Papers by Keyword: Resistivity

Abstract: Mg/Al bilayer thin films were successfully deposited by using D.C. magnetron sputtering technique. To study the effect of hydrogenation on structural, optical and electrical properties of Mg/Al thin films, the hydrogenation of the annealed thin films was done under different hydrogen pressure (15, 30 & 30psi). The structural properties of the films were investigated by Raman spectroscopy and decrease in intensity of Raman peaks with increasing hydrogen pressure was observed; this typically confirms the existence of hydrogen in Mg/Al thin films. The thin film is of semiconducting nature and it was found that the electrical conductivity of the film decreases with increasing hydrogen pressure applied. In the hydriding kinetics of the films, it was seen that the resistivity increased along with hydrogen absorption time. Eventually, it attains the equilibrium stage indicating the hydrogen absorption in the thin films. The rate of absorption of hydrogen increases with the pressure of hydrogen over different time ranges and decreases with the absorption of hydrogen over time.

Abstract: Alkaline activated materials and geopolymers are recently widely involved in studies concerning their potential for advanced composites with enhanced electrical properties. This paper reports self-sensing behaviour of fly ash mortar doped with carbon black or graphite conductive admixture subjected to loading in three-point flexural test. Development of self-sensing properties and deformations of all mortars was initially investigated under flexural loading cycles with constant amplitude, final stage of the experimental part consisted in loading till fracture. Both reference and modified geopolymers failed to achieve satisfactory self-sensing performance during the cyclic loading but certain differences in fractural properties were observed.

Abstract: 200 mm diameter n-type 4H SiC wafers were produced from bulk crystals grown using a physical vapor transport (PVT) method. The configuration of the growth cell was modified to both allow for the growth of larger crystals with respect to the standard 150 mm process, and to induce a thermal environment necessary to increase the mass deposition rate. A 25% increase in deposition rate was achieved relative to the standard process. The resulting wafers exhibited resistivity uniformity comparable to commercial 150 mm product. Optical and x-ray techniques were used to evaluate wafer quality, and revealed surface and bulk crystal defect densities acceptable for epilayer growth.

Abstract: In this work, we study the impact of the dose rate on the electrical properties of aluminum (p-body, p⁺-body-contact) and phosphorous (n-source/drain) implanted 4H-SiC. We find no significant differences for dose rates ranging from 1×10¹¹ cm^-2s^-1 to 2−7×10¹² cm^-2s^-1. AFM scans across implanted and non-implanted regions after thermal oxidation and subsequent oxide etching reveal a clear dependence of the oxidation rate on the conduction type and doping concentration. In addition, we observe an increasing (decreasing) oxidation rate for increasing doping concentrations of the n-type (p-type) ion implanted areas.

Abstract: Due to their low leakage current, low noise levels, high thermal conductivity, and potential radiation hardness, SiC devices offer various advantages over Si devices in certain applications. As a result, they are being considered for operation in harsh environments, such as plasma diagnostic systems in future nuclear fusion reactors or in high energy physics applications. We report on relevant results of the GRACE project, which seeks to deliver a new generation of SiC sensors with graphene-enhanced contacts. Such devices are aimed to be radiation-hard and functional at high temperatures. The work presented in this paper focuses on the optimisation of the electrical contacts, along with the electrical characterisation and radiation-tolerance assessment of the first sensor prototypes produced.

Abstract: The relationship between electrical resistivity and temperature of carbon fiber reinforced concrete ( CFRC) road ma-terial are studied, from which the temperature sensibility of carbon fiber reinforced concrete is discovered, the electrical resistivity of CFRC decreases with increasing temperature and increases with decreasing temperature. The function mechanisms of the tem-perature are also analyzed. Using this property , carbonfiber reinforced concrete can be used as a kind of temperature sensor and self-diagnose the temperature of airfield runways or bridge deck.

Abstract: Information of subsurface stratigraphy is needed during the process of preparing multi-story buildings to avoid problems in determining the level of multi-story building piles. This research was conducted using the geoelectric method to study the subsurface stratigraphic conditions in the area. Based on the measurement results, we find an overview of the subsurface stratigraphic conditions consisting of soil in the first layer with resistivity values ​​ranging from 305 to 570 Ωm, the soil in the study area is red-yellow, namely podsolic soil mixed with sand and gravel. The second layer is clay layer by water saturated with resistivity values ​​between 15 to 44 Ωm, and the third layer with resistivity values ​​varying from 112 to 341 detected from the surface is sandy clay. Insertion of coal at the first measurement point was detected buried at a depth of 17 m from the surface with a resistivity value of 962 Ωm.

Abstract: Resistivity, r (T), and Hall coefficient in weak (B < 1 T) magnetic fields, R (T), are investigated in Ca₂Si and CaSi₂ films at temperatures T between ~ 20 - 300 K. In CaSi₂, r (T) is typical of metals increasing with T within the whole temperature range. On the other hand, the resistivity of Ca₂Si is pertinent of semiconductors. Namely, it is activated below T ~ 200 K, exhibiting different slopes of ln r vs. T ^-1 plots at lower and higher T, and a weak increase between T ~ 200 - 300 K. Both materials demonstrate a complex dependence of R (T), including a change of the sign. Transport properties above have been analyzed assuming two groups of charge carriers, electrons and holes, contributing them.

Abstract: We report the results of the resistivity measurement on La_2-xSr_xCuO₄ nanoparticles with x = 0, 0.05, and 0.20 evaluated by the four-point probe method. The high resistivity value shows the predominance of the inter-grain part. The temperature dependence of the conductivity can be analyzed by variable range hopping model showing the charge carriers are formed by thermal activation. There is no superconducting behavior that could be observed in La_2-xSr_xCuO₄ nanoparticles with x = 0.05 and 0.20.

Abstract: The addition of metal nanoparticles in the Bi-based superconductors has shown the disorder produced by the cations incorporation in the crystal structure affects the TC (Critical temperature) of the system. the addition of new mixture of (Cr2O3: SnO)x on high temperature superconductors HTS Bi1.6Pb0.4 Sr2Ca2Cu3O10+δ (Bi-2223) with ratio 1:1 where x = 0.0, 0.05, 0.10, 0.15 and 0.20 was investigated by solid-state reaction technique was used to prepare superconductor samples. Samples were characterized by X-Ray Diffraction (XRD), Field Emission Scanning Electron Microscopy (FS-EM), Energy Dispersive X-ray (EDX), and electrical resistivity. the results of XRD proved that the structure of 2223 remains the same even with the addition of (Cr2O3: SnO)x nanoparticles. The phase 2223 has the majority even phase Bi-2212 and phase Ca2PbO4 showed a contribution inside structure. As a result of the change physico-chemical properties resistivity of the doped optimized sample x = 0.10 was increasing 2.2 K approximately rather than the undoped one then decreased gradually up to x = 0.20. From resistivity measurement, the TC of 2223 doped with (Cr2O3: SnO)x at x = 0.10 was 113.2 K approximately. The addition of metal oxides in superconductor materials has been considered to be one of the most promising materials for large scale applications in superconducting industry.