Methods and devices for forming nanostructure monolayers and devices including such monolayers
View Patent ↗Methods for forming or patterning nanostructure arrays are provided. The methods involve formation of arrays on coatings comprising nanostructure association groups, formation of arrays in spin-on-dielectrics, solvent annealing after nanostructure deposition, patterning using resist, and/or use of devices that facilitate array formation. Related devices for forming nanostructure arrays are also provided, as are devices including nanostructure arrays (e.g., memory devices). Methods for protecting nanostructures from fusion during high temperature processing are also provided.
1. A method for patterning a nanostructure monolayer, the method comprising:
a) disposing resist and a monolayer of nanostructures on a first layer, wherein the nanostructures are embedded in the resist, to provide a resist layer;
b) exposing a predetermined pattern on the resist layer, to provide exposed resist in at least a first region of the resist layer and unexposed resist in at least a second region of the resist layer, wherein exposing a predetermined pattern on the resist layer to provide exposed resist in at least a first region comprises exposing the resist in the first region to ionizing radiation sufficient to incompletely cure the resist in the first region;
c) i) removing the unexposed resist and its embedded nanostructures from the first layer without removing the exposed resist and its embedded nanostructures,
whereby at least one nanostructure monolayer array defined by the first region remains on the first layer;
c) ii) after step c) i) and before step d), exposing the incompletely cured resist in the first region to ionizing radiation sufficient to further cure the resist in the first region; and
d) after step c) ii), exposing the first layer, the exposed resist and its embedded nanostructures to a temperature of at least about 300° C.
2. The method of claim 1 , wherein in step b) exposing a predetermined pattern on the resist layer comprises exposing the predetermined pattern to ultraviolet light or an electron beam.
3. The method of claim 1 , wherein in step b) the resist in the first region is exposed to about 10 mJ/cm 2 -1 J/cm 2 ultraviolet light to incompletely cure the resist in the first region; and wherein in step c) ii) the resist in the first region is exposed to about 1 J/cm 2 -50 J/cm 2 ultraviolet light to further cure the resist in the first region.
4. The method of claim 1 , wherein the density of nanostructures in the monolayer array after step d) is at least 90% of the density of nanostructures in the monolayer array before step d).
5. The method of claim 1 , wherein following step d), the monolayer array of nanostructures has a density greater than about 1×10 12 nanostructures/cm 2 .
6. The method of claim 1 , wherein, following step d), the size distribution of the nanostructures in the monolayer array exhibits an rms deviation of less than 20%.
7. The method of claim 6 , wherein, following step d), the size distribution of the nanostructures in the monolayer array exhibits an rms deviation of less than 15%.
8. The method of claim 6 , wherein, following step d), the size distribution of the nanostructures in the monolayer array exhibits an rms deviation of less than 10%.
9. The method of claim 1 , wherein in step a) disposing the resist and the monolayer of nanostructures on the first layer comprises spin coating the first layer with a solution comprising the resist and the nanostructures.
10. The method of claim 1 , wherein in step c) i) removing the unexposed resist and its embedded nanostructures from the first layer without removing the exposed resist and its embedded nanostructures comprises contacting the unexposed resist with at least one organic solvent.
11. The method of claim 1 , wherein the resist comprises a silicon compound.
12. The method of claim 1 , wherein the resist comprises a silsesquioxane.
13. The method of claim 12 , wherein the resist comprises mercapto-propyl-cyclohexyl polyhedral oligomeric silsesquioxane, hydrogen silsesquioxane, methyl silsesquioxane, octavinyl dimethyl silyl silsesquioxane, octasilane silsesquioxane, octavinyl-T8 silsesquioxane, aminopropylcyclohexyl polyhedral oligomeric silsesquioxane, acrylo silsesquioxane, or methacrylo silsesquioxane.
14. The method of claim 1 , wherein the first layer comprises a dielectric material, an oxide, a nitride, silicon oxide, silicon nitride, hafnium oxide, or alumina.
15. The method of claim 14 , wherein the first layer comprises silicon oxide coated with hexamethyldisilizane, or wherein the first layer comprises silicon nitride coated with hexamethyldisilizane.
16. The method of claim 1 , wherein the first layer is disposed on a substrate.
17. The method of claim 16 , wherein the substrate comprises a semiconductor.
18. The method of claim 17 , wherein the first layer comprises a dielectric material and has a thickness of between about 1 nm and about 10 nm.
19. The method of claim 17 , comprising disposing a gate electrode on the exposed resist.
20. The method of claim 19 , comprising disposing a dielectric layer on the exposed resist prior to disposing the gate electrode on the exposed resist.
21. The method of claim 1 , wherein the nanostructures comprise substantially spherical nanostructures or quantum dots.
22. The method of claim 1 , wherein the nanostructures have a work function of about 4.5 eV or higher.
23. The method of claim 1 , wherein the nanostructures comprise metal nanostructures.
24. The method of claim 1 , wherein the nanostructures comprise palladium, platinum, nickel, or ruthenium.
25. A method for protecting nanostructures from fusion during high temperature processing, the method comprising:
a) disposing the nanostructures and a silsesquioxane on a first layer;
b) curing the silsesquioxane, to provide cured silsesquioxane in which the nanostructures are embedded, by:
i) exposing the silsesquioxane to ionizing radiation in a predetermined pattern, whereby the silsesquioxane in at least a first region is exposed and incompletely cured while the silsesquioxane in a least a second region remains unexposed and uncured;
ii) removing the unexposed silsesquioxane and nanostructures therein from the second region without removing the incompletely cured silsesquioxane and its embedded nanostructures from the first region; and
iii) after step ii), exposing the incompletely cured silsesquioxane in the first region to ionizing radiation to further cure the silsesquioxane, to provide the cured silsesquioxane; and
c) heating the first layer, the cured silsesquioxane, and its embedded nanostructures.
26. The method of claim 25 , wherein exposing the silsesquioxane and the incompletely cured silsesquioxane to ionizing radiation comprises exposing the silsesquioxane and the incompletely cured silsesquioxane to ultraviolet light or an electron beam.