GOALI/Collaborative Research: Manufacturing of Carbon Nanotube Contacts for High-Performance Microelectromechanical Switches

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In applications ranging from switches to electronic packaging assemblies, there is a critical need for electrical contacts with very low resistance. Typical metal contacts have rough surfaces that limit the size of the contact area and thus cause high electrical contact resistance. While larger forces can be applied to increase the contact area, this often results in failure of the contact and thus the device. Repeated cycling of the contact, such as in microelectromechanical switches, accelerates the failure. The poor performance of existing metal-to-metal contacts limits the design and performance of a number of electronic devices. This Grant Opportunity for Academic Liaison with Industry (GOALI) Program project will investigate the manufacturing, performance and integration of carbon nanotube (CNT) contacts that aim to overcome the limitations of current metal-to-metal contacts. This collaborative project will involve expertise in controlled carbon nanotube growth, microdevice fabrication, and small-scale mechanical characterization. It will also involve collaboration with industry to ensure the solutions developed are scalable and commercially relevant. This work will have broad technical impact because improved electrical contacts will enable high reliability microscale switches that can improve the performance and reduce the power consumption of a range of electronic devices, such as mobile phones, and low-power wearable devices. The project will involve training of students in nanomanufacturing and materials engineering as well as the education of K-12 students and the public through demonstrations that illustrate basic principles of nanomaterials and nanomanufacturing at museums and outreach events. This project will investigate the manufacturing, integration, and characterization of a new class of electrical contact materials based on vertically aligned CNTs. These nanostructured materials will have high electrical conductivity, high elastic recoverability, and low elastic modulus and thus allow surface roughness to be accommodated elastically in order to achieve high real contact area and very low electrical resistance. Vertically aligned CNTs ('forests') will be grown on micro-patterned conductive layers by thermal chemical vapor deposition (CVD), and then optionally coated by secondary materials to enhance their mechanical and electrical properties. The properties of these contact materials will be characterized using nanoindentation and electrical measurements. The techniques used to manufacture the contact materials allow the properties of the contacts to be tuned over several orders of magnitude so the materials can be engineered for specific applications by controlling process parameters. The project will generate an understanding of how to robustly and precisely control the properties of CNT-based contacts by our integrated nanomanufacturing approach, leading to strategies for manufacturing contact materials with high uniformity and yield. This project is primarily motivated by the need for new materials for switches based on microelectromechanical systems (MEMS) technology, and novel strategies for the integration of CNT contact materials into silicon MEMS, based on low temperature growth processes, will be investigated.