Method for reducing thin films on low temperature substrates
A method for producing an electrically conductive thin film on a substrate is disclosed. Initially, a reducible metal compound and a reducing agent are dispersed in a liquid. The dispersion is then deposited on a substrate as a thin film. The thin film along with the substrate is subsequently exposed to a pulsed electromagnetic emission to chemically react with the reducible metal compound and the reducing agent such that the thin film becomes electrically conductive.
1. A method comprising:
dispersing in a liquid an organic reducer and a plurality of particles containing metal oxide;
depositing said dispersion on a substrate as a non-conductive thin film, wherein said depositing is performed by printing; and
exposing said non-conductive thin film to a plurality of pulsed electromagnetic emissions in an ambient atmosphere for said organic reducer to initially react with said metal oxide chemically via a redox reaction to form metal particles, and for sintering said metal particles to render said thin film from electrically non-conductive to electrically conductive, wherein each of said pulsed electromagnetic emissions has a pulse length less than 20 ms and a radiated power more than 2 KW/cm 2 , wherein the repetition rate of said pulsed electromagnetic emissions is synchronized with a conveyor belt speed of a conveyor belt system having an electromagnetic emission pulse rate f given by:
f= 0.2 *s*o/w
wherein s=converyor belt speed [ft/min];
o=average number of electromagnetic emmisions received by said substrate at any one location; and
w=width of electromagnetic emissions [in].
2. The method of claim 1 , wherein said substrate is paper.
3. The method of claim 1 , wherein said substrate is polyethylene terephthalate (PET).
4. The method of claim 1 , wherein said substrate is polymer.
5. The method of claim 1 , wherein said reducer is polyvinylpyrrolidone (PVP).
6. The method of claim 1 , wherein said reducer is ascorbic acid.
7. The method of claim 1 , wherein said reducer is ethylene glycol/glycerol.
8. The method of claim 1 , wherein said metal oxide is copper oxide.
9. The method of claim 1 , wherein said pulsed electromagnetic emission is generated by a laser.
10. The method of claim 1 , wherein said pulsed electromagnetic emission is generated by a flash lamp.
11. The method of claim 1 , wherein said pulsed electromagnetic emission is generated by an arc lamp.
12. The method of claim 1 , wherein said pulsed electromagnetic emission is generated by a radio-frequency induction heater.
13. The method of claim 1 , wherein said pulsed electromagnetic emission is microwave.
14. The method of claim 1 , wherein said pulsed electromagnetic emission is an electron beam.
15. The method of claim 1 , wherein said pulsed electromagnetic emission is greater than 500 W/cm 2 .
16. The method of claim 1 , wherein said initial redox reaction and said sintering occur within said single pulsed electromagnetic emission.