Duan Research Group

Hetero-integrated Nanostructures and Nanodevices


Fundamental Phase Transformations

In order to probe the underlying principles that govern the way nanocrystals are synthesized, and then further manipulated, we use our expertise in chemistry, physics, thermodynamics and diffusion to find a greater understanding of how these nanostructures are formed, and how we can manipulate them with greater control and more advantageous properties.

This aspect of our research includes the nanodevice contact engineering by fundamentally understanding the kinetic behaviors of materials at the nanoscale. One notable example is the metal silicide system, whose kinetics have been extensively studied in bulk and thin film systems due to their indispensible significance in the IC industry for applications as contacts, electrodes and recent potential as interconnect materials at deep nanometer scale. Despite the significant impact, silicide transformation processes within quasi-one-dimensional systems are not well understood or controlled. To fill this gap, we have carried out a series of mechanistic studies to interrogate the unique kinetic behaviors of nanowire materials and their structural transformations at the nanoscale.

We presented a modified kinetic competition model to explain a unique size dependant first phase selection and different phase transformation sequences of nickel silicides observed in Si nanowires. With the fundamental understanding we continue to explore structure engineering at the nanoscale as a means to modulate phase transformation kinetics to achieve reliable control over the formation of high quality silicides or germanides as nanoscale device contacts. These seminal studies represent a significant leap forward in mechanistic understanding of nanoscale phase transformation and contact engineering, and have attracted wide academic and industrial interests.

UCLA, Department of Chemistry and Biochemistry
607 Charles E. Young Drive East, Box 951569
Los Angeles, CA 90095-1569
E-mail: xduan@chem.ucla.edu