Covalent chemical surface modification of surfaces with available silicon or nitrogen
The invention provides a method to form and functionalize monolayers on a silicon-rich silicon nitride surface or a silicon surface formed by a nanopore fabrication method known as dielectric breakdown. Thermal, photochemical and radical processing can be used to hydrosilylate nascent silicon and silicon nitride surfaces with various reagents. The conventional need for hydrofluoric acid etching prior to coupling functional groups to the surfaces is thereby completely avoided.
1. An etching-free method for hydrosilylating a silicon nitride surface, the method comprising sequential steps of:
(a) placing a silicon nitride substrate in an electrolyte solution;
(b) applying an electric potential across a section of the substrate that is no more than 100 nm in thickness until a nanopore of less than about 100 nm in diameter is formed across the section, the nanopore having freshly formed, silicon-rich silicon nitride surface lining its passageway; and
(c) directly attaching a functional group onto the freshly formed silicon-rich silicon nitride surface inside the nanopore by contacting the surface with a reagent having at least one terminal, unsaturated bond, thereby covalently linking the functional group to the silicon on the surface to form a monolayer and such that the resulting nanopore is no more than 100 nm wide in diameter.
2. The etching-free method of claim 1 , wherein the resulting nanopore is no more than 50 nm wide in diameter.
3. The etching-free method of claim 1 , wherein the resulting nanopore is no more than 40 nm wide in diameter.
4. The etching-free method of claim 1 , wherein the resulting nanopore is no more than 30 nm wide in diameter.
5. The etching-free method of claim 1 , wherein the resulting nanopore is no more than 20 nm wide in diameter.
6. The etching-free method of claim 1 , wherein the resulting nanopore is no more than 10 nm wide in diameter.
7. The etching-free method of claim 1 , wherein the resulting nanopore is about 3-5 nm wide in diameter.
8. The etching-free method of claim 1 , wherein step (c) comprises adding an alkene or alkyne to access the freshly formed silicon-rich silicon nitride surface inside the nanopore, thereby forming a Si—C bond on the surface.
9. The etching-free method of claim 1 , wherein step (c) is carried out under a stimulus selected from the group consisting of photo-radiation, heat, electricity, a metal catalyst, a radical initiator, and a chemical catalyst.
10. The etching-free method of claim 1 , further comprising an additional step of preventing the freshly formed, silicon-rich silicon nitride surface from any significant oxidization before step (c).
11. The etching-free method of claim 10 , wherein the additional step comprises submerging the silicon nitride surface under a liquid.
12. The etching-free method of claim 1 , further comprising, after the step (c), a step of attaching at least an additional functional group to the monolayer.
13. An etching-free method for hydrosilylating a silicon surface, the method comprising the steps of:
a. placing a silicon substrate in an electrolyte solution;
b. applying an electric potential across a section of the substrate that is no more than 100 nm in thickness until a nanopore of less than about 100 nm in diameter is formed across the section, the nanopore having freshly formed silicon surface lining its passageway; and
c. directly attaching a functional group onto the freshly formed silicon surface inside the nanopore by contacting the surface with a reagent having at least one terminal, unsaturated bond, thereby covalently linking the functional group to the silicon on the surface to form a monolayer and such that the resulting nanopore is no more than 100 nm wide in diameter.
14. The etching-free method of claim 13 , wherein the resulting nanopore is no more than 50 nm wide in diameter.
15. The etching-free method of claim 13 , wherein the resulting nanopore is no more than 40 nm wide in diameter.
16. The etching-free method of claim 13 , wherein the resulting nanopore is no more than 30 nm wide in diameter.
17. The etching-free method of claim 13 , wherein the resulting nanopore is no more than 20 nm wide in diameter.
18. The etching-free method of claim 13 , wherein the resulting nanopore is no more than 10 nm wide in diameter.
19. The etching-free method of claim 13 , wherein the resulting nanopore is about 3-5 nm wide in diameter.
20. The etching-free method of claim 13 , wherein step (c) comprises adding an alkene or alkyne to access the freshly formed silicon surface inside the nanopore, thereby forming a Si—C bond on the surface.
21. The etching-free method of claim 13 , wherein step (c) is carried out under a stimulus selected from the group consisting of photo-radiation, heat, electricity, a metal catalyst, a radical initiator, and a chemical catalyst.
22. The etching-free method of claim 13 , further comprising an additional step of preventing the freshly formed, silicon surface from any significant oxidization before step (c).
23. The etching-free method of claim 22 , wherein the additional step comprises submerging the silicon surface under a liquid.
24. The etching-free method of claim 13 , further comprising, after the step (c), a step of attaching at least an additional functional group to the monolayer.
25. An etching-free method for functionalizing a silicon nitride surface, the method comprising the steps of:
a. placing a silicon nitride substrate in an electrolyte solution;
b. applying an electric potential across a section of the substrate that is no more than 100 nm in thickness until a nanopore of less than about 100 nm in diameter is formed across the section, the nanopore having a freshly formed, silicon-rich silicon nitride surface lining its passageway; and
c. directly attaching an isocyanate-terminated species onto the freshly formed silicon-rich silicon nitride surface inside the nanopore by contacting the surface with a reagent having a terminal isocyanate group, thereby covalently linking the isocyanate group to the nitrogen on the surface via click chemistry to form a monolayer, and such that the resulting nanopore is no more than 100 nm wide in diameter.
26. The etching-free method of claim 25 , wherein the reagent is 3,5-bis(trifluoromethyl)phenyl isocyanate.