Nanofabrication Through Molding
Date of Award
Doctor of Philosophy (PhD)
Mechanical Engineering & Materials Science (ENAS)
The development of today’s nanotechnology relies on the capabilities of nanofabrication techniques. An ideal nanofabrication method would cover a broad range of length scales, control of geometries, and a versatile material and composition choice. However, most of the existing nanofabrication methods are limited in some of these aspects. Molding is a fabrication method used for materials that can be realized in a soft state. Molding forms materials by deforming them with an applied bias, typically a pressure gradient, and drive the materials against a hard mold with pre-defined geometries. By using molds of nanoscale patterns, molding has been achieved down to ~ 10 nm and proved to be a promising nanofabrication technique. However, nanomolding is limited to polymers, gels, and metallic glasses and lack the ability to work with general materials, especially crystals, that are the material of choice in many applications.In this thesis, I report a general molding method that can be applied to a wide range of materials, broad range of length scales, with control over geometry, compositions, and composition structures. This newly developed method, which we call Thermomechanical Nanomolding (TMNM), enables nanofabrication in a high-throughput, low-cost and easy to operate manner. When developing this technique, I systematically investigated the deformation mechanism of various materials in a nanoconfinement. Through scaling experiments combined with structural and compositional characterizations, I revealed a size- and temperature- dependent mechanism for the deformation and crystalline materials and amorphous materials. Utilizing these fundamental mechanisms, I show TMNM as a powerful nanofabrication toolbox to precisely control the geometry of the nanostructures, cover broad length scales, work with general crystalline and amorphous materials, fabricate high-quality single crystal nanostructures, and control and design complex composition structures. Control over the composition of molded materials is achieved by using the competition between thermodynamical and kinetic energies in TMNM, where the compositions of solid solutions can be tuned and that for ordered phases are always maintained. Through the work reported in this thesis, I was able to prove TMNM as a highly versatile toolbox for nanofabrication. It is promising for nanofabrication of a variety of functional materials and structures which are demanded by different research fields. This work also brings new insight into nano-mechanics and materials science on the deformation of matter in a nanoconfinement and will inspire new possibilities in research in nanodevices, nanotechnologies and various related applications.
Liu, Naijia, "Nanofabrication Through Molding" (2022). Yale Graduate School of Arts and Sciences Dissertations. 495.