Papers by Keyword: Resistivity

Abstract: The aim of this study was to create a practical water filter to improve the quality of Muara Angke well water. There are three main steps in this research, namely initial testing of Muara Angke residents' well water, making water filters, and testing filtered well water. There are three types of tests carried out, namely resistivity, pH, and turbidity. The water filter uses sedimentation techniques using natural materials. The composition of the materials from top to bottom is gravel (30 cm), silica sand (40 cm), manganese zeolite (40 cm), and activated carbon (40 cm). Well water, whether filtered or not, still contains more dissolved ions which causes its resistivity to be lower than bottled water. The filtration process using silica sand, manganese sand, and activated carbon does not directly cause a significant decrease in pH. However, if the source water has certain chemical characteristics or there are reactions that result in increased acidity (such as from CO₂ or oxidation reactions), the pH of the water may decrease slightly. The filtration media used helps reduce water turbidity, but has not reached the desired standard.

Abstract: The VN thin films were deposited on glass and Al₂O₃ substrates using reactive magnetron sputtering with a vanadium target in an Ar/N₂ mixed atmosphere. The deposition process was carried out at a substrate temperature of 25 °C and a sputtering power of 250 W. VN thin films were systematically prepared on glass substrates by varying the N₂/(Ar+N₂) ratio to 25%, 33%, 42%, and 56%. The results demonstrated that all as-deposited films consistently exhibited a face-centered cubic (FCC) NaCl-type crystal structure, regardless of the N₂/(Ar+N₂) ratio. Notably, the crystallization phase remained stable even when annealed at temperatures ranging from room temperature to 400 °C. As the nitrogen content increased, the resistivity of the films decreased, and the temperature coefficient of resistance (TCR) shifted toward smaller values. At a nitrogen content of 56%, the film exhibited the lowest resistivity of 63 μΩ-cm, along with a TCR of-460 ppm/°C. Furthermore, the resistivity demonstrated good stability, with only a 3% variation observed over one month.

Abstract: The carbonized materials structure levels from molecular to macrostructure is analyzed. A study was conducted to find correlations between the granular carbonized materials electrical resistance and other substance physicochemical properties. It is proven theoretically and experimentally that determining the electrical resistance for a granular material, rather than a finely ground sample, is a more informative indicator for reflecting the microstructural features of the material, its reactivity, strength, and clarifying the carbonization conditions. A method is developed for determining the granular materials electrical resistance in the rotating drum interelectrode space, with determination of the indicator value in the cold and hot state for the substance under investigation. An indicator of the granular matter electrical resistance based on the heating time to 670 °C at a drum power supply constant voltage is introduced. Calculated dependencies is obtained for predicting, based on experiment results, some quality indicators for such a carbonized material as metallurgical coke: structural strength, apparent density, reactivity, gasification degree, and electrical resistivity. Better correlations is achieved with these indicators than with the standard electrical resistance on the "micropress" device, which indicates a better reflection of the carbonized materials substance supramolecular structure.

Abstract: The NbN thin films were deposited onto glass and Al₂O₃ substrates using reactive magnetron sputtering, employing a niobium target sputtered with a mixture of Ar and N₂ gases. The investigation focused on the phase structures, microstructures, and electrical properties of the NbN thin films under various deposition powers and annealing temperatures. The results indicated the presence of a face-centered cubic (FCC) crystal structure in the as-deposited films at a power of 125 W. Interestingly, the crystallization phase remained unchanged within an annealing temperature range from room temperature to 500 °C. It was observed that the resistivity of the NbN thin films increased with higher nitrogen content, while the temperature coefficient of resistance (TCR) showed a tendency towards more negative values as the nitrogen content rose. Notably, at a nitrogen content of 9%, the film exhibited the lowest resistivity of 273 μΩ-cm with a TCR of -240 ppm/°C.

Abstract: This work only investigated the x-direction scanning of atomic force microscopy, which can accurately measure porous silicon's width, depth, and roughness. Pores on p-type Si (100) surfaces fabricated by electrochemical anodization method with the variation of resistivity and current density, i.e., 0.001-0.005 Ω.cm (high dopant) and 1-10 Ω.cm (low dopant), and 4, 6, 8, and 10 mA/cm², respectively. Macroporous silicon was obtained for both high and low dopants. Pore width, pore depth, and roughness of silicon increase with increasing the current density. Characteristics of porous silicon for high dopants are smaller than that for low dopants. It indicates that large amounts of dopant in silicon can slow the etching process.

Abstract: Silicon on insulator (SOI) wafer has allowed the integrated circuit (IC) industry to create superior, high-performance solutions. In addition, doping techniques are vital in the silicon sector due to the need to regulate the material electrical properties. The spin on dopant (SOD) approach is an alternative method that involves spinning a solution containing dopant onto SOI wafers. This research aims to determine the impact of thermal diffusion temperature and soaking time on sheet resistance of doped SOI wafer using SOD approach. Additionally, the homogeneity of doping was studied by utilizing mapping techniques. Three inches boron-doped SOI wafers were cut and cleaned according to Radio Corporation of America (RCA) standards. N-type dopants of Filmtronics SOD P509 were deposited on SOI wafer by using a spin coater, for 40 seconds at 4,000 revolutions per minute (rpm). The thermal diffusion temperature and soaking time were set between 700°C to 1000°C for 30 to 120 minutes. After thermal diffusion, hydrofluoric acids (HF) were diluted and used to etch samples. All materials were evaluated using a four-point probe, Hall Effect and Atomic Force Microscope (AFM). The results show that when the thermal diffusion soaking time increases, sheet resistance decreases until activated dopants are saturated. When sheet resistance decreases, dopant concentration rises. Temperature and soaking time increase carrier density and surface roughness, while decreasing Hall mobility. From mapping techniques, it shows low non-uniformity value which less than 10% suggests good thermal diffusion control.

Abstract: Electrically conductive composites based on silicates offer new possibilities for the use of composites not only in civil engineering but in the construction industry in general. These materials can be used, for example, for resistive heating of roads and highways, surge protection for buildings, EMI shielding, or smart sensors. This article focuses on cement composites where graphite powders are used as electrically conductive fillers. The research focuses on the behaviour and the change of the electrically conductive properties of these materials under mechanical loading. The changes in the resistivity of the composites when loaded in different directions on the electric current flow was investigated and studied. The specimens were loaded in the direction of electric current and in the direction perpendicular to the electric current.

Abstract: We investigate the temperature-dependent resistivity (ρ(T)) and Hall coefficient (R_H(T)) of heavily Al-doped 4H-SiC and discuss the underlying conduction mechanisms. The sign of R_H(T) changes from positive to negative in nearest-neighbor hopping (NNH) and variable-range hopping (VRH) conduction, whereas it is positive in band conduction because Al-doped 4H-SiC is a p-type semiconductor. We propose a general physical model to explain why R_H(T) in hopping conduction becomes negative at low temperatures, which is applicable to both NNH and VRH conduction. Moreover, we elucidate why the activation energy for negative R_H(T) becomes similar to that of ρ(T) in NNH conduction.

Abstract: We present a calibrated bulk mobility model for 4H-SiC. Hall measurements are performed on 4H-SiC samples to determine the bulk mobility/resistivity in the temperature range of 200-500K. We observe that temperature dependence of bulk resistivity cannot be predicted by popular mobility models available within TCAD tools. A careful investigation reveals that these popular mobility models need to be revised and replaced by a comprehensive model that can describe the impurity scattering effects dominant at low temperatures. We present a well calibrated bulk mobility model for 4H-SiC exhibiting excellent agreement with measured data, making it suitable for device simulation purposes using TCAD tools.

Abstract: High-quality, low resistivity n-type (nitrogen-doped) single crystal 4H-SiC wafers are needed to grow high-quality epitaxial SiC layers used for the active blocking layers of high-voltage power devices. The resistance of the substrate constitutes a portion of the device resistance for vertical devices, and therefore the SiC substrate properties must be fully characterized. In this study we report the 4H-SiC substrate electrical properties as a function of temperature measured using van der Pauw structures to measure resistivity from 4-point measurements, and carrier concentration and mobility from Hall effect measurements. We find that the SiC substrate resistivity has a minimum around 425K for typical substrate doping levels, due to a competition between the decreasing mobility and increasing carrier concentration with increasing temperature. The measured energy levels of the N donor (hexagonal / cubic sites) are extracted for a 5.8×10¹⁸ cm^-3 N-doped substrate, and found to be 15 meV and 105 meV, respectively.