IRG 1: Stress in Thin Films and Small Scale Structures
Functional thin films and small scale structures are at the core of many advanced technologies -- microelectronics, optoelectronics, information storage, high-performance coatings, for example -- and they are key to emerging technologies -- micro-electromechanical systems (MEMS), quantum dot lasers, quantum computers, for example. A critical factor for the fabrication, performance and reliability of these structures is the residual stress acting within the material. Excessive stress can lead to defect formation, cracking, delamination or stress-induced material transport. Stress is not always detrimental, of course; it can enhance functional properties of a film or be exploited in the self-assembly of nanostructure arrays with unique functional characteristics. As the size scale of devices shrinks, the need for stress management becomes even more important. A fundamental understanding of the origins and consequences of stress will enable us to predict and manipulate stress evolution during processing and to quantitatively anticipate the performance of the resulting material structures.
As a focus for this IRG, two areas are identified that have a proper blend of need for advance of emerging technologies, of opportunity for progress on the basis of the most recent scientific developments, and of scope which demands the coordination of expertise from multiple disciplines and integration of a range of methodologies, both experimental and analytical. The first of these areas is the growth and stability of surfaces or surface domains in nanostructured materials, particularly in situations in which mechanical stress plays a significant role. The second area identified is the time evolution of stress during growth of thin films with non-epitaxial microstructures on substrates and the closely coupled role of stress in influencing subsequent film growth. The group comprising this IRG consists of materials scientists, mechanical engineers, physicists and electrical engineers with extensive experience in the collaborative modeling and measurement of thin films and material nanostructures.