Thermal Plastic Imprinting of Bulk Metallic Glass for Fabrication of Terahertz Plasmonic Devices

In the past two decades, bulk metallic glass (BMG) has gradually evolved from a scientific curiosity to a family of engineering materials which possess unique combinations of properties and find applications as functional materials as well as structural materials. Such developments are resulted from numerous empirical investigations of properties augmented by innovations in the processing technologies which make full use of the casting and thermal plastic behaviours of BMG. Recently, with the better understanding of the size-dependent properties of BMG, applications on length scales from 1 nm to several mm, such as micro-electromechanical systems (MEMS), etc., are considered the most promising. The principal investigator (PI) of this proposed research noticed that the possibility of high throughput and low cost production of systems or components in such length scales by thermal plastic forming makes BMG especially suitable for making terahertz passive components. Terahertz technology is a rapidly developing field and brings applications like high precision spectrum detection, super resolution imaging, and high performance communication, etc. Terahertz radiation lies between infrared and microwaves and has wavelength in the order of 10μm to mm. Passive devices for guiding and manipulating THz radiation therefore contain features in similar length scales. Currently, most of such devices are fabricated by micromachining of silicon or by moulding of polymer. Silicon devices are brittle and the process is expensive, while the long-term dimensional stability of polymers is not satisfactory. We therefore propose to develop the thermal plastic processing technology for producing high aspect ratio structures with BMG with the precision necessary for high performance terahertz devices. Another challenge for thermal plastic forming of BMG is to produce nanoscale surface patterns or structures on a metallic glass thin film. If that can be done with high precision and good reproducibility, the complex procedures involving photolithography for producing nano-electromechanical systems (NAMS) may be replaced by the relatively simple process of nano-imprinting of metallic glass thin film. The second objective of this proposed research is therefore to develop a reliable and reproducible nano-imprinting process for MG thin film. Both of these proposed objective will have tremendous potential for application but they are hitherto not investigated and reported extensively. When this proposed project is successfully completed, it is anticipated that the thermal plastic processing windows for some suitable metallic glass materials will be unambiguously identified for producing practical terahertz devices with BMG and for imprinting nanostructures on metallic glass thin films.