| Micro- and nano-scale engineering, especially as it applies to integrated circuits, has impacted society in revolutionary ways. These integrated circuits are characterized by huge numbers of small electronic devices manufactured on semiconductor wafers. Some emerging technologies will require assemblies of these micro/nano-devices on substrates that are very different from semiconductor wafers in terms of processing schemes and properties. Integration of high quality semiconductors and devices onto large, low-cost, mechanically- deformable, polymeric (plastic or elastomer), and/or functional substrates for unconventional electronics applications (displays, systems-on-a-chip) are a few examples. This dissertation presents methods for assembling small-scale (∼nm to ∼mm) materials elements and devices on many classes of substrate (planar or simply-curved with nearly arbitrary composition) via transfer printing, a form of soft lithography. The approach uses rubber stamps to manipulate arrays of small-scale objects including but not limited to carbon nanotubes, metal thin films, single-crystal silicon and III-V semiconductor microstructures and devices, few-layer graphene, and silica microspheres. Presented here are the techniques for preparing printable materials elements and devices from solution (e.g. surfactant stabilized aqueous carbon nanotube solutions) and from donor/source substrates (e.g. semiconductor wafers) as well as the mechanical phenomena that govern the transfer of materials to and from the stamp. Among these are kinetically-switchable adhesion to a viscoelastic stamp and stress focusing via sharp geometries for controlling fracture. Also presented here are thin-film transistors, photodiodes, and inorganic light-emitting diodes on plastic substrates as well as semiconductor woodpile structures and silicon-III-V heterogeneous integration, examples of the capabilities of the transfer printing approach. |
