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This paper introduces an optimized computational domain for fully flooded circular elastohydrodynamic lubrication (EHL) contacts, enhancing the accuracy of numerical calculations of pressure and oil film thickness. First, the computational domain was configured based on Kapitza's analytical solution. Then, a resolution sensitivity study for the mesh of the 2D computational domain for the Reynolds equation was conducted to investigate the effect of mesh resolution on the accuracy of the numerical solution. Subsequently, the impact of the size of the full 3D computational domain on the simulation's accuracy and computational efficiency was analyzed. The main result is the 3D computational domain, which automatically adapts to operating conditions within the piezoviscous rigid, the isoviscous rigid, the piezoviscous elastic, and the isoviscous elastic regions, as well as in the transition regions between them. This results in a model which provides accurate predictions across a wide range of operational conditions. Another outcome is a new approximate expression for the central oil film thickness, showing a maximum relative difference of less than 4.6% compared to the numerical model. [ABSTRACT FROM AUTHOR]

Kesterite solar cells often suffer from low open‐circuit voltage due to interface recombination. To address this, a passivation approach is explored using a dielectric layer between the absorber and buffer layer, coupled with a point contact structure. In this method, carrier transport is enabled through point contacts while effectively passivating regions covered by oxide. In this study, although forming point contacts on the front surface poses processing challenges, a novel solution is presented. Herein, in situ formed ZnS nanoparticles (NPs) during Cu2ZnSn(S, Se)4 (CZTSSe) absorber fabrication is utilized as a nanomask for front surface point contacts. A thin TaOx layer, acting as the passivation layer, is deposited over the CZTSSe surface with ZnS NPs by using atomic layer deposition (ALD). The selective removal of these NPs by deionized water soaking creates size‐controlled point contacts without damaging the absorber surface. In this approach, the first successful implementation of TaOx in enhancing CZTSSe solar cell efficiency, which jumps from 6.17% to 9.02% due to this strategy, is marked. The passivation mechanism involves sodium attraction during ALD, reduced interface defects, and the generation of positive fixed oxide charges. In this innovative method, not only solar cell efficiency is improved but new insights are also provided into using secondary phases as nanomasks in interface engineering. [ABSTRACT FROM AUTHOR]

Compound TiSe2 has received much attention among the transition metal chalcogenides because of its thrilling physical properties concerning atypical resistivity behavior, the emergence of charge density wave (CDW) state, induced superconductivity, etc. Here, we report the discovery of a new feature of TiSe2, namely, the observation of resistive switching in voltage biased point contacts (PCs) based on TiSe2 and its derivatives doped by S and Cu (TiSeS, CuxTiSe2). The switching occurs between a low resistive mainly "metallic-type" state and a high resistive "semiconducting-type" state when a bias voltage is applied (usually < 0.5 V), and reverse switching occurs when a voltage of opposite polarity is applied (usually < 0.5 V). The difference in resistance between these two states can reach up to two orders of magnitude at room temperature. The origin of this effect can be attributed to the variation of stoichiometry in the PC core due to the drift/displacement of Se/Ti vacancies under a high electric field. Additionally, we demonstrated that heating occurs in the PC core, which can facilitate the electric field-induced effect. At the same time, we did not find any evidence for CDW spectral features in our PC spectra for TiSe2. The observed resistive switching allows proposing TiSe2 and their derivatives as promising materials, e.g., for non-volatile resistive random access memory (ReRAM) engineering. [ABSTRACT FROM AUTHOR]

Compound TiSe2 has received much attention among the transition metal chalcogenides because of its thrilling physical properties concerning atypical resistivity behavior, the emergence of charge density wave (CDW) state, induced superconductivity, etc. Here, we report the discovery of a new feature of TiSe2, namely, the observation of resistive switching in voltage biased point contacts (PCs) based on TiSe2 and its derivatives doped by S and Cu (TiSeS, CuxTiSe2). The switching occurs between a low resistive mainly "metallic-type" state and a high resistive "semiconducting-type" state when a bias voltage is applied (usually < 0.5 V), and reverse switching occurs when a voltage of opposite polarity is applied (usually < 0.5 V). The difference in resistance between these two states can reach up to two orders of magnitude at room temperature. The origin of this effect can be attributed to the variation of stoichiometry in the PC core due to the drift/displacement of Se/Ti vacancies under a high electric field. Additionally, we demonstrated that heating occurs in the PC core, which can facilitate the electric field-induced effect. At the same time, we did not find any evidence for CDW spectral features in our PC spectra for TiSe2. The observed resistive switching allows proposing TiSe2 and their derivatives as promising materials, e.g., for non-volatile resistive random access memory (ReRAM) engineering. [ABSTRACT FROM AUTHOR]

Hertzian formulas are commonly used for the evaluation of deformation and pressure distribution of non-conformal and slightly conformal mechanical pairs to estimate component stiffness and durability. For the sake of simplicity, their use is extended even to those cases in which Hertz's hypotheses do not hold. This paper summarizes Hertz's theory and compares the results obtained with theoretical and finite element analysis of the point contact of non-conformal and conformal pairs made of spheres, caps, and spherical seats. This study was motivated by the non-Hertzian behavior of a tilting pad bearing ball-and-socket pivot conforming contact observed by the authors in previous experiments. In particular, the displacement and force relation were investigated by varying the geometrical parameters, the materials, the boundary conditions, and the friction coefficient. In the case of non-conformal contact, the parameter variations had negligible effect in agreement with Hertz's theory while for conformal contact, the cap and seat height and width and the relative clearance were the most influential parameters on the non-Hertzian behavior. These novel results indicate that in conformal pairs, such as for tilting pad bearing ball-and-socket pivots, whenever Hertz's hypotheses are not satisfied and the assessment of contact stiffness is crucial, Hertzian formulas should not be applied as done in common practice, instead more accurate numerical or experimental evaluation should be made. [ABSTRACT FROM AUTHOR]

This study proposes a tribo‐dynamic model for point contacts under lubrication, focusing on the excitations caused by surface movement, defect and load impact. Surface movement and load impact can cause changes in contact force, resulting in acceleration and dynamic displacement, which may affect the flow of the lubricant. The traditional lubrication model is usually steady or transient, and load balance is used to correct the normal height, ignoring a series of influences such as the mass, stiffness and damping. It requires repeated corrections to obtain a balanced position, which is very time‐consuming. By combining tribology and dynamics, dynamic excitation is introduced in the contact process in this study. After determining the initial value, the normal height can be directly obtained from the dynamic equation. Besides, a comparison between the tribo‐dynamic model and the steady‐state model is presented. It is found that the film thickness and pressure distribution calculated by the two models are almost the same at medium and low speeds, while the calculation results of the two models are different at high speed or under load impact, which emphasises the importance of considering the dynamic behaviour in the study of contacts. [ABSTRACT FROM AUTHOR]

Hertzian formulas are commonly used for the evaluation of deformation and pressure distribution of non-conformal and slightly conformal mechanical pairs to estimate component stiffness and durability. For the sake of simplicity, their use is extended even to those cases in which Hertz’s hypotheses do not hold. This paper summarizes Hertz’s theory and compares the results obtained with theoretical and finite element analysis of the point contact of non-conformal and conformal pairs made of spheres, caps, and spherical seats. This study was motivated by the non-Hertzian behavior of a tilting pad bearing ball-and-socket pivot conforming contact observed by the authors in previous experiments. In particular, the displacement and force relation were investigated by varying the geometrical parameters, the materials, the boundary conditions, and the friction coefficient. In the case of non-conformal contact, the parameter variations had negligible effect in agreement with Hertz’s theory while for conformal contact, the cap and seat height and width and the relative clearance were the most influential parameters on the non-Hertzian behavior. These novel results indicate that in conformal pairs, such as for tilting pad bearing ball-and-socket pivots, whenever Hertz’s hypotheses are not satisfied and the assessment of contact stiffness is crucial, Hertzian formulas should not be applied as done in common practice, instead more accurate numerical or experimental evaluation should be made.

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The tribo-performance behaviors of lubricated textured point contacts have been explored herein at relatively high contact loads (up to 3 GPa) under reciprocating motion (0.2 and 0.4 m/s) employing low (ν@40 ℃ = 100 cSt) and high (ν@40 ℃ = 422 cSt) viscous oils. In this experimental study, two contacts (flat conventional surface vs. polished ball and textured flat surface vs. polished ball surface) have been created for the investigations of friction, wear, and contact potential (ability for film formation). It is found that in the presence of texture at the concentrated contacts, the coefficient of friction and wear have reduced considerably with high viscous oil irrespective of operating parameters. However, low viscous oil has yielded an increase in the wear under identical operating parameters. The contact potential (an indirect indication of film formation during the running-in period) in the presence of texture develops rapidly as compared to the conventional surface with both oils. It has demonstrated a reduction in the running-in period in the presence of textures at the contacts. The optical microscope images of worn surfaces of balls and tracks have also been presented for the quantification of wear and understanding of the associated mechanisms. [ABSTRACT FROM AUTHOR]

We consider theoretically the spin blockade effect on the spin polarization of a current passing through a geometrically confined head-to-head 180∘ domain wall at a magnetic point contact in a two-dimensional (2D) metallic nanowire. The analysis is based on coherent scattering of the carriers by spin-dependent potential associated with the wall structure. The transmission properties of coherent states are obtained by introducing an algorithm to solve the coupled spin channels Schrödinger equation with mixed Dirichlet–Neumann boundary conditions applied far from the domain wall. It has been shown that a domain wall separating two media of opposite magnetization direction can act as a spin filter, allowing controllable modification of the spin polarization via the wall width. [ABSTRACT FROM AUTHOR]

Many studies have already considered starved lubrication. However, there have been no reports on the oil film thicknesses under steady starved EHL (elastohydrodynamic lubrication), where the ultra-low volume of oil supplied per unit time is uniform. The present study examined the relationship between the supplied oil flow rate and oil film thickness under steady starved lubrication. A ball-on-disk testing machine was used in experiments to measure the oil film thickness by means of optical interferometry. A microsyringe pump was used to accurately control the supplied oil flow rate. The supplied oil flow rate was kept constant, and the minimum oil film thickness was measured for 1 h after the start of the tests to determine the relationship between the supplied oil flow rate and oil film thickness.

The aim of the present study is to investigate the effect of operating parameters (load, speed, and temperature) on the tribological performance and surface characteristics (skewness and kurtosis) of lubricated point contacts. For this purpose, experimental studies were carried out on a four-ball wear tester, using the Taguchi design of experiments concept. The tribo-contact performance in terms of contact friction and wear is monitored and recorded. The used test specimens thereafter were examined using the microscope and 3D surface profilometer at the end of the experiments. The combined effects of operating parameters on tribological performance and surface characteristics have been analyzed using the statistical technique of analysis of variance. Further, the composite desirability optimization method associated with response surface methodology has been employed to develop the regression equations in order to predict the contact performance characteristics for any given combination of operating conditions. The study undertaken reveals that the operating parameters significantly influence the tribo-performance and surface characteristics of lubricated point contacts. The developed regression equations are expected to offer an effective analytical tool for accurately predicting the performance characteristics of lubricated point contacts. [ABSTRACT FROM AUTHOR]

This paper deals with optical experimental methods for improving current knowledge on particle entrapment in elastohydrodynamic contacts. Particular attention was paid to the possibilities offered by fluorescence-based techniques for mapping lubricant flow and tracking contaminant trajectories. A ball-on-disk tribometer, a fluorescent medium, and particle image velocimetry equipment were used together for this purpose. This original experimental setup enabled us to obtain lubricant streamlines and velocity vector maps in the contact area. Moreover, it allowed us, for the first time, to capture the details of trapping as the rejection of contaminating particles, in the context of lubrication, as it happened. Dynamic in situ observations clearly showed that the entrapment of debris-like particles was competing against the backflow occurring upstream, in particular in elliptical contacts. The results reported in this work confirm and expand previous results obtained with different methods, i.e., using a twin-disk machine and CFD computations. Finally, we briefly describe as future work the potential for applying these fluorescence-based methods to questions that are still under debate in the lubrication community. [ABSTRACT FROM AUTHOR]

We investigated the Josephson effect between the conventional superconductor PbIn and BaK (FeAs) single crystals by performing directional point-contact experiments. The junctions were irradiated with microwaves and the behavior of the Shapiro steps as a function of the square root of the microwave power was studied by means of the RSJ model extended to the nonautonomous case with an rf current-source term. The analysis reveals that, for current injection along the ab plane, the current-phase relation deviates from being simply described by the standard sin( ϕ) (as we indeed observed along the c axis) and a dominant sin(2 ϕ) component is observed. The results are compared with a theory of the dc Josephson effect, formulated by using a method based on the calculation of temperature Green's function in the junction within the tight-binding model (Burmistrova et al., Phys. Rev. B 91, 214501, ). The comparison shows that the experimental results here presented strongly favor an s-wave symmetry of the order parameter in this compound. [ABSTRACT FROM AUTHOR]

We have investigated point contacts between ferromagnetic Fe and different BCS-type superconductors using Andreev reflection spectroscopy. With the standard BTK-type analysis, the extracted spin polarization of Fe does not depend on the superconductor and agrees well with literature data. However, the characteristics of the Andreev reflection spectra vary with the superconductor. While most of the contacts with the strong superconductors Nb and Ta appear to be barely affected by the presence of Fe, the contacts with weaker superconductors Sn and Al have a reduced critical temperature $$T_\mathrm{c}$$ and occasionally a second superconducting transition at still lower temperature, and contacts with the weakest superconductor Zn have strongly reduced superconducting anomalies. We propose that this variation is related to the magnetic field generated by the ferromagnetic electrode, which can also affect the extracted spin polarization. [ABSTRACT FROM AUTHOR]

We studied the electrical transport through epitaxial, 8 nm long and about 100 nm diameter, GaAs pillars. They are fabricated with molecular beam epitaxy using a self-assembling method called local droplet etching. The nanopillars are embedded in an AlGaAs tunneling barrier between two epitaxial GaAs layers. Because of the epitaxial growth, the pillars are connected to these GaAs layers without additional interfaces. They thus can be considered as electronic point contacts between three-dimensional electron reservoirs. Voltage-current characteristics of the structures feature a characteristic asymmetry that is not observed in reference samples. Furthermore, the behavior of the resistance in magnetic fields applied parallel and perpendicular to the current direction is compared for samples with and without pillars. Clear differences are found that are associated with current-carrying states in the pillars. [ABSTRACT FROM AUTHOR]

Electrostatically operated RF-MEMS switches are known to suffer from discrete switch bounce events during switch closure that increase wear and tear and lead to increased switching times. Here, we use laser Doppler vibrometer to analyze the switch response of three types of cantilevered dc-contact switches at a 200 ns time resolution. We find that bounce events are multiple time scale events with distinct motion occurring at 10-1 and 101 s timescales in effect high frequency bounces within a bounce. To understand the origin of this effect, we develop a multiple eigenmode model of a cantilever switch with electrostatics, repulsive and adhesive contact forces, and rarefied gas damping and find that the high frequency bounce arises from the transient excitation of the 2nd eigenmode of the cantilever structure of the RF-MEMS switch. This phenomenon not only describes the multiple time scales involved in bounce events, but also shows that the transient excitation of the second mode leads to complex drum roll like dynamics, leading to a series of closely spaced impacts in each actuation cycle. A careful study of the dependence of the phenomenon on contact stiffness and adhesion shows how the landing pad stiffness, adhesion, and actuation voltage in dc contact switches can increase or diminish repeated impacts during actuation. [ABSTRACT FROM AUTHOR]

We explore the potential of laser processing aluminium oxide (Al2O3)/amorphous silicon carbide (a-SiC x:H) stacks to be used at the rear surface of p-type crystalline silicon (c-Si) solar cells. For this stack, excellent quality surface passivation is measured with effective surface recombination velocities as low as 2 cm/s. By means of an infrared laser, the dielectric film is locally opened. Simultaneously, part of the aluminium in the Al2O3 film is introduced into the c-Si, creating p+ regions that allow ohmic contacts with low-surface recombination velocities. At optimum pitch, high-efficiency solar cells are achievable for substrates of 0.5-2.5 Ω cm. Copyright © 2012 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

We study the thermal transport through only few nanometer long GaAs pillars. The pillars are epitaxially embedded between two otherwise isolated thermal reservoirs. Because of the short length and absence of defects and interfaces, the heat current through the pillars is free of distracting influences and perfectly controlled. This enables simple understanding of the observed thermal transport, regarding the pillars as ballistic thermal point contacts. The adjacent figure sketches a side view of the structures employed for the experiments. The thermal conductance of the pillars was measured with the 3 ω method. [ABSTRACT FROM AUTHOR]

Surface roughness plays an important role in the performance of soft elastohydrodynamically lubricated contacts. When a soft and smooth body is in contact with a very rigid and rough one, the roughness creates pressure fluctuations, resulting in the deformation of the soft body. As the contact pressure is low, the fluid can be considered isoviscous and incompressible. An extension of the amplitude reduction theory from the piezoviscous to isoviscous elastic regime is performed under pure rolling conditions. It shows that a single master curve can be obtained by providing an analytic formula, but the power on the load parameter is different in the piezoviscous and isoviscous elastic zones. [ABSTRACT FROM AUTHOR]

Abstract: We performed Point Contact Andreev Reflection Spectroscopy experiments on crystals. The variety of the measured spectra are all explained in terms of a modified BTK model considering a d-wave symmetry of the superconducting order parameter. We give an estimation of the energy gap and of the ratio . We measured the temperature evolution of the vs. V characteristics and we extracted a conventional BCS temperature dependence of the superconducting energy gap. Finally, in order to explain the conductance spectra showing higher voltage gap-like features we consider a model in which the formation of a Josephson junction in series with the Point Contact junction is realized due to the tip pressure. [ABSTRACT FROM AUTHOR]

Abstract: The Finite-Element-Method (FEM) was used for the simulations of the effect of a changing current distribution during AC impedance spectrum recording on electroceramic point contact and thin film model electrodes. For pure electronic conducting point contact electrodes the transition from the primary current distribution to the DC current distribution restricted to the Three-Phase-Boundary (TPB) zone introduces an error in the determination of the reaction resistance, R reac = Z(freq.→0)− Z(freq.→∞). The error is estimated for different width of the effective TPB zone and a rule of thumb regarding its significance is provided. The associated characteristic impedance spectrum shape change is simulated and its origin discussed. Furthermore, the characteristic shape of impedance spectra of thin electroceramic film electrodes with lateral ohmic resistance is studied as a function of an increasing lateral ohmic resistance. The characteristic change in the shape of the complex plane impedance plot with increasing lateral ohmic resistance is discussed in terms of extracting kinetic parameters such as electrolyte and reaction resistance. [Copyright &y& Elsevier]

In order to investigate the influence of body temperature of contact solids on the lubrication performance of machine components such as gears and roll-bearings, full numerical solution for the non-Newtonian thermal elastohydrodynamic lubrication (EHL) problem in point contacts has been achieved, assuming that the body temperature is different from the temperature of the supplied lubricating oil. The Ree-Eyring rheology model has been used to describe the non-Newtonian behaviour of the lubricant. The effects of the body temperature, the slide- roll ratio, and the velocity parameter have been discussed. The results for the body temperature being higher or lower than the temperature of the supplied oil have been compared with that of the conventional thermal EHL solution, where the temperature of the contact bodies and the temperature of the supplied oil are assumed to be the same. Results show that, if the entrainment velocity is not very high, the solid body temperature plays a dominant role in the EHL behaviour; however, the influence of body temperature decreases as the entrainment velocity increases. Comparisons between the non-Newtonian and Newtonian numerical results have been made under some operating conditions. It has been shown that, compared with the Newtonian solution, the non-Newtonian property of the lubricant can always lead to lower frictional coefficient and lower temperature, but has little effect on the film thickness, no matter the temperature of the contact bodies is lower than, equal to, or higher than that of the supplied oil. [ABSTRACT FROM AUTHOR]

We report on a novel ballistic electron spectrometer that images the k-space structure of open orbits confined by a magnetic field gradient. Magnetoresistance measurements were performed on a AlGaAs/GaAs/Dy device which supported magnetic edge states. Point contacts were used to ensure the commensurability of edge state period to the length of the waveguide. Periodic oscillations in the non-local magnetoresistance were observed, which we ascribe to the discrete nature of the orbits. A semi-classical model is used to describe the device, and gives good agreement with experimental results. [ABSTRACT FROM AUTHOR]

Abstract: In the first part of the present paper we discuss the fabrication and the characterization of an MgB2-based SQUID magnetometer with a directly coupled large-area pick-up loop, made on an MgB2 film deposited by an all in situ technique. The coarse structure of the SQUID was defined by optical lithography and Ar-ion milling, while the two nanobridges acting as weak links in the superconducting loop were made by focused ion beam (FIB) milling. The device was characterized at different temperatures and showed Josephson quantum interference up to 20K as well as a noise level already compatible with the recording of an adult magnetocardiogram. In the second part, concerning the fundamental physics of MgB2, we present the results of very recent point-contact measurements on Mg1−x Mn x B2 single crystals with 34.1⩾ T c ⩾13.3K (i.e. 0.37%⩽ x ⩽1.5%). The experimental conductance curves were fitted with the generalized two-band BTK model and their behaviour in magnetic fields was studied to check if both the order parameters (OPs) of the σ and π bands were present in the whole doping range. The dependence of the OPs (evaluated through the fit) on the Andreev critical temperature of the junctions is analyzed in the framework of the two-band Eliashberg theory by including the effects of magnetic impurities. The results give an evidence of a dominant effect of the magnetic impurities on the σ-band channel. [Copyright &y& Elsevier]

Abstract: An overview on recent efforts in point-contact (PC) spectroscopy of title superconductors is given. Distinct phonon features and crystalline-electric field effects are observed in PC spectra of HoNi2B2C. Results of study of superconducting (SC) gap and excess current versus temperature and magnetic field reflecting specific multi-band electronic structure in MgB2 are presented. The nature of the extremely nonlinear curves in the antiferromagnetic (AF) and SC state are elucidated for UPd2Al3 break junctions and MgCNi3 point contacts. [Copyright &y& Elsevier]

Magnetic anisotropy and spin polarization are fundamental parameters in ferromagnetic materials that have use in spintronic device applications. As the need for screening properties of new magnetic materials rises, it is important to have measurement probes for quantities such as anisotropy and spin polarization. We have developed two unconventional yet powerful techniques to study these parameters. A resonant RF transverse susceptibility method is used to map the characteristic anisotropy and switching fields over a wide range in temperature and magnetic fields. For studies of spin polarization, the phenomenon of Andreev reflection across ferromagnet-superconductor junctions is used to extract values of the transport spin polarization. The effectiveness of these approaches is demonstrated in candidate spintronic materials such as half-metallic CrO2 thin films and arrays of monodisperse, single-domain Fe nanoparticles. [ABSTRACT FROM PUBLISHER]

We propose a new fabrication technique of room-temperature operating silicon single-electron transistors (SETs). The devices are in the form of ultranarrow wire channel MOSFETs, where a sub-10-nm channel is formed by wet etching and slight thermal oxidation. Large Coulomb blockade (CB) oscillations whose peak-to-valley current ratio at room temperature is as high as 6.8 are observed in the fabricated ultranarrow wire channel MOSFETs. It is found that larger CB oscillations are obtained in the ultranarrow wire channel SETs than in the point-contact channel SETs. It is considered that the potential fluctuations induced during the channel formation processes give rise to multiple-dot SET structures in the ultranarrow wire channel MOSFETs. [ABSTRACT FROM PUBLISHER]

The film thickness under steady state conditions can be measured by using an optical interferometer. An inverse approach is proposed for estimating the pressure distribution on the basis of film thickness measurement in elastohydrodynamic lubrication (EHL) circular contacts. This approach is constructed from the approximated model of elastic deformation and force balance equations. To obtain an accurate pressure, it is necessary to divide the domain into a few regions on account of the singularity at the pressure spike. The principle of measuring point selection is proposed, and the problem of pressure fluctuation is overcome. On the basis of the smoothed pressure distribution, the apparent viscosity of the film can be obtained from the Reynolds equation. The least-squares method is used to compute the optimum value of the pressure-viscosity index. Results show that the best region for estimating the pressure-viscosity index is along the x axis because the Poiseuille term becomes zero in the Reynolds equation on account of the symmetry. In this region, the estimated pressure-viscosity index shows very good agreement with the exact value when measurement errors are neglected. When measurement errors are taken into account, the close agreement shows the potential of the proposed approach in estimating accurate values of the pressure-viscosity index. Generally, the error in estimating the pressure-viscosity index increases with increasing standard deviation of the measurement error, load, speed, material parameter and absolute error of the measured film thickness. The inverse approach can also be used to estimate the pressure distribution on a film thickness map obtained from an optical EHL tester. Moreover, the agreement between the actual and the estimated values of z is quite good. [ABSTRACT FROM AUTHOR]

We investigate the tunneling barrier structures in the room-temperature operating silicon single-electron transistors (SETs). The devices are fabricated in the form of the point-contact channel metal-oxide-semiconductor field-effect transistors with gate oxide formed by thermal oxidation or low-pressure chemical vapor deposition (LP-CVD). From the gate voltage and temperature dependence of the peak current in the SET characteristics, it is found that the thermal oxidation process leads to higher and narrower tunneling barriers. In some SETs with CVD-deposited gate oxide, thermally activated conduction over the low tunneling barriers is clearly observed in a wide temperature range from 100 K-300 K. [ABSTRACT FROM PUBLISHER]

The numerical simulation of temperature distribution of point contacts in mixed lubrication is presented. The calculating includes two steps. First, temperature rises on two surfaces are obtained by a temperature integration method of transient point heat source. Second, the partition coefficients of heat flux are determined by matching the temperature of two surfaces. Similar to the calculation of elastic deformation, double linear interpolation function is used to get a better accuracy, and moving grid method is used to increase the efficiency of the computation. Due to the symmetry of influence coefficient matrix in the direction perpendicular to the velocity, storage and computational work are further reduced by 50%. Numerical samples validate the algorithm and program. The calculating results of the cases of smooth surface and isotropic sinusoidal surface are presented. [ABSTRACT FROM AUTHOR]

Surface roughness effects in line and point elastohydrodynamically lubricated contacts are compared and it is shown that the underlying behaviours in both types of contact are identical. Long wavelength components of roughness are attenuated; short wavelength components pass through the conjunction unaltered. It is also shown that the roughness attenuation, plotted against a non-dimensional wavelength, follows almost identical curves in both cases. [ABSTRACT FROM AUTHOR]