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Papers by Mert Emre Yıldırım

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

Indian Journal of Pure & Applied Physics, 2017

Polymeric materials have gained great importance in electron devices. There has been considerable... more 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 10 4 . Also, current conduction mechanisms and the density of interface states in the SBDs have been investigated. Calculated values of density of interface s...

Research paper thumbnail of CdTe Kuantum Noktası Katkısının E63, E7 ve SCLP Sıvı Kristal Malzemelerin Akım-Voltaj Karakteristikleri Üzerine Etkisi

Düzce Üniversitesi Bilim ve Teknoloji Dergisi, 2020

The usage of nano-sized quantum dots (QDs) particularly in guest-host based hybrid mediums reveal... more The usage of nano-sized quantum dots (QDs) particularly in guest-host based hybrid mediums revealed enhancements in electro-optical properties of the mediums, therefore the focus of considerable amount of contemporary studies has been about dispersal of QDs for improvements in medium. This study investigates the effects of CdTe QD dispersal on current-voltage characteristics of some liquid crystalline materials such as E63, E7 and SCLP. Current is increased for all samples due to QD dispersal, however the best improvement is obtained for E7. Hence, current-voltage characteristics of E7 and QD dispersed E7 mediums were also investigated under UV light exposure. Current values of both mediums were found to increase with increasing UV light power due to generation of electron-hole pairs. Photocurrent's dependence on light power revealed that QD dispersal does not affect recombination mechanism in the medium. On the other hand, UV light responsivity of QD dispersed E7 was obtained approximately twice of that of E7. Thus, it was concluded that CdTe QDs make considerable contribution to current-voltage and photoconductivity characteristics of E7 in dark and under UV light illumination.

Research paper thumbnail of Controlling the electrical characteristics of Au/n-Si structures by interfacial insulator layer

Materials Science in Semiconductor Processing, 2012

Admittance (C-V and G/o-V) measurements of Au/n-Si (metal-semiconductor, MS) and Au/SnO 2 /n-Si (... more Admittance (C-V and G/o-V) measurements of Au/n-Si (metal-semiconductor, MS) and Au/SnO 2 /n-Si (metal-insulator-semiconductor, MIS) structures were carried out between 1 kHz and 1 MHz at room temperature to investigate the interfacial insulator layer effect on the electrical characteristics of Au/n-Si structures. Experimental results showed that MIS structure's capacitance (C) values, unlike those of MS structure, became stable especially at high frequencies in the accumulation region. Also, the insulator layer caused structure's shunt resistance (R sh) to increase. It was found that series resistance (R s) is more effective in the accumulation region at high frequencies after the correction was applied to C and G/o data to eliminate the R s effect. The density of interface states (D is) was obtained using Hill-Coleman method, D is values MIS structure was obtained smaller than those of MS structure. Results indicate that interfacial insulator layer brings about some improvements in electrical characteristics of Au/n-Si structures.

Research paper thumbnail of Influence of interfacial layer thickness on frequency dependent dielectric properties and electrical conductivity in Al/Bi4Ti3O12/p-Si structures

Journal of Vacuum Science & Technology A: Vacuum, Surfaces, and Films, 2014

ABSTRACT Three Al/Bi4Ti3O12/p-Si structures were fabricated with different interfacial layer thic... more ABSTRACT Three Al/Bi4Ti3O12/p-Si structures were fabricated with different interfacial layer thickness values (10, 25, and 53 nm) and admittance measurements of the structures were carried out between 1 kHz and 1 MHz in order to investigate the influence of interfacial layer thickness on dielectric properties of these structures. For the structure with thicker interfacial layer, higher dielectric constant (e0) and dielectric loss (e00) values were obtained at low frequencies. At high frequencies, these parameters tend to be saturated and become almost constant. Loss tangent versus frequency plots exhibit a peak and magnitude of the peak weakens with increasing frequency and shifts toward high frequency region. The dispersion in e0 and e00 with varying thickness at low frequencies was ascribed to interfacial polarization. In addition, obtained e00 values indicated higher energy dissipation in the structure with thicker interfacial layer. Admittance data of the structures were also considered in terms of modulus formalism to interpret the relaxation processes in the structures. Moreover, dc electrical conductivity values were derived using frequency dependent ac electrical conductivity of the structures.

Research paper thumbnail of Gaussian distribution of inhomogeneous barrier height in Au/n-Si (111) Schottky barrier diodes at low temperatures

Materials Science in Semiconductor Processing, 2014

The current-voltage (I-V) measurements on Al/ZnS Schottky barrier diodes in the temperature range... more The current-voltage (I-V) measurements on Al/ZnS Schottky barrier diodes in the temperature range 303-423 K by the step of 15 K were carried out. The forward I-V characteristics were analyzed on the basis of the thermionic emission theory. The temperature dependence I-V parameters such as ideality factor (n) and barrier height ( b0) have been explained on the basis of inhomogeneity. An abnormal increase of apparent barrier height and decrease of ideality factor with increasing temperature have been explained due to the barrier height inhomogeneities on the basis of the thermionic emission theory with Gaussian distribution. Experimental results reveal the existence of a single Gaussian distribution with apparent barrier height value () of 1.091 eV and standard deviations ( s) of 0.18 V. Richardson constant (A*) was obtained as 8.49 x 10-2 A.m-2 K-2 from the ln(I 0 /T 2) vs. q/kT plot, which is far from the calculated value of 5.6 x 10 5 A.m-2 K-2. The modified Richardson plotof ln(I 0 /T 2)-(q 2  s 2 /2k 2 T 2) gives  and A* values as 1.093 eV and 6.07 x 10 5 A.m-2 K-2 , without using the temperature coefficient of the barrier height. This obtained value of A* is extremely close to the previously calculated value. So, the temperature dependence of the forward bias I-V characteristics of the Schottky device can be successfully explained on the basis of the thermionic emission mechanism with a single Gaussian distribution of the barrier heights.

Research paper thumbnail of UV Light Response of Electrical and Dielectric Properties in Zinc Phthalocyanine and Fullerene Dispersed Liquid Crystal Composites

Canadian Journal of Physics, 2015

Liquid crystal composites form an attractive research area in liquid crystal studies. Among these... more Liquid crystal composites form an attractive research area in liquid crystal studies. Among these composites, nematic liquid crystal composited E63 is of particular interest. In the present study, E63 coded liquid crystal composites were dispersed with zinc phthalocyanine (Zn-Pc) and fullerene (C60), and three samples were prepared as E63, E63/Zn-Pc, and E63/Zn-Pc/C60 in indium tin oxide coated cells via capillary action. Later, current and capacitance measurements of the samples were carried out in darkness and under ultraviolet (UV) illumination (365 nm) of 100 mW/cm2 power intensity. It was found that both current and capacitance in the samples are affected by UV light and dispersal of Zn-Pc and C60. Particularly, dispersal of Zn-Pc led to occurrence of photovoltaic properties, which yielded open-circuit voltage of 0.37 V for the E63/Zn-Pc sample. Furthermore, dielectric constant and dielectric anisotropy values were extracted from capacitance values, and UV light was seen to inc...

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

Bulletin of Materials Science, 2014

Present study focuses on the effects of interfacial ferroelectric BTO layer on the electrical cha... more Present 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/ω-V) of both structures were conducted between 10 kHz and 1 MHz at room temperature. Results showed that C-V and G/ω-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. Keywords. Metal-ferroelectric-semiconductor (MFS) structures; Bi 4 Ti 3 O 12 (BTO); series resistance; interface states.

Research paper thumbnail of The effect of gamma irradiation on electrical and dielectric properties of organic-based Schottky barrier diodes (SBDs) at room temperature

Radiation Physics and Chemistry, 2012

... Mert Yıldırım b ... al., 2004], [Feteha et al., 2002], [Gomaa, 2001], [Gökçen et al., 2008], ... more ... Mert Yıldırım b ... al., 2004], [Feteha et al., 2002], [Gomaa, 2001], [Gökçen et al., 2008], [Jayavel et al., 2000], [Karataş et al., 2009], [Karataş and Türüt, 2010], [Radwan, 2007], [Uğurel et al., 2008], [Umana-Membreno et al., 2003], [Ma, 1989], [Oldham and McLean, 2003], [Taşcıoğlu ...

Research paper thumbnail of Investigation of current-voltage characteristics and current conduction mechanisms in composites of polyvinyl alcohol and bismuth oxide

Polymer Engineering & Science, 2013

Temperature dependent current-voltage (I–V) measurements of Au/Polyvinyl Alcohol + Bi2O3/n-Si str... more Temperature dependent current-voltage (I–V) measurements of Au/Polyvinyl Alcohol + Bi2O3/n-Si structure were conducted between 100 and 350 K for investigating the temperature dependence of I–V characteristics and current conduction mechanisms in the structure. Series resistance of the structure is calculated using Ohm's law and Cheungs' method. Ideality factor (n) and zero-bias barrier height (ΦBo) were obtained considering thermionic emission theory. From 100 to 350 K, n changed from 32.1 to 3.54, and ΦBo changed from 0.27 to 0.99 eV. Obtained temperature dependent values of n and ΦBo suggested that thermionic emission is not the dominant current conduction mechanism. Therefore, Ln(I)–Ln(V) curves of the studied structure were plotted for investigating current conduction mechanisms in the structure and current flow is explained considering space charge limited current. Moreover, density of interface states (Dit) in the structure were calculated and its temperature dependence was investigated such that Dit values are reduced to the order of ∼1013 eV−1 cm−2 from ∼1014 eV−1 cm−2 with increasing temperature. POLYM. ENG. SCI., 54:1811–1816, 2014. © 2013 Society of Plastics Engineers

Research paper thumbnail of Investigation on dielectric properties of atomic layer deposited Al2O3 dielectric films

Journal of Vacuum Science & Technology A: Vacuum, Surfaces, and Films, 2014

ABSTRACT Al/Al2O3/p-Si Schottky barrier diodes (SBDs) were fabricated using atomic layer depositi... more ABSTRACT Al/Al2O3/p-Si Schottky barrier diodes (SBDs) were fabricated using atomic layer deposition technique in order to investigate dielectric properties of SBDs. For this purpose, admittance measurements were conducted at room temperature between −1 V and 3 V in the frequency range of 10 kHz and 1 MHz. In addition to the investigation of Al2O3 morphology using atomic force microscope, dielectric parameters; such as dielectric constant (ε′), dielectric loss (ε″), dielectric loss tangent (tan δ), and real and imaginary parts of dielectric modulus (M′ and M″, respectively), were calculated and effect of frequency on these parameters of Al/Al2O3/p-Si SBDs was discussed. Variations in these parameters at low frequencies were associated with the effect of interface states in low frequency region. Besides dielectric parameters, ac electrical conductivity of these SBDs was also investigated.

Research paper thumbnail of Dielectric and AC electrical conductivity characteristics of liquid crystal doped with graphene

The European Physical Journal Applied Physics, 2012

The dielectric response of the liquid crystal (LC) and LC doped with graphene was studied by usin... more The dielectric response of the liquid crystal (LC) and LC doped with graphene was studied by using dielectric spectroscopy technique in the frequency range of 100 kHz to 10 MHz at room temperature. The LC material used in this experiment was E7 and the concentration of doping material graphene was acquired as 0.05 wt.% in E7. Dielectric constant (ε), dielectric loss (ε), dielectric loss tangent (tan δ) and AC conductivity of pure LC and graphene-doped LC mixture were also calculated. Results showed that all dielectric parameters are strong functions of frequency and applied bias voltage. Also, it was found that doping LC with graphene strongly influenced threshold voltage.

Research paper thumbnail of Controlling the electrical characteristics of Al/p-Si structures through Bi4Ti3O12 interfacial layer

Current Applied Physics, 2013

ABSTRACT In this study, the effects of high permittivity interfacial Bi4Ti3O12 (BTO) layer deposi... more ABSTRACT In this study, the effects of high permittivity interfacial Bi4Ti3O12 (BTO) layer deposition on the main electrical parameters; such as barrier height, series resistance, rectifying ratio, interface states and shunt resistance, of Al/p-Si structures are investigated using the currentevoltage (I-V) and admittance measurements (capacitance-voltage, C-V and conductance-voltage, G/omega-V) at 1 MHz and room temperature. I-V characteristics revealed that, due to BTO layer deposition, series resistance values that were calculated by both Ohm's law and Cheung's method decreased whereas shunt resistance values increased. Therefore, leakage current value decreased significantly by almost 35 times as a result of high permittivity interfacial BTO layer. Moreover, rectifying ratio was improved through BTO interfacial layer deposition. I-V data indicated that high permittivity interfacial BTO layer also led to an increase in barrier height. Same result was also obtained through C-V data. Obtained results showed that the performance of the device is considerably dependent on high permittivity BTO interfacial layer.

Research paper thumbnail of UV illumination effects on electrical characteristics of metal–polymer–semiconductor diodes fabricated with new poly(propylene glycol)-b-polystyrene block copolymer

Composites Part B: Engineering, 2014

Au/poly(propylene glycol)-b-polystyrene/n-Si (D1) and Au/poly(propylene glycol)-b-polystyrene(HAu... more Au/poly(propylene glycol)-b-polystyrene/n-Si (D1) and Au/poly(propylene glycol)-b-polystyrene(HAuCl 4 dispersed)/n-Si (D2) diodes were fabricated and their response to UV illumination was investigated using current-voltage measurements in dark and under various illumination intensities (50-250 mW/cm 2). Scanning Electron Microscope micrographs of the diodes were provided for morphological analysis. Main electrical parameters; such as ideality factor, barrier height and reverse saturation current, are calculated using Thermionic Emission and Norde's method, and it was found that they show dependence on UV illumination. Ideality factor values of D1 and D2 diodes in dark is 2.53 and 2.29 whereas they are 3.37 and 3.39 under 100 mW/cm 2 UV illumination, respectively. A noticeable effect of UV illumination is the considerable increase of current in the reverse bias region compared with current in dark such that current value increases by $10 3 times with 100 mW/cm 2 UV illumination for both diodes. Furthermore, density distribution profiles of surface states in these diodes were also investigated.

Research paper thumbnail of The Fe 3 O 4 nanoparticle doping effect in liquid crystal on electrical and dielectric properties

Canadian Journal of Physics, 2013

ABSTRACT Fe3O4 nanoparticles were doped into E63 coded liquid crystal (LC) with 0.1 wt% to invest... more ABSTRACT Fe3O4 nanoparticles were doped into E63 coded liquid crystal (LC) with 0.1 wt% to investigate the effect of Fe3O4 on the electrical and dielectric properties of LC in a wide range of frequency, bias voltage, and illumination. The frequency, bias voltage, and illumination level dependence of the electrical and dielectric properties of pure E63 and doped mixture (E63–Fe3O4) has been investigated using the current–voltage (I–V) and admittance spectroscopy (C–V and G/ω–V) data in the frequency range of 10 kHz – 1 MHz at room temperature. Results show that the increment in current with Fe3O4 doping is due to the metallic nature of the Fe3O4 nanoparticles. The current switching voltage of reorientation is shifted to lower voltage values as a result of Fe3O4 doping. Same behavior is also observed with increasing illumination level. The polarization contribution of Fe3O4 doping is evident considering the values of Δε′=εE63/Fe3O4′−εE63′ at low frequencies. Moreover, depending on the existence of Fe3O4 doping agent, there is a split in σ ac–f plots where σ ac values increase with frequency, especially at high frequencies.

Research paper thumbnail of Analyses of temperature-dependent interface states, series resistances, and AC electrical conductivities of Al/p—Si and Al/Bi4Ti3O12/p—Si structures by using the admittance spectroscopy method

Chinese Physics B, 2013

ABSTRACT In this study, Al/p—Si and Al/Bi4Ti3O12/p—Si structures are fabricated and their interfa... more ABSTRACT In this study, Al/p—Si and Al/Bi4Ti3O12/p—Si structures are fabricated and their interface states (N ss), the values of series resistance (R s), and AC electrical conductivity (σac) are obtained each as a function of temperature using admittance spectroscopy method which includes capacitance—voltage (C—V) and conductance—voltage (G—V) measurements. In addition, the effect of interfacial Bi4Ti3O12 (BTO) layer on the performance of the structure is investigated. The voltage-dependent profiles of N ss and R s are obtained from the high-low frequency capacitance method and the Nicollian method, respectively. Experimental results show that N ss and R s, as strong functions of temperature and applied bias voltage, each exhibit a peak, whose position shifts towards the reverse bias region, in the depletion region. Such a peak behavior is attributed to the particular distribution of N ss and the reordering and restructuring of N ss under the effect of temperature. The values of activation energy (E a), obtained from the slope of the Arrhenius plot, of both structures are obtained to be bias voltage-independent, and the E a of the metal-ferroelectric-semiconductor (MFS) structure is found to be half that of the metal—semiconductor (MS) structure. Furthermore, other main electrical parameters, such as carrier concentration of acceptor atoms (N A), built-in potential (V bi), Fermi energy (E F), image force barrier lowering (Δ φb), and barrier height (φb), are extracted using reverse bias C −2—V characteristics as a function of temperature.

Research paper thumbnail of Investigation of the inhomogeneous barrier height of an Au/Bi 4 Ti 3 O 12 /n-Si structure through Gaussian distribution of barrier height

Chinese Physics B, 2012

Tamer GUZEL *(a), Ahmet Kursat BILGILI (b) , Metin OZER (b)

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

Indian Journal of Pure & Applied Physics, 2017

Polymeric materials have gained great importance in electron devices. There has been considerable... more 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 10 4 . Also, current conduction mechanisms and the density of interface states in the SBDs have been investigated. Calculated values of density of interface s...

Research paper thumbnail of CdTe Kuantum Noktası Katkısının E63, E7 ve SCLP Sıvı Kristal Malzemelerin Akım-Voltaj Karakteristikleri Üzerine Etkisi

Düzce Üniversitesi Bilim ve Teknoloji Dergisi, 2020

The usage of nano-sized quantum dots (QDs) particularly in guest-host based hybrid mediums reveal... more The usage of nano-sized quantum dots (QDs) particularly in guest-host based hybrid mediums revealed enhancements in electro-optical properties of the mediums, therefore the focus of considerable amount of contemporary studies has been about dispersal of QDs for improvements in medium. This study investigates the effects of CdTe QD dispersal on current-voltage characteristics of some liquid crystalline materials such as E63, E7 and SCLP. Current is increased for all samples due to QD dispersal, however the best improvement is obtained for E7. Hence, current-voltage characteristics of E7 and QD dispersed E7 mediums were also investigated under UV light exposure. Current values of both mediums were found to increase with increasing UV light power due to generation of electron-hole pairs. Photocurrent's dependence on light power revealed that QD dispersal does not affect recombination mechanism in the medium. On the other hand, UV light responsivity of QD dispersed E7 was obtained approximately twice of that of E7. Thus, it was concluded that CdTe QDs make considerable contribution to current-voltage and photoconductivity characteristics of E7 in dark and under UV light illumination.

Research paper thumbnail of Controlling the electrical characteristics of Au/n-Si structures by interfacial insulator layer

Materials Science in Semiconductor Processing, 2012

Admittance (C-V and G/o-V) measurements of Au/n-Si (metal-semiconductor, MS) and Au/SnO 2 /n-Si (... more Admittance (C-V and G/o-V) measurements of Au/n-Si (metal-semiconductor, MS) and Au/SnO 2 /n-Si (metal-insulator-semiconductor, MIS) structures were carried out between 1 kHz and 1 MHz at room temperature to investigate the interfacial insulator layer effect on the electrical characteristics of Au/n-Si structures. Experimental results showed that MIS structure's capacitance (C) values, unlike those of MS structure, became stable especially at high frequencies in the accumulation region. Also, the insulator layer caused structure's shunt resistance (R sh) to increase. It was found that series resistance (R s) is more effective in the accumulation region at high frequencies after the correction was applied to C and G/o data to eliminate the R s effect. The density of interface states (D is) was obtained using Hill-Coleman method, D is values MIS structure was obtained smaller than those of MS structure. Results indicate that interfacial insulator layer brings about some improvements in electrical characteristics of Au/n-Si structures.

Research paper thumbnail of Influence of interfacial layer thickness on frequency dependent dielectric properties and electrical conductivity in Al/Bi4Ti3O12/p-Si structures

Journal of Vacuum Science & Technology A: Vacuum, Surfaces, and Films, 2014

ABSTRACT Three Al/Bi4Ti3O12/p-Si structures were fabricated with different interfacial layer thic... more ABSTRACT Three Al/Bi4Ti3O12/p-Si structures were fabricated with different interfacial layer thickness values (10, 25, and 53 nm) and admittance measurements of the structures were carried out between 1 kHz and 1 MHz in order to investigate the influence of interfacial layer thickness on dielectric properties of these structures. For the structure with thicker interfacial layer, higher dielectric constant (e0) and dielectric loss (e00) values were obtained at low frequencies. At high frequencies, these parameters tend to be saturated and become almost constant. Loss tangent versus frequency plots exhibit a peak and magnitude of the peak weakens with increasing frequency and shifts toward high frequency region. The dispersion in e0 and e00 with varying thickness at low frequencies was ascribed to interfacial polarization. In addition, obtained e00 values indicated higher energy dissipation in the structure with thicker interfacial layer. Admittance data of the structures were also considered in terms of modulus formalism to interpret the relaxation processes in the structures. Moreover, dc electrical conductivity values were derived using frequency dependent ac electrical conductivity of the structures.

Research paper thumbnail of Gaussian distribution of inhomogeneous barrier height in Au/n-Si (111) Schottky barrier diodes at low temperatures

Materials Science in Semiconductor Processing, 2014

The current-voltage (I-V) measurements on Al/ZnS Schottky barrier diodes in the temperature range... more The current-voltage (I-V) measurements on Al/ZnS Schottky barrier diodes in the temperature range 303-423 K by the step of 15 K were carried out. The forward I-V characteristics were analyzed on the basis of the thermionic emission theory. The temperature dependence I-V parameters such as ideality factor (n) and barrier height ( b0) have been explained on the basis of inhomogeneity. An abnormal increase of apparent barrier height and decrease of ideality factor with increasing temperature have been explained due to the barrier height inhomogeneities on the basis of the thermionic emission theory with Gaussian distribution. Experimental results reveal the existence of a single Gaussian distribution with apparent barrier height value () of 1.091 eV and standard deviations ( s) of 0.18 V. Richardson constant (A*) was obtained as 8.49 x 10-2 A.m-2 K-2 from the ln(I 0 /T 2) vs. q/kT plot, which is far from the calculated value of 5.6 x 10 5 A.m-2 K-2. The modified Richardson plotof ln(I 0 /T 2)-(q 2  s 2 /2k 2 T 2) gives  and A* values as 1.093 eV and 6.07 x 10 5 A.m-2 K-2 , without using the temperature coefficient of the barrier height. This obtained value of A* is extremely close to the previously calculated value. So, the temperature dependence of the forward bias I-V characteristics of the Schottky device can be successfully explained on the basis of the thermionic emission mechanism with a single Gaussian distribution of the barrier heights.

Research paper thumbnail of UV Light Response of Electrical and Dielectric Properties in Zinc Phthalocyanine and Fullerene Dispersed Liquid Crystal Composites

Canadian Journal of Physics, 2015

Liquid crystal composites form an attractive research area in liquid crystal studies. Among these... more Liquid crystal composites form an attractive research area in liquid crystal studies. Among these composites, nematic liquid crystal composited E63 is of particular interest. In the present study, E63 coded liquid crystal composites were dispersed with zinc phthalocyanine (Zn-Pc) and fullerene (C60), and three samples were prepared as E63, E63/Zn-Pc, and E63/Zn-Pc/C60 in indium tin oxide coated cells via capillary action. Later, current and capacitance measurements of the samples were carried out in darkness and under ultraviolet (UV) illumination (365 nm) of 100 mW/cm2 power intensity. It was found that both current and capacitance in the samples are affected by UV light and dispersal of Zn-Pc and C60. Particularly, dispersal of Zn-Pc led to occurrence of photovoltaic properties, which yielded open-circuit voltage of 0.37 V for the E63/Zn-Pc sample. Furthermore, dielectric constant and dielectric anisotropy values were extracted from capacitance values, and UV light was seen to inc...

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

Bulletin of Materials Science, 2014

Present study focuses on the effects of interfacial ferroelectric BTO layer on the electrical cha... more Present 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/ω-V) of both structures were conducted between 10 kHz and 1 MHz at room temperature. Results showed that C-V and G/ω-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. Keywords. Metal-ferroelectric-semiconductor (MFS) structures; Bi 4 Ti 3 O 12 (BTO); series resistance; interface states.

Research paper thumbnail of The effect of gamma irradiation on electrical and dielectric properties of organic-based Schottky barrier diodes (SBDs) at room temperature

Radiation Physics and Chemistry, 2012

... Mert Yıldırım b ... al., 2004], [Feteha et al., 2002], [Gomaa, 2001], [Gökçen et al., 2008], ... more ... Mert Yıldırım b ... al., 2004], [Feteha et al., 2002], [Gomaa, 2001], [Gökçen et al., 2008], [Jayavel et al., 2000], [Karataş et al., 2009], [Karataş and Türüt, 2010], [Radwan, 2007], [Uğurel et al., 2008], [Umana-Membreno et al., 2003], [Ma, 1989], [Oldham and McLean, 2003], [Taşcıoğlu ...

Research paper thumbnail of Investigation of current-voltage characteristics and current conduction mechanisms in composites of polyvinyl alcohol and bismuth oxide

Polymer Engineering & Science, 2013

Temperature dependent current-voltage (I–V) measurements of Au/Polyvinyl Alcohol + Bi2O3/n-Si str... more Temperature dependent current-voltage (I–V) measurements of Au/Polyvinyl Alcohol + Bi2O3/n-Si structure were conducted between 100 and 350 K for investigating the temperature dependence of I–V characteristics and current conduction mechanisms in the structure. Series resistance of the structure is calculated using Ohm's law and Cheungs' method. Ideality factor (n) and zero-bias barrier height (ΦBo) were obtained considering thermionic emission theory. From 100 to 350 K, n changed from 32.1 to 3.54, and ΦBo changed from 0.27 to 0.99 eV. Obtained temperature dependent values of n and ΦBo suggested that thermionic emission is not the dominant current conduction mechanism. Therefore, Ln(I)–Ln(V) curves of the studied structure were plotted for investigating current conduction mechanisms in the structure and current flow is explained considering space charge limited current. Moreover, density of interface states (Dit) in the structure were calculated and its temperature dependence was investigated such that Dit values are reduced to the order of ∼1013 eV−1 cm−2 from ∼1014 eV−1 cm−2 with increasing temperature. POLYM. ENG. SCI., 54:1811–1816, 2014. © 2013 Society of Plastics Engineers

Research paper thumbnail of Investigation on dielectric properties of atomic layer deposited Al2O3 dielectric films

Journal of Vacuum Science & Technology A: Vacuum, Surfaces, and Films, 2014

ABSTRACT Al/Al2O3/p-Si Schottky barrier diodes (SBDs) were fabricated using atomic layer depositi... more ABSTRACT Al/Al2O3/p-Si Schottky barrier diodes (SBDs) were fabricated using atomic layer deposition technique in order to investigate dielectric properties of SBDs. For this purpose, admittance measurements were conducted at room temperature between −1 V and 3 V in the frequency range of 10 kHz and 1 MHz. In addition to the investigation of Al2O3 morphology using atomic force microscope, dielectric parameters; such as dielectric constant (ε′), dielectric loss (ε″), dielectric loss tangent (tan δ), and real and imaginary parts of dielectric modulus (M′ and M″, respectively), were calculated and effect of frequency on these parameters of Al/Al2O3/p-Si SBDs was discussed. Variations in these parameters at low frequencies were associated with the effect of interface states in low frequency region. Besides dielectric parameters, ac electrical conductivity of these SBDs was also investigated.

Research paper thumbnail of Dielectric and AC electrical conductivity characteristics of liquid crystal doped with graphene

The European Physical Journal Applied Physics, 2012

The dielectric response of the liquid crystal (LC) and LC doped with graphene was studied by usin... more The dielectric response of the liquid crystal (LC) and LC doped with graphene was studied by using dielectric spectroscopy technique in the frequency range of 100 kHz to 10 MHz at room temperature. The LC material used in this experiment was E7 and the concentration of doping material graphene was acquired as 0.05 wt.% in E7. Dielectric constant (ε), dielectric loss (ε), dielectric loss tangent (tan δ) and AC conductivity of pure LC and graphene-doped LC mixture were also calculated. Results showed that all dielectric parameters are strong functions of frequency and applied bias voltage. Also, it was found that doping LC with graphene strongly influenced threshold voltage.

Research paper thumbnail of Controlling the electrical characteristics of Al/p-Si structures through Bi4Ti3O12 interfacial layer

Current Applied Physics, 2013

ABSTRACT In this study, the effects of high permittivity interfacial Bi4Ti3O12 (BTO) layer deposi... more ABSTRACT In this study, the effects of high permittivity interfacial Bi4Ti3O12 (BTO) layer deposition on the main electrical parameters; such as barrier height, series resistance, rectifying ratio, interface states and shunt resistance, of Al/p-Si structures are investigated using the currentevoltage (I-V) and admittance measurements (capacitance-voltage, C-V and conductance-voltage, G/omega-V) at 1 MHz and room temperature. I-V characteristics revealed that, due to BTO layer deposition, series resistance values that were calculated by both Ohm's law and Cheung's method decreased whereas shunt resistance values increased. Therefore, leakage current value decreased significantly by almost 35 times as a result of high permittivity interfacial BTO layer. Moreover, rectifying ratio was improved through BTO interfacial layer deposition. I-V data indicated that high permittivity interfacial BTO layer also led to an increase in barrier height. Same result was also obtained through C-V data. Obtained results showed that the performance of the device is considerably dependent on high permittivity BTO interfacial layer.

Research paper thumbnail of UV illumination effects on electrical characteristics of metal–polymer–semiconductor diodes fabricated with new poly(propylene glycol)-b-polystyrene block copolymer

Composites Part B: Engineering, 2014

Au/poly(propylene glycol)-b-polystyrene/n-Si (D1) and Au/poly(propylene glycol)-b-polystyrene(HAu... more Au/poly(propylene glycol)-b-polystyrene/n-Si (D1) and Au/poly(propylene glycol)-b-polystyrene(HAuCl 4 dispersed)/n-Si (D2) diodes were fabricated and their response to UV illumination was investigated using current-voltage measurements in dark and under various illumination intensities (50-250 mW/cm 2). Scanning Electron Microscope micrographs of the diodes were provided for morphological analysis. Main electrical parameters; such as ideality factor, barrier height and reverse saturation current, are calculated using Thermionic Emission and Norde's method, and it was found that they show dependence on UV illumination. Ideality factor values of D1 and D2 diodes in dark is 2.53 and 2.29 whereas they are 3.37 and 3.39 under 100 mW/cm 2 UV illumination, respectively. A noticeable effect of UV illumination is the considerable increase of current in the reverse bias region compared with current in dark such that current value increases by $10 3 times with 100 mW/cm 2 UV illumination for both diodes. Furthermore, density distribution profiles of surface states in these diodes were also investigated.

Research paper thumbnail of The Fe 3 O 4 nanoparticle doping effect in liquid crystal on electrical and dielectric properties

Canadian Journal of Physics, 2013

ABSTRACT Fe3O4 nanoparticles were doped into E63 coded liquid crystal (LC) with 0.1 wt% to invest... more ABSTRACT Fe3O4 nanoparticles were doped into E63 coded liquid crystal (LC) with 0.1 wt% to investigate the effect of Fe3O4 on the electrical and dielectric properties of LC in a wide range of frequency, bias voltage, and illumination. The frequency, bias voltage, and illumination level dependence of the electrical and dielectric properties of pure E63 and doped mixture (E63–Fe3O4) has been investigated using the current–voltage (I–V) and admittance spectroscopy (C–V and G/ω–V) data in the frequency range of 10 kHz – 1 MHz at room temperature. Results show that the increment in current with Fe3O4 doping is due to the metallic nature of the Fe3O4 nanoparticles. The current switching voltage of reorientation is shifted to lower voltage values as a result of Fe3O4 doping. Same behavior is also observed with increasing illumination level. The polarization contribution of Fe3O4 doping is evident considering the values of Δε′=εE63/Fe3O4′−εE63′ at low frequencies. Moreover, depending on the existence of Fe3O4 doping agent, there is a split in σ ac–f plots where σ ac values increase with frequency, especially at high frequencies.

Research paper thumbnail of Analyses of temperature-dependent interface states, series resistances, and AC electrical conductivities of Al/p—Si and Al/Bi4Ti3O12/p—Si structures by using the admittance spectroscopy method

Chinese Physics B, 2013

ABSTRACT In this study, Al/p—Si and Al/Bi4Ti3O12/p—Si structures are fabricated and their interfa... more ABSTRACT In this study, Al/p—Si and Al/Bi4Ti3O12/p—Si structures are fabricated and their interface states (N ss), the values of series resistance (R s), and AC electrical conductivity (σac) are obtained each as a function of temperature using admittance spectroscopy method which includes capacitance—voltage (C—V) and conductance—voltage (G—V) measurements. In addition, the effect of interfacial Bi4Ti3O12 (BTO) layer on the performance of the structure is investigated. The voltage-dependent profiles of N ss and R s are obtained from the high-low frequency capacitance method and the Nicollian method, respectively. Experimental results show that N ss and R s, as strong functions of temperature and applied bias voltage, each exhibit a peak, whose position shifts towards the reverse bias region, in the depletion region. Such a peak behavior is attributed to the particular distribution of N ss and the reordering and restructuring of N ss under the effect of temperature. The values of activation energy (E a), obtained from the slope of the Arrhenius plot, of both structures are obtained to be bias voltage-independent, and the E a of the metal-ferroelectric-semiconductor (MFS) structure is found to be half that of the metal—semiconductor (MS) structure. Furthermore, other main electrical parameters, such as carrier concentration of acceptor atoms (N A), built-in potential (V bi), Fermi energy (E F), image force barrier lowering (Δ φb), and barrier height (φb), are extracted using reverse bias C −2—V characteristics as a function of temperature.

Research paper thumbnail of Investigation of the inhomogeneous barrier height of an Au/Bi 4 Ti 3 O 12 /n-Si structure through Gaussian distribution of barrier height

Chinese Physics B, 2012

Tamer GUZEL *(a), Ahmet Kursat BILGILI (b) , Metin OZER (b)