MEMS-compatible processes for fabricating nanostructures and their applications

During the past decades, many different nanostructures have been successfully synthesized and developed. Due to their nanoscale dimensions, the nanostructures (i.e., nanostructured film, nanotubes, quantum dots) usually exhibit unique optical, electronic, or mechanical properties, which differ from those of the same bulk material. This dissertation focuses on the development and applications of two types of nanostructures: high aspect ratio (HAR) silicon nanostructures and anodic aluminum oxide (AAO) nanopores. (i) High aspect ratio (HAR) silicon nanostructures, including nanopillars, nanoforest and nanotubes, have attracted enormous attention in the fields of energy harvesting and storage, biomedical sensing, drug delivery, and template-based nanofabrication. Recently, several technologies, such as e-beam lithography and AAO template-based process, have been developed to synthesize HAR nanostructures such as silicon nanotubes. However, these technologies are expensive and usually complicated. In this effort, silicon nanopillars fabrication using nanospheres lithography (NSL) and nanoforest formation through a maskless Bosch process have been successfully developed. Nanomaterial grafted-nanopillar antireflection surface and a nanoforest-based SERS substrate have been demonstrated. Furthermore, a new simple process for fabricating silicon nanotubes at room temperature based on the Bosch process has been developed successfully, offering a unique platform for many potential exciting applications. (ii) Among many different applications, anodic aluminum oxide (AAO) nanopores have been utilized as nanopore thin film interferometers for biochemical sensing. Using a two-step anodization process, AAO nanopores are usually fabricated from a piece of high purity Al foil. However, the process is not compatible with a standard lithography- based microfabrication process. As a result, it is very difficult to fabricate arrayed AAO nanopore-based optical microsensors in a cost- effective manner. To address these issues, a new process has been developed to fabricate micropatterned AAO nanopores thin film on glass slide using a standard lithography based microfabrication process. Also, the electron-beam evaporation coated Al thin films become optically transparent after anodization, making it possible to use the transmitted optical signals as the transducing signals. The arrayed AAO thin film-based interferometers have been integrated into a microfluidic chip and the detection of the binding between biomolecules has been demonstrated successfully