Method for the detection of defects in gas-barrier films using quantum dots
By forming nanoparticles from gas-phase precursors within cracks or defects in a gas-barrier film, crack-width may be determined from the diameter of the nanoparticles formed within. The optical absorption and emission wavelengths of a quantum dot are governed by the particle size. For a particular material, the absorption and/or emission wavelengths may therefore be correlated to the particle size (as determined from techniques such as transmission electron microscopy, TEM). Thus, fluorescence measurement techniques and/or confocal microscopy may be used to determine the size of quantum dots formed within a gas-barrier film, allowing both the size and nature of a defect to be determined. The method may be used to assess the potential effects of defects on the integrity of the gas-barrier film.
1. A method for characterizing defects in a gas-barrier film comprising:
synthesizing quantum dots within defects in the film using gaseous precursors;
detecting light emission or light absorbance by the quantum dots.
2. A method as recited in claim 1 wherein the defects comprise channel cracks in the film.
3. A method as recited in claim 1 wherein the defects comprise open pores in the film.
4. A method as recited in claim 1 wherein the fluorescence is detected using confocal microscopy.
5. A method as recited in claim 1 wherein the quantum dots comprise Group II-VI nanoparticles.
6. A method as recited in claim 1 wherein the quantum dots comprise Group III-V nanoparticles.
7. A method as recited in claim 1 wherein the quantum dots comprise Group II-V nanoparticles.
8. A method as recited in claim 1 wherein the quantum dots comprise Group III-VI nanoparticles.
9. A method as recited in claim 1 wherein the gaseous precursors are supplied via a carrier gas selected from the group consisting of helium (He), nitrogen (N 2 ), argon (Ar) and hydrogen (H 2 ).
10. A method as recited in claim 1 wherein the quantum dots are synthesized in the presence of a Lewis base.
11. A method as recited in claim 10 wherein the Lewis base is pyridine gas.
12. A method as recited in claim 1 wherein the gaseous precursors comprise two streams flowing in opposite directions.
13. A method as recited in claim 1 wherein the gaseous precursors comprise two streams flowing in parallel.
14. A method as recited in claim 13 wherein the two streams flow in tandem.
15. A method as recited in claim 13 wherein the two streams flow sequentially.
16. A method as recited in claim 1 wherein the quantum dots comprise nanoparticles selected from the group consisting of CdS, CdSe, ZnS, ZnSe and InP.
17. A method as recited in claim 1 wherein the fluorescence is detected by stimulated emission depletion microscopy.
18. A method as recited in claim 1 further comprising correlating the photoluminescence wavelength of the quantum dots with their particle size.
19. A method as recited in claim 1 further comprising determining the size of pores in the film using confocal microscopy.
20. A method as recited in claim 1 further comprising correlating the absorption wavelengths of the quantum dots to particle size determined by transmission electron microscopy.
21. A method as recited in claim 1 further comprising correlating the emission wavelengths of the quantum dots to particle size determined by transmission electron microscopy.