| AVS 60th International Symposium and Exhibition | |
| Plasma Science and Technology | Thursday Sessions |
| Session PS+AS+NS+SS-ThM |
| Session: | Plasma Synthesis of Nanostructures |
| Presenter: | S. Ghosh, Case Western Reserve University |
| Authors: | S. Ghosh, Case Western Reserve University R. Yang, Case Western Reserve University C.A. Zorman, Case Western Reserve University P. X.-L. Feng, Case Western Reserve University R.M. Sankaran, Case Western Reserve University |
| Correspondent: | Click to Email |
In situ approaches to synthesizing metal nanoparticles from metal-organic or metal-polymer films have recently emerged as a simple and viable method to fabricating flexible, conductive patterns.1,2 In general, a metal precursor is mixed or reacted with an organic or monomer, cast as a film, and exposed to ultraviolet, laser, heat, or electron beam (e-beam). Recently, we have demonstrated that an atmospheric-pressure microplasma can be similarly used to initiate reduction of metal ions and formation of metal nanoparticles in polymer films.3 In this study, we present electrical characterization of the reduced lines and show that conductive patterns are achieved similar to other methods including e-beam irradiation.
Polymer films containing ionic metal precursors were prepared by first dissolving metal salts [e.g., silver nitrate (AgNO3), palladium acetate (Pd(OAc)2] with polymers [e.g., polyvinyl alcohol (PVA), polymethymethacrylate (PMMA)] in solution. The solvent was chosen according to the metal salt-polymer system. For AgNO3 and PVA, we used a 1:1 ratio of water:ethanol, and for Pd(OAc)2 and PMMA, acetonitrile was used. The mixed metal-organic solutions were drop cast or spin coated onto Si substrates to form thin films (100nm~1µm thick). The films were dried in vacuum and then exposed to the microplasma process. An Ar microplasma was formed by applying DC power to a stainless steel capillary tube and the substrate holder. Patterns were generated by scanning the microplasma at constant discharge current. After exposure, the films were peeled off from the substrate and transferred to a glass substrate. The conductivity was measured using a two point probe method. The as-prepared films were also characterized by scanning electron microscopy (SEM) and energy-dispersive spectroscopy (EDX) to confirm metallization (i.e., reduction) over the exposed areas.
Our results show that plasma exposure leads to conductive patterns on a free-standing flexible substrate. SEM and EDX confirm the reduction of metal ions to metal nanoparticles. We have also compared these results with exposure to an e-beam. In the case of the plasma, the polymer is removed, probably due to oxidation, whereas the e-beam causes conformational changes to the polymer. The effects of annealing following exposure to increase the conductivity of the films will also be discussed.
References:
1. B. Radha et al., J. Am. Chem. Soc. 133, 12706–12713 (2011).
2. S. W. Lee et al., Adv. Funct. Mater. 21, 2155-2161 (2011).
3. S. W. Lee et al., Macromolecules 45, 8201–8210 (2012).