Abstract
Conductive-atomic force microscopy (C-AFM) and molecular dynamics (MD) simulations are used to investigate time-dependent electrical contact resistance (ECR) at the nanoscale. ECR is shown to decrease over time as measured using C-AFM and estimated using two approaches from MD simulations, although the experiments and simulations explore different time scales. The simulations show that time dependence of ECR is attributable to an increase in real contact area due to atoms diffusing into the contact. This diffusion-based aging is found to be a thermally activated process that depends on the local contact pressure. The results demonstrate that contact aging, previously identified as an important mechanism for friction, can significantly affect electrical conduction at the nanoscale.Graphical
Highlights
Electrical contact resistance (ECR) plays a key role in the function and performance of a variety of electromechanical components used in a wide range of applications, including switches/relays [1,2,3,4,5,6,7] and electronic connectors [8, 9]
This difference is attributable to the fact that the calculation methods are based on intrinsically different approaches: EChemDID couples the system to a voltage bias and obtains the current flowing through the system by describing the equilibration of electrochemical potential throughout the system, while the other approach estimates the conduction between the tip and the substrate by identifying atomic channels through the contact and evaluates the conduction at each channel using a density functional theory (DFT)-derived current-separation relationship
ECR at the nanoscale was shown to decrease with time using Conductive-atomic force microscopy (C-AFM) experiments and molecular dynamics (MD) simulations with two approximations for conduction
Summary
Electrical contact resistance (ECR) plays a key role in the function and performance of a variety of electromechanical components used in a wide range of applications, including switches/relays [1,2,3,4,5,6,7] and electronic connectors [8, 9]. Beyond the conventional engineering scale, ECR is important for electromechanical components at the micrometer scale, due to their large surface-to-volume ratio. At such small length scales, it has been found that ECR is affected by multiple parameters and conditions, including contact pressure, temperature, surface properties, and the environment [1, 3]. Applications that rely on ECR for proper function must ensure that these parameters are tightly controlled during operation Another factor that affects the reliability of electrical connections, but cannot be controlled, is time. Time-dependent ECR at the microscale has been extensively studied using radio frequency microelectromechanical system (RFMEMS) switches [2, 5,6,7]. These devices have very short contact times (i.e., very high switching frequency), so the
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