SGER: Epitaxial Electrodeposition for Large Area Single Crystals

Brown University, Providence RI

Investigators

Abstract

TECHNICAL: In many thin film applications, single crystals have much better performance than polycrystalline material. The long-range order, preferred orientation and lack of grain boundaries in single crystals significantly enhance material properties for many applications such as photovoltaics, high temperature superconductors and magnetic information storage. In spite of the benefits, however, polycrystalline films are often used because single crystal substrates (such as Si wafers) are prohibitively expensive, limited in area or difficult to work with. To make single crystal substrates available to a wider range of applications, PI plans to develop a method that will enable free-standing single crystal substrates to be fabricated inexpensively over large areas. The process is based on a sequence of electrodeposition and etching steps in which a sacrificial layer is first electrodeposited epitaxially on a starting single crystal template, followed by a thicker final layer. The sacrificial layer is then selectively etched from between the substrate and final layer, releasing the final layer and making the substrate available for re-deposition. By forming the initial substrate into a loop that can pass through sequential electrochemical cells, the process can be extended into a technique for continuous formation of a seamless product layer. In preliminary work, PI has shown that electrodeposition and etching can be used to make small samples of free-standing single crystal Ni; the resulting films have crystalline quality that is as good as the starting template. However, significant research is necessary to understand and improve the individual etching and deposition processes and to develop equivalent capabilities for other single component and alloy material systems. In addition, scientific and technological challenges must be overcome to integrate these steps into a continuous process. NON-TECHNICAL: The broader impact of this work will be in its effect on numerous technologies. As PI?s processing method develops, PI will work with collaborators in industry and academics to explore the improvements that can be gained by using our material. In addition, this program will educate graduate and undergraduate students, both in the science of electrodeposition and epitaxial growth and by exposing them to numerous technologies where this material can have an impact.