Papers by Keyword: Dielectric Constant

Abstract: The main technical requirements for the development of an electromagnetic detection method for explosive materials are considered. The main elements of interference that increase the detection error are classified. The probability of detecting explosives at different soil depths is modeled. It was found that the frequency of the scanning signal has the greatest influence. Thus, reducing the scanning frequency increases the probability of detecting an object. However, reducing the irradiation frequency is limited by the resolution for objects of a given size. It is shown that reducing the dielectric constant of the soil does not lead to satisfactory detection probabilities even in the upper soil layer. In the size range of real explosives (0.1–0.5 m), the detection probability decreases by 10-25%. The analysis of the characteristic time signatures of explosives imitations showed that the development of a database of such signatures will reduce the number of false signals. An algorithm for the implementation of the method of electromagnetic detection of explosives consisting of 18 functional blocks and three logical blocks has been developed. The obtained results made it possible to describe the procedure for detecting explosive materials in a contaminated area. The use of the obtained results in humanitarian demining will increase the speed of surveying the territory, increase the probability of detecting explosive objects and reduce the risk of injury to personnel conducting humanitarian demining.

Abstract: This study investigates the role of the electrical failure of the SiO₂ film in the breakdown of SiO₂/ZrO₂ and SiO₂/HfO₂ stacks. Our findings indicate that the breakdown is governed by the SiO₂ film, regardless of its thickness. This highlights the importance of carefully considering the interfacial SiO₂ layer when using high-k materials in SiC devices. We demonstrate that thicker SiO₂ layers offer several benefits, including reduced leakage, enhanced thermal stability and electrical strength, and decreased trapping. In contrast, stacks with thinner SiO₂ have a higher effective k value, exploiting the benefits of high-k dielectrics. Our experimental results suggest that a 7 nm SiO₂ layer underlying 30 nm crystalline ZrO₂ or HfO₂ provides optimal performance. Furthermore, we present calculations that reveal the trade-off between SiO₂ thickness, k value, and breakdown voltage for a 50 nm thick dielectric stack. Our results imply that a k value exceeding 20 does not yield significant benefits in 50 nm thick SiO₂/dielectric stacks.

Abstract: This study focuses on developing a composite material using graphene oxide (GO) as a dielectric film. First, GO was mixed with DI water and dried to form a film. Then, a titanium (Ti) film was deposited on the film surface through electron beam evaporation. The composite comprising graphene oxide with the Ti metal film was then dispersed in water, to which cellulose nanofiber (CNF)—noted for its high mechanical strength, stability, and lightweight attributes—was added. The mixture was then re-layered with cellulose nanofibers by agitating it in water, and subsequently dried to form a composite film. The electrical properties of the material were studied using an LCR meter. The results show that pure GO has a dielectric constant of about 1600 at 1 kHz and a dielectric loss of about 25. After adding Ti, the Ti composite film maintained a dielectric constant above 1000 at 1 kHz while significantly reducing the dielectric loss to 1.5. Additionally, the resistivity of pure GO at 1 kHz is approximately 1200 Ω·m, whereas the Ti composite film with Ti and cellulose nanofibers shows a resistivity as high as 50 k Ω·m at 1 kHz. The relationship between dielectric strength and resistivity indicates that the Ti composite film can withstand higher voltages compared to pure GO, demonstrating a significant increase in dielectric strength. Compared to graphene oxide, the Ti composite film combines high dielectric constant, low dielectric loss, and increased dielectric strength.

Abstract: Strontium Calcium Titanate (Sr_0.9Ca_0.1TiO₃) ceramic powders were synthesised using a solid sintering technique and were uniaxially pressed and sintered at different temperatures of 1100 °C, 1150 °C, 1200 °C, 1250 °C, and 1300 °C for three hours. Physical, phase, microstructure and dielectric properties were studied. Perovskite Cubic Strontium Calcium Titanate phase was crystallized. With an increase in sintering temperature, the density and grain size of Sr_0.9Ca_0.1TiO₃ ceramics increased. Grain boundaries were observed in the microstructure of Sr_0.9Ca_0.1TiO₃ sintered at higher temperatures. At room temperature, the dielectric constant and dielectric loss are observed to increase with the increase in sintering temperature. AC conductivity enhanced with sintering temperature.

Abstract: We investigated the electrical and structural effects of silicon (Si), yttrium (Y) and lanthanum (La) doping in 10-45 nm thick hafnium dioxide (HfO₂) films on silicon carbide (SiC) and Si substrates. We show that the introduction of Si dopants leads to a significant enhancement of the electric breakdown field and a reduction of the leakage current density by elevating the crystallization temperature. This effect becomes stronger with higher Si content. In contrast, Y and La doping does not raise T_C but increases the tetragonal and orthorhombic phase portion within the crystalline films and therefore enhances the dielectric constant k. Furthermore, we show that larger grains in crystalline films are associated with a higher leakage current density.

Abstract: Chemical oxidation reactions were used to create composite materials made of polythiophene (PTh) and reduced graphene oxide with varying compositions. To describe the samples, Fourier transform infrared spectroscopy (FTIR) was used. The hydroxyl (OH) stretching vibrations of the -COOH functional group and adsorbed H₂O molecules are responsible for the intense bands at 3386 cm^-1 and 1302 cm^-1. O-H vibrations can be attributed to absorption at a wavelength of 1610 cm^-1. C-S bending mode of thiophene ring has produced the peak at 666 cm^-1. The dielectric constant, tangent loss, and electric modulus with the applied AC frequency for the polythiophene/reduced graphene oxide composites were studied.

Abstract: The purpose of this research is to study the interrelation between Urbach energy (E_u), optical band gap energy (E_g), and complex dielectric constant (ε) in relation to the disorder induced properties of SiO₂/rGO thin films. The rGO-like carbon was created by annealing coconut shell carbon (csc) at different temperatures of 400°C, 600 ^oC, and 800 ^oC. From the analyses, it obtained E_g which was varied from 2.01 eV until 2.67 eV. While E_u from 0.13 eV until 0.26 eV. The results showed that the E_u varied inversely to the E_g. The Penn model and hydrogen-like atom model theories were used to investigate the interrelation between E_u and ε. Finally, it is shown that the Urbach energy is linearly and inversely related to the imaginary and real parts of dielectic constant, respectively.

Abstract: Different material thickness with medium and high dielectric constant can impact the performance and reliability of high electron mobility transistor device. With varying the thickness of the passivation layer, the effect of it towards the device performance is still unclear. Two different insulator layers with a medium dielectric and a high dielectric constant namely Aluminium Nitride and Hafnium Oxide are used as passivation layer in AlGaN/GaN HEMT. Both material performance was simulated via COMSOL software by varying the thickness and the drain current output were compared. The passivation layer thickness of 10nm at V_ds=6 V and V_gs=5 V, HfO₂ outperforms AlN with the output drain current of 39 mA compared to 35 mA respectively. It was observed that HfO₂ can attain higher threshold voltage, V_th as compared to the AlN because of the influence of its material properties that shows a direct proportional relationship between V_th and dielectric constant. Using high dielectric constant material like HfO₂, we observe the ON-voltage gradually decreases as the thickness of the passivation layer increased. Out of all the thickness simulated for HfO₂ and AlN, 10nm produced the highest drain current output instead of layer thickness of 20nm.

Abstract: Cerium oxide, also known as CeO₂, can be synthesized by the hydrothermal process with cerium nitrate precursor solution. After drying and sintering at 800,900, and 1100 C, different-sized cerium oxide nanoparticles were produced from the solution. Using x-ray diffractometers, the researchers were able to determine that all of the cerium oxide nanoparticles have a unique structure called fluorite crystalline structures. The structural, morphological and optical properties of films were investigated by a set of characterization techniques such as X-ray diffraction (XRD) and scanning electron microscopy (SEM). The estimation of crystallite size is (22.12,27.34 and 42.02 nm), which is confirmed by Scherrer formulae from XRD pattern. The dielectric constant increased with the increase of crystallite size due to the size effect. The crystal size increased with increased sintering temperature. Keywords: Cerium oxide (CeO₂), structural, crystal size, , morphology,Dielectric constant.

Abstract: Establishing the relationship between the structure of solids, on the one hand, and macroscopic physical properties, on the other, makes it possible to obtain detailed information about the structure and nature of interactions in the system involved. The solution to this problem makes it possible to formulate recommendations for the creation of materials with specified properties. In this work, much attention is paid to polymer films of syndiotactic 1,2-polybutadiene (1,2-SPB). The properties of polymer films differ from the properties of bulk materials of the same chemical composition as films. The polymer (1,2-SPB) has an amorphous, irregular structure and, due to its significant irregular structure and makeup, has important electrical, physical and chemical properties. Its physical properties make this polymer promising for use in various fields of mechanical engineering, agriculture, construction, and healthcare. The paper reports the results of a study of relaxation processes by the method of thermoactivation spectroscopy of a relatively new polymer - syndiotactic 1,2-polybutadiene. The mechanisms of deformation and relaxation polarization are described and studied in detail. A technique for preparing samples and processing the experimental results of the dielectric characteristics of polymer films are described. Dielectric measurements were performed using a standard R-571 bridge. Experimental temperature dependences of dielectric constant, dielectric loss factor and loss tangent before and after exposure to a high-frequency electromagnetic field are shown. An atomic force microscopy (AFM) survey of a 1,2-SPB polymer film is presented. Particle analysis by AFM provides a unique opportunity to determine the size and shape of particles.