Collaborative Research: Photoassisted CVD for Low Temperature Area Selective Deposition

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Non-technical AbstractWith support from the Ceramics and the Solid State and Materials Chemistry programs in the Division of Materials Research, Professor Amy Walker of the University of Texas at Dallas and Professor Lisa McElwee-White of the University of Florida are developing light driven chemical synthesis methods to prepare patterns of metal on surfaces that are too heat sensitive to withstand conventional methods for deposition of metals. This process, called photoassisted chemical vapor deposition (PACVD), enables area-selective deposition of materials during the manufacture of electronic devices. Professors Walker and McElwee-White are growing metal films with high precision using a new approach: PACVD on regularly arranged regions of molecules called self-assembled monolayers, in which the ends of the molecules can be chosen for specific chemical reactions. By arranging regions of reactive ends and non-reactive ends, the placement of the metal on the surface can be controlled. The novel low-temperature deposition technique for metallic films could in the future enable the formation of layered heterostructured materials with interconnects on glassy or ceramic materials without damaging a carefully tailored microstructure. Thereby advances could lead to improvements in manufacturing for technologies ranging from sensors to energy harvesting equipment. Other fields, like integrating organic electronics onto cloth or plastic supports could benefit from insights gained from this project as well. Graduate and undergraduate students working on this interdisciplinary project learn technical and collaborative skills valuable in both academia and industry, preparing them for a variety of careers. To communicate the excitement of science to the general public, the PIs generate a series of 90-second “Tiny Tech” radio modules and podcasts that feature real world applications of materials and chemistry-based nanoscience.Technical AbstractThe goal of the proposed work is to develop a new class of area selective deposition (ASD) methods in which low temperature photoassisted chemical vapor deposition (PACVD) processes are employed for the selective deposition of metals onto functionalized thermally sensitive materials. The continued downscaling of device structures has led to significant challenges for conventional top-down lithographic approaches. In contrast, ASD leads to the deposition of materials only in a desired area – the target “growth” surface – without as many complex lithography steps. The development of reliable low temperature ASD of metallic thin films as part of heterostructures involving glassy materials or tailored ceramic substrates, as well as on organic materials, is therefore critical to many technologies including energy harvesting, sensing, magnetoelectronics and organic electronics. The proposed approach to ASD relies on mechanism-based design of precursors that upon photolysis, generate intermediates that react with specific functional groups on the growth surface, nucleating the metal deposit. The non-growth surface will be functionalized with groups that are unreactive (or less reactive) with the intermediates, resulting in ASD. In these studies, self-assembled monolayers (SAMs) will be used for both growth and non-growth surfaces. SAMs have highly organized structures with a uniform density of terminal functional groups and can be easily patterned enabling quantitative investigation of the precursor-molecule interactions and deposition selectivity.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.