ABSTRACT
Self-healing microelectronics are needed for costly applications with limited or without access. They are needed in fields such as space exploration to increase lifetime and decrease both costs and the environmental impact. While advanced self-healing mechanisms for polymers are numerous, practical ways for self-healing in metal films have yet to be found. A concept for an autonomous intrinsic self-healing metallic film system is developed, allowing the healing of cracks in metallic films on flexible substrates. The concept relies on stabilizing metastable thin films with high mixing enthalpy via segregation barriers. This allows the films to possess autonomous intrinsic self-healing capabilities triggered by cracking at temperatures not detrimental to flexible microelectronics. The effect will be shown on metastable Mo1-xAgx thin films, stabilized via a Mo segregation barrier. Without a segregation barrier, the system is known to exhibit spontaneous Ag particle formation on the surface. This property is controlled and directed to heal cracks and partially restore the electro-mechanical properties of the multilayer system. This mechanism opens up the field of self-healing thin metallic films that could profoundly impact the design of future microelectronics.
ABSTRACT
More and more flexible, bendable, and stretchable sensors and displays are becoming a reality. While complex engineering and fabrication methods exist to manufacture flexible thin film systems, materials engineering through advanced metallic thin film deposition methods can also be utilized to create robust and long-lasting flexible devices. In this review, materials engineering concepts as well as electro-mechanical testing aspects will be discussed for metallic films. Through the use of residual stress, film thickness, or microstructure tailoring, all controlled by the film deposition parameters, long-lasting flexible film systems in terms of increased fracture or deformation strains, electrical or mechanical reliability, can be generated. These topics, as well as concrete examples, will be discussed. One objective of this work is to provide a toolbox with sustainable and scalable methods to create robust metal thin films for flexible, bendable, and stretchable applications.
ABSTRACT
Oxide glasses are an integral part of the modern world, but their usefulness can be limited by their characteristic brittleness at room temperature. We show that amorphous aluminum oxide can permanently deform without fracture at room temperature and high strain rate by a viscous creep mechanism. These thin-films can reach flow stress at room temperature and can flow plastically up to a total elongation of 100%, provided that the material is dense and free of geometrical flaws. Our study demonstrates a much higher ductility for an amorphous oxide at low temperature than previous observations. This discovery may facilitate the realization of damage-tolerant glass materials that contribute in new ways, with the potential to improve the mechanical resistance and reliability of applications such as electronic devices and batteries.
