Formation of metal-containing nano-particles for use as catalysts for carbon nanotube synthesis
View Patent ↗The present invention relates to a method for forming metal-silicide catalyst nanoparticles with controllable diameter. The method according to embodiments of the invention leads to the formation of ‘active’ metal-suicide catalyst nanoparticles, with which is meant that they are suitable to be used as a catalyst in carbon nanotube growth. The nano-particles are formed on the surface of a substrate or in case the substrate is a porous substrate within the surface of the inner pores of a substrate. The metal-silicide nanoparticles can be Co-silicide, Ni-silicide or Fe-silicide particles. The present invention relates also to a method to form carbon nanotubes (CNT) on metal-silicide nanoparticles, the metal-silicide containing particles hereby acting as catalyst during the growth process, e.g. during the chemical vapor deposition (CVD) process. Starting from very defined metal-containing nanoparticles as catalysts, the diameter of grown CNT can be well controlled and a homogeneous set of CNT will be obtained.
1. A method for forming metal-silicide nanoparticles for use as catalysts in carbon nanotube growth, the method comprising:
depositing a barrier layer on a substrate;
depositing a thin layer of silicon containing material having a thickness of from 1 nm to 10 nm on the barrier layer;
depositing a thin metal film onto the thin layer of silicon containing material, the thin metal film having a thickness of from 1 nm to 10 nm; and
annealing the thin metal film and the thin layer of silicon containing material to form metal-silicide nanoparticles having a diameter smaller than 10 nm, wherein the barrier layer prevents diffusion of the metal-silicide nanoparticles into the substrate.
2. The method of claim 1 , wherein annealing is performed at a temperature higher than 500° C. and lower than 900° C.
3. The method of claim 1 , wherein the thin metal film has a thickness of from 1 nm to 5 nm.
4. The method of claim 1 , wherein the substrate is a silicon wafer.
5. The method of claim 1 , wherein the metal-silicide nanoparticles are selected from the group consisting of Ni-silicides, Co-silicides, and Fe-silicides nanoparticles.
6. The method of claim 1 , wherein the barrier layer is a thermally grown SiO 2 layer with a thickness of from 50 nm to 100 nm.
7. The method of claim 1 , wherein the barrier layer comprises at least one material selected from the group consisting of Si 3 N 4 , TaN, HfN, and TiN.
8. The method of claim 1 , wherein the thin metal film is selected from the group consisting of a Co film, a Ni film, and a Fe film.
9. The method of claim 8 , wherein the thin metal film is deposited by a sputter or deposition technique selected from the group consisting of physical vapor deposition, atomic layer deposition, and electrochemical deposition.
10. A method for growing carbon nanotubes on a substrate having metal-silicide nanoparticles thereon prepared according to the method of claim 1 , the method comprising:
growing carbon nanotubes using the metal-silicide nanoparticles as a catalyst.
11. Use of the method of claim 1 in the manufacturing of a semiconductor device.
12. The method of claim 1 , wherein the thin metal layer is a uniformly deposited continuous thin metal layer.
13. The method of claim 1 , wherein the thin metal layer is a non-uniform sub-atomic layer deposited by at least one technique selected from the group consisting of atomic layer deposition, electrodeposition, and electroless deposition.
14. The method of claim 1 , wherein the thin layer of silicon containing material is consumed to form metal-silicide nanoparticles.
15. The method of claim 1 , wherein the thin layer of silicon containing material has a thickness of from 1 nm to 5 nm.
16. The method of claim 1 , wherein the metal-silicide nanoparticles are uniformly dispersed and situated on top of the barrier layer.
17. The method of claim 1 , wherein the metal-silicide nanoparticles are situated on top of the barrier layer but are not embedded in or attached to the barrier layer.
18. The method of claim 1 , wherein the silicon containing material is silicon.
19. The method of claim 18 , wherein the silicon containing material is poly-Si.
20. A device comprising:
a substrate;
a barrier layer on the substrate, the barrier layer configured for preventing diffusion of metal-silicide nanoparticles into the substrate; and
uniformly dispersed metal-silicide nanoparticles situated on the barrier layer, but not embedded in or attached to the barrier layer, and having a diameter smaller than 10 nm.