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1
Kim, Youngbeom, Sungho Choi, Kyung-Young Jhang e Taehyeon Kim. "Experimental Verification of Contact Acoustic Nonlinearity at Rough Contact Interfaces". Materials 14, n. 11 (31 maggio 2021): 2988. http://dx.doi.org/10.3390/ma14112988.
Abstract (sommario):
When a longitudinal wave passes through a contact interface, second harmonic components are generated due to contact acoustic nonlinearity (CAN). The magnitude of the generated second harmonic is related to the contact state of the interface, of which a model has been developed using linear and nonlinear interfacial stiffness. However, this model has not been sufficiently verified experimentally for the case where the interface has a rough surface. The present study verifies this model through experiments using rough interfaces. To do this, four sets of specimens with different interface roughness values (Ra = 0.179 to 4.524 μm) were tested; one set consists of two Al6061-T6 blocks facing each other. The second harmonic component of the transmitted signal was analyzed while pressing on both sides of the specimen set to change the contact state of the interface. The experimental results showed good agreement with the theoretical prediction on the rough interface. The magnitude of the second harmonic was maximized at a specific contact pressure. As the roughness of the contact surface increased, the second harmonic was maximized at a higher contact pressure. The location of this maximal point was consistent between experiments and theory. In this study, an FEM simulation was conducted in parallel and showed good agreement with the theoretical results. Thus, the developed FEM model allows parametric studies on various states of contact interfaces.
2
VANDAMME, L. K. J. "CHARACTERIZATION OF CONTACT INTERFACE, FILM SHEET RESISTANCE AND 1/f NOISE WITH CIRCULAR CONTACTS". Fluctuation and Noise Letters 10, n. 04 (dicembre 2011): 467–84. http://dx.doi.org/10.1142/s0219477511000740.
Abstract (sommario):
The resistance and noise of films prepared with poor contacts are dominated by the contact interface and for perfect contacts holds that resistance and noise stem from outside the contact interface region. The proposed test pattern to study the different contributions uses one mask. It permits two- and four-point measurements enabling the detection of a weak contribution from outside the contact interface on top of a strong interface contribution. The resistance and noise for poor and perfect contacts are calculated between pairs of circular top electrodes of equal diameters 2r at distances L with L/2r = 10. The dependences of resistance and noise on the contact diameter are quite different for perfect and poor contacts. 1/f noise of films taken from literature are compared in the noise figure of merit K = Cus [ cm 2]/Rsh[Ω]. K is the ratio of 1/f noise normalized for bias, frequency and unit surface to sheet resistance. Materials can be classified based on K-values. Very high K-values point to inhomogeneous electric fields on a microscopic scale (percolation conduction). The contact interface 1/f noise and specific contact resistance are characterized by Cust [ cm 2] and ρct [Ω cm 2]. Reviews of K for films and Cust for interfaces show that 1/f noise is a more sensitive tool than merely the resistance parameters Rsh and ρct.
3
Nimmala, Seshu, S. Aria Hosseini, Jackson Harter, Todd Palmer, Eric Lenz e P. Alex Greaney. "Characterizing Macroscopic Thermal Resistance Across Contacting Interfaces Through Local Understanding of Thermal Transport". MRS Advances 3, n. 44 (2018): 2735–41. http://dx.doi.org/10.1557/adv.2018.485.
Abstract (sommario):
ABSTRACTThermal resistance across the interface between touching surfaces is critical for many industrial applications. We developed a network model to predict the macroscopic thermal resistance of mechanically contacting surfaces. Contacting interfaces are fractally rough, with small islands of locally intimate contact separated by regions with a wider gas filled boundary gap. Heat flow across the interface is therefore heterogeneous and thus the contact model is based on a network of thermal resistors representing boundary resistance at local contacts and the access resistance for lateral transport to contacts. Molecular dynamics simulations have been performed to characterize boundary resistance of Silicon Alumina interfaces for testing the sensitivity of thermal resistance to contact opening. Boltzmann transport simulations of access resistance in Si are conducted in the ballistic transport regime.
4
Yang, Ai Mei, Gui Zhong Li, Shao Ying Zhen e Lai Jun Liu. "Electrode Interface Polarization in BaTiO3-Based PTC Ceramics". Key Engineering Materials 697 (luglio 2016): 248–52. http://dx.doi.org/10.4028/www.scientific.net/kem.697.248.
Abstract (sommario):
Electrodes play a vital role on the electrical properties of positive temperature coefficient (PTC) ceramics. An ohmic contract between ceramics and electrodes is necessary for the PTC effect. In this work, silver mixed aluminium electrode and pure silver electrode were pasted on BaTiO3-based PTC ceramics, which results in an ohmic contact and non-ohmic contact, respectively. Impedance spectroscopy and dielectric and conductivity properties was investigated at different temperature for the two contacts. Small difference of electrical properties was found between the two contacts above the Curie temperature. Below the Curie temperature, however, carriers could pass through the interface of ohmic contract but gather on the interface of non-ohmic contact. The latter resulted in a space charge polarization, which increased low-frequency dielectric permittivity.
5
Shi, Linquan, e Qiang Li. "Numerical simulation and experimental study of contact thermal resistance under high temperature conditions". Thermal Science and Engineering 5, n. 1 (27 febbraio 2022): 1. http://dx.doi.org/10.24294/tse.v5i1.1523.
Abstract (sommario):
Contact thermal resistance is an important indicator of the efficiency of heat transfer between contact interfaces.The contact thermal resistance between the interfaces of superalloy GH4169 in high temperature was investigated byusing ANSYS. The real surface morphology of superalloy was obtained with optical microscope, and its surface modelwas reconstructed in ANSYS. Based on the theory of structural mechanics, the elastoplastic deformation of the microstructure of the contact interface is simulated, and analyzed and obtained the contact thermal resistance between contactinterfaces. The effect of interface temperature on the radiative heat transfer between the contact interfaces was studied.At the same time, the impact of radiation heat transfer between contact interfaces in high temperature is considered.Finally, it was tested by using an experimental test device. The result show that the maximum deviation between thecontact thermal resistance and the contact thermal resistance was 12.60%, and the contact thermal resistance betweensuperalloy interfaces decreases with the increase of interface temperature and contact pressure; the contact interfacetemperature difference increases first and then decreases with the increase of interface temperature.
6
Banerjee, Sneha, e Peng Zhang. "Review of recent studies on nanoscale electrical junctions and contacts: Quantum tunneling, current crowding, and interface engineering". Journal of Vacuum Science & Technology A 40, n. 3 (maggio 2022): 030802. http://dx.doi.org/10.1116/6.0001724.
Abstract (sommario):
The study of charge carrier transport at nanoscale electrical contacts is crucial for the development of next-generation electronics. This paper reviews recent modeling efforts on quantum tunneling, current crowding, and contact resistance across electrical interfaces with nanometer scale dimensions. A generalized self-consistent model for quantum tunneling induced electron transport in metal–insulator–metal (MIM) junctions is summarized. Rectification of a dissimilar MIM junction is reviewed. A modified two-dimensional (2D) transmission line model is used to investigate the effects of spatially varying specific contact resistivity along the contact length. The model is applied to various types of electrical contacts, including ohmic contacts, MIM junction based tunneling contacts, and 2D-material-based Schottky contacts. Roughness engineering is recently proposed to offer a possible paradigm for reducing the contact resistance of 2D-material-based electrical contacts. Contact interface engineering, which can mitigate current crowding near electrical contacts by spatially designing the interface layer thickness or properties, without requiring an additional material or component, is briefly reviewed. Tunneling engineering is suggested to eliminate severe current crowding in highly conductive ohmic contacts by introducing a thin tunneling layer or gap between the contact members. Unsolved problems and challenges are also discussed.
7
Kartal, Mehmet E., Daniel M. Mulvihill, David Nowell e Dawid A. Hills. "Measurement of Tangential Contact Stiffness in Frictional Contacts: The Effect of Normal Pressure". Applied Mechanics and Materials 70 (agosto 2011): 321–26. http://dx.doi.org/10.4028/www.scientific.net/amm.70.321.
Abstract (sommario):
The tangential contact stiffness of frictional interfaces affects both the vibration response and structural integrity of structures comprising frictional joints. Vibration and structural response of monolithic structures can be predicted very accurately; however, when assemblies of components involve frictional interfaces, additional damping and compliance are present due to these interfaces. These features make it more challenging to predict the vibration characteristics of assemblies with the same degree of accuracy as can be achieved for single components. If these interface properties can be determined, it should then be possible to significantly enhance current models of the vibration of engineering assemblies. Measurements of both force and displacement in the tangential direction are obtained from a series of in-line fretting tests involving flat pads with rounded corners clamped against the flat surface of a specimen which is oscillated by a hydraulic tensile testing machine. In order to measure the local displacement field very close to the contact interface, the digital image correlation (DIC) method is employed. The effect of normal contact pressure on tangential contact stiffness is investigated. Multiple experiments with the same parameters show good repeatability given the number of variables involved.
8
Liu, Yuwei, Yameng Ji, Fuhao Ye, Weizheng Zhang e Shujun Zhou. "Effects of contact pressure and interface temperature on thermal contact resistance between 2Cr12NiMoWV/BH137 and γ-TiAl/2Cr12NiMoWV interfaces". Thermal Science 24, n. 1 Part A (2020): 313–24. http://dx.doi.org/10.2298/tsci191018470l.
Abstract (sommario):
Thermal contact resistance between interfaces is an important parameter in the analysis of temperature distribution for structural components. Thermal contact resistance between heat resistant steel 2Cr12NiMoWV/aluminum alloy BH137 interfaces and 2Cr12NiMoWV/titanium alloy ?-TiAl interfaces were experimentally investigated in the present paper. The effects of contact pressure and interface tem-perature were detailed. The temperature of contacting surfaces was from 80- 250?, and the contact pressure ranged from 2-17 MPa. All experiments were conducted in ambient atmosphere. Results showed that thermal contact resistance decreases with an increment of interface temperature or contact pressure. Under the same conditions of contact pressure and interface temperature, thermal contact resistance between 2Cr12NiMoWV and BH137 interfaces is lower than that between 2Cr12NiMoWV and ?-TiAl interfaces. The temperature dependence of thermal conductivity and mechanical properties was analyzed to explain the results. Furthermore, with the piston and piston pin as the research object, steady state temperature fields were simulated in cases of considering thermal contact resistance and without considering thermal contact resistance, respectively. The results showed that the maximum temperature of the piston pin will be lower when thermal contact resistance is considered.
9
Nouira, Dorra, Davide Tonazzi, Anissa Meziane, Laurent Baillet e Francesco Massi. "Numerical and Experimental Analysis of Nonlinear Vibrational Response due to Pressure-Dependent Interface Stiffness". Lubricants 8, n. 7 (10 luglio 2020): 73. http://dx.doi.org/10.3390/lubricants8070073.
Abstract (sommario):
Modelling interface interaction with wave propagation in a medium is a fundamental requirement for several types of application, such as structural diagnostic and quality control. In order to study the influence of a pressure-dependent interface stiffness on the nonlinear response of contact interfaces, two nonlinear contact laws are investigated. The study consists of a complementary numerical and experimental analysis of nonlinear vibrational responses due to the contact interface. The laws investigated here are based on an interface stiffness model, where the stiffness property is described as a nonlinear function of the nominal contact pressure. The results obtained by the proposed laws are compared with experimental results. The nonlinearity introduced by the interface is highlighted by analysing the second harmonic contribution and the vibrational time response. The analysis emphasizes the dependence of the system response, i.e., fundamental and second harmonic amplitudes and frequencies, on the contact parameters and in particular on contact stiffness. The study shows that the stiffness–pressure trend at lower pressures has a major effect on the nonlinear response of systems with contact interfaces.
10
Huang, Lingqin, Sumin Pan, Xuliang Deng e Wenwen Cui. "4H-SiC Ohmic contacts formation by MoS2 layer intercalation: A first-principles study". Journal of Applied Physics 132, n. 24 (28 dicembre 2022): 245702. http://dx.doi.org/10.1063/5.0122722.
Abstract (sommario):
Due to the difficulty of forming a low Schottky barrier at the interface of a metal/SiC contact, preparing Ohmic contacts is still a key technical problem in developing SiC devices. In this paper, the effects of MoS2 intercalation on the interface properties of metal/SiC (Al, Ag, Ti, Au, and Mg) systems were investigated by first-principles calculation. The calculations show that all the metal/SiC contacts exhibit p-type Schottky contacts with strong Fermi level pinning (FLP) at the interfaces. After inserting a layer of MoS2, the Schottky barrier heights are significantly reduced. All the metal/MoS2/SiC systems are tuned to be n-type Ohmic contacts. By calculating and analyzing electron localization functions, projected band structure, partial density of states, and planar-averaged charge density difference, the Ohmic contact formation mechanism may be due to the saturation of dangling bonds of the SiC surface, the reduction in metal-induced gap states, the formation of interface dipole layer, and the shift of FLP position to the interface of metal/MoS2.
11
Liu, Yang, Qi Yuan, Pu Li e Guangyu Zhu. "Modal Analysis for a Rod-Fastened Rotor considering Contact Effect Based on Double Fractal Model". Shock and Vibration 2019 (2 maggio 2019): 1–10. http://dx.doi.org/10.1155/2019/4027353.
Abstract (sommario):
The rod-fastened rotor is the core component of the gas turbine. It comprises several discs and tie rods. The flexural stiffness of the contact interface is the key factor for rotordynamic analysis. The contact interfaces of the discs are usually manufactured by grinding. The measured contour curve of the contact interfaces of an experimental rod-fastened rotor is analyzed by the structural function method, which shows that the contact interfaces can be well described by the double fractal model with fractal dimensions D1 and D2 and the fractal roughness parameters G1 and G2. The Hertz model is used to analyze the contact of the single asperity on the contact interface. On this basis, the flexural stiffness of the contact interface considering the pretightening force and the bending moment is derived. Modal frequencies of the experimental rod-fastened rotor under different pretightening forces and the bending moment (caused by gravity) are obtained by three-dimensional finite element analysis and experimental modal tests. It is observed that the modal frequencies increase with the nominal pressure of the contact interface, and the experimental results are consistent with the calculated results.
12
Sundaramoorthy, Vinoth, Stephan Wirths e Lars Knoll. "Ohmic Contact Formation on 4H-SiC with a Low Thermal Budget by Means of Shallow Phosphorous Ion Implantation". Materials Science Forum 1062 (31 maggio 2022): 224–28. http://dx.doi.org/10.4028/p-c277as.
Abstract (sommario):
In this manuscript Ohmic contact formation at low annealing temperatures is demonstrated using shallow implantation technique. Remarkably, Ni Ohmic contacts with a specific contact resistivity of 1.9x10-5 Ωcm2 have been achieved at as-deposited condition. Smooth interfaces along with reduced Schottky barrier at the metal/SiC interface contributed to improved Ohmic performance at as-deposited and 450°C anneal conditions.
13
Biwa, Shiro, Yukiko Inoue e Nobutada Ohno. "OS02W0060 Influence of contact pressure on guided wave propagation at contact interface". Abstracts of ATEM : International Conference on Advanced Technology in Experimental Mechanics : Asian Conference on Experimental Mechanics 2003.2 (2003): _OS02W0060. http://dx.doi.org/10.1299/jsmeatem.2003.2._os02w0060.
14
Xiao-Kai, HU, ZHANG Shuang-Meng, ZHAO Fu, LIU Yong e LIU Wei-Shu. "Thermoelectric Device: Contact Interface and Interface Materials". Journal of Inorganic Materials 34, n. 3 (2019): 269. http://dx.doi.org/10.15541/jim20180248.
15
Petrov, E. P. "Method for Direct Parametric Analysis of Nonlinear Forced Response of Bladed Disks With Friction Contact Interfaces". Journal of Turbomachinery 126, n. 4 (1 ottobre 2004): 654–62. http://dx.doi.org/10.1115/1.1776588.
Abstract (sommario):
An effective method for direct parametric analysis of periodic nonlinear forced response of bladed disks with friction contact interfaces has been developed. The method allows, forced response levels to be calculated directly as a function of contact interface parameters such as the friction coefficient, contact surface stiffness (normal and tangential coefficients), clearances, interferences, and the normal stresses at the contact interfaces. The method is based on exact expressions for sensitivities of the multiharmonic interaction forces with respect to variation of all parameters of the friction contact interfaces. These novel expressions are derived in the paper for a friction contact model, accounting for the normal load variation and the possibility of separation-contact transitions. Numerical analysis of effects of the contact parameters on forced response levels has been performed using large-scale finite element models of a practical bladed turbine disk with underplatform dampers and with shroud contacts.
16
Benes, J., E. Vesely, H. Šebková, D. Gabriel e F. Mu. "Contact impact interface modelling". Mathematical and Computer Modelling 28, n. 4-8 (agosto 1998): 135–52. http://dx.doi.org/10.1016/s0895-7177(98)00114-9.
17
Chatterjee, Debanjali, Kaustubh Girish Naik, Bairav Sabarish Vishnugopi e Partha P. Mukherjee. "Mechanics-Coupled Interface Kinetics in Solid-State Batteries". ECS Meeting Abstracts MA2023-02, n. 4 (22 dicembre 2023): 632. http://dx.doi.org/10.1149/ma2023-024632mtgabs.
Abstract (sommario):
Solid-state batteries (SSBs) utilizing lithium metal anode are promising candidates for next-generation energy storage systems, offering high energy density and enhanced safety. However, imperfect electrochemical contact at the lithium-solid electrolyte (SE) interface results in transport limitations and high interfacial resistance, posing a critical bottleneck on rate performance. Solid-solid point contacts at the interface lead to stress hotspots and current-focusing, resulting in localized lithium deposition, filament growth and mechanical fracture of the SE. The application of external pressures potentially enables enhanced electrochemical contact at such solid-solid interfaces. Under these circumstances, non-uniform stresses arising due to the heterogeneous nature of interface morphology and surface defects play a critical role in the onset of interface instability. In this work, we present a mechanistic description of stress-coupled reaction kinetics governing the evolution of solid-solid interfaces in SSBs. We demonstrate how the energetic contribution of interfacial stresses alters the open circuit potential and exchange current density, which further affects the Butler-Vomer kinetics and morphological stability of the lithium-SE interface. Through our analysis, we illustrate the strong dependence of mechanical stress contributions to reaction current on the material characteristics of the electrode-SE pair and delineate interface stability regimes for different formulations of mechanics-coupled reaction kinetics interactions.
18
Cole, M. W., W. Y. Han, D. W. Eckart, L. M. Casas e K. A. Jones. "Microstructure and contact-resistance temperature dependence of Pt/Ti/Ge/Pd ohmic contacts to GaAs". Proceedings, annual meeting, Electron Microscopy Society of America 52 (1994): 866–67. http://dx.doi.org/10.1017/s0424820100172061.
Abstract (sommario):
The development of GaAs device technology has demonstrated the need for fabrication of low resistance thermally stable ohmic contacts. Gold based contacts have been the overwhelming choice for ohmic contacts in device applications. In particular, Au/Ge/Ni and Zn/Au alloyed contacts have been used for n and p-GaAs respectively. Numerous investigations have shown that Au-based contacts to GaAs have avery complex morphology after annealing. Specifically, structural interface inhomogeneities, such as protrusions and newly formed lateral interface phases lead to non-planar metalsemiconductor interfaces which in turn cause nonuniform current flow and consumption of the GaAs substrate. This type of interface morphology is not acceptable for device applications where a large electrical field or a shallow contact is required. In particular, devices such as heterojunction bipolar transistors (HBT's) cannot tolerate contacts with lateral and vertical interface inhomogeneities.This study employed crosssectional transmission electron microscopy (TEM), Auger electron spectroscopy (AES) and electrical measurements (transmission line mode), to systematically investigate the structural, chemical and electrical properties of the Pt/Ti/Ge/Pd contacts to both n and p+ GaAs as a function of annealing temperatures.
19
Wang, Hong, Guoqiang Gao, Deng Lei, Qingsong Wang, Song Xiao, Yunlong Xie, Zhilei Xu et al. "Influence of Interface Temperature on the Electric Contact Characteristics of a C-Cu Sliding System". Coatings 12, n. 11 (10 novembre 2022): 1713. http://dx.doi.org/10.3390/coatings12111713.
Abstract (sommario):
Electrical contact resistance (ECR) and discharge are the key parameters of electrical contact performance for carbon-copper (C-Cu) contacts in the pantograph-contact line system. The change in physical and chemical properties of the C-Cu interface caused by interface temperature is the main reason for the variation in ECR and discharge. In this paper, an electric contact test platform based on interface temperature control was established. The influence of interface temperature on ECR and the discharge characteristics under different current amplitudes were studied. There are opposite trends in the change in ECR and the discharge characteristics with interface temperature under different currents, which results from the competition between interface oxidation and a softening of the contact spots caused by high temperature. The trend of interface oxidation with temperature was analyzed via the quantitative analysis of the composition and content of the oxides at the C-Cu contact interface and is discussed here. The relationship between interface oxidation, ECR, and discharge characteristics was studied. Furthermore, a finite element simulation model was established for estimating the temperature distribution throughout the C-Cu contact spots. The competitive process of the softening and oxidation of the contact spots at different temperatures and currents was analyzed, and the variation mechanism of the ECR and discharge characteristics with interface temperature was studied.
20
Chen, Jiaqi, Zhaofu Zhang, Yuzheng Guo e John Robertson. "Metal contacts with Moire interfaces on WSe2 for ambipolar applications". Applied Physics Letters 121, n. 5 (1 agosto 2022): 051602. http://dx.doi.org/10.1063/5.0091504.
Abstract (sommario):
The rational design of metal contacts on transition metal dichalcogenides can significantly improve the performance of 2D devices. We have previously shown that a Moire interface between n-type monolayer MoS2 and metal contacts enhances the stability of physisorptive interface sites, thereby enabling weaker Fermi level pinning and allowing easier variation of the Schottky barrier height at these interfaces. We extend these calculations to p-type and ambipolar WSe2 contacts in this work. The analysis shows that the Moire interfaces again have a weaker Fermi level pinning, while most metals have chemisorptive sites with stronger pinning. We find that the most stable site of Pd is a Moire site with an unusually low p-type Schottky barrier height (p-SBH), while Au has a metastable low p-SBH. In and Al retain their low n-type SBHs, which together with Pd enable ambipolar contacts by the choice of contact metals, indicating that WSe2 can be used for high-performance ambipolar devices with the rational design of contact metals.
21
Asif, Mohammad, Saddam Husain, Sanaur Rehman, Taliv Hussain e Rafiuddin Mohd. "Experimental studies on selected thermal interface materials". Thermal Science, n. 00 (2023): 284. http://dx.doi.org/10.2298/tsci230911284a.
Abstract (sommario):
The current work is an experimental study, with the primary goal of investigating and exploring ways to improve thermal contact conductance through a detailed examination and analysis of metallic contacts and discovering opportunities for enhancement, increased efficiency, and thus heat dissipation using thermal interface materials. The steady-state experiments have been carried out on a simple and calibrated experimental set-up. A comprehensive investigation was conducted to assess the thermal performance of Copper-Aluminum contacts for the selected range of contact pressures and temperatures to suit the electronic industry's distinctive characteristics and technical requirements. As a thermal interface material, Graphene paste has been tested under various combinations of interface pressure and heating circumstances against the bare metallic contacts. Error analysis has also been performed for the current experimental investigation. It has been demonstrated that using Graphene paste as a thermal interface material thermal contact conductance is improve, significantly enhancing heat dissipation. The results of Thermal contact conductance for graphene paste have been compared with the same for silicon grease from literature. The present results thus demonstrate the application and suitability of the selected thermal interface material in the specified range of heating and contact pressure conditions in the context of particularly thermal management applications.
22
Holland, Anthony, Yue Pan, Mohammad Alnassar e Stanley Luong. "Circular test structures for determining the specific contact resistance of ohmic contacts". Facta universitatis - series: Electronics and Energetics 30, n. 3 (2017): 313–26. http://dx.doi.org/10.2298/fuee1703313h.
Abstract (sommario):
Though the transport of charge carriers across a metal-semiconductor ohmic interface is a complex process in the realm of electron wave mechanics, such an interface is practically characterised by its specific contact resistance. Error correction has been a major concern in regard to specific contact resistance test structures and investigations by finite element modeling demonstrate that test structures utilising circular contacts can be more reliable than those designed to have square shaped contacts as test contacts become necessarily smaller. Finite element modeling software NASTRAN can be used effectively for designing and modeling ohmic contact test structures and can be used to show that circular contacts are efficient in minimising error in determining specific contact resistance from such test structures. Full semiconductor modeling software is expensive and for ohmic contact investigations is not required when the approach used is to investigate test structures considering the ohmic interface as effectively resistive.
23
Dwyer-Joyce, R. S., B. W. Drinkwater e A. M. Quinn. "The Use of Ultrasound in the Investigation of Rough Surface Interfaces". Journal of Tribology 123, n. 1 (21 settembre 2000): 8–16. http://dx.doi.org/10.1115/1.1330740.
Abstract (sommario):
The measurement of ultrasonic reflection has been used to study the contact between rough surfaces. An incomplete interface will reflect some proportion of an incident wave; this proportion is known as the reflection coefficient. If the wavelength is large compared with the width of the gaps in the plane of the interface then the reflection mechanism can be modeled by considering the interface as a spring. The proportion of the incident wave reflected (reflection coefficient) is then a function of the stiffness of the interface and the frequency of the ultrasonic wave. The sensitivity of the ultrasonic technique has been quantified using a simple model, from which the stiffness of individual gaps and contacts are calculated and their effect on the ultrasonically measured stiffness predicted. The reflection of ultrasound at a static interface between a rough, nominally flat aluminum plate and a rough, nominally flat hardened steel punch has been investigated. Plastic flow on first loading was evident, while repeated loading was largely elastic. However, subsequent cycles indicate a small amount of further plasticity and contact irreversibility. The effect of surface roughness on the resultant contact has also been investigated. A simple plastic contact model is described which allows prediction of the average size of the asperity contacts and their number. This model shows that the average size of the contacts remains constant over most of the loading whereas the number of contacts increases almost linearly. The contact stiffness has also been modeled with two well known elastic rough surface contact models. These models predicted a lower interface stiffness than was observed in the experiments. However they provide a useful way of interpreting the ultrasonically measured interface stiffness data.
24
Li, Y. D., W. L. Zhen, S. R. Weng, H. J. Hu, R. Niu, Z. L. Yue, F. Xu, W. K. Zhu e C. J. Zhang. "Interface effects of Schottky devices built from MoS2 and high work function metals". Journal of Physics: Condensed Matter 34, n. 16 (21 febbraio 2022): 165001. http://dx.doi.org/10.1088/1361-648x/ac50db.
Abstract (sommario):
Abstract Schottky junctions, formed by high work function metals and semiconductors, are important devices in electronics and optoelectronics. The metal deposition in traditional Schottky interfaces usually damages the semiconductor surface and causes defect states, which reduces the Schottky barrier height and device performance. This can be avoided in the atomically smooth interface formed by two-dimensional (2D) metals and semiconductors. For better interface tailoring engineering, it is particularly important to understand various interface effects in such 2D Schottky devices under critical or boundary conditions. Here we report the fabrication and testing of three types of MoS2 devices, i.e., using PtTe2, Cr and Au as contact materials. While the Cr/MoS2 contact is an ohmic contact, the other two are Schottky contacts. The van-der-Waals interface of PtTe2–MoS2 results in a well-defined OFF state and a significant rectification ratio of 104. This parameter, together with an ideality factor 2.1, outperforms the device based on evaporated Au. Moreover, a device in the intermediate condition is also presented. An abrupt increase in the reverse current is observed and understood based on the enhanced tunneling current. Our work manifests the essential role of doping concentration and provides another example for 2D Schottky interface design.
25
Wang, Zong Ren, Wei Fang Zhang e Ming Yuan Yang. "Experimental Study of Thermal Contact Conductance with Compensation Heater". Advanced Materials Research 337 (settembre 2011): 774–78. http://dx.doi.org/10.4028/www.scientific.net/amr.337.774.
Abstract (sommario):
This article describes an experimental setup to measure the TCC between interfaces of two contact solid materials. A new kind of design scheme of the compensation heater is put forward. An experimental investigation of thermal contact conductance is conducted with pressed pairs of GH4169 and K417 contacts in the range 130~280°C. The results show that TCC over this condition increases with temperature, but it is not monotonic. Moreover, the thermal contact conductance measured by experiment with compensation heater at the interface is higher than that without compensation heater.
26
Dwyer-Joyce, R. S. "The Application of Ultrasonic NDT Techniques in Tribology". Proceedings of the Institution of Mechanical Engineers, Part J: Journal of Engineering Tribology 219, n. 5 (1 maggio 2005): 347–66. http://dx.doi.org/10.1243/135065005x9763.
Abstract (sommario):
The use of ultrasonic reflection is emerging as a technique for studying tribological contacts. Ultrasonic waves can be transmitted non-destructively through machine components and their behaviour at an interface describes the characteristics of that contact. This paper is a review of the current state of understanding of the mechanisms of ultrasonic reflection at interfaces, and how this has been used to investigate the processes of dry rough surface contact and lubricated contact. The review extends to cover how ultrasound has been used to study the tribological function of certain engineering machine elements.
27
Turak, Ayse. "On the Role of LiF in Organic Optoelectronics". Electronic Materials 2, n. 2 (3 giugno 2021): 198–221. http://dx.doi.org/10.3390/electronicmat2020016.
Abstract (sommario):
Organic optoelectronic device behaviour is heavily dependent on interfacial effects due to the device architecture and thickness. Interfaces between the inorganic electrodes and the active organic layers play a defining role in the all of the electronic and stability processes that occur in organic light emitting diodes (OLEDs) and organic solar cells (OPVs). Amongst the many interlayers introduced at these interfaces to improve charge carrier movement and stability, LiF has proven to be the most successful and it is almost ubiquitous in all organic semiconductor devices. Implemented at both top and bottom contact interfaces, doped into the charge transporting layers, and used as encapsulants, LiF has played major roles in device performance and lifetime. This review highlights the use of LiF at both top and bottom contacts in organic optoelectronics, discusses the various mechanisms proposed for the utility of LiF at each interface, and explores its impact on device lifetimes. From examples relating to charge carrier flow, interfacial electronic level modification, and interfacial stability, a comprehensive picture of the role of LiF in organic devices can be formed. This review begins with a brief overview of the role of the interface in OLEDs and OPVs, and the general properties of LiF. Then, it discusses the implementation of LiF at the top contact electrode interface, followed by the bottom substrate contact electrode, examining both performance and degradation effects in both cases.
28
Mucheroni, Marcos Luiz. "Interface Tesseracto UI and the Hologram". International Journal of Creative Interfaces and Computer Graphics 10, n. 1 (gennaio 2019): 56–64. http://dx.doi.org/10.4018/ijcicg.2019010105.
Abstract (sommario):
Building Tesseracto UI-type holographic interfaces is one step significant interaction in interfaces of computational devices with interaction in 3D. This follows the idea that the best user interface is no interface device, in the space of the hypercube and the fourth dimension. The contact device detects haptic interfaces, at the same time the touch in a free space as contact is made from fine ultrasonic sensors corresponding to the hologram images. The prototype was developed using the vertical and horizontal ultrasonic devices and a display hologram. The device is still in the testing phase, but the connection with the computer screens is already possible, in a prototype environment.
29
Armand, J., L. Pesaresi, L. Salles, C. Wong e C. W. Schwingshackl. "A modelling approach for the nonlinear dynamics of assembled structures undergoing fretting wear". Proceedings of the Royal Society A: Mathematical, Physical and Engineering Sciences 475, n. 2223 (marzo 2019): 20180731. http://dx.doi.org/10.1098/rspa.2018.0731.
Abstract (sommario):
Assembled structures tend to exhibit nonlinear dynamic behaviour at high excitation levels due to the presence of contact interfaces. The possibility of building predictive models relies on the ability of the modelling strategy to capture the complex nonlinear phenomena occurring at the interface. One of these phenomena, normally neglected, is the fretting wear occurring at the frictional interface. In this paper, a computationally efficient modelling approach which enables considerations of the effect of fretting wear on the nonlinear dynamics is presented. A multi-scale strategy is proposed, in which two different time scales and space scales are used for the contact analysis and dynamic analysis. Thanks to the de-coupling of the contact and dynamic analysis, a more realistic representation of the contact interface, which includes surface roughness, is possible. The proposed approach is applied to a single bolted joint resonator with a simulated rough contact interface. A tendency towards an increase of real contact area and contact stiffness at the interface is clearly observed. The dynamic response of the system is shown to evolve over time, with a slight decrease of damping and an increase of resonance frequency, highlighting the impact of fretting wear on the system dynamics.
30
Shi, Xi, e Andreas A. Polycarpou. "Measurement and Modeling of Normal Contact Stiffness and Contact Damping at the Meso Scale". Journal of Vibration and Acoustics 127, n. 1 (1 febbraio 2005): 52–60. http://dx.doi.org/10.1115/1.1857920.
Abstract (sommario):
Modeling of contact interfaces that inherently include roughness such as joints, clamping devices, and robotic contacts, is very important in many engineering applications. Accurate modeling of such devices requires knowledge of contact parameters such as contact stiffness and contact damping, which are not readily available. In this paper, an experimental method based on contact resonance is developed to extract the contact parameters of realistic rough surfaces under lightly loaded conditions. Both Hertzian spherical contacts and flat rough surfaces in contact under normal loads of up to 1000 mN were studied. Due to roughness, measured contact stiffness values are significantly lower than theoretical values predicted from smooth surfaces in contact. Also, the measured values favorably compare with theoretical values based on both Hertzian and rough contact surfaces. Contact damping ratio values were found to decrease with increasing contact load for both Hertzian and flat surfaces. Furthermore, Hertzian contacts have larger damping compared to rough flat surfaces, which also agrees with the literature. The presence of minute amount of lubricant and wear debris at the interface was also investigated. It was found that both lubricant and wear debris decrease the contact stiffness significantly though only the lubricant significantly increases the damping.
31
Huang, Wei, Shao Hui Chang, Xue Chao Liu, Zheng Zheng Li, Tian Yu Zhou, Yan Qing Zheng, Jian Hua Yang e Er Wei Shi. "Effect of Interface Native Oxide Layer on the Properties of Annealed Ni/SiC Contacts". Materials Science Forum 740-742 (gennaio 2013): 485–89. http://dx.doi.org/10.4028/www.scientific.net/msf.740-742.485.
Abstract (sommario):
The near-SiC-interfaces of annealed Ni/SiC contacts were observed directly by high-resolution transmission electron microscopy (HRTEM). 1 nm native oxide layer was observed in the as-deposited contact interface. The native oxide layer cannot be removed at 650°C through rapid thermal annealing (RTA) and it was completely removed at 1000°C RTA. The residue of native oxide layer resulted in the Schottky characters. High temperature annealing (>950°C) not only removes the oxide layer in the near-SiC-interface, but also forms a well arranged flat Ni2Si/SiC interface, which contribute to the formation of ohmic behavior.
32
TAMAI, T. "Friction and Contact Resistance through True Contact Interface". IEICE Transactions on Electronics E89-C, n. 8 (1 agosto 2006): 1122–28. http://dx.doi.org/10.1093/ietele/e89-c.8.1122.
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Yegnasubramanian, S., V. C. Kannan, R. Dutto e P. J. Sakach. "Microstructure of sputter deposited Ni-Sb ohmic contacts on GaAs". Proceedings, annual meeting, Electron Microscopy Society of America 47 (6 agosto 1989): 450–51. http://dx.doi.org/10.1017/s0424820100154226.
Abstract (sommario):
Recent developments in the fabrication of high performance GaAs devices impose crucial requirements of low resistance ohmic contacts with excellent contact properties such as, thermal stability, contact resistivity, contact depth, Schottky barrier height etc. The nature of the interface plays an important role in the stability of the contacts due to problems associated with interdiffusion and compound formation at the interface during device fabrication. Contacts of pure metal thin films on GaAs are not desirable due to the presence of the native oxide and surface defects at the interface. Nickel has been used as a contact metal on GaAs and has been found to be reactive at low temperatures. Formation Of Ni2 GaAs at 200 - 350C is reported and is found to grow epitaxially on (001) and on (111) GaAs, but is shown to be unstable at 450C. This paper reports the investigations carried out to understand the microstructure, nature of the interface and composition of sputter deposited and annealed (at different temperatures) Ni-Sb ohmic contacts on GaAs by TEM. Attempts were made to correlate the electrical properties of the films such as the sheet resistance and contact resistance, with the microstructure. The observations are corroborated by Scanning Auger Microprobe (SAM) investigations.
34
Li, Zhan Hui, Yun Xin Wu e Zhi Li Long. "Higher Order Harmonic Wave and its Effect on Thermosonic Bond System". Advanced Materials Research 97-101 (marzo 2010): 2644–49. http://dx.doi.org/10.4028/www.scientific.net/amr.97-101.2644.
Abstract (sommario):
Thermosonic bond is widely used in package of semiconductor chip due to its advantages, such as simple process, high efficiency, and no pollution. Ultrasonic play important role inspired interconnection interface atomic energy and soften metallic materials in thermosonic bond. The vibration of bond tool is nonlinear and bond strength is unstable with contact interface condition changing due to discontinuity characteristic parameters of contact interfaces. In order to improve bond strength of chip, model of ultrasonic propagation across a rough contact interface was established. Aluminium wire bond was performed on a thermosonic bond test platform. The harmonic waves of bond tool and the bond strength were measured. The experiment results show that the best bond strength and the less higher order harmonic is achieve when the contact interface pressure is in moderate range.
35
Fang, Xingxing, Dahan Li, Yucheng Xin, Songquan Wang, Yongbo Guo, Ningning Hu e Dekun Zhang. "Dynamic contact stress and frictional heat analysis of femoral head-on-acetabular cup interface based on calculation and simulation methods". Industrial Lubrication and Tribology 73, n. 10 (17 novembre 2021): 1302–9. http://dx.doi.org/10.1108/ilt-07-2021-0261.
Abstract (sommario):
Purpose The purpose of this paper is to systematically study the dynamic contact stress, frictional heat and temperature field of femoral head-on-acetabular cup contact pairs in a gait cycle. Design/methodology/approach In this paper, four common femoral head-on-acetabular cup contact pairs are used as the research objects, mathematical calculations and finite element simulations are adopted. The contact model of hip joint head and acetabular cup was established by finite element simulation to analyze the stress and temperature distribution of the contact interface. Findings The results show that the contact stress of the head-on-cup interface is inversely proportional to the contact area; high contact stress directly leads to greater frictional heat. However, hip joints with metal-on-polyethylene or ceramic-on-polyethylene paired interfaces have lower frictional heat and show a significant temperature rise in one gait cycle, which may be related to the material properties of the acetabular cup. Originality/value Previous studies about calculating the interface frictional heat always ignore the dynamic change process in the contact load and the contact area. This study considered the dynamic changes of the contact stress and area of the femoral head-on-acetabular cup interface, and four common contact pairs were systematically analyzed.
36
Franklin, Aaron D. "(Invited) Influence of Materials and Processing on Edge Contacts to 2D Semiconductors". ECS Meeting Abstracts MA2022-01, n. 12 (7 luglio 2022): 871. http://dx.doi.org/10.1149/ma2022-0112871mtgabs.
Abstract (sommario):
The most common approach for establishing electrical contacts to 2D semiconductors, such as MoS2, is by fabricating metal contacts on top of the inert crystal surface. From an electron transport perspective, these top-contact interfaces can be awkward, with a van der Waals gap or some difficult-to-control form of interfacial bonding. Pure edge contacts (where the interface between the metal and 2D semiconductor occurs completely along the open bonds of the 2D crystal edge) provide a more natural bonding structure and potentially better carrier transport behavior; however, edge contacts have proven more difficult to realize. In this talk, recent success with establishing clean, pure edge contacts between metals and 2D semiconductors will be discussed, including an approach involving an in situ ion beam within a thin-film deposition system. Evaluation of these edge contacts compared to other approaches will be provided, along with demonstration of how edge-contact scaling affects the performance of 2D transistors compared to top-contact scaling. While there remains much to be learned about these interesting metal-2D edge interfaces, results thus far show significant promise for yielding a more scalable and potentially reproducible contact for 2D-based devices.
37
Jurkowska, Renata Z., Arumugam Rajavelu, Nils Anspach, Claus Urbanke, Gytis Jankevicius, Sergey Ragozin, Wolfgang Nellen e Albert Jeltsch. "Oligomerization and Binding of the Dnmt3a DNA Methyltransferase to Parallel DNA Molecules". Journal of Biological Chemistry 286, n. 27 (12 maggio 2011): 24200–24207. http://dx.doi.org/10.1074/jbc.m111.254987.
Abstract (sommario):
Structural studies showed that Dnmt3a has two interfaces for protein-protein interaction in the heterotetrameric Dnmt3a/3L C-terminal domain complex: the RD interface (mediating the Dnmt3a-3a contact) and the FF interface (mediating the Dnmt3a-3L contact). Here, we demonstrate that Dnmt3a-C forms dimers via the FF interface as well, which further oligomerize via their RD interfaces. Each RD interface of the Dnmt3a-C oligomer creates an independent DNA binding site, which allows for binding of separate DNA molecules oriented in parallel. Because Dnmt3L does not have an RD interface, it prevents Dnmt3a oligomerization and binding of more than one DNA molecule. Both interfaces of Dnmt3a are necessary for the heterochromatic localization of the enzyme in cells. Overexpression of Dnmt3L in cells leads to the release of Dnmt3a from heterochromatic regions, which may increase its activity for methylation of euchromatic targets like the differentially methylated regions involved in imprinting.
38
Patel, Ruchita, Zulfiqar Ahmad Khan, Vasilios Bakolas e Adil Saeed. "Numerical Simulation of the Lubricant-Solid Interface Using the Multigrid Method". Lubricants 11, n. 6 (23 maggio 2023): 233. http://dx.doi.org/10.3390/lubricants11060233.
Abstract (sommario):
Solid asperity interactions are common and inevitable under severe loading conditions for any lubricated contact. Heavy-duty machine components (gears, bearings, etc.) generally operate under Mixed Lubrication (ML), where uneven surface features contact each other when the generated fluid pressure is not enough to support the external load. The Reynolds equation is commonly used to simulate smooth lubricated contacts numerically. In rough lubricated interfaces where opposite surface asperities make contact, the Reynolds equation alone cannot accurately predict pressure using the traditional numerical simulation method. In this paper, lubrication–contact interface conditions (LCICs) have been implemented and extended to solve the multiple asperity contact problem using the full-multigrid approach. The developed novel algorithm has significantly accelerated the solution process and improved the accuracy and efficiency of pressure calculation for fluid–solid sub-interactions that can occur in ML regions. The results of the finite difference method (FDM) results have been compared with those of computational fluid dynamics (CFD) simulation to validate the newly developed model. Hence, the proposed optimized solution method will provide valuable insight to researchers and industry engineers interested in simulating the ML problem where the effect of the fluid–solid interface can be captured effectively to improve reliability in the calculation of the life expectancy of the lubricated parts.
39
Sundaramoorthy, Vinoth Kumar, Lukas Kranz e Giovanni Alfieri. "Microstructural Analysis of Ti/Ni Bilayer Ohmic Contacts on 4H-SiC Layers". Materials Science Forum 963 (luglio 2019): 494–97. http://dx.doi.org/10.4028/www.scientific.net/msf.963.494.
Abstract (sommario):
The micro-structural analysis of Ti/Ni bilayer as Ohmic contacts to n-type 4H-SiC is reported. There was no carbon segregation at the interface between the NiSi layer and the 4H-SiC layer for Ti/Ni contacts, unlike pure Ni contacts. The diffraction pattern image shows the presence of the cubic NiSi film which grows on the SiC surface. The film interface with the SiC was uniform and more planar. An optimized contact in terms of contact morphology was achieved using a bilayer contact Ti/Ni (20/100nm) annealed at 1100 °C for 5 minutes in vacuum.
40
McDonnell, Stephen, Christopher Smyth, Christopher L. Hinkle e Robert M. Wallace. "MoS2–Titanium Contact Interface Reactions". ACS Applied Materials & Interfaces 8, n. 12 (21 marzo 2016): 8289–94. http://dx.doi.org/10.1021/acsami.6b00275.
41
Shvarts, A. G., e V. A. Yastrebov. "Trapped fluid in contact interface". Journal of the Mechanics and Physics of Solids 119 (ottobre 2018): 140–62. http://dx.doi.org/10.1016/j.jmps.2018.06.016.
42
Xie, Hong, Zhiping Zeng, Miao Su, Jun Luo e Gonglian Dai. "On Mechanical and Motion Behavior of the Normal Impact Interface between a Rigid Sphere and Elastic Half-Space". Applied Sciences 12, n. 21 (1 novembre 2022): 11094. http://dx.doi.org/10.3390/app122111094.
Abstract (sommario):
This paper presents exact solutions for the mechanical behavior of the interface during the normal collision between a rigid sphere and an elastic half-space based on kinematics and particle dynamics theory. The interfacial contact stress is significantly different from the static solution obtained from the Hertz contact theory. Firstly, according to the kinematics theory, the elastic half-space interface deformation of the sphere and the half-space interface in the collision process is divided into the deformation of the contact area and the non-contact area. The curve of the non-contract area is strictly antisymmetric to the deformation curve of the contact area, and the lateral deformation for each particle at the interface can be neglected when the collision depth is relatively small. Then, the vertical deformation equation of the contact area of the half-space interface, the dynamic equation of the rigid sphere, and the dynamic equation of the interface particle in the contact region are established. The proportional relationship between the stress or strain of any particle in the contact area, the stress or strain of the collision center point, and the method for determining the maximum collision depth are obtained. The equal deformation depth in the contact and non-contact regions, and the proportional relationship between the stress or strain in the contact area and the center point of the collision at any moment are consistent with the Hertz contact theory, which verifies the reliability of the current study. Taking the sphere of no initial velocity collides with the half-space under pure gravity as an example, when the elastic half-space Poisson’s ratio is taken as 0.2–0.4, the ratio of the maximum contact stress determined by the Hertz theory and the current solution when the sphere reaches the maximum collision depth is 0.58–0.54. Based on this study, the contact stress and its distribution in the interfacial contact region can be obtained when the motion state of the sphere and the interface are determined.
43
Mallem, Siva Pratap Reddy, Woo-Hyun Ahn, Jung-Hee Lee e Ki-Sik Im. "Influence of Thermal Annealing on the PdAl/Au Metal Stack Ohmic Contacts to p-AlGaN". Crystals 10, n. 12 (28 novembre 2020): 1091. http://dx.doi.org/10.3390/cryst10121091.
Abstract (sommario):
In this study, a PdAl (20 nm)/Au (30 nm) metal stack scheme is used for forming low-ohmic-resistance contact on Mg-doped (1.5 × 1017 cm−3) p-type AlGaN at various annealing temperatures. Using a circular-transmission line model, the specific contact resistance (ρc) of PdAl/Au/p-AlGaN ohmic contact is determined via the current–voltage (I–V) characteristics. As-deposited contacts demonstrate non-linear behavior. However, the contact exhibits linear I–V characteristics with excellent ohmic contact of ρc = 1.74 × 10−4Ωcm2, when annealed at 600 °C for 1 min in a N2 atmosphere. The Ga and Al vacancies created at the PdAl/Au and p-AlGaN interfaces, which act as acceptors to increase the hole concentration at the interface. The out-diffusion of Ga as well as in-diffusion of Pd and Au to form interfacial chemical reactions at the interface is observed by X-ray photoelectron spectroscopy (XPS) measurements. The phases of the Ga–Pd and Ga–Au phases are detected by X-ray diffraction (XRD) analysis. Morphological results show that the surface of the contact is reasonably smooth with the root-mean-square roughness of 2.89 nm despite annealing at 600 °C. Based on the above experimental considerations, PdAl/Au/p-AlGaN contact annealed at 600 °C is a suitable p-ohmic contact for the development of high-performance electronic devices.
44
Montero, Jorge A., e Ghadir Haikal. "Modeling Beam–Solid Finite Element Interfaces: A Stabilized Formulation for Contact and Coupled Systems". International Journal of Applied Mechanics 10, n. 09 (novembre 2018): 1850094. http://dx.doi.org/10.1142/s1758825118500941.
Abstract (sommario):
A number of engineering applications involve contact with bodies modeled using specialized theories of solid mechanics like beams or shells. While computational models for contact in 2D and 3D solid mechanics have been extensively developed in the literature, problems involving contact with beams or shells have received less attention. When modeling contact between a solid body represented with beam or shell theory and a domain discretized with solid finite elements, the contact model faces the typical challenges of enforcing geometric compatibility and the transfer of a complete pressure field along the contact interface, with the added complications stemming from the different underlying mathematical formulations and finite element discretizations in the connecting domains. Resultant-based beam and shell theories do not provide direct estimates of surface tractions, therefore rendering the issue of pressure transfer on beam–solid and shell–solid interfaces more problematic. In the absence of specialized contact formulations for solid–beam and solid–shell interfaces, contact models have relied almost exclusively on the Node-To-Surface (NTS) geometric compatibility approach. This formulation suffers from well-known drawbacks, including instability, surface locking and incomplete pressure fields on the interface. The NTS approach, however, remains the method most readily applicable to contact with beam or shell elements among the vast variety of available methods for computational contact modeling using finite elements. The goal of this paper is to bridge the gap in the literature on coupling domains with beam and solid finite element discretizations. We propose an interface formulation for beam–solid interfaces that ensures the transfer of a complete pressure field while enforcing geometric compatibility using standard NTS constraints. The formulation uses a stabilization approach, based on a special form of the Discontinuous Galerkin method, to enforce weak continuity between the stress fields on the solid side of the interface, and the moment and shear resultants in the contacting beam. We show that the proposed formulation is a robust approach for satisfying compatibility constraints while ensuring the transfer of a complete pressure field on beam–solid finite element interfaces that can be used with bilinear and quadratic interpolations in the solid, and Euler or Timoshenko formulations for the beam.
45
Chern, Shin-Yuh, Yang-Yuan Chen, Wei-Lun Liu e Jeng-Haur Horng. "Contact Characteristics at Interface in Three-Body Contact Conditions with Rough Surfaces and Foreign Particles". Lubricants 10, n. 7 (19 luglio 2022): 164. http://dx.doi.org/10.3390/lubricants10070164.
Abstract (sommario):
Nanoparticles as lubricant additives under a certain average diameter and concentration may reduce wear, friction and scuffing damage. However, atmospheric dust particles affect not only human health but also the efficiency of components, and even cause component failures. Therefore, the contact characteristics at interfaces with foreign particles require careful investigation. In this work, a 3-body microcontact mechanics concept is used to analyze the effects of wear debris and foreign particles on real contact area, contact mode, asperity deformation type and separation at interface. The results show that the relationship profile between dimensionless real contact area (At*) and dimensionless normal contact load (Ft*) is wedge-shaped in a 3-body contact interface. Using surface-to-surface 2-body contact area as upper bound and surface-to-particle 3-body contact as lower bound, the 3-body hybrid contact situation is in between upper and lower bounds. As the dimensionless normal contact load increases, At* increases gradually as well. The order of contact mode is p-s contact, hybrid contact and then s-s contact. If the 3-body contact interface is in hybrid contact mode, the decrease in the hardness and average third body diameter will cause the At* to increase significantly at the same Ft*. Conversely, the separation and real contact area ratio of plastic deformation decrease gradually. The turning point of contact area (TPCA) occurs when the contact mode is within hybrid contact mode and the ratio of average third body diameter to the composite equivalent surface RMS roughness is about 50–70% for foreign particles and wear debris. When the Ft* is slightly larger than Ftpca*, the third body and surface share the total interface load approximately equally which will help reduce the real contact pressure and plastic contact area to improve surface performance.
46
Hertel, Stefan, Andreas Finkler, Michael Krieger e Heiko B. Weber. "Graphene Ohmic Contacts to n-Type Silicon Carbide (0001)". Materials Science Forum 821-823 (giugno 2015): 933–36. http://dx.doi.org/10.4028/www.scientific.net/msf.821-823.933.
Abstract (sommario):
Epitaxial graphene on silicon carbide (SiC) can easily be grown by thermal decomposition. A well-defined epitaxial interface between graphene and substrate is formed, especially when the silicon face of hexagonal polytypes is employed. It is found that as-grown monolayer graphene with interfacial buffer layer provides perfectly ohmic contacts to n-type SiC – even to low-doped epitaxial layers without contact implantation. Contact resistances to highly doped samples are competitive with conventional annealed nickel (Ni) contacts; a direct comparison of Ni and graphene contacts on 4H-SiC resulted in an one order of magnitude reduction of the contact resistance in the case of graphene contacts. On highly doped 6H-SiC, a specific contact resistance as low asρC= 5.9·10-6Ωcm2was found. This further improvement compared to 4H-SiC is assigned to better matching of work functions at the Schottky-like interface.
47
Savtchouk, Alexander, Marshall Wilson e Jacek Lagowski. "Non-Contact Photo-Assisted Charge-Based Characterization of Dielectric Interfaces in SiC: Evidence of Slow States". Materials Science Forum 897 (maggio 2017): 139–42. http://dx.doi.org/10.4028/www.scientific.net/msf.897.139.
Abstract (sommario):
In this work we present novel photo-assisted characterization of dielectric interfaces in SiC using a modified non-contact corona-Kelvin technique. This technique eliminates the cost and time associated with fabrication of electrical test structures. UV illumination in deep depletion is used to generate minority carriers that empty deep interface states too slow to be emptied by thermal emission. After illumination, the interface state charging current is measured with time resolved voltage decay. This enables novel non-contact corona-Kelvin characterization of hole emission and electron capture processes involving slow interface states. This novel application complements standard corona-Kelvin measurement of dielectric, interface and semiconductor parameters.
48
Deng, Xu-Liang, Xian-Fei Ji, De-Jun Wang e Ling-Qin Huang. "First principle study on modulating of Schottky barrier at metal/4H-SiC interface by graphene intercalation". Acta Physica Sinica 71, n. 5 (2022): 058102. http://dx.doi.org/10.7498/aps.71.20211796.
Abstract (sommario):
In the production of SiC electronic devices, one of the main challenges is the fabrication of good Ohmic contacts due to the difficulty in finding the metals with low Schottky barriers of wide band gap SiC. Therefore, reducing the Schottky barrier height (SBH) at the metal/SiC interface is of great importance. In this paper, the effects of graphene intercalation on the SBH in different metals (Ag, Ti, Cu, Pd, Ni, Pt)/4H-SiC interfaces are studied by combining the average electrostatic potential and local density of states calculation methods based on first-principles plane wave pseudopotential density functional theory. The calculation results show that single-layer graphene intercalation can reduce the SBH of metal/4H-SiC contact. When the two layers of graphene are inserted, the SBH are further reduced. Especially, the contact between Ni and Ti exhibits negative SBH values, inferring that good Ohmic contacts are formed. When layers of graphene continue to increase, the SBH no longer changes obviously. By analyzing the differential charge density and the local density of states of the interface, the mechanism of SBH reduction may be that the dangling bonds on the SiC surface are saturated by the graphene C atoms and the influence of the metal-induced energy gap state at the interface is reduced, thereby reducing the interface state density. In addition, graphene and the corresponding new phases at the interface have low work functions. Moreover, an interfacial electric dipole layer may be formed at the SiC/graphene interface which also contributes to barrier reduction.
49
Wang, Y. S., e G. L. Yu. "Transmission of SH Waves Through an Elastic Layer Between Two Solids With Frictional Contact Interfaces". Journal of Applied Mechanics 66, n. 3 (1 settembre 1999): 729–37. http://dx.doi.org/10.1115/1.2791686.
Abstract (sommario):
The propagation of SH waves in a three-layered medium containing an interlayer between two semi-infinite solids with frictional contact interfaces is studied. The incident wave, which propagates through the layer from one half-space to another with subcritical angle, is assumed to be strong enough so that friction may be broken, and the local slip may take place at the interfaces. The mixed boundary conditions involving inequalities and unknown intervals lead to a set of recurrence relations. Special examples are given for the case of identical materials to illustrate the mathematical procedure to obtain final results. The interface tractions and relative slip velocities are presented. The interaction between the two interfaces is discussed. It is shown that the slip of the interface near the incident wave may restrain the slip of the interface far from the incident wave, while that the latter may facilitate the former. We also find the instability of the system for similar values of the two interface friction coefficients. Finally, the energy transmitted through the interlayer and dissipated by the friction of the two interfaces are examined.
50
Li, Hongfei, Zhaoming Qu, Yazhou Chen, Linsen Zhou e Yan Wang. "Electronic Structure and External Electric Field Modulation of Polyethylene/Graphene Interface". Polymers 14, n. 14 (21 luglio 2022): 2949. http://dx.doi.org/10.3390/polym14142949.
Abstract (sommario):
Polymer nanocomposites can serve as promising electrostatic shielding materials; however, the underlying physical mechanisms governing the carrier transport properties between nanofillers and polymers remain unclear. Herein, the structural and electronic properties of two polyethylene/graphene (PE/G) interfaces, i.e., type-H and type-A, have been systematically investigated under different electric fields using first principle calculations. The results testify that the bandgaps of 128.6 and 67.8 meV are opened at the Dirac point for type-H and type-A PE/G interfaces, respectively, accompanied by an electron-rich area around the graphene layer, and a hole-rich area around the PE layer. Moreover, the Fermi level shifts towards the valence band maximum (VBM) of the PE layer, forming a p-type Schottky contact at the interface. Upon application of an electric field perpendicular to the PE/G interface, the Schottky contact can be transformed into an Ohmic contact via the tuning of the Schottky barrier height (SBH) of the PE/G interface. Compared with the A-type PE/G interfaces, the H-type requires a lower electric field to induce an Ohmic contact. All these results can provide deeper insights into the conduction mechanism of graphene-based polymer composites as field-shielding materials.