Nükleer Radyasyon Dedektörleri Uygulama ve Araştırma Merkezi

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https://hdl.handle.net/20.500.12491/10787

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Evolution of basic features of Bi1.8Pb0.4Sr2Ca2.2Cu3Oy ceramic systems with NiO impurity
(Springer, 2023) Kara, Emre; Doğan, Muhsin Uğur; Kaya, Şenol; Terzioğlu, Rıfkı; Yıldırım, Gürcan; Terzioğlu, Cabir
In the current work, we have investigated the role of different nickel oxide (NiO)(x) impurity addition levels (0 & LE; x & LE; 1.2) on the fundamental crystallographic, morphological, electrical, magnetic, critical current density, and superconducting features of Bi1.8Pb0.4Sr2Ca2.2Cu3Oy (Bi-2223) by the temperature-dependent electrical resistivities (& rho;-T), X-ray diffraction data (XRD), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), and magnetic hysteresis (M-H) measurements for the first time. The NiO-added Bi-2223 ceramics have been produced by the standard solid-state reaction method at 840 & DEG;C for 36 h in the air atmospheric conditions. EDX investigations have demonstrated that there appear no extra contamination and additional phases for any anionic or cation-including phases. Besides, the Ni impurity concentration has been observed to increase systematically depending on the impurity amount. Thus, the NiO impurities have been added to the ceramic matrix as requested. Similar findings have been confirmed by the XRD examinations. The experimental results have pointed out the multiple substitution reaction of Ni-sites with the Bi-sites, Ca-sites, and Cu-sites in the Bi-2223 system. Moreover, the experimental results have shown that all the fundamental features are strongly dependent upon the NiO addition level due to the variation of Cu-O-2 interlayer bonding forces, grain alignment distributions, mobile carrier concentrations in the in-plane Cu-O-2 layer x(2)-y(2) bands, and coupling probabilities between the adjacent layers in the crystal structure. Similarly, the induction of new impurity phase formations, grain boundaries, modulation of Bi-O double layers, spin fluctuations, inhomogeneities, structural defects, and non-recoverable structural problems have also triggered the decrease in the main characteristic quantities. On this basis, the microstructural morphology and related crystallographic features have been noted to degrade with the impurity. Furthermore, the presence of NiO impurity has resulted in a decrement in the flux-pinning centers due to the increase in the lower resistance regions against the flux drifts in the bulk crystal system. All in all, the addition of NiO impurity in the Bi-2223 ceramic matrix is not a good idea for the improvement in the fundamental features of the Bi-2223 superconducting structure.
Evolution of operable slip systems, lattice strain fields and morphological view of Bi-2223 ceramic system with optimum NiO addition
(Elsevier, 2023) Mercan, Ali; Kara, Emre; Doğan, Muhsin Uğur; Kaya, Şenol; Terzioğlu, Rıfkı; Erdem, Ümit; Yıldırım, Gürcan; Terzioğlu, Cabir
The current work extensively reveals the influence of different nickel oxide (NiO) impurity addition levels on the morphological, microstructural, key mechanical performance, and mechanical characteristic properties of Bi1.8Pb0.4Ca2.2Sr2Cu3Oy (Bi-2223) ceramics using scanning electron microscopy (SEM), powder X-ray diffraction (XRD), and Vickers micro-indentation (Hv) hardness measurements. It was observed that the addition of NiO impurity in the Bi-2223 crystal structure affected seriously the fundamental characteristic features. In the case of the optimum NiO concentration level of x = 0.1, the Bi-2223 materials exhibited the best crystallinity quality and coupling strengths between the adjacent layers, the most uniform surface view, and the densest, and the smoothest crystal structure. Similarly, the compound was noted to possess the hardest, highest mechanical strength, durable tetragonal phase, resistance toward failure by fatigue, and elastic recovery properties. Besides, it was observed that the characteristic Bi-2223 superconducting phase fraction and stabilization of the tetragonal crystal system reached the maximum level for the optimum concentration. Moreover, optimum NiO particles brought about a considerable increase in the number of operable slip systems, surface residual compressive force regions, and lattice strain fields. Correspondingly, the mobility of defects was blocked significantly depending on the preference of defects through transcrystalline regions. Additionally, optimum addition strengthened the typical indentation size effect due to the improvement of the recovery mechanism. In this regard, the NiO-added sample exhibited the least response to the applied loads. Thus, the Bi-2223 sample with the optimum NiO concentration was found to present the highest hardness parameter of 0.496 GPa, greatest elastic deformation value of 16.493 GPa, largest stiffness value of 1.044 MN/m, and smallest contact depth of 5.849 mu m. On the other hand, after the optimum concentration level of x = 0.1, there appeared serious increase in problems including internal defects, impurity residues, microscopic structural problems, and connection problems between the grains. All experimental findings were theoretically supported by semi-empirical mechanical methods. To sum up, the addition of NiO particles was noticed to increase the potential application areas of Bi-2223 ceramic
Effect of high-radiation-dose-induced structural modifications of HfSiO4/n-Si on electrical characteristics
(Pergamon-Elsevier Science Ltd, 2022) Kahraman, Ayşegül; Mutale, Alex; Lök, Ramazan; Yılmaz, Ercan
High-k/n-Si structures were formed with HfSiO4 films annealed at the temperature range of RT (room temperature)-900 degrees C and radiation-induced structural modifications were determined by XRD (X-ray diffraction) and XPS (X-ray photoelectron spectroscopy) techniques in the study. The effect of oxygen-deficient bond contents on the electrical characteristics of HfSiO4 pMOS (n type Metal Oxide Semiconductor) capacitors whose radiation response was investigated in the 0-50 kGy dose range was investigated. While no XRD peak was observed before and after irradiation at RT and 500 degrees C-HfSiO4/n-Si, crystallization started with irradiation at 900 degrees C. The dielectric constant of the film was found in the range of 16-23. It was determined that Hf-Hf oxygen-deficient bonds act as negative charge trapping centers, while Hf-Si and Si-Si oxygen-defective bonds act as positive charge trapping centers. The direction of the C-V (Capacitance-Voltage) curve changed continuously with increasing radiation dose. The change in the interface trap charge density was found to be higher than the change in the oxide trap charge density for all doses in RT-HfSiO4 pMOS capacitor and for 1 kGy at 500 degrees C-HfSiO4 pMOS capacitor. Oxygen defective bond content and Hf-O-Si/Si-O-Si ratios were sufficient to establish a link between structural analyses and electrical characteristics at some doses. In some cases, the frequency-dependent charges had a more dominant effect on the radiation response of the device compared to the oxide trap charges.
Design and AC loss analyze of a 10 MW-Rated HTS wind turbine generator
(Springer, 2022) İnanır, Fedai; Erciyas, Abdurrahman; Terzioğlu, Rıfkı
We present key design parameters of an innovative 10 MW low-speed direct-drive superconducting generator by high-temperature superconductor coated conductors for the rotor windings. In the simulations, the generator has an iron rotor with the superconducting coils operating at 20 K while the rotor core and the cooper stator are at room temperature. The calculations have been performed by Finite Element Software Comsol Multiphysics. Electromagnetic design parameters, magnetic flux distributions, phase current, voltage, and loss distributions of the superconducting generator are introduced. In addition, the AC losses that arise during the current increase in the superconducting rotor were calculated separately using both the H- and AV-formulation forms of Maxwell's equations employing the non-linear current-voltage relation of the superconductor. The current distribution and magnetic field distribution of the superconductor coils, volumetric loss density distribution, and comparison of the losses of each coil layer have been analyzed and discussed in detail.
Improvement of parameters of micro-pixel avalanche photodiodes
(IOP Publishing Ltd, 2022) Sadigov, A. Z.; Ahmadov, F. I.; Sadygov, Z. Y.; Ahmadov, G. S.; Berikov, D.; Doğancı, Emre; Yılmaz, Ercan
The paper is concerned with the parameter study of a new generation of micro-pixel avalanche photodiodes (MAPD) with deeply buried pixel structure, also named silicon photomultipliers (SiPM) or multi-pixel photon counter (MPPC). The new MAPD of type MAPD-3NM was manufactured in the frame of collaboration with Zecotek Company. Measurements were carried out and discussed in terms of the important parameters such as the current-voltage and capacitance-voltage characteristic, gain, the temperature coefficient of breakdown voltage, breakdown voltage, and gamma-ray detection performance using an LFS scintillator. The obtained results showed that the newly developed MAPD-3NM photodiode outperformed the previous generation in most parameters and can be successfully applied in space application, medicine, high-energy physics, and security. New proposals are also discussed, for further improvement of the parameters of the MAPD photodiodes that will be produced in the coming years.
Investigation of parameters of new MAPD-3NM silicon photomultipliers
(IOP Publishing Ltd, 2022) Ahmadov, F.; Ahmadov, G.; Akbarov, R.; Aktağ, Aliekber; Budak, Erhan; Doğancı, Emre; Gürer, Umutcan; Karaçalı, Hüseyin
In the presented work, the parameters of a new MAPD-3NM-II photodiode with buried pixel structure manufactured in cooperation with Zecotek Company are investigated. The photon detection efficiency, gain, capacitance and gamma-ray detection performance of photodiodes are studied. The SPECTRIG MAPD is used to measure the parameters of the MAPD-3NM-II and scintillation detector based on it. The obtained results show that the newly developed MAPD3NM-II photodiode outperforms its counterparts in most parameters and it can be successfully applied in space application, medicine, high-energy physics and security.
Fabrication and characterization of resistance temperature detector by smart mask design
(Springer London Ltd, 2022) Lök, Ramazan; Karaçalı, Hüseyin; Varol, Ali; Çamlı, Uğur; Yılmaz, Ercan
The purpose of this study is to give detailed information about fabrication and characterization of resistance temperature detector by smart mask design. The effects of annealing on both structural and electrical properties were investigated. Changes in microstrain, lattice parameter and grain size values were observed by means of annealing. It has been shown that the structural changes cause a decrease in resistivity and sheet resistance values. Thousands of sensors can be fabricated according to the substrate size of thin film RTD produced. It is almost impossible to fabricate thousands of sensors with the same resistance value. But by the agency of the smart mask design proposed in this study, it is possible to adjust each RTD to the same resistance value by using the resistance adjustment points. Maximum TCR value was found to be around 3.98 × 10–3 at 0 0C. This value is very close to the standard TCR value 3.90 × 10–3 at 0 0C used for industrial applications.
Optical-electrical characteristics of Al/Gd2O3/(CZ-pSi)/Al diodes under gamma ray irradiation
(Taylor & Francis Ltd, 2022) Al-Esaifer, Husam Raed Sabeeh; Aktağ, Aliekber; Nayef, Uday Muhsin; Doğancı, Emre
This article aimed to report the results on the properties of Gd2O3/(CZ-pSi) diodes under various gamma ray irradiation dose rates (3, 6, 12, 18, 24, 30, 36, 42, 50 Gy). n-type Gd2O3 films were deposited on a p-type Czochralski-grown monocrystalline silicon (CZ-pSi) wafers by pulsed laser deposition (PLD) technique with varying building laser energies (500, 600, 700, 800, 900 mJ) at room temperature and pressure (3.3 x 10(-2) Pa). Amorphous structures were perceived for all films by XRD. Band gaps of the films were modified by controlling the amount of Gd2O3 on CZ-pSi wafers by laser power during deposition and determined to be between 5.30 and 5.75 eV. The Gd2O3/(CZ-pSi) films were irradiated by a Co-60 gamma-ray source system. The current and voltage (I-V) measurements, before and after irradiation (0-50 Gy), indicated that the current decreases toward zero with increasing doses. Capacitance and voltage (C-V) measurements at frequencies of 10-1000 kHz before and after irradiation showed a shift towards the right side of the pre-irradiation curves for each film. The shift was observed in both I-V and C-V curves with increasing radiation doses at 100 kHz as the average of the frequencies used. Contrary to the decrease in current curves, there was an upward increase in capacitance curves of all films with increasing radiation dose. The best build-in potentials of 0.1 V (800 mJ), 1.2 V (500 mJ) and 1.4 V (600 mJ) were obtained for the laser deposition powers of the Gd2O3/(CZ-pSi) diodes. These results are promising for diodes to be used in the radiation detection applications such as in neutron and alpha particles detectors.
Influences of gamma irradiation on structural, morphological and luminescence characteristics of Nb doped TiO2 nanophosphors
(Elsevier, 2023) Büyükuslu, Halim; Kutlu, Nermin; Kaya, Şenol
The irradiation induced effects on structural, morphological and luminescence characteristics of Nb:TiO2 phosphors were systematically investigated. Possible defect centers present in the Nb:TiO2 phosphors were also characterized. Anatase phase of TiO2 with minor parasitic Nb-containing phases was specified in crystallographic structure of phosphors. Crystalline size and internal stress enhance with enhancing the exposed dose. The observed rise in the crystalline size was also confirmed in morphological evolution. Moreover, the Nb:TiO2 phosphor exhibits five different photoluminescence peaks. Intensity variations and blue-green-red shifts on the PL peaks were observed after irradiation exposures. Similarly, various trap sites/centers with depth energies between 1.09 eV and 1.99 eV were found in the thermoluminescence analysis. The irradiation exposures both enhance the oxygen vacancies and cation interstitial defects in the structure. The results have depicted that gamma exposure significantly affects the crystallographic and luminescence features of the Nb:TiO2 nanophosphors.
Role of hemp fiber addition on thermal stability, heat insulation, air permeability and cellular structural features of rigid polyurethane foam
(Sage Publications Ltd, 2023) Soykan, Uğur; Kaya, Şenol
In this current study, rigid polyurethane foams (RPUFs) composites were prepared using different percentage (3, 6, 9 and 12%) of the hemp fibers via one-shut one-step polymerization method. The influences of the hemp fiber addition on the RPUFs were investigated meticulously by means of Fourier-transform infrared spectroscopy (FTIR), thermo gravimetric analysis (TGA), thermal conductivity measurement and scanning electron microscopy (SEM) techniques by evaluating the alternations in the chemical structures of the component, thermal stability, apparent density, insulation performance and cellular topology of the produced samples. The structural analysis revealed that there existed the strong secondary chemical bonds between the functional groups belonging to the components and, depending on that, the improvement in the thermal stability of the foam samples was recorded accompanied by the formation of the better interfacial adhesion. Furthermore, thermal conductivity values of the hemp fiber-loaded RPUFs were observed to increase regularly with the increasing of the content level of the hemp fibers. This was explained by enhancement in the bulk phase conduction level depending of the apparent density rising, reduction in CO2 concentration inside cells as well as the formation of the distorted cellular structures. The obtained air permeability results displayed that the hemp fibers incorporated successfully with RPUF structure, which provides the occurrence of the novel micro barriers and pathways limiting the passage of the air throughout the matrix. The taken scanning electron microscopy images also indicated that the cellular morphology and dimensional stability of the produced foams affected negatively by the hemp fiber addition. At high contents, the wrinkled, non-uniform and irregular cellular structures were observed with ruptured and collapsed walls and struts.
Gamma-ray spectroscopy with MAPD array in the readout of LaBr3:Ce scintillator
(Iop Publishing Ltd, 2021) Ahmadov, Gadir; Ahmadov, Faig N.; Holik, Michael; Yılmaz, Ercan; Doğancı, Emre; Berikov, Daniyar
This paper presented a new detector module consisting of a micropixel avalanche photodiode (MAPD-3NM), LaBr3:Ce scintillator, and a compact read-out interface system for detecting gamma-rays in a wide energy range. The MAPD array (4 x 4 channels) was assembled using a single MAPD-3NM characterized by its high photon detection efficiency (similar to 25%), pixel density (10000 pixel s/mm(2)), low operation voltage (74.5 V), and low dark current. An active area of a single MAPD-3NM was 3.7 x 3.7 mm(2), while this value was 17 x 17 mm(2) for the assembled array with pixel density of 2190000. The size of the tested LaBr3:Ce scintillator was 15 x 15 x 15 mm(3). According to the characteristics of the detector module, a compact read-out interface device (SPECTRIG MAPD) was developed. SPECTRIG MAPD was designed as a miniature device with low power consumption, which continues to provide a wide spectrum of functions needed for measurement and test silicon photomultipliers (SiPM) and scintillation detectors on their basis. The various experiments were implemented to test the detection performance of a detector module to gamma radiation in the range from 30 keV to 4400 keV.
Effects of the oxide/interface traps on the electrical characteristics in Al/Yb2O3/SiO2/n-Si/Al MOS capacitors
(SPRINGER, 2021) Morkoç, Berk; Kahraman, Ayşegül; Yılmaz, Ercan
In the present work, we examine the effect of structural modifications occurring during the fabrication of Al/Yb2O3/SiO2/n-Si/Al MOS capacitors under different annealing temperatures on the electrical characteristics of the capacitors. The structural properties depending on post-deposition annealing (PDA) were evaluated based on the crystal properties, elemental compositions, and bonding structures of Yb2O3/SiO2 films, while the electrical characteristics were determined by capacitance-voltage (C-V) measurements. The smallest particle size was found in the film annealed at the highest PDA temperature. In all films, the Yb atom concentration was determined higher than the others. The non-stoichiometric silicate (YbSixOy) layer was detected in film structure annealed at 400 degrees C. The Yb 4d and O 1s spectra shifted toward higher binding energies with increasing depth in the films. The density of bonded oxygen species decreased with increasing PDA temperature. It was obtained that capacitance in accumulation region (C-acc), dielectric constant (epsilon(k)), and series resistance (R-s) values tend to decrease with both increasing frequency and PDA temperature. The highest and lowest interface state density (N-it) was found for capacitors obtained from as-deposited and annealed at 400 degrees C structures, respectively. The effective oxide charge density (Q(eff)), which expresses the net charge trapped in the oxide layer, is at the 10(11) level. The barrier heights (phi(B)), which generally tend to increase, have shown that acceptor-type interface states are active on electrical characteristics.
Effect of oxide and interface traps on electrical characteristics of post-deposition annealed HfSiO4/n-Si structures
(IOP PUBLISHING LTD, 2021) Kahraman, Ayşegül; Yılmaz, Ercan
This study presents detailed results on the modifications in chemical composition, defective bonds, crystal properties based on x-ray photoelectron spectroscopy (XPS) depth profiles and x-ray diffraction of post-deposition annealed HfSiO4/Si structure. It also leads to a link to defect centers and their effect on the electrical characteristics of MOS capacitors. The HfSiO4 films were deposited on n-Si wafers by RF magnetron sputtering and annealed at room temperature (RT), 300 degrees C, 700 degrees C, 900 degrees C, 1100 degrees C under N-2 ambient. That the atomic concentration values of each element in the oxide did not change significantly depending on the annealing temperature showed that the film was deposited with high homogeneity. It was determined that the shift direction of the binding energies of Hf 4f and O 1s XPS spectra were related to the bonding preference of oxygen rather than its concentration. The increase in Hf-M and Hf-Si oxygen defective bonds decreased the binding energy of the XPS spectra. It was determined from the XPS analyses of amorphous films that Hf-Si and Si-Si oxygen defective bonds may cause the positive charge trapping, resulting in the highest negative charge trapping/positive effective oxide charge density (Q(eff) ) in the 300 degrees C-MOS capacitor. It was determined that Hf-Hf oxygen defective bonds may be the precursors of negative charge trapping. Interface states only contributed to the dielectric constant (k) in the RT-MOS capacitor. The Phi(B) (barrier height) values showed that the efficiency of acceptor-like and donor-like interface states changes depending on the frequency.
Structural characterization and electrical properties of Nd2O3 by sol-gel method
(Springer, 2020) Lök, Ramazan; Budak, Erhan; Yılmaz, Ercan
In the current study, Neodymium oxide (Nd2O3) was prepared by sol-gel method and deposited on P-type < 100 > silicon wafer. The chemical characterization of samples was done by Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), scanning electron microscopy (SEM), energy-dispersive spectra (EDS) and atomic force microscopy (AFM). Nd-O bond formation was proven by FTIR, also cubic- Nd2O3 (c-Nd2O3) phase was detected by XRD. According to EDS analysis, neodymium concentration was approximately 59.41% while oxygen concentration was calculated as 10.21%. The amount of excess oxygen was 9.45% was originated by cristobalite formation. In addition, electrical characterizations of Nd2O3/p-Si MOS capacitor was performed by capacitance-voltage (C-V), conductance-voltage G/omega-V measurements at different frequencies between 250 kHz and 1 MHz. The maximum value of measured capacitance-voltage (C-V) and conductance-voltage (G/omega-V) was increased with decreasing in the applied voltage frequencies and after series resistance (R-s) correction, the measured C-V and G/omega-V characteristics, G/omega behavior started to decrease with rising the frequencies. According to the observed frequency dispersion, the deposited Nd2O3 on P-type < 100 & rang; silicon exhibits stable insulation property for future microelectronic applications.
Influence of frequency and gamma irradiation on the electrical characteristics of Er2O3, Gd2O3, Yb2O3, and HfO2 MOS-based devices
(Springer, 2020) Kahraman, Ayşegül; Deevi, Seetharama C.; Yılmaz, Ercan
The unique physical, chemical, and electronic properties of rare earth oxides have been of immense interest to replace SiO2 as a dielectric material in metal-oxide-semiconductor (MOS)-based sensors applications to accurately measure the radiation dosage and increase sensor sensitivities in as diverse applications as space radiation, nuclear physics, medical diagnostics, radiation cancer therapy, and personal dosimetry devices. Hence, the electrical characteristics of oxides prior to and after irradiation of MOS-based devices are needed since they are the backbone of the devices such as MOSFETs and ICs. In addition, an understanding of the behaviour of high-k dielectric oxides in an MOS configuration is necessary since the radiation-induced damage occurs in the bulk oxide film and/or near the oxide-semiconductor interface resulting in creation of lattice defects. Hence, MOS structures with the rare earth oxides of Er2O3, Gd2O3, Yb 2 O3, and a transition metal oxide of HfO2 were produced by RF magnetron sputtering to determine (a) the structure of the films, (b) dielectric constants, (c) capacitance versus voltage behaviour of Er2O3, Gd2O3, Yb2O3, and HfO2 prior to and after irradiation of the devices in the dose range of 0-76 Gy. The experimental results were analysed with a theoretical framework on the energy band diagram and the radiation effects on the electrical characteristics of the MOS capacitors. The characteristics of the devices were evaluated by using effective oxide charge density (QEFF), variation in the oxide trapped charge density (DNox), and interface trapped charge density (DNit). In addition, barrier height (/b), image force barrier lowering (D/b), acceptor concentration (Na) were calculated before and after irradiation and examined the nature of interface states. The radiation responses of the Er2O3 and HfO2 MOS capacitors did not show a stable behaviour with an increase in radiation dose due to possible neutral electron trap centres. Contrary to expectations, we infer that more negative charges are trapped in Gd2O3-based device than positive charges with an increase in radiation dose. The C-V curves of the Yb2O3 MOS capacitor shifted in the same direction at both 100 kHz and 1 MHz, and as expected, positive charge traps in the structure are more efficient than negative charges. The observed sensitivities of Yb2O3 MOS capacitors are 4-7 times higher than those of SiO2, and the sensitivities of the Yb2O3 MOS capacitors with a total radiation dose of 70 Gy were found to be around 28.08 mV/Gy at both 100 kHZ and 1 MHz frequencies. The Yb2O3 appears to be a promising dielectric candidate for developing a new generation of radiation sensors with an excellent interface quality when compared to rare earth mixed oxides such as silicates, transition metal oxides, and the silicates based on transition metals, Al2O3, and BiFeO3. Our review of the literature suggests that while the radiation damage has been assessed comprehensively based on the C-V characteristics, microstructural characterization of the irradiated films and their interfaces is lacking even though the quality of oxide/Si interface is the most important feature of the devices. The electrical data should be correlated with the inferences from XPS, AFM, TEM, XRD, and other techniques. Further progress requires selection and validation of material properties based on theoretical calculations and predications, utilization of diverse thin film processing and characterization techniques, determining the effect of thickness on the properties of MOS capacitors, a thorough understanding of the interfaces, effect of frequency on the MOS capacitors and the interface characteristics, effect of radiation on the physical, interfacial, and electrical characteristics of MOS capacitors, and preparation and characterization of sensors based on thin films of novel mixed oxides and silicates of different chemistries.
Determination of frequency and voltage dependence of electrical properties of Al/(Er2O3/SiO2/n-Si)/Al MOS capacitor
(Springer, 2020) Aktağ, Aliekber; Mutale, Alex; Yılmaz, Ercan
In this study, we investigated the effects of applied voltage and frequencies on the electrical properties of Al/(Er2O3(150 nm)/SiO2(20 nm)/n-Si)/Al MOS capacitor. The e-beam deposited Er2O3/SiO2 films were annealed at 650 degrees C in N-2 ambient and the crystal and phase identification of the films were confirmed by X-ray diffractometry. The capacitance-voltage (C-V) and the conductance-voltage (G/omega-V) measurements of the MOS capacitor were carried out for voltage frequencies from 50 kHz to 1 MHz at several steps. The parameters of doping concentration, diffusion potential, built-in potential, barrier height, Fermi energy level, the image force barrier lowering and the depletion layer width were calculated by C-V and G/omega-V data. While the depletion layer width decreased with increasing frequencies, the diffusion potential and the barrier height increased a little with small frequencies (200 kHz <= f) first, then decreased insignificantly. We also studied the frequency effects on the series resistance (R-s) and the interface state density (D-it) through the C-V and G/omega-V curves, and found noticeable decreases in R-s and D-it values with increasing frequency. The measured and calculated results reveal that both R-s and D-it frequency dependence have significant impacts on Er2O3/SiO2/n-Si MOS capacitor properties. These effects are basically because of the interfacial charge behavior of thin SiO2 layer contained in between n-Si and Er2O3.
Radiation response of zirconium silicate P-MOS capacitor
(Pergamon-Elsevier Science Ltd, 2020) Lök, Ramazan; Budak, Erhan; Yılmaz, Ercan
The chemical bonding of zirconium silicate films were examined by FTIR. The capacitance-voltage (C-V) measurements before and after irradiation were performed at high frequency. Furthermore, significant changes were observed depending on the radiation dose of the oxide traps and the intensity of the interface state. The sensitivity of this MOS capacitor is 4.3, 31.3 and 15.6 times less sensitive compared to the same thickness as Sm2O3, Al2O3 and Gd2O3. Therefore, it can be used as radiation-resistant material in nuclear reactors and space applications due to its stable electrical characteristics compared to other defined dielectrics. Interface states, (Nit) Barrier potential (Phi(b)) and oxide traps (Not) have also been investigated depending on the radiation effects. Ob is one of these important electrical properties. Phi(b) values decreased with increasing in radiation dose. Besides, radiation and frequency dependent dielectric constant (epsilon'), dielectric loss (epsilon '') and dielectric loss tangent (tan delta) and conductivity (sigma(ac)) of zirconium silicate were investigated. It is concluded that high-k zirconium Silicate is suitable for electronics applications in radiation harsh environment.
Co-60 gamma radiation influences on the electrochemical, physical and electrical characteristics rare-earth dysprosium oxide (Dy2O3)
(Pergamon-Elsevier Science Ltd, 2020) Gürer, Umutcan; Yılmaz, Ozan; Karaçalı, Hüseyin; Kaya, Şenol; Yılmaz, Ercan
Dysprosium Oxide (Dy2O3) gate dielectric layers were deposited by Electron-Beam evaporation onto p-Si (100) wafers. The effects of gamma irradiation on the physical, electrochemical, and electrical properties of Dy2O3/p-Si thin films were investigated in detail. The evolutions on the crystallographic and morphologic characteristics of the films under gamma irradiation were analyzed by X-ray diffraction (XRD) and Atomic Force Microscopy (AFM), respectively; while irradiation effects on the electrochemistry of the films were characterized by X-ray photoelectron spectroscopy (XPS). Furthermore, variations on the electrical characteristics of Dy2O3/p-Si thin films were also specified by Capacitance-Voltage (C-V) and Conductance-Voltage (G/omega-V) measurements. No significant changes on the crystallographic orientation were observed after gamma irradiation exposures. However, the grain size of the films was increased slightly due to the local heating aggregated the smaller grains into a bigger cluster. In addition, the surface roughness was increased after irradiation indicating that deforms the films' surface morphology. The XPS analysis revealed that electrochemically two different phases exist in the virgin Dy2O3/p-Si thin films. These phases are Dysprosium sub-Oxide (DyxOy) and oxygen deficient in Dy2O3 films. After irradiation exposures, oxygen incorporation, vacancy, and interstitial defects formation were observed in the electrochemical characteristics of the films. On the other hand, the capacitance curves exhibit kinks in the region between depletion and accumulation due to the presence of the intermixing phases of Dy2O3 films. The capacitance of samples significantly increased with the increasing dose, which are correlated with the generated interface state density and/or improvement of dielectric characteristics of Dy2O3 owing to oxygen diffusion.
Impact and origin of the oxide-interface traps in Al/Yb2O3/n-Si/Al on the electrical characteristics
(Elsevier Science Sa, 2020) Kahraman, Ayşegül; Karaçalı, Hüseyin; Yılmaz, Ercan
This study presents comprehensive results on the changes of the crystal properties, surface morphology, chemical composition and bonding structures based on X-ray photoelectron spectroscopy (XPS) at different depths of the Yb2O3/Si as depending on post-deposition annealing (PDA) temperature. It also includes a detailed examination of the structural properties and the electrical characteristics of the Yb2O3 MOS capacitors. 125 nm-thick Yb2O3 thin films were deposited on n-Si by RF magnetron sputtering system and the Yb2O3/Si structures were annealed at 200 degrees C, 400 degrees C, 600 degrees C, 800 degrees C under nitrogen ambient. The largest grain size was obtained to be 17.3 nm from the sample annealed at 400 degrees C. The lowest roughness root-mean-square (R-q) value was measured as 0.464 nm in the Yb2O3 film annealed at 200 degrees C. Yb 4 d and O 1s spectra shifted to higher binding energies at Yb2O3/Si interface due to the approaching Si with high electronegativity. The peaks assigned to 2+ oxidation states were observed intensely at 400 degrees C and above due to the conversion of Yb3+-> Yb2+. The intensity of the bonded oxygen species in O 1s spectra measured at surface decreased with increasing annealing temperature, which may cause decreasing in the dielectric constant value. The Yb-O bond was mostly observed within the film, while Si-rich (positively charged interface traps) or Yb-rich (negatively charged interface traps) silicate layers (Yb-Si-O) were formed at the interface depending on the PDA temperature. It has been determined that the thickness of the silicate-like layer increases with PDA temperature, resulting in decreasing dielectric constant. The interface state density (N-ir) decreased with decreasing concentrations of Yb-Yb, Yb-Si and Si-Si at the interface. It was found that the presence of the Yb3+/Yb2+ ions within the film cause of negative oxide charge trapping and they were more active in the electric characteristics that the interface states. Whether the donor-like and acceptor-line interface states are active depending on the frequency makes it difficult to establish a link between the structural analyses and the electrical characteristics in some cases. The barrier height (phi(b)), dopant concentration (N-d), Fermi energy level (E-F) were determined depending on frequency. (C) 2020 Elsevier B.V. All rights reserved.
Impact of SiO(2)interfacial layer on the electrical characteristics of Al/Al2O3/SiO2/n-Si metal-oxide-semiconductor capacitors
(Springer, 2020) Kimbugwe, Nakibinge Tawfiq; Yılmaz, Ercan
The aim of this study is to reduce the oxide and interface-trap charges and also improve the stability at the oxide-semiconductor interface by growing a SiO(2)interface layer on a Si wafer then depositing Al(2)O(3)thin film. Effective oxide charges density (N-ox), border trap charges density (N-bt), interface states density (N-it), diffusion potential (V-D), donor concentration (N-D), and barrier height(Phi(B)) were calculated using the capacitance-voltage (C-V) and conductance-voltage (G/omega-V) measurements at different annealing temperatures. The flat-band voltage (V-fb) changed with annealing temperature and the V(fb)value for the 450 degrees C annealed sample was closest to the idealV(fb). The sample also possessed a high dielectric constant. For these reasons,C-V and G/w-V values of this sample at different frequencies were obtained. Compared to previous studies, very low N-bt values (similar to 10(9) eV(-1) cm(-2)), lowN(it)values (similar to 10(10) eV(-1) cm(-2)) and high Phi(B) values for the annealed samples were obtained due to the SiO2 interface layer.

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