Prof. Michael Becker of the Department of Electrical and Computer Engineering at UT Austin (UT ECE) and Prof. Desiderio Kovar of UT Mechanical Engineering have received a National Science Foundation (NSF) award for work on "A Manufacturing Process for Producing Thick Films with Controlled Microstructures." The work will focus on "advancing a new method for depositing thick films that can dramatically reduce processing temperatures and would allow deposition on lower-cost and flexible substrates, while also allowing novel material structures that have the potential to produce films with superior properties." These films could have applciations in high power electronics, solar cells and other applications.
To deposit films quickly to thickness as great as 100 microns or more, impacting a stream of nanoparticles (1-100 nm in size) is a fast way to do the job. The goal of this project is to insure that instead of a pile of random particles with uncontrolled porosity and crystal structure, that a film with controlled crystal structure and porosity is created. The process uses laser ablation to turn a flowing aerosol of micron-sized particles into an aerosol of nanoparticles. The atmospheric pressure nanoparticle aerosol is then impacted onto the target substrate in vacuum through a supersonic jet, and they arrive at speeds from 200 m/s to over 1,000 m/s. The project also aims at correlating experimental results with Molecular Dynamic (MD) simulations that will allow many deposition conditions to be explored quickly.
Example: Silver nanoparticles impacted from 400 and 800 m/s. Possible structures are polycrystalline or epitaxial growth depending on deposition velocity.
Molecular Dynamic Simulations
Spherical 3 nm silver nanoparticle impacted onto a silver substrate at 400 m/s. The final stable result is part epitaxial and part polycrystalline.
Spherical 3 nm silver nanoparticle impacted onto a silver substrate at 800 m/s. The final stable result is fully epitaxial.
High-resolution TEM image of a small spherical silver nanoparticle impacted at 900 m/s. It is flattened on top of a much larger silver particle. The crystal structure is continuous with the single-crystal substrate particle but shows crystal twins.