Semiconductor nanowires are major building blocks for many nanotechnology applications including electronics, sensors, optoelectronics, and energy harvesting and storage. The ultra-large-scale integration of such nanodevices leads to high power density and thus high operating temperature. Though very important, fundamental understanding on the mechanical properties of semiconductor nanowires at high temperature is currently lacking. The objective of this proposal is to develop an on-chip thermomechanical testing stage based on microelectromechanical systems (MEMS) and carry out thermomechanical testing of semiconductor nanowires by in-situ transmission electron microscopy (TEM). Specifically, this proposal will investigate the effect of temperature as well as other fundamental parameters (size, surface area to volume ratio, axial and surface orientations) on mechanical properties including phase transformation of ZnO nanowires.
If successful, the proposed research will make fundamental contributions to understanding the nanoscale phase transformation. The experimental results will be widely disseminated to facilitate collaboration with atomistic simulations to pin down the size effects on this behavior. In addition, the new experimental tools developed in this project will enable controlled thermomechanical characterization of a broad range of nanostructures such as silicon nanowires. The proposed work will be closely integrated with several educational activities including: 1) training of graduate students for multidisciplinary research; 2) integration of research into undergraduate and graduate courses that PI offers at NCSU, and web-based dissemination of the new course module; 3) Involvement of undergraduate students especially women and underrepresented minorities in the interdisciplinary research in MEMS and nanomechanics; 4) Collaboration with the Engineering Place program at NCSU by participating in the summer camps and organizing high school teacher workshops.
) has resulted in significant advance in the instrumentation capabilities for nanomechanical testing. Microelectromechanical system (MEMS) has been widely used for nanomechancial testing of nanostructures such as nanowires and nanotubes. Our work under this grant has demonstrated the first feedback control of the MEMS testing stage. Feedback control is important in achieving true displacement-controlled nanomechanical testing experiments to capture deformation signatures such as dislocation nucleation. In addition, we have developed a MEMS stage with heating and temperature sensing capabilities. Thermomechanical testing of nanostructures have not been widely studied due to the lack of instrumentation capability. Our work is expected to significantly facilitate study on temperature effect on mechanical properties of nanostructures. Using the developed novel MEMS testing stages, we have captured interesting mechanical properties such as brittle to ductile transition in Si nanowires. The PI has presented the findings in journal publications and conference presentations. For example, his group published several journal articles on development of the MEMS devices and mechanical properties of several semiconductor nanowires. In addition, their grant supported exploration of applying semiconductor nanowires in applications like stretchable electronics harnessing their excellent mechanical and electronic properties. This grant has partly supported four graduate research assistants and two undergraduate research assistants. Materials coming out of this grant have been adopted in undergraduate and graduate courses and in outreach activities such as Nanodays at North Carolina State University.
