Mar 17, 2009
Ion implantation embeds catalyst nanoparticles
Ion implantation, a well established technique in silicon microfabrication, could offer significant technological advantages as a way of introducing catalyst nanoparticles for nanowire growth.
One-dimensional nanostructures, such as nanotubes and nanowires, offer unique structural, optical, electrical and mechanical properties. However, the lack of control in the growth and synthesis of these 1D nanostructures is preventing their widespread use in commercial applications.
SiO2 is a material that is of great technological importance in silicon very-large-scale integration (VLSI) technology. Nanowires of silicon oxide have a great potential in applications such as low-dimensional waveguides, scanning near-field optical microscopy, blue light emitters, nanoscale optical devices and sensors, sacrificial templates and biosensors.
Nanoscale catalyst particles play an essential role in the production process and are required to nucleate the growth of the nanowires. In a recent study published in Nanotechnology, researchers at the University of Florida have demonstrated a simple and novel approach for growing silicon oxide nanowires using ion implantation to create catalyst nanoparticles.
Iron atoms were introduced into thermally grown SiO2 layers on silicon wafers using ion implantation, and silicon oxide nanowires were grown by annealing these wafers at high temperature. Patterned growth of silicon oxide nanowires in localized areas by lithographic patterning and etching of the ion-implanted SiO2 layers before growth was also demonstrated. In contrast to most previous work, both reactants (silicon and oxygen) come from the SiO2 substrate, which acts as a solid source.
An ion-implanted catalyst is much easier to pattern into very small features and over high aspect ratio topography compared with other types of catalyst, and it offers extremely accurate control of the dose of atoms introduced into the substrate. As a result, the work presented by the team opens up the possibility of growing nanowires directly from solid substrates, controlling the origin/location of nanowires at the submicron scale and integrating them into nonplanar three-dimensional nanoscale device structures.
This method of nucleating nanowire growth is not limited to silicon oxide nanowires; it could also be generally applied to the growth of other types of nanowires for potential device applications. The authors have recently shown that single-walled carbon nanotubes, GaN nanowires, Ga2O3 nanowires and Ga2O3 nanoribbons can be produced by the process of ion implantation and subsequent chemical vapor deposition (CVD) growth.
About the author
This work was performed by the Nanotechnology Group at the University of Florida. Yongho Choi and Jason L Johnson are PhD students and Prof. Ant Ural is an assistant professor in the Department of Electrical and Computer Engineering at the University of Florida.