Nanolithography of Amorphous Semiconductors
Award year: 2001-2002
This proposal seeks to develop computational underpinnings for a new lithographic scheme for fabricating arrays of nanoparticles starting from an amorphous thin film. The lithography is based on the notion that optical illumination can be used in a spatially resolved manner to selectively ripen subcritical nuclei present in amorphous semiconductors after film deposition under carefully controlled low-energy ion bombardment. Patterned optical exposure will yield a spatially varying surface mass flux that, when performed at an annealing temperature just below the cusp of crystallization, provides the extra impetus to crystallize sub-critical nuclei in regions dictated by the light flux. The full-fledged crystallites will then grow by surface diffusion and Ostwald ripening until the desired fraction of the film has accreted onto the original nuclei. Applications of lithographically defined arrays of nanoparticles occur in advanced ceramics, sensors, high-density storage media, flat panel displays, rechargeable batteries, solar cells, and photonic band gap materials. The delicate optimization of conditions needed for successful lithography will require guidance in several respects from computationally intensive modeling. Molecular dynamics simulations will elucidate a newly discovered nonlinear interaction between low-energy ion bombardment and thermal activation for forming mobile surface species. Quantum calculations will guide the development of an atomic-level theory for nonthermal optical activation of mass transport on amorphous surfaces. Multiscale modeling will be needed to connect the calculations to experimentally observable data. These efforts will draw upon the expertise of three NCSA faculty and staff in computational scaleup, visualization, and multiscale model construction.