ABSTRACT
Over the years, one-dimensional (1-D) nanomaterials have continuously gained a lot of interest among researchers due to their unique physical properties. Silicon nanowires (SiNWs) are typical 1-D nanomaterials that have tunable aspect ratio, intrinsic structural defect, good photoluminescence properties, and excellent insulator and biocompatibility, which make them suitable to be used as biosensors and in electronic, communication and optoelectronic devices. SiNWs can be fabricated using the conventional chemical vapor technique (CVD) process that requires a high-temperature process and a catalyst, making the process expensive. On the other hand, low-temperature processes, such as photolithography, involve multiple processing steps. Moreover, this process requires hydrofluoric acid, which is highly toxic and corrosive. In this chapter, we demonstrate an alternative technique to fabricate SiNWs at low temperatures, using atomic force microscopy (AFM) lithography through local anodic oxidation (LAO) process. The LAO process involves the application of a positive voltage between the AFM tip and the surface of the silicon-on-insulator (SOI) wafer in an atmosphere with high relative humidity from the ambient. This will generate a water meniscus between the AFM tip and the SOI wafer. The applied voltage on the tips will ionize water molecules, producing OH- ions, which will react with silicon on SOI wafer to form SiO2 nanowires. The SiO2 nanowires can be further processed to form SiNWs by using a wet chemical etching process. Several important AFM lithography parameters, such as applied voltage, writing speed, type of cantilever tips coating materials and relative humidity are reviewed.
