Haluk KORALAY

In this study, thermal properties of Bi2Sr2Ca1Cu2Ox (BSCCO) doped PbO and Se in different ratios has been investigated. The glass transition temperature (Tg), the temperature of crystallization initiation (Tc) and the peak temperature of crystallization peak (Tx) values according to DTA measurements were obtained as 733-749 K, 739-759 K and 746-766 K, respectively. The thermal properties of the samples were determined by Differential Thermal Analysis (DTA). The activation energy values were estimated by using the Kissenger, Takhor, and Augis-Bennett methods, and found to increase with the increasing the amount of incorporation, except PS05 sample. In addition, the thermal stability parameters were calculated by using Mahadevan equality. The PS01 sample is found to be the most stable sample according to the calculations.

Bu calismada ulkemiz icin stratejik bir oneme sahip olan bor elementi ile elde edilen ve teknolojik acidan cok genis olcekli bir kullanim alanina sahip olan magnezyum diborur, kimyasal buhar biriktirme (CVD) yontemi ile elde edilen karbon katkilanmis bor kullanilarak uretilmistir. Oncelikle amorf nano bor tozlari belirlenen optimum sartlarda, CVD yontemi ile 90 dakika boyunca 700 oC’de etilen hidrokarbon kaynagi ve inert gaz akisi altinda karbon katkilanmistir. Karbon katkilanan amorf nano bor tozlari belli stikiyometrik oranlarda tartilan magnezyum tozlari ile karistiricida karistirilmistir. Elde edilen karisim 2,5 gramlar halinde tartilip manuel presleme yontemi ile 4 adet tablete donusturulmustur. Her bir tablet zirkonyum folyoya sarilarak, kapali argon gazi altinda 700-800-900 ve 1000 oC sicakliklarda sinterlenmistir. Elde edilen numunelerin yapisal ve mekanik ozellikleri incelenmistir. Yapilan analiz sonuclarina gore uretilen numunelerde MgB2’ye ait karakteristik piklerin baskin bir sekilde goruldugu ve numunelerin mikro sertlik ozelliklerini en iyi aciklayan modelin, Meyer yaklasimi ve IIC (Centik Kaynakli Yarilma) yaklasimi oldugu gorulmustur. Ayrica tum numunelerde RISE (Ters Centik Boyut Etkisi) davranisinin ortaya ciktigi saptanmistir.

We have formed a nearly ideal Au/n-Si Schottky contact and deposited gold (Au) metal on n-Si (100) using thermally evaporation method for an explanation of space charge limited current (SCLC) from current-voltage (I-V) characteristic, interface trap density from capacitance-conductance-voltage (C-G-V) characteristics and hopping conduction from conductance-frequency (G-f) characteristic in nearly ideal metal/semiconductor contacts. The device showed good intimate rectifying behavior. To observe the SCLC mechanism and determine interface trap density of the sample, the log (I)−log (V) and C-G-V characteristics are plotted. The interface trap density values for low frequency (5 kHz) and high frequency (1 MHz) are determined as 4.98 x 1014 eV-1 cm-3 and 7.81 x 1012 eV-1 cm-3, respectively. At the same time the main diode parameters such as ideality factor and barrier height are determined as 1.048 and 0.807 eV, respectively. These diode parameters refer a nearly ideal metal-semiconduct...

Inorganic-organic Schottky contacts based on Gelatin on n-Si wafer have been prepared by a spin coating technique. The reverse and forward bias capacitance-voltage and conductance-voltage properties of the Al/Gelatin/n-Si Schottky diode at room temperature in the frequency range from 30 kHz to 1 MHz have been explored by the series resistance and interface states effects into account. The conductance and Hill-Coleman method were used to determine interfacial layer capacitance, the "R" _"s" and D_it. Result of experiments approved that the "R" _"s" and "D" _"it" are considerable parameters which severely impact the basic electrical parameters of Al/Gelatin/n-Si Schottky diode. Both the measured capacitance and conductance were corrected to obtain the real diode capacitance ("C" _"c" ) and conductance ("G" _"c" ). Schottky diode parameters such as barrier height ("Φ" _"B&...

In this work, the effect of the partial substitution of Sn for Cu on structural, electrical and magnetic properties in the superconducting ceramic glass Bi1.75Pb0.25Sr2Ca2Cu3-xSnxO10+y system (x = 0, 0.1, 0.5) has been examined. The structural characterization of samples produced by glass-ceramic technique were done by X-ray diffraction (XRD) and scanning electron microscopy (SEM) measurements. The electrical and magnetic properties were determined by resistance-temperature (R-T) measurement and magnetization-magnetic field measurement (M-H) in the low temperature by using vibrating sample magnetometer (VSM), respectively. From the results of R-T measurement, the value of critical temperature (Tcoffset) has been decreased from 98 K to 73 K with increasing Sn- concentration. The critical current density has also been decreased with increasing magnetic field intensity. It has been observed from M-H plots that it was decreased with increasing the value of temperature. We have observed ...

Bu calismada, MgB2’nin superiletkenlik ozellikleri uzerinde iyilestirici bir rol oynadigi bilinen karbon, CVD (kimyasal buhar biriktirme) yontemi ile MgB2’ye katkilanarak sinterleme sicakliginin degisimine bagli olarak MgB2’de gozlenen yapisal ve manyetiksel ozelliklerin degisimi incelendi. Bu kapsamda, numune hazirlama basamaginda kimyasal buhar biriktirme yontemi ile karbon katkilanmis amorf nano bor tozlari, belirli kutle oranlarinda magnezyum tozlari ile karistirilip klasik katihal reaksiyon yontemi ile de dort farkli sicaklikta (700-800-900-1000 0C) sinterlenerek karbon katkilanmis MgB2 numunelerine donusturuldu. Karbon katkilanan amorf nano bor tozlarinin SEM fotograflari alinarak elementel analize tabi tutuldu. Elde edilen numunelerin XRD yontemi ile x-isini kirinimi grafigi, manyetizasyon degerleri ile Manyetik Alan-Manyetik Moment (M-H) grafigi ve Bean Yontemi ile de kritik akim yogunlugu degerleri bulunarak Manyetik Alan-Kritik Akim Yogunlugu (Jc-H) grafigi olusturuldu. El...

A new Schottky barrier diode of Al/Coronene/n-GaAs/In was successfully prepared using spincoating method. The interface state and electrical properties of Al/Coronene/n-GaAs Schottky barrier diode have been studied by current– voltage (I–V) data in dark and light. The key diode parameters such as ideality factor, Schottky barrier height, rectification ratio, series and shunt resistances were evaluated from I–V data. The effective forward conduction mechanisms were determined as the thermionic emission at low voltage. Results obtained at room temperature (300 K) showed highly rectifying devices under dark and light. The barrier height ( B  ) of the diode was obtained as 0.901 eV and 0.842 eV under dark and light, respectively. The ideality factor (n) of the diode was calculated to be 1.49 and 1.82 under dark and light, respectively. The values of series resistance ) ( s R obtained from Cheung-Cheung technique were determined to be 18  and 16  under dark and light, respectively. Th...

Polycrystalline Zn0.95Co0.05O bulk sample was prepared by using a sol–gel method. The temperature dependence and frequency dependence of AC conductivity, dielectric and electrical modulus of bulk Zn0.95Co0.05O in a pellet form were investigated in the temperature range of 300–500 K and frequency range of 1 kHz–1.5 MHz. While the real values of dielectric constant (ε') increased with increasing temperature, they decreased with increasing frequency. Its calculated values for 300 K ranged from 30.65 to 11.24 in the frequency range from 1 kHz to 1 MHz. The density of localized states N(Ef) values near the Fermi level were obtained in the order of 5.21 × 1035–5.39 × 1036 eV−1 m−3 for the studied frequency and temperature range. The maximum barrier height Wm value was found to be 0.132 eV. The variation of AC conductivity with temperature showed a semiconductor behavior. We observed that second semicircle started to form in the graph of the real and imaginary parts of the modulus. It can show that two separate conduction processes caused by grain and grain boundary. The maximum frequency values of the imaginary part of the modulus were different indicating a non-Debye type of relaxation process. Also, the non-coincidence of peaks corresponding to the frequency dependence of impedance and modulus confirmed deviation from Debye-type relaxation for the Zn0.95Co0.05O sample. The average value of the activation energy calculated from the modulus was 0.499 eV. The activation energy values calculated from the AC conductivity decreased as the frequency increased and its values varied between 0.54 eV and 0.42 eV. These activation energy values of the sample are very similar, suggesting that the relaxation process may refer to the same type of charge carriers.

Zn0.95Co0.05O was synthesized by sol-gel method and then Zn0.95Co0.05O pellet was prepared to investigate its structural, morphological, electrical, and impedance properties. For this purpose, the pellet was characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), and impedance measurement techniques. SEM images showed that the particle sizes of Zn0.95Co0.05O were between 1 and 100 μm. The frequency and temperature dependence of capacitance, conductance, and complex impedance characteristics of Zn0.95Co0.05O in a pellet form were investigated within the temperature range of 300–500 K and frequency range of 1 kHz–1.5 MHz. The radii of the semicircular arc reduced with increasing temperature revealing that the Zn0.95Co0.05O shows negative temperature coefficient of resistance as in semiconductors. The impedance analysis revealed the contribution of grains and grain boundaries to the conduction and polarization processes. Zn0.95Co0.05O was synthesized by sol-gel technique and then Zn0.95Co0.05O pellet form was prepared. Morphological and structural properties of the Zn0.95Co0.05O were examined by SEM and XRD. Impedance and electrical properties of the Zn0.95Co0.05O were examined within the large range of temperature and frequencies. Relaxation times were obtained at different temperatures. Zn0.95Co0.05O was synthesized by sol-gel technique and then Zn0.95Co0.05O pellet form was prepared. Morphological and structural properties of the Zn0.95Co0.05O were examined by SEM and XRD. Impedance and electrical properties of the Zn0.95Co0.05O were examined within the large range of temperature and frequencies. Relaxation times were obtained at different temperatures.

Abstract In present work, Coronene thin films on Si wafer have been deposited by the spin coating method. It has been ultimately produced Al/Coronene/n-Si/In Schottky diode. Current–voltage (I-V) measurements have been used to determine the effect of illumination intensity in the Schottky diodes. The barrier height ( Φ B ) values increased as ideality factor (n) values decreased with a increase in illumination intensity. The Φ B values have been found to be 0.697 and 0.755 eV at dark and 100 mW/cm2, respectively. The n values have been found to be 2.81 and 2.07 at dark and 100 mW/cm2, respectively. Additionally, the series resistance (Rs) values from modified Norde method and interface state density (Nss) values using current-voltage measurements have been determined. The values of Rs have been found to be 1924 and 5094 Ω at dark and 100 mW/cm2, respectively. The values of Nss have been found to be 4.76 × 1012 and 3.15 × 1012 eV−1 cm−2 at dark and 100 mW/cm2, respectively. The diode parameters are improved by applying the variation of illumination intensity to the formed Schottky diodes.

Dual-cure core build-up resins have been developed to take advantages of both self and light-cured resin. The aim of present study was to determine the polymerization characteristics of self and dual-cured modes of dual-cure core build-up composites evaluating degree of conversion (DC) and crosslink density by measurement of glass-transition temperature (Tg) and hardness decrease in ethanol. Clearfil Dc Core Automix (CLF) and Grandio Core Dc (GR) core build-up resins were selected. Twelve specimens for both composites were polymerized using quartz-halogen-tungsten light curing unit (QTH) and 12 specimens polymerized chemically. DC was determined by ATR-FTIR spectroscopy. TG/DTA analysis was performed to determine Tg. Microhardness value of specimens was determined by Vickers-tester before and after specimens stored in absolute ethanol for 24h. One-way ANOVA showed no different DC values between dual and self-cured mode of GR and dual-cured CLF composites had higher DC than self-cured mode. Tg and percentage of softening in ethanol values of GR and CLF revealed significant difference between self and dual-cured mode. In comparison of GR and CLF, DC showed no statistical difference in both curing modes. However, dual and self-cured GR has statistically higher Tg values and lower percentage of softening in ethanol than CLF. Polymerization characteristics of dual-cure core build-up composites have superiority in dual-cured mode than self-cured.

In the present work, the detailed device parameters of Au/n-Si (100)/Al Schottky devices are calculated by means of the conductance–voltage–frequency (G–V–f), capacitance–voltage–frequency (C–V–f) and current–voltage (I–V) measurements at 300 K. The structure of the device shows a good rectifying behavior. The barrier height $$\left( {\Phi_{\rm{B}} } \right)$$ΦB value of 0.822 eV from the C–V is determined to be higher than the 0.774 eV from the I–V. The barrier height $$\left( {\Phi_{\rm{B}} } \right)$$ΦB and series resistance $$\left( {R_{\rm{s}} } \right)$$Rs values of the sample determined from the Cheung and Cheung technique are 0.755 eV and 220.5 Ω, respectively. The values of the carrier donor concentration ($$N_{\rm{D}}$$ND), the level of Fermi ($$ E_{\rm{F}}$$EF), the lowering of image force ( $$\Delta \Phi_{\rm{b}}$$ΔΦb), the space charge layer width ($$ W_{\rm{D}}$$WD) and the maximum electric field ( $$E_{\rm{max}}$$Emax) are determined as 1.305 × 1015 cm−3, 0.258 eV, 0.0136 eV, 7.6 × 10−5 cm and 1.52 × 104 V/cm, respectively. The density of the interface state $$(N_{\rm{ss}})$$(Nss) determined from the I–V characteristic ranges from 8.80 × 1012 eV−1 cm−2 to 5.44 × 1011 eV−1 cm−2.

Au Schottky contacts (50 dots) on n-Si (100) were fabricated by thermal evaporation under the same conditions. The mean of the electrical parameters of the diodes were investigated by means of capacitance–voltage (C–V) measurements at 1 MHz. Even if the diodes were all equally fabricated, there was a diode-to-diode change. The values of barrier height (ΦB) were determined from the C−2–V characteristics, which ranged from 0.812 eV to 0.837 eV. The Gaussian fit of the barrier height distributions gave a mean of barrier height value of 0.822 eV and a standard value of 0.005 eV. Furthermore, the mean values of other parameters such as the carrier donor concentration (ND), the diffusion potential at zero bias (V0), the Fermi level (EF), the image force lowering (ΔΦb) and the space charge layer width (WD) were investigated and determined to be 1.311 × 1015 cm−3, 0.575 V, 0.257 eV, 1.363 × 10−2 eV, and 7.573 × 10−5 cm, respectively.

A glass of nominal Bi 2 Sr 2 CaCu 3 O x composition prepared by rapid-quenching of the melt, showed a glass transition temperature of 438 °C, crystallization temperature of 454 °C and melting temperature of 860 °C at 10 °C/min heating rate. The activation energy for ...