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Öğe Determination of temperature sensitivity and current-transport mechanisms of the GaAs-based MS contact(Elsevier, 2023) Kaymaz, Ahmet; Baydilli, Esra Evcin; Tecimer, Hueseyin; Tecimer, Habibe Uslu; Altindal, SemsettinIn this study, the GaAs-based metal-semiconductor (MS) contact was prepared as a reference sample for com-parison with other devices in the literature, especially some interfacial layered Schottky structures and tem-perature sensors. The study also includes investigating and evaluating essential device parameters for determining current-transport mechanisms (CTMs) and temperature-sensing behavior. In fact, the benefits of the insulator/organic interfacial layer in devices, such as controlling charge transfers and preventing diffusion at the MS interface, have been mentioned a lot in the literature. However, since the production processes of the MS contact are easier and less costly than interfacial-layered devices, it would be more logical/suitable to prefer it in applications where this device may be sufficient, especially as a temperature sensor. Therefore, the current-voltage (I-V) data of the produced MS contact was obtained in a wide temperature range to determine the CTMs, and it was observed that two linear areas with different slopes, known as the two-parallel diode model, existed in the GaAs-based MS contact. Therefore, essential contact parameters and graphs were obtained for both two regions, and it was obtained that quantum mechanical tunneling mechanisms, the T0 effect, and the Double Gaussian Distribution (DGD) with Thermionic Emission theory play a role as CTMs of the GaAs-based MS contact such as some interfacial layered devices given in the literature. On the other hand, the temperature sensitivity of the MS contact was examined, and it was observed that the sensitivity parameter values exhibit an excellent quality sensing behavior compared to other devices in the literature, including devices with high-temperature sensitivity. Therefore, it can be preferred as a temperature sensor in many applications due to its low cost and easy production processes.Öğe Doğrultucularla kontrol edilen dc motorlarda modların tanımlanması ve analizi(Karabük Üniversitesi, 2015) Kaymaz, Ahmet; Akbaba, MehmetBu çalışmada, dc motorların kontrollü tek-fazlı ve üç-fazlı doğrultucular ile sürülmesi esnasındaki çalışma modları incelenmiştir. Doğrultucu ateşleme açısı, motor parametreleri, motor yükü (veya hızı), besleme gerilimi ve frekansa bağlı olarak motor performansı farklı davranış göstermektedir. Motor çalışma modu olarak adlandırılan bu farklı çalışma durumlarının herbirinde motor üzerindeki gerilim ve motordan geçen akım farklı şekiller almaktadır. Motor akımı ve motor geriliminin ortalama değerlerinin bulunabilmesi için bunların bir periyodunun matematiksel modelinin belirlenmesi gerekmektedir. Böylece, motorun kararlı hal performansı süresince motor üzerindeki gerilimin ortalama değeri ve motor armatür sargılarından geçen akımın ortalama değeri belirlenebilir. Bu çalışmalar elektrik zaman sabitinin (motor direnci, endüktansı ve besleme frekansı ile ilgili), mekanik zaman sabitinden (özellikle motor yükü ve motor milinin toplam eylemsizlik momenti ile ilgi) çok daha küçük olduğu zaman, motorun sabit çalışma hızında ve dolayısıyla motorun zıt elektromotor kuvvetinin sabit olarak kabul edildiği durumda yapılmıştır. Buradaki analiz ve simülasyonlar kontrollü doğrultucuların üç farklı tipleri için yapılmıştır: a) Tek-fazlı tam kontrollü köprü doğrultucu DC sürücü bu devre ile kontrol edilirken dört farklı çalışma modu tanımlanmış ve bu modlar Mod-1, Mod-2, Mod-3 ve Mod-4 olarak adlandırılmıştır. Bu tez çalışmasında adı geçen modların her biri için analiz ve simülasyonlar ayrıntılı olarak sunulmuştur. b) Boşluk diyodunun dahil edildiği tek-fazlı yarım kontrollü köprü doğrultucu DC sürücü bu devre ile kontrol edilirken üç ayrı çalışma modu tanımlanmış ve bu modların her biri Mod-5, Mod-6 ve Mod-7 olarak adlandırılmıştır. Yine bu modların her birinin ayrıntılı analizleri ve simülasyonları çalışmanın ilgili bölümünde gösterilmiştir. c) Üç-fazlı tam kontrollü köprü doğrultucu DC sürücü bu şekildeki bir devre ile kontrol edilirken üç farklı çalışma modu sunulmuş ve bu modlar da Mod-8, Mod-9 ve Mod-10 olarak adlandırılmışlardır. Benzer şekilde tüm bu modların analiz ve simülasyonları ilgili bölümde ayrıntılı olarak gösterilmiştir. Kısaca, motor üç farklı doğrultucu devre ile sürülürken DC sürücü, her biri farklı karakteristiğe sahip olan 10 adet çalışma modu ortaya çıkarmıştır. Dolayısıyla uygulama ile ilgilenen mühendisler ve güç mühendisliği öğrencileri bu çalışma modlarını tamamen anlamadıkça DC sürücülerin performansını doğru bir şekilde değerlendiremezler. Çünkü aynı yük, sürekli akım veya süresiz akımların farklı türlerindeki DC sürücüler ile sürülebilir. Motor akımının süreksiz olduğu durumda akım toplam harmonik bozulma faktörü yüksek olacaktır. Hatta daha önemlisi motor armatüründe kıvılcımlı komütasyon oluşacaktır ki bu durum motorun komütatör ömrünün azalmasına yol açacaktır. Öyleyse bu çalışmanın temel amacının dc sürücülerin çalışma modlarını anlamak ve uygulama ile ilgilenen mühendisler ile güç mühendisliği öğrencilerinin bu sürücülerin davranışlarını daha iyi anlamasına olanak sağlamak olduğu söylenebilir.Öğe Evaluation of gamma-irradiation effects on the electrical properties of Al/(ZnO-PVA)/p-Si type Schottky diodes using current-voltage measurements(Pergamon-Elsevier Science Ltd, 2021) Kaymaz, Ahmet; Baydilli, Esra Evcin; Tecimer, Habibe Uslu; Altindal, Semsettin; Azizian-Kalandaragh, YasharIn this study, Al/(ZnO-PVA)/p-Si (MPS) type Schottky diodes (SDs) were produced and the radiation effects on their electrical properties were investigated using the current-voltage (I?V) measurements. The I?V measurements were performed before irradiation and after various irradiation doses in the wide voltage range (?4 V) at room temperature. To determine gamma-irradiation effects on the MPS-type SDs accurately, one SD was preferred as a sample, and its significant electrical parameters such as zero-bias barrier height (?B0), ideality factor (n), and reverse-saturation-current (I0) were calculated using the linear parts of the ln(I)?V characteristics. Besides, to observe the effects of gamma-rays on MPS-type SDs in different voltage regions, some diode parameters were obtained by different calculation methods such as Cheung and Norde functions as well as Thermionic Emission (TE) theory. The calculations showed that high doses of gamma-irradiation (>5 kGy) caused the annealing effect, which leads to an improvement in some electrical parameters of SD, especially in the high electric field region. On the other hand, the energy distribution of the surface states (Nss) was obtained by utilizing the voltage-dependent ideality factor and the effective barrier height, with and without considering the series resistance (Rs) effect. It was observed that Nss values decreased almost as exponentially from the mid-band gap of the semiconductor towards the upper edge of the valance-band. Also, the density of surface states decreased with increasing radiation doses. As a result, almost all diode parameters are affected by irradiation. However, no significant defect has been detected that would affect the stable operation of the diode. Hence, Al/ (ZnO-PVA)/p-Si type SD can be used as an MPS-type detector instead of MIS/MOS-type detectors due to some advantages of the organic/polymer interlayer such as being cheap, light per molecule, flexible and requiring low energy consumption.Öğe Investigation of gamma-irradiation effects on electrical characteristics of Al/(ZnO-PVA)/p-Si Schottky diodes using capacitance and conductance measurements(Springer, 2020) Kaymaz, Ahmet; Tecimer, Habibe Uslu; Baydilli, Esra Evcin; Altindal, SemsettinIn this study, Al/(ZnO-PVA)/p-Si (MPS type) Schottky diodes (SDs) were fabricated instead of metal-semiconductor (MS) type SDs with traditional insulator interfacial layer. Additionally, basic electrical parameters of these MPS-type SDs (such as doping acceptor atoms (N-A), depletion layer width (W-D), series resistance (R-s), barrier height (phi(B)), and surface states/traps (N-ss/N-it)) were found as a function of gamma-irradiation by using the capacitance/conductance-voltage (C/G-V) measurements. These measurements under 0-60 kGy radiation doses show that radiation-induced N-ss are more effective in the depletion layer. On the other hand, voltage-dependent profiles of R-s and N-ss were also obtained using Nicollian-Brews and Castagne-Vapaille methods, respectively. Additionally, the C/G-V characteristics were corrected before irradiation and after 60 kGy doses by considering the effects of R-s. These calculations show that R-s is more effective especially in the accumulation region and therefore, it must be considered in the calculations. All these results have indicated that MS-type SDs with (ZnO-PVA) polymer interfacial layer are very sensitive to gamma-irradiation. Hence, they can be successfully used as MPS-type detectors instead of MIS/MOS-type detectors. Hence, they can be successfully used as MPS-type detectors instead of MIS/MOS-type detectors, since polymer layers can be easily grown compared to insulator/oxide layers. Also, they are cheaper, lighter, more flexible, and require low energy consumption. In conclusion, it can be said that although all parameters were affected by gamma-irradiation, no significant defect/deterioration was observed in applied dose range which would hinder the operation of these MPS-type SDs.Öğe INVESTIGATION OF RADIATION EFFECTS ON THE ELECTRICAL PROPERTIES OF METAL-SEMICONDUCTOR STRUCTURES WITH ORGANIC INTERFACIAL LAYER(2020-07-03) Kaymaz, AhmetBu çalışmada, geleneksel yalıtkan arayüzey tabakalı metal-yarıiletken (MS) yapıları yerine Al/(ZnO-PVA)/p-Si (MPS) tipi Schottky diyotları (SDs) hazırlanmış ve bu diyotların gama-ışınlama etkileri araştırılmıştır. Gama-ışınlama etkilerinin anlaşılabilmesi amacıyla akım-gerilim (I-V), kapasitans-gerilim (C-V) ve kondüktans-gerilim (G/??-V) karakteristiklerinin ölçümleri, radyasyon öncesinde ve çeşitli ışınlama dozları sonrasında gerçekleştirilmiştir. Böylece, ln(I)-V karakteristiklerinden faydalanılarak sıfır-beslem bariyer yüksekliği (??B0), idealite faktörü (n) ve ters doyum akımı (I0) gibi akıma bağlı temel diyot parametreleri, radyasyon öncesi ve sonrası için elde edilmiştir. Yine I-V ölçümlerinden faydalanılarak seri direnç (Rs), şönt direnç (Rsh) ve diyot kalitesini temsil eden doğrultma oranı (RR) gibi diğer önemli diyot parametreleri de hesaplanmıştır. Bazı parametrelerin diyot üzerindeki etkilerini ve radyasyona bağlı değişimlerini daha doğru bir şekilde anlayabilmek için Rs, n ve ??B0 parametrelerinin değerleri ikinci bir yöntem olarak Cheung fonksiyonları metoduyla ve Rs ile ??B0 parametrelerinin değerleri de üçüncü bir yöntem olarak Norde fonksiyonları metoduyla elde edilmiştir. Böylece üç yöntemle elde edilen sonuçlar karşılaştırılarak yorumlanmıştır. Diğer yandan, ölçümleri yüksek bir frekans değerinde (f=500 kHz) gerçekleştirilen C-V ve G/??-V karakteristiklerinden faydalanılarak hesaplanan difüzyon potansiyeli (VD), alıcı katkı atomları yoğunluğu (NA), Fermi enerji seviyesi (EF), maksimum elektrik alanı (Em), tüketim tabakası genişliği (WD) ve bariyer yüksekliği (??B) gibi diğer diyot parametreleri, gama-ışınlamasının malzeme üzerindeki etkilerini detaylıca analiz etme olanağı sunmuştur. Ayrıca, Castagne-Vapaille ve Hill-Coleman yöntemleri olmak üzere iki ayrı metotla hesaplanan arayüzey durumları (Nss), diyotun radyasyon altındaki davranışını tamamen açığa çıkarmıştır. Sonuçlar, Rs’nin daha çok birikim bölgesinde Nss’nin ise özellikle tüketim bölgesinde daha etkili olduğunu göstermiştir. Öte yandan, tüm diyot parametrelerinin radyasyondan belirgin bir şekilde etkilendiği gözlemlenmiş olmasına karşın, 0-60 kGy doz aralığındaki ışınlamada Al/(ZnO-PVA)/p-Si tipi SD’nin çalışmasını önleyecek önemli bir kusur veya bozulma tespit edilmemiştir. Sonuç olarak, polimer tabakası, geleneksel yalıtkan/oksit tabakasıyla karşılaştırıldığında, daha az enerji gerektirmesinin yanı sıra esnek, ucuz ve molekül başına hafif olma gibi bazı avantajlara sahiptir. Dolayısıyla, organik/polimer ara tabakası kullanılarak hazırlanmış olan bu Schottky diyotlar, uygulamalarda MIS/MOS tipi dedektörler yerine MPS tipi dedektörler olarak başarılı bir şekilde kullanılabilirler.Öğe Ionizing radiation response of bismuth titanate-based metal-ferroelectric-semiconductor (MFS) type capacitor(Pergamon-Elsevier Science Ltd, 2022) Kaymaz, AhmetIn this study, the ionizing radiation (gamma-irradiation) response of the metal-ferroelectric-semiconductor (MFS) type capacitors whose interfacial layer is bismuth titanate (Bi4Ti3O12), which is from the Aurivillius family, was investigated. The capacitance-voltage (C-V) and conductance-voltage (G/omega-V) characteristics and the device parameters derived from these characteristics provide essential information about the radiation response. Therefore, MFS-type capacitors in which their Schottky/rectifier contacts Au and interfacial layer Bi4Ti3O12 (BTO) were prepared and exposed to various doses of gamma-rays. The voltage-dependent C and G/omega data were obtained before irradiation and after some irradiation doses using the Hewlett Packard Impedance Analyzer. Experimental results showed that the C-V curves exhibited multilayer capacitor behavior before and after radiation rather than conventional Schottky structures due to the very thin Silicon dioxide (SiO2) interlayer at the BTO/Si interface, which was assumed to form during the annealing of BTO films in air ambient. On the other hand, the C-G/omega-V curves exhibited asymmetric and hysteretic behavior because of the different electrical properties at the bottom and top interfaces and the natural ferroelectric behavior of the BTO. On the other hand, considering the radiation effects, the C-G/omega-V characteristics and other device parameters did not show any significant changes at the 5 kGy irradiation dose, but significant differences were observed in all parameters at the 22 kGy dose. Therefore, it can be concluded that these MFS-type structures with the BTO interlayer can be used as a capacitor or radiation sensor at doses around 5 kGy and below 22 kGy. However, it is not recommended to use them as capacitors at doses close to 22 kGy due to the large capacitive change (approximately tenfold decrease) at this dose. Besides, the tendency of the device to deteriorate at 22 kGy doses indicates that it is not suitable for use as a capacitor or radiation sensor above 22 kGy gamma-irradiation doses.Öğe Multi-Gaussian distribution of barrier height in diamond-like carbon interfacial-layered Schottky devices(Elsevier Sci Ltd, 2024) Kaymaz, AhmetPieces of information about the physical and electronic properties of diamond -like carbon (DLC) interfaciallayered Schottky devices are crucial because DLC is known for its durability against harsh conditions such as high voltage, high temperature, and radiative environments. Therefore, this study focused on determining some critical properties of DCL interlayered Schottky devices, such as current -conduction mechanisms (CCMs) and the shape of the barrier height of the device. Some graphics, such as n- Phi B0 vs T , Phi B0 vs n , Phi B0 vs q/ 2kT, 1/n -1 vs q/ 2kT, and ln(I 0 /T 2 -(q sigma s )/2k 2 T 2 vs kT/q were obtained from the temperature -dependent current -voltage ( I - V-T ) data to determine the shape of the barrier height (BH) and to understand CCMs of this MIS -type device. Obtained results revealed that the device exhibited different behaviours in three different temperature regions: 80-170 K, 200-290 K and 320-410 K, which were called Low Temperatures (LTs), Moderate Temperatures (MTs) and High Temperatures (HTs), respectively. It was also observed that all these graphs exhibited linear behaviour separately for these three temperature regions. Therefore, these results showed that the barrier shape of this DLC interlayered Schottky device is not homogeneous, and it has a Multi -Gaussian distribution due to three different linear behaviours. On the other hand, in addition to the Thermionic Emission (TE) mechanism, it was also understood that Field Emission (FE) and Thermionic Field Emission (TFE) mechanisms, known as Quantum Mechanical Tunnelling (QMT) mechanisms, were effective current conduction mechanisms, especially at low and moderate temperatures for this device.Öğe Overview of the irradiation-dependent behaviour of the negative dielectric properties of GaAs-based MIS devices(Pergamon-Elsevier Science Ltd, 2024) Baydilli, Esra Evcin; Kaymaz, Ahmet; Altindal, SemsettinIn this study, negative dielectric properties of the natural oxide interfacial-layered metal-insulator-semiconductor (MIS) type structure have been investigated under different radiation doses. Some essential parameters of the GaAs-based MIS structure, such as dielectric constant (e '), dielectric loss (e) and loss factor (tan6), were obtained from the capacitance/conductance-voltage (C-G/w-V) data for before and after radiation to investigate the effects of gamma-rays on the dielectric properties of the device. Measurements were performed in the voltage range of +/- 4 V, 500 kHz frequency and at room temperature for before irradiation and after 5 and 10 kGy radiation doses to obtain C-G/w-V data under various conditions. On the other hand, the voltage-dependent variation of the ac-conductivity (aac) and complex electric modulus (M*) (including its real (M ') and the imaginary (M '') parts) of the structure were calculated before and after radiation. As a result, the peaks at approximately 1.75 V were observed in the voltage-dependent variation of the dielectric constant before irradiation and after all radiation doses. It was also observed from this point that the dielectric constant quickly took negative values, and these behaviours were attributed to the structure's differential change of charge, polarization, and electrical resonance. However, there was no significant change in the radiation-dependent dielectric properties of the structure up to the abnormal peak values. In conclusion, it can be said that although the device is generally resistant to ionizing radiation, it exhibits significant change behaviour in the negative dielectric region. This result means that when the device is operated under appropriate conditions, it can respond as a radiationresistant rectifier diode or electronic device that can benefit from its negative dielectric properties.Öğe The Role of Co/Zn-Doped Organic Interlayer on the Operating Performance of Schottky Devices as an Ionizing Radiation Sensor(Ieee-Inst Electrical Electronics Engineers Inc, 2024) Kaymaz, Ahmet; Baydilli, Esra EvcinThis study was carried out to investigate the suitability of a Schottky device with a Co/Zn-doped organic interlayer polyvinyl alcohol (PVA) for use in radiation environments such as space (satellite systems) or nuclear plants. The current and capacitance-conductance data were obtained before and after radiation exposure and for some specific days after irradiation to understand whether the device is suitable for use as a rectifier contact or an ionizing radiation sensor, especially for satellite systems. Thus, it was observed that the current parameters tended to return to their original state in the early days, although the device showed a significant response to gamma rays. On the other hand, it was observed that the parameters obtained from the impedance spectroscopy methods remained stable for a while after radiation and then tended to approach their initial state. These behaviors occur due to the relaxation time of the radiation-induced surface states, and these sensitive parameters cannot prevent the device from being used as a radiation sensor or rectifier contact (i.e., MPS-type Schottky diode). As a result, it can be said that the device is a good candidate for use as a radiation sensor at first glance. However, these pieces of information are insufficient to use the device as a commercial sensor, and the device must successfully pass further experimental tests to decide this result.
