Papers by Keyword: Mobility

Abstract: Polymer concretes are used in construction, engineering, electrical and chemical industries. Polymer concrete mixes are characterized by low mobility mixtures, due to their high viscosity. It makes difficult to use them in the production of thin-walled and high-reinforced structures, monolithic floors, application of finishing and protective coatings and repairing of roads. The influence of additives of dibutyl-phthalate, chlorinated paraffin, technical glycerin and engine oil on the mobility of the concrete mix and the physical and mechanical properties of fine-grained concrete, based on polyester resin, was studied. For polymer concretes with different type and quantity of plasticizer the density and bending and compression strength were determined. To improve the workability of the concrete mix and obtain a polymer concrete with a homogeneous structure and high strength, it is recommended to use chlor-paraffin ChP-470A and “Lukoil” engine oil as a plasticizer.

Abstract: In this paper, we have explored planar junctionless FET (JLFET) in 4H-SiC as a potential device for future industrial applications. We show the differences in static electrical characteristics (I_d-V_g, I_d-V_d, subthreshold current and I_on/I_off ratio) between n and p-type JLFETs whilst varying the lattice temperature (T) from 300 K to 700 K using 2D numerical simulations. The oxide-SiC interface traps have shown minimum influence on the device current conduction characteristics. For the same one-micron channel length and an equal area of cross-section, the p-type JLFET exhibits lower off-state current (I_off) leading to higher I_on/I_off ratio, a higher threshold voltage (V_TH) and lower subthreshold current in comparison to the n-type JLFET.

Abstract: We employed the thermal dielectric relaxation current method (TDRC) for the cryogenic characterization of ammonia (NH₃) post oxidation annealed 4H silicon carbide (4H-SiC) trench MOSFETs. We studied differences and similarities between annealing in nitric oxide (NO) and NH₃. In NO and NH₃ annealed trench MOSFETs, the same type of traps was found near the conduction band edge of 4H-SiC. The TDRC-signal consists of two peaks caused by interface states with a thermal emission barrier of 0.13 eV and near interface traps (NITs) with an emission barrier of approximately 0.3 eV. Significantly more interface traps close to the conduction band edge were found for the NH₃ annealed devices compared to the NO annealed ones. Our TDRC results indicate that NH₃ post oxidation anneal (POA) affects trap levels in a different way than NO POA.

Abstract: We report on a novel method of stacking multiple oxide layers on 4H-SiC 20 kV IGBT. Instead of SiO₂/SiC interface which is common for any SiC based MOS device, we found that the AlN/SiC interface would yield better results. We have performed 2D numerical simulations to analyze static characteristics for three combinations of dielectric stacks on IGBT: HfO₂-SiO₂, HfO₂-AlN, and HfO₂-SiO₂-AlN (by maintaining the same equivalent oxide thickness value). In addition to higher transconductance (g_m) and lower subthreshold swing (SS), the device with AlN/SiC interface offer comparatively lower R_SP,ON and higher mobility with respect to temperature. Nevertheless, with a partial compromise on device characteristics improvement, insertion of SiO₂ in the dielectric stack helps in suppressing the subthreshold current owing to higher band offset with respect to SiC. The turn off characteristics of the device is analysed using a clamped inductive circuit. Device with AlN/SiC has shown better dI_c/dt and fall time compared to SiO₂/SiC interface.

Abstract: Abstract:Electron mobility limited by surface roughness scattering in free-standing GaAs thin ribbon with an internal parabolic quantum well caused by surface state is investigated in detail. Based on analyzing the parabolic quantum well including the energy subband level, wave function and the confined potential profile in the thin ribbon by solving Schrödinger and Poisson equations self-consistently, the electron mobility could be investigated. Conclusion indicates that remote surface roughness (RSR) of the thin ribbon will change the two dimensional electron gas (2DEG) mobility through the medium of barrier height fluctuation of the parabolic well in atomic scale. Calculation results reveal that the 2DEG mobility decreases with increasing roughness amplitude, which is characterized in terms of the surface roughness height and the roughness lateral size.

Abstract: In this work, 3’-flouro-2,2',6,6'-tetraphenyl-4,4'-dipyranylidene (3FDP) was originally synthesized and investigated with density functional theory (DFT) calculations, ultraviolet–visible spectroscopy (UV–Vis) and cyclic voltammetry (CV) in comparison with 2,2',6,6'-tetraphenyl-4,4'-dipyranylidene (DP) and 4’-flouro-2,2',6,6'-tetraphenyl-4,4'-dipyranylidene (4FDP). 3FDP-based organic field-effect transistors (OFETs) were fabricated with bottom contact configuration on bare SiO₂/Si substrate, 1,1,1,3,3,3-hexamethyldisilazane (HMDS) and octadecyltrichlorosilane (OTS) treated substrate, respectively. The HMDS-treated device showed highest mobility of 4 × 10⁻⁴ cm² V⁻¹ s⁻¹, on/off ratio of 4 × 10³ and threshold voltage of −10 V. Finally, vacuum deposited 3FDP films morphology was investigated by X-ray diffraction (XRD) analyses and the results showed higher crystallinity of HMDS-treated 3FDP film compared to the OTS-treated film, leading to a better FET performance.

Abstract: We report the development of a low-temperature (600 °C) gate oxidation approach to minimize the density of interface traps (D_IT) at the SiC/SiO₂ interface, ultimately leading to a significantly higher channel mobility in SiC MOSFETs of 81 cm²·V^-1·s^-1, >11x higher than devices fabricated alongside but with a conventional 1150 °C gate oxide. We further report on the comparison made between the D_IT and channel mobilities of MOS capacitors and n-MOSFETs fabricated using the low-and high-temperature gate oxidation.

Abstract: The gate insulator process for SiC-MOSFET was examined and high-quality interface was realized by employing the pre-annealing process before high-temperature N₂ annealing. The pre-annealing evidently activated the interface to introduce nitrogen, and then field-effect mobility exceeded 50 cm²/Vs. The fabricated sample also demonstrated superior bias temperature instability (BTI) and excellent breakdown electric field of 11.7 MV/cm.

Abstract: The article deals with the mobility during crisis situations. In these situations, there is not always possible to use the roads or ways and the vehicles have to move on different areas, mostly on terrain like meadows, forests etc. That is why we should be able to evaluate whether the terrain is traffiacable or not, whether the vehicles mire or not. The approaches of evaluating the terrain traffiability are described here as well as the instruments used for these purposes, procedures of measuring and calculations. Another aim of this article is to apprise with the means for negotiation the low endurable terrain – traditional wooden and perspective mats.

Abstract: Comparative study of p-type 4H-SiC epitaxial layers grown simultaneously on two different 4H-SiC substrates, namely n-type and semi-insulating have been done by different structural, optical and electrical experimental techniques.