| AVS 61st International Symposium & Exhibition | |
| Thin Film | Tuesday Sessions |
| Session TF+SE-TuM |
| Session: | Energetic Thin Films/Optical Characterization |
| Presenter: | Matthew Steiner, University of Virginia |
| Authors: | M.A. Steiner, University of Virginia P.J. Steiner, University of Virginia J.M. Fitz-Gerald, University of Virginia |
| Correspondent: | Click to Email |
Matrix assisted pulsed laser evaporation (MAPLE) was developed in the late 1990s at the U.S. Naval Research Laboratory as a non-destructive method of thin film deposition for polymers that could potentially be damaged by the ultraviolet radiation utilized for pulsed laser deposition. Conventionally MAPLE starts with a dilute organic compound dissolved in a volatile solvent that serves as a solid matrix when frozen at liquid nitrogen temperatures. By choosing a solvent with a significant UV absorption coefficient, the frozen matrix can be heated by preferential photothermal excitation during irradiation, leading to evaporation and desorption of the less volatile solute molecules onto a substrate in thin film form. Since its conception, use of MAPLE has expanded from the deposition of molecular polymers and proteins to more macroscopic species such as carbon nanotubes, living cells, and recently a number of inorganic nanoparticles.
Inspired by the laser decomposition of metal-acetate based sol-gels to form nanoparticle networks, it is also possible to simultaneously synthesize and deposit well-dispersed nanoparticles or nanoporous films through an inversion of the conventional MAPLE process, utilizing weakly absorbing solvents and photo-sensitive chemical precursor solutes. The chain of events following the laser pulse first entering the target and culminating with observation of nanoparticles on the substrate has been principally interpolated backwards from the nanoparticles produced; suggesting photothermal decomposition of the acetate precursors and formation of nanoparticles within the target prior to and eventually driving ejection. The research presented represents major developments in the understanding of the underlying sequence of multi-scale events controlling the inverse MAPLE deposition process. Modeling addresses optical absorption via Mie theory and the role of matrix conduction in solving nanoparticle heat balance within the target, which in turn is shown to play critical role in the deposition process. New supporting evidence is offered through direct observation of irradiated targets via cryo-stage scanning electron microscopy, as well and conventional scanning and transmission electron microscopy of deposited films and nanoparticles.