for making the samples feasible for this research

The effects of Bi4Ti3O12 interfacial ferroelectric layer on the dielectric properties of Au/n-Si structures

YILDIRIM, Mert/0000-0002-8526-1802; Gokcen, Muharrem/0000-0001-9063-3028WOS: 000357932200004Au/n-Si metal-semiconductor (MS) and Au/Bi4Ti3O12/n-Si metal-ferroelectricsemiconductor (MFS) structures were fabricated and admittance measurements were held between 5 kHz and 1 MHz at room temperature so that dielectric properties of these structures could be investigated. The ferroelectric interfacial layer Bi4Ti3O12 decreased the polarization voltage by providing permanent dipoles at metal/semiconductor interface. Depending on different mechanisms, dispersion behavior was observed in dielectric constant, dielectric loss and loss tangent versus bias voltage plots of both MS and MFS structures. The real and imaginary parts of complex modulus of MFS structure take smaller values than those of MS structure, because permanent dipoles in ferroelectric layer cause a large spontaneous polarization mechanism. While the dispersion in AC conductivity versus frequency plots of MS structure was observed at high frequencies, for MFS structure it was observed at lower frequencies.Duzce University Scientific Research ProjectDuzce University [2010.05.02.056, 2013.05.02.195]This work is supported by Duzce University Scientific Research Project (Project Nos. 2010.05.02.056 and 2013.05.02.195)

Double parallel barrier height behavior of Au/Poly (linoleic acid)-g-poly (methyl methacrylate) (PLiMMA)/n-Si structure

Taran, Songul/0000-0001-8115-2169WOS: 000496833600015The main electrical parameters and current conduction mechanisms of Au/Poly (linoleic acid)-g-poly (methyl methacrylate)/n-Si diode were carried out in the range of 300 K-400 K with a temperature increment of 10 K. Two distinct linear regions were observed in semi-logarithmic current-voltage (I-V) plots for each investigated temperature. For each linear region, leakage currents, barrier heights and ideality factors which are main electrical parameters of the diode were extracted from the experimental I-V measurements. Also, interface state density was derived by Card and Rhoderick's function. To obtain effective current conduction mechanisms, lnI versus lnV plots were obtained by taking into account of double linear region of current-voltage plots and abnormal increasing of barrier height and ideality factor at above the room temperature

Effect of frequency on dielectric properties of liquid crystal doped with side-chain liquid crystalline polymer

Gokcen, Muharrem/0000-0001-9063-3028WOS: 000294092500076The frequency and applied bias voltage dependence of the dielectric properties and dielectric anisotropy of liquid crystal (LC) doped with side-chain liquid crystalline polymer (SLCP) mixture have been investigated using the admittance spectroscopy method (C-V and G/omega-V) in the frequency range of 10 kHz to 10 MHz at room temperature. The liquid crystal used in this experiment is E63. The doping material used in this study is SLCP and its concentration is ensured 1 wt % in E63. Dielectric constant (epsilon'), dielectric loss (epsilon), dielectric loss tangent (tan delta) and real and imaginary parts of electrical modulus (M' and M '') of the E63/SLCP mixture was also calculated. Moreover, dielectric anisotropy (Delta epsilon) as a function of frequency was obtained. Results show that the values of the all dielectric parameters are strong functions of frequency and applied bias voltage. After a critical frequency, dielectric anisotropy has negative values according to p/n type changing. (C) 2011 Elsevier B.V. All rights reserved

A comparative study regarding effects of interfacial ferroelectric Bi4Ti3O12 (BTO) layer on electrical characteristics of Au/n-Si structures

Gokcen, Muharrem/0000-0001-9063-3028; YILDIRIM, Mert/0000-0002-8526-1802WOS: 000336899800011Present study focuses on the effects of interfacial ferroelectric BTO layer on the electrical characteristics of Au/n-Si structures, hence Au/n-Si (MS) and Au/BTO/n-Si (MFS) structures were fabricated and admittance measurements (capacitance-voltage: C-V and conductance-voltage: G/omega-V) of both structures were conducted between 10 kHz and 1MHz at room temperature. Results showed that C-V and G/omega-V characteristics were affected not only by frequency but also through deposition of BTO layer. Some effects can be listed as sharper peaks in C-V plots, higher capacitance and conductance values. Structure's series resistance (R-s) also decreased due to BTO layer. Interface states (N-ss) profiles of the structures were obtained using Hill-Coleman and high-low frequency capacitance (C-HF-C-LF). Some of the main electrical parameters were extracted from C-2-V plots using depletion capacitance approach. Furthermore, current-voltage characteristics of MS and MFS structures were presented.Duzce University Scientific Research ProjectDuzce University [2010.05.02.056]This work is supported by Duzce University Scientific Research Project (project no. 2010.05.02.056)

Investigation of electrical and photovoltaic properties of Au/poly(propylene glycol)-b-polystyrene/n-Si diode at various illumination intensities

Gokcen, Muharrem/0000-0001-9063-3028WOS: 000333484600005Electrical and photovoltaic properties of Au/poly(propylene glycol)-b-polystyrene/n-Si diode were investigated under various illumination intensities. Field emission scanning electron microscope micrographs of the interfacial polymer layer were provided for verification of the nano-fibre pattern. The current-voltage (I-V) measurements of the diode in the dark and under various illumination intensities (50-250 mW/cm(2)) were carried out and the main electrical parameters of the diode such as leakage current (I-0), ideality factor (n), zero-bias barrier height (phi(B0)), series and shunt resistance (R-s and R-sh), density of surface states (N-ss), open circuit voltage (V-oc) and short-circuit current (I-sc) were obtained in these conditions.Turkish Scientific Research CouncilTurkiye Bilimsel ve Teknolojik Arastirma Kurumu (TUBITAK) [110T884]; Duzce University Scientific Research ProjectDuzce University [2011.05.03.068, 2011.05.HD.026, 2012.05.02.110, 2012.05.HD.052]This work is supported financially by Turkish Scientific Research Council [grant number: 110T884], Duzce University Scientific Research Project [project numbers 2011.05.03.068, 2011.05.HD.026, 2012.05.02.110, 2012.05.HD.052]