Method of producing silicon nanoparticles from stain-etched silicon powder

• US 20040166319A1
• Filed: 02/21/2003
• Published: 08/26/2004
• Est. Priority Date: 02/21/2003
• Status: Active Grant

• Current Assignee: SI Diamond Technology, Inc. (Nano Magic, Inc.)
• Original Assignee: SI Diamond Technology, Inc. (Nano Magic, Inc.)
• Inventors: Li, Yunjun, Pavlovsky, Igor
• Granted Patent: US 7,244,513 B2
• Time in Patent Office: Days
• US Class Current: 428/404
• CPC Class Codes: C01B 33/02 Silicon forming single crystals or homogeneous polycrystalline material with defined structure C30B
• CPC Class Codes: C01B 33/021 Preparation chemical coating from the vapour phase C23C16/00
• CPC Class Codes: Y10S 977/90 having step or means utilizing mechanical or thermal property, e.g. pressure, heat
• CPC Class Codes: Y10T 428/12479 Porous [e.g., foamed, spongy, cracked, etc.]
• CPC Class Codes: Y10T 428/2982 Particulate matter [e.g., sphere, flake, etc.]
• CPC Class Codes: Y10T 428/2991 Coated
• CPC Class Codes: Y10T 428/2993 Silicic or refractory material containing [e.g., tungsten oxide, glass, cement, etc.]

Abstract

The present invention is for a porous silicon powder comprising silicon particles wherein the outermost layers of said particles are porous. The present invention is also directed to a method of making this porous silicon powder using a stain etch method. The present invention is also directed to a method of making silicon nanoparticles from the porous silicon powders using a process of ultrasonic agitation. The present invention also includes methods of processing these silicon nanoparticles for use in a variety of applications.

Claims

1. A porous silicon powder comprising a plurality of silicon particles wherein the outermost layers of said particles are porous.

2. The porous silicon powder of claim 1, wherein the silicon particles have an average particle diameter which ranges from at least about 10 nanometers to at most about 1 millimeter.

3. The porous silicon powder of claim 1, wherein the outermost porous layers of said silicon particles comprise a thickness which ranges from at least about 1 angstrom to at most about 500 nanometers.

4. The porous silicon powder of claim 1, wherein the outermost porous layers of said silicon particles comprise a porosity which ranges from at least about 5 percent to at most about 95 percent.

5. The porous silicon powder of claim 1, wherein the outermost porous layers of said silicon particles comprise pores having sizes which range from at least about 1 nanometer to at most about 100 nanometers.

6. The porous silicon powder of claim 1, wherein said powder has a purity which ranges from at least about 80 percent to at most about 100 percent.

7. The porous silicon powder of claim 1, further comprising a dopant species dispersed in the matrix of the silicon particles.

8. The porous silicon powder of claim 7, wherein the dopant species renders the porous silicon powder n-doped.

9. The porous silicon powder of claim 7, wherein the dopant species renders the porous silicon powder p-doped.

10. A method for making porous silicon powder comprising the steps of:

a) providing a quantity of silicon powder comprising a plurality of silicon particles; and

b) etching said silicon particles using a stain-etch process.

11. The method of claim 10, further comprising a process for making the silicon powder comprising the steps of:

a) providing a bulk silicon object;

b) grinding the bulk silicon object into smaller silicon pieces; and

c) ball milling the smaller silicon pieces into a silicon powder comprised of a plurality of silicon particles.

12. The method of claim 10, wherein the silicon powder has a purity which ranges from at least about 80 percent to at most about 100 percent.

13. The method of claim 10, wherein the silicon particles range in diameter from at least about 1 nanometer to at most about 1 millimeter.

14. The method of claim 10, wherein the silicon powder is n-doped.

15. The method of claim 10, wherein the silicon powder is p-doped.

16. The method of claim 10, wherein the silicon powder is doped with a species selected from the group consisting of P, B, As, Ga, Sb, Er, and combinations thereof.

17. The method of claim 10, wherein the stain-etch process comprises treatment of the silicon powder with a mixture of hydrofluoric acid and a nitro-containing species.

18. The method of claim 17, wherein the mixture of hydrofluoric acid and a nitro-containing species is dispersed in solution.

19. The method of claim 18, wherein the solution is aqueous in nature.

20. The method of claim 17, wherein the nitro-containing species is selected from the group consisting of nitric acid, iron nitrate, nitrous acid, cobalt nitrate, nickel nitrate, sodium nitrate, potassium nitrate, and combinations thereof.

21. The method of claim 17, wherein the nitro-containing species is iron nitrate.

22. The method of claim 10, wherein the stain-etch process has a rate that is monitored by nitrogen dioxide evolution.

23. The method of claim 10, wherein the stain-etch process has a rate that is modulated by temperature.

24. The method of claim 10, wherein the stain-etch process has a rate that is modulated by hydrofluoric acid and a nitro-containing species concentration.

25. The method of claim 10, wherein the stain-etch process has a rate that is modulated by the selection of particular nitro-containing species.

26. The method of claim 10, wherein the stain-etch process has a rate that is enhanced by illumination.

27. The method of claim 10, wherein the stain-etch process has a quiescent period.

28. A method of making silicon nanoparticles comprising:

a) providing porous silicon powder; and

b) ultrasonically agitating said powder in a solvent to break up porous outermost layers of silicon particles comprising said powder to provide for a dispersion of silicon nanoparticles in said solvent.

29. The method of claim 28, wherein the porous outermost layers of the silicon particle are broken up by a mechanical interaction between the porous layers and cavitation bubbles induced by the ultrasonic agitation.

30. The method of claim 28, wherein the step of ultrasonically agitating the porous silicon powder further comprises ultrasonic frequencies in the range of at least about 10 kHz to at most about 10 MHz.

31. The method of claim 28, wherein the step of ultrasonically agitating the porous silicon powder has a duration of from at least about 10 seconds to at most about 10 hours.

32. The method of claim 28, further comprising the step of centrifuging to separate the silicon nanoparticles from remnants of the porous silicon particles.

33. The method of claim 28, further comprising the step of filtration to separate the silicon nanoparticles from remnants of the larger silicon particles.

34. The method of claim 28, further comprising the step of filtration to separate the silicon nanoparticles into desired size ranges.

35. The method of claim 28, further comprising the addition of a dispersal agent.

36. The method of claim 28, wherein the silicon nanoparticles have an average diameter which ranges from at least about 1 nanometer to at most about 100 nanometers.