- I am professor in Abant Izzet Baysal University. My group is working on MEMS, NEMS device fabrication and characterizationedit
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In this letter, we consider a Schrodinger equation for a well potential with varying width. We solve one dimensional time-dependent Schrodinger equation subject to time-dependent boundary conditions for a spinless particle inside infinite... more
In this letter, we consider a Schrodinger equation for a well potential with varying width. We solve one dimensional time-dependent Schrodinger equation subject to time-dependent boundary conditions for a spinless particle inside infinite potential well, both wall of which move opposite direction with different velocities v1 and v2, respectively.
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ABSTRACT The purposes of this paper are to investigate the post deposition annealing (PDA) effect on structural and electrical characterizations of HfO2 MOS capacitor and the frequency dependency of series resistance and interface states... more
ABSTRACT The purposes of this paper are to investigate the post deposition annealing (PDA) effect on structural and electrical characterizations of HfO2 MOS capacitor and the frequency dependency of series resistance and interface states in this device. PDA processes on the HfO2 films deposited using RF magnetron sputtering system were performed in N2 ambient at 350, 550, 650, and 750 °C. The phase identifications and crystallization degrees of the HfO2 films were determined by using X-ray diffractometry. The grain size of the films was varied from 4.5 to 15.23 with increasing in PDA temperature. The HfO2 MOS capacitors were fabricated using the as-deposited and annealed films for electrical characterization. C–V and G/ω–V measurements were performed at 1 MHz frequency. The C–V characteristics of the MOS capacitor fabricated with film annealed at 550 °C show a better behaviour in terms of the high dielectric constant and low effective oxide charge compared to others. For this device, C–V and G/ω–V measurements were performed in different frequencies ranging from 10 kHz to 1 MHz at room temperature. Obtained results show that series resistance and interface states strongly influence the C–V and G/ω–V behaviour of the MOS capacitor.
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The effects of gamma-ray exposures on the electrical characteristics of Silicon Nitride (Si3N4) metal–insulator–semiconductor (MIS) structures have been investigated at room temperature. The MIS structures were irradiated with the... more
The effects of gamma-ray exposures on the electrical characteristics of Silicon Nitride (Si3N4) metal–insulator–semiconductor (MIS) structures have been investigated at room temperature. The MIS structures were irradiated with the GAMMACELL 220 Co-60 radioactive source. The distributions of interface states and series resistance were determined from the C–V and G/ω-V characteristics by taking into account the irradiation-dependent the barrier height. Both the values of series resistance, interface states and barrier heights enhanced with increasing dose. Experimental results demonstrate that gamma-ray irradiation have the significant effects on electrical characteristics of Si3N4 MIS structures.
ABSTRACT The frequency dependent irradiation influences on Sm2O3 MOS capacitors have been investigated and possible use of Sm2O3 in MOS-based radiation sensor was discussed in this study. To examine their gamma irradiation response over a... more
ABSTRACT The frequency dependent irradiation influences on Sm2O3 MOS capacitors have been investigated and possible use of Sm2O3 in MOS-based radiation sensor was discussed in this study. To examine their gamma irradiation response over a range of doses, the fabricated MOS capacitors were irradiated up to 30 grays. Capacitance–Voltage (C–V) measurements were recorded for various doses and the influences of irradiation were determined from the mid-gap and flat-band voltage shifts. In addition, the degradations of irradiation have been studied by impedance based leakage current–voltage (J–V) characteristics. The results demonstrate that J–V characteristics have not been significantly change by irradiation and implying that the excited traps have a minor effect on current for given dose ranges. However, the frequency of applied voltage during the C–V measurements affects the irradiation response of devices, significantly. The variations on the electrical characteristics may be attributed to the different time dependency of acceptor and donor-like interface states. In spite of the variations on the device characteristics, low frequency measurements indicate that Sm2O3 is a potential candidate to be used as a dielectric layer in MOS based irradiation sensors.
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ABSTRACT Radiation-sensing Field Effect Transistors (RadFETs or MOSFET dosimeters) with SiO2 gate dielec- tric have found applications in space, radiotherapy clinics, and high-energy physics laboratories. More sensitive RadFETs, which... more
ABSTRACT Radiation-sensing Field Effect Transistors (RadFETs or MOSFET dosimeters) with SiO2 gate dielec- tric have found applications in space, radiotherapy clinics, and high-energy physics laboratories. More sensitive RadFETs, which require modifications in device design, including gate dielectric, are being con- sidered for personal dosimetry applications. This paper presents results of a detailed study of the RadFET energy response simulated with PENELOPE Monte Carlo code. Alternative materials to SiO2 were inves- tigated to develop high-efficiency new radiation sensors. Namely, in addition to SiO2, Al2O3 and HfO2 were simulated as gate material and deposited energy amounts in these layers were determined for photon irradiation with energies between 20 keV and 5 MeV. The simulations were performed for capped and uncapped configurations of devices irradiated by point and extended sources, the surface area of which is the same with that of the RadFETs. Energy distributions of transmitted and backscattered photons were estimated using impact detectors to provide information about particle fluxes within the geometrical struc- tures. The absorbed energy values in the RadFETs material zones were recorded. For photons with low and medium energies, the physical processes that affect the absorbed energy values in different gate mate- rials are discussed on the basis of modelling results. The results show that HfO2 is the most promising of the simulated gate materials.
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ABSTRACT In this work, we study the structural and electrical properties of BiFeO3 MOS capacitors with a special focus on the oxide–semiconductor interface for gate dielectric applications. For this purpose BiFeO3 thin films with a... more
ABSTRACT In this work, we study the structural and electrical properties of BiFeO3 MOS capacitors with a special focus on the oxide–semiconductor interface for gate dielectric applications. For this purpose BiFeO3 thin films with a thickness of 300 nm were deposited on p-type Si (100) substrates at 0 °C by RF sputtering. Half of the films were annealed at 550 °C for 30 min in atmospheric environment while the other half were kept as-deposited. XRD and SEM measurements were performed for both samples for structural characterization. MOS capacitors were fabricated by evaporation technique using Al from samples. For electrical characterizations of MOS capacitors, capacitance–voltage (C–V), conductance–frequency (Gp/ω–F) and leakage current density–voltage (J–V) measurements were performed. The XRD analyses show that BiFeO3 thin films are polycrystalline with some impurity phases, which influence the electronic device properties. The formation of crystallization is confirmed by SEM measurements. Debye length, barrier height and flat band voltages showed variations due to the frequency dependent charges, partially originating from interface defects, in the device structure. Therefore ignoring effects of frequency dependent charges can lead to significant errors in the analysis of electrical characteristics of MOS capacitors. Moreover, the obtained results from analyses of C–V, Gp/ω–F and J–V characteristics of annealed samples depict that all measured and calculated parameters are of the same order for novel MOS devices. Hence, the BiFeO3 dielectric layer in fabricated MOS devices exhibits a stable insulation property for gate dielectric applications.
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ABSTRACT The effects of substrate temperature on the microstructure and morphology of CdZnTe thin films were investigated in detail. The CdZnTe thin films were deposited on glass substrates at 200°C, 300°C and 400°C by radio frequency... more
ABSTRACT The effects of substrate temperature on the microstructure and morphology of CdZnTe thin films were investigated in detail. The CdZnTe thin films were deposited on glass substrates at 200°C, 300°C and 400°C by radio frequency magnetron sputtering and annealed at 450°C for an hour under N2 ambient at atmospheric pressure. The microstructure and morphology of the CdZnTe films were analyzed by using x-ray diffractometry, scanning electron microscopy, energy dispersive x-ray spectroscopy and atomic force microscopy. The effects of substrate temperature on transmission spectra of the CdZnTe films were also investigated. The experimental results show that the optimum morphology and crystalline thin film structures were achieved at 400°C growth temperature. At higher substrate temperatures, atomic mobility and diffusion are promoted, which can stabilize the uniformity and crystallite size. The crystalline grains enlarge and the surface morphology becomes smoother due to growth of grains in the CdZnTe thin films. In addition, the transmission spectra of the films are consistent with the morphological changes. It may be concluded that substrate temperature in growing CdZnTe films has a substantial effect on morphological characteristics, and desired quality of the CdZnTe thin films may be fabricated at higher substrate temperatures.
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ABSTRACT Effects of gamma-ray irradiation on the electrical characteristics of Al2O3 MOS capacitors such as barrier height, acceptor concentration, series resistance and interface state parameters have been studied by analyzing... more
ABSTRACT Effects of gamma-ray irradiation on the electrical characteristics of Al2O3 MOS capacitors such as barrier height, acceptor concentration, series resistance and interface state parameters have been studied by analyzing capacitance–voltage (C –V ) and conductance–voltage ( G/w–V) measurements. The fabricated MOS capacitors wereirradiated with gamma-rays at doses up to five grays. C–V and G/w–V measurements were recorded prior to and after irradiation at high frequency. The results show that the measured capacitance and conductance values decreased with increasing in irradiation dose and C–V and G/x curves has been shifted toward the negative voltages. Moreover, the series resistance ( Rs) and density of interfacestates increased with increasing in irradiation dose and density of interface states (Dit) were calculated as order of 10^12 eV-1cm-2 prior to and after irradiation. Due to presence and variations in the Rs values, the corrected and the measured C –V and G/w–V exhibited different behaviors. Therefore other electrical characteristics were assessed from corrected Cc characteristics. It was observed that acceptor concentration decreased with increasing in barrier height of device due to changes in interface states and diffusion potential..
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ABSTRACT In this study, the effects of increase in sputtering power and substrate temperature on the microstructural, morphological and electrical characteristics of Sm2O3 thin films have been reported. All films were deposited at 50 °C... more
ABSTRACT In this study, the effects of increase in sputtering power and substrate temperature on the microstructural, morphological and electrical characteristics of Sm2O3 thin films have been reported. All films were deposited at 50 °C with varying in sputtering power from 100 to 250 W in 50 W steps by the reactive sputtering technique. The crystallization, grain size, and d-spacing of the films were determined by an X-ray diffractometer (XRD). The semi-quantitative compositional changes were investigated by energy-dispersive X-ray (EDX) spectroscopy while microstructural and morphological modifications were studied by atomic force microscopy (AFM). In addition, the electrical evolutions of the films were determined by alternating current (a.c.) conductivity. It was observed that the crystallization of the films was increased with increase in sputtering power up to 200 W and decreased at the power of 250 W. Therefore, the films deposited at 200 W were annealed at 50 °C, 125 °C, and 200 °C, and a continuous crystallization improvement was observed. The composition of the films was improved by both sputtering power and increase in substrate temperature. The grain boundaries and surface roughness of the films were also found to be significantly affected by the change in substrate temperature. The a.c. conductivity of the films gradually decreases from 1.10×108 Ω−1 cm−1 to 2.50×106 Ω−1 cm−1 by increase in sputtering power and substrate temperature. The results show that the Sm2O3 thin films fabricated at 200 W sputtering power and 200 °C substrate temperature exhibit requested structural and morphological characteristics.
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ABSTRACT In this paper, we report comprehensive frequency-dependent electrical characterizations of samarium oxide (Sm2O3) MOS capacitors. The Sm2O3 crystal structure and phase identifications of the films were confirmed by X-ray... more
ABSTRACT In this paper, we report comprehensive frequency-dependent electrical characterizations of samarium oxide (Sm2O3) MOS capacitors. The Sm2O3 crystal structure and phase identifications of the films were confirmed by X-ray diffractometry. The electrical characterizations were performed in the wide frequency ranges by the capacitance-voltage (C-V) and conductance-voltage (G/ω-V) measurements at room temperature and series resistance effects were investigated following the correction of the measured C-V and G/ω-V characteristics. Significant changes have been observed in capacitance, especially in conductance curves following the corrections. Interestingly, the corrected conductance gives two distinct peaks in the corresponding depletion and inversion edge. The Gc/ω-V characteristics in the low-frequency regions decrease with increasing in the frequency, in the high-frequency regions slightly increase with increasing infrequency. In addition, similar distinct behaviors have been observed for the calculated interface state density, diffusion, and barrier potential at low-high frequencies. The main reason of these behaviors can be attributed to the acceptor-/donor-like interface states and/or different relaxation time dependences of interface states. These results demonstrate that series resistance and interface states should be considered during the electrical characterization. Calculated interface density and barrier potential are suitable to use the Sm2O3 as a dielectric layer for MOS-based applications.
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Abstract Escape of photoelectrons, Compton-scattered photons and Ge x-rays from an HPGe detector was studied as a function of energy in the range 852 keV. A variable-energy source producing Cu, Rb, Mo, Ag, Ba, and Tb x-rays was used. All... more
Abstract Escape of photoelectrons, Compton-scattered photons and Ge x-rays from an HPGe detector was studied as a function of energy in the range 852 keV. A variable-energy source producing Cu, Rb, Mo, Ag, Ba, and Tb x-rays was used. All three mechanisms for ...
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To evaluate maternal and cord blood serum adropin concentrations in pregnant women with gestational diabetes mellitus (GDM). Twenty pregnant women with GDM and 20 gestational age-matched healthy pregnant women participated in the study.... more
To evaluate maternal and cord blood serum adropin concentrations in pregnant women with gestational diabetes mellitus (GDM). Twenty pregnant women with GDM and 20 gestational age-matched healthy pregnant women participated in the study. Maternal serum and cord blood adropin levels were assessed using an enzyme immunosorbent assay, at the time of birth. The relation of maternal serum and cord blood adropin levels with metabolic parameters were also assessed. The mean maternal and cord serum adropin in the GDM group were significantly lower than those of the control women (P=0.01 and P<0.001, respectively). Maternal serum adropin levels did not correlate with either fetal serum adropin levels or maternal metabolic values. The data suggest that low adropin levels may contribute to the underlying pathogenesis of GDM.
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To determine whether concentrations of oxidative stress markers of follicular fluid and serum are different in GnRH agonist protocol from GnRH antagonist protocol. This was a cross-sectional study. Eighty-four women undergoing controlled... more
To determine whether concentrations of oxidative stress markers of follicular fluid and serum are different in GnRH agonist protocol from GnRH antagonist protocol. This was a cross-sectional study. Eighty-four women undergoing controlled ovarian stimulation with either GnRH agonist (n = 39) or GnRH antagonist protocols (n = 45) for IVF/ICSI treatment were assigned by a physician. Blood was obtained at the time of oocyte retrieval, and follicular fluid (FF) from the mature follicles of each ovary was centrifuged and frozen until analysis. Malondialdehyde (MDA), nitric oxide (NO), protein carbonyl (PC), hydroxyl proline (OH-P), sodium oxide dismutase (SOD), reduced glutathione (GSH), glutathione peroxidase (GSH-Px), adenosine deaminase (ADA) and xanthine oxidase (XO) were assessed in the serum and follicular fluid of each participants. The mean serum concentrations of GSH-Px, GSH and MDA were lower in the GnRH antagonist group compared to GnRH agonist group, but mean serum SOD was higher in the GnRH antagonist group. The mean follicular SOD, ADA and NO were higher in GnRH antagonist group than GnRH agonist group. The IVF/ICSI outcomes were similar in both groups. GnRH antagonist protocol is associated with increased oxidative stress. The relation of GnRH analogues with oxidative stress and its implication in follicular growth needs to be addressed in further studies.
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... All the data observed and control functions have been performed from monitor. ... These features can be titled as real time data collection, failure state record, long-term data save, state display of the control system and remote... more
... All the data observed and control functions have been performed from monitor. ... These features can be titled as real time data collection, failure state record, long-term data save, state display of the control system and remote control. ...
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Objective: The purpose of this study was to investigate the relationship between the serum apelin, salusin-alpha, and salusin-beta levels and preeclampsia. Method: Twenty-one healthy pregnant women (control group) and 48 patients with... more
Objective: The purpose of this study was to investigate the relationship between the serum apelin, salusin-alpha, and salusin-beta levels and preeclampsia. Method: Twenty-one healthy pregnant women (control group) and 48 patients with preeclampsia (study group) were included in the study between August 2010 and February 2011. Serum apelin, salusin-alpha, and salusin-beta levels of the groups were compared. Results: The patients in the study group were divided into two categories: mild preeclampsia and severe preeclampsia. The mild preeclampsia group consisted of 31 patients, and the severe preeclampsia group consisted of 17 patients. Serum salusin-alpha and salusin-beta levels of the control and study groups were not significantly different (P>0.05). Apelin levels were statistically significantly higher in the study group. No statistically significant difference was detected between the mild and severe preeclampsia groups in terms of the mean serum apelin levels. Conclusion: The ...
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In the current study, we aimed to investigate whether serum orexin-A (OXA) levels are different in polycystic ovary syndrome (PCOS) subjects. Thirty-six women with PCOS and 40 healthy, age and body mass index-matched controls were... more
In the current study, we aimed to investigate whether serum orexin-A (OXA) levels are different in polycystic ovary syndrome (PCOS) subjects. Thirty-six women with PCOS and 40 healthy, age and body mass index-matched controls were included in the prospective cross-sectional study. All subjects underwent venous blood draws during the early follicular phase after overnight fasting. Serum OXA levels were measured with an enzyme immunoassay (EIA). The relationships between the serum OXA levels and the anthropometric and metabolic parameters were also assessed. The serum OXA levels were lower in the women with PCOS compared to the control group. The serum OXA levels were correlated negatively with systolic blood pressure, the Ferriman-Gallway score and LH and free testosterone levels. Our results indicate that serum OXA levels decrease in the serum of women with PCOS.
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In the current study, we aimed to investigate whether serum salusin α and β levels are different in PCOS subjects. Fifty women with PCOS and 50 healthy, age- and body mass index matched controls were included to the prospective... more
In the current study, we aimed to investigate whether serum salusin α and β levels are different in PCOS subjects. Fifty women with PCOS and 50 healthy, age- and body mass index matched controls were included to the prospective cross-sectional study. All subjects underwent venous blood drawing on the early follicular phase after an overnight fasting. Serum salusin α and β levels were measured with EIA, and ELISA respectively. The relationships between serum salusin levels and anthropometric and metabolic parameters were also assessed. Plasma salusin α and β levels were higher in women with PCOS compared to control group. Serum salusin α level correlated positively with salusin β and fasting serum insulin levels. The serum salusin β levels were correlated positively with HOMA-IR, TG, LDL-C, LH, FSH, and total testosterone levels. Our results indicate that salusins, newly identified regulators of hemodynamics and mitogenesis, are increased within the serum of women with PCOS.
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Gastroschisis is a rare anomaly and it is usually not associated with other syndromic or nonsyndromic anomalies. The first case of gastroschisis with aneuploidy (Turner syndrome) is presented. A fetal huge cystic hygroma was diagnosed by... more
Gastroschisis is a rare anomaly and it is usually not associated with other syndromic or nonsyndromic anomalies. The first case of gastroschisis with aneuploidy (Turner syndrome) is presented. A fetal huge cystic hygroma was diagnosed by prenatal sonography at 12 weeks of pregnancy and chorionic villi sampling (CVS) was performed. Cytogenetic analysis revealed 45, X0. The pregnancy was terminated by induction of labor at 16 weeks of pregnancy. The female fetus had a big membrane of cystic hygroma surrounding the fetal neck. Additionally, a full abdominal thickness defect with multiple loops of bowel outside the abdomen, which could not be diagnosed on prenatal ultrasound scan, was detected on postnatal examination.
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ÖZET Objektif: Yardımcı Üreme Teknikleri arasında yer alan intra stoplazmik sperm enjeksiyonu (ICSI) sonrası artan kromozomal anomali görülme sıklığının bir olgu sunumu olarak tartışılması Planlama: YÜT tedavilerinde kromozomal anomali... more
ÖZET Objektif: Yardımcı Üreme Teknikleri arasında yer alan intra stoplazmik sperm enjeksiyonu (ICSI) sonrası artan kromozomal anomali görülme sıklığının bir olgu sunumu olarak tartışılması Planlama: YÜT tedavilerinde kromozomal anomali görülme sıklığının ...
To compare the serum and follicular fluid (FF) concentrations of stem cell factor (SCF) as well as the serum urocortin 1 (UCN1) concentration in gonadotropin-releasing hormone antagonist (GnRH-ant) and gonadotropin-releasing hormone... more
To compare the serum and follicular fluid (FF) concentrations of stem cell factor (SCF) as well as the serum urocortin 1 (UCN1) concentration in gonadotropin-releasing hormone antagonist (GnRH-ant) and gonadotropin-releasing hormone agonist (GnRH-a) protocols for controlled ovarian hyperstimulation (COH) in IVF patients. Follicular fluids and blood samples of 42 infertile women undergoing COH for IVF-embryo transfer with either GnRH agonist (n = 22) or GnRH antagonist (n = 20) protocols from 2010 to 2011 were collected during oocyte retrieval. SCF concentrations of serum and FF were assessed by sandwich enzyme immunoassay using ELISA Kit for SCF kid. Serum UCN1 concentration were measured using commercially available enzyme-linked immunosorbent assay. Concentrations of serum UCN1, serum and FF SCF were similar in the two groups. The serum SCF levels correlated strongly with the follicular SCF levels (r = 0.770, p < 0.001). The mean implantation rate, biochemical and clinical pregnancy rate and live birth rate per cycle were also similar in the groups. These observations suggest that there is no significant difference in follicular microenvironment in terms of SCF and UCN1 between agonist and antagonist protocols.