Process for forming shaped group III-V semiconductor nanocrystals, and product formed using process

• US 6,306,736 B1
• Filed: 02/04/2000
• Issued: 10/23/2001
• Est. Priority Date: 02/04/2000
• Status: Expired due to Term

• Current Assignee: Regents of the University of California (University of California)
• Original Assignee: Regents of the University of California (University of California)
• Inventors: Alivisatos, A. Paul, Peng, Xiaogang, Manna, Liberato
• Primary Examiner(s): Bowers, Charles
• Assistant Examiner(s): SARKAR, ASOK K
• Application Number:
  US09/499,096
• Time in Patent Office: 627 Days
• Field of Search: 420/513, 420/525, 420/526, 423/289, 423/249, 257/64, 438/46, 438/102, 438/497, 438/962
• US Class Current: 438/497
• CPC Class Codes: B82Y 30/00 Nanotechnology for materials or surface science, e.g. nanocomposites
• CPC Class Codes: C30B 29/40 AIIIBV compounds wherein A is B, Al, Ga, In or Tl and B is N, P, As, Sb or Bi
• CPC Class Codes: C30B 29/605 Products containing multiple oriented crystallites, e.g. columnar crystallites
• CPC Class Codes: C30B 7/00 Single-crystal growth from solutions using solvents which are liquid at normal temperature, e.g. aqueous solutions from molten solvents C30B9/00; by normal or gradient freezing C30B11/00; under a protective fluid C30B27/00
• CPC Class Codes: H01L 21/02538 Group 13/15 materials
• CPC Class Codes: H01L 21/02601 Nanoparticles fullerenes H10K85/211
• CPC Class Codes: H01L 21/02603 Nanowires
• CPC Class Codes: H01L 21/02628 using solutions
• CPC Class Codes: H01L 33/007 comprising nitride compounds
• CPC Class Codes: Y10S 438/962 Quantum dots and lines
• CPC Class Codes: Y10S 977/813 Of specified inorganic semiconductor composition, e.g. periodic table group IV-VI compositions
• CPC Class Codes: Y10S 977/815 Group III-V based compounds, e.g. AlaGabIncNxPyAsz

Abstract

A process for the formation of shaped Group III-V semiconductor nanocrystals comprises contacting the semiconductor nanocrystal precursors with a liquid media comprising a binary mixture of phosphorus-containing organic surfactants capable of promoting the growth of either spherical semiconductor nanocrystals or rod-like semiconductor nanocrystals, whereby the shape of the semiconductor nanocrystals formed in said binary mixture of surfactants is controlled by adjusting the ratio of the surfactants in the binary mixture.

Claims

1. A process for the formation of Group III-V semiconductor nanocrystals comprises introducing the precursors into a heated binary mixture of first and second different surfactants capable of promoting the growth of either spherical semiconductor nanocrystals or rod-like semiconductor nanocrystals, whereby the shape of said semiconductor nanocrystals formed in said binary mixture of surfactants is capable of being controlled by adjusting the ratio of said first and second surfactants in said binary mixture.

2. The process of claim 1 wherein said heated binary mixture of surfactants comprises two different phosphorus-containing surfactants.

3. The process of claim 2 wherein said binary mixture of surfactants is maintained at a temperature sufficiently high to promote said growth of said semiconductor nanocrystals.

4. The process of claim 2 wherein said ratio of said first and said second surfactants in said heated binary mixture of surfactants permits growth of substantially spherical semiconductor nanocrystals in said binary mixture.

5. The process of claim 2 wherein said ratio of said first and said second surfactants in said heated binary mixture of surfactants permits growth of rod-like semiconductor nanocrystals in said binary mixture.

6. The process of claim 5 wherein said phosphorus-containing surfactant in said binary mixture of surfactants comprises a phosphorus-containing organic acid.

7. The process of claim 6 wherein said phosphorus-containing organic acid surfactant comprises a phosphonic acid surfactant having the formula ROP(OH)₂₁, where R is a 3-18 carbon organic group.

8. The process of claim 6 wherein said phosphorus-containing organic acid surfactant is a phosphinic acid having the formula R′

R_xH<sub>(1−

x)</sub>POOH, where R and R′

are the same or different 3-18 carbon organic groups and x is 0-1.

9. A process for forming shaped Group III-V semiconductor nanocrystals in a heated binary mixture of surfactants which comprises:

a) forming one or more solutions, each comprising one or more Group III and/or Group V semiconductor nanocrystal precursors dissolved in a liquid which is a solvent for said one or more semiconductor precursors;

b) forming a binary mixture of high boiling organic surfactants comprising;

i) a first surfactant; and

ii) a second surfactant;

c) adjusting the ratio of said first and second surfactants in said binary mixture to control the shape of said semiconductor nanocrystals to be formed therein;

d) heating said binary mixture of surfactants to a temperature at which said Group III and Group V precursors will react in said heated binary mixture of surfactants to form said Group III-V semiconductor nanocrystals;

e) adding said one or more solutions of Group III and Group V semiconductor nanocrystal precursors to said heated binary mixture of surfactants to form said semiconductor nanocrystals; and

f) subsequently reducing the temperature of said heated binary mixture of surfactants containing said semiconductor nanocrystals to stop said growth of said semiconductor nanocrystals.

10. The process of claim 9 wherein said step of forming said one or more solutions, each comprising one or more Group III and/or Group V semiconductor nanocrystal precursors dissolved in a liquid which is a solvent for said one or more semiconductor precursors further comprises:

(a) forming a first solution containing at least one Group III metal selected from the group consisting of Al, Ga, and In; and

(b) forming a second solution containing at least one Group V element selected from the group consisting of P, As, or Sb.

11. The process of claim 9 wherein said step of forming said one or more solutions, each comprising one or more Group III and/or Group V semiconductor nanocrystal precursors dissolved in a liquid which is a solvent for said one or more semiconductor precursors further comprises forming a single solution containing;

a) at least one or more Group III metals, or compounds containing Group III metals, selected from the group consisting of Al, Ga, and In; and

(b) at least one or more Group V elements, or compounds containing Group V elements, selected from the group consisting of P, As, and Sb.

12. The process of claim 9 wherein at least one of said one or more solutions comprises

a) a particular Group III metal;

and

b) a particular Group V element.

13. The process of claim 9 wherein:

a) said heating step is carried out until said binary mixture of surfactants reaches a temperature at which said semiconductor nanocrystals will nucleate when said one or more solutions are added to said binary mixture;

b) said nucleation temperature is lowered to a crystal growth temperature after said step of adding said solution to said heated binary mixture of surfactants; and

c) said heated binary mixture of surfactants containing said one or more solutions is maintained at said crystal growth temperature until said step of reducing the temperature of said mixture containing said solution sufficiently to stop formation of said semiconductor nanocrystals.

14. The process of claim 9 wherein said concentration of said first surfactant in said binary mixture of surfactants is increased sufficiently to permit growth of substantially spherical semiconductor nanocrystals in said binary mixture of surfactants.

15. The process of claim 9 wherein said concentration of said second surfactant in said binary mixture of surfactants is increased sufficiently to permit growth of rod-like semiconductor nanocrystals in said binary mixture of surfactants.

16. The process of claim 9 wherein said heated binary mixture of surfactants comprises two different phosphorus-containing surfactants.

17. The process of claim 16 wherein said second phosphorus-containing surfactant in said binary mixture of surfactants in said binary mixture comprises a phosphorus-containing organic acid.

18. The process of claim 17 wherein said phosphorus-containing organic acid second surfactant comprises a phosphonic acid surfactant having the formula ROP(OH)₂, where R is a 3-18 carbon organic group.

19. The process of claim 17 wherein said phosphorus-containing organic acid second surfactant is a phosphinic acid having the formula R′

R_xH<sub>(1−

x)</sub>POOH, where R and R′

are the same or different 3-18 carbon organic groups and x is 0-1.

20. A process for forming shaped Group III-V semiconductor nanocrystals in a heated binary mixture of surfactants which comprises:

a) forming a solution comprising;

i) a first semiconductor precursor comprising one or more particular Group III metals, or compounds containing one or more particular Group III metals;

ii) a second semiconductor precursor comprising one or more particular Group V elements, or compounds containing one or more particular Group V elements; and

iii) a liquid which is a solvent for said first and second precursors;

b) forming a binary mixture of high boiling phosphorus-containing organic surfactants comprising;

i) a first surfactant capable of promoting the growth of spherical semiconductor nanocrystals when a sufficient amount of said surfactant is present in said binary mixture of surfactants; and

ii) a second surfactant comprises a phosphorus-containing organic acid surfactant capable of promoting the growth of rod-like semiconductor nanocrystals when a sufficient amount of said surfactant is present in said binary mixture of surfactants;

c) adjusting the ratio of said first and second surfactants in said binary mixture to control the shape of said semiconductor nanocrystals to be formed therein;

d) heating said binary mixture of phosphorus-containing organic surfactants to a temperature sufficient to permit formation of Group III-V semiconductor nanocrystals therein;

e) adding said solution of Group III and Group V semiconductor nanocrystal precursors to said heated binary mixture of surfactants to form said semiconductor nanocrystals; and

f) subsequently reducing the temperature of said heated binary mixture of surfactants containing said semiconductor nanocrystals to stop said growth of said semiconductor nanocrystals.

21. The process of claim 20 wherein:

a) said heating step is carried out until said binary mixture of surfactants reaches a temperature at which said semiconductor nanocrystals will nucleate when said one or more solutions are added to said binary mixture;

b) said nucleation temperature is lowered to a crystal growth temperature during or after said step of adding said solution to said heated binary mixture of surfactants; and

c) said heated binary mixture of surfactants containing said one or more solutions is maintained at said crystal growth temperature until said step of reducing the temperature of said mixture containing said solution sufficiently to stop formation of said semiconductor nanocrystals.

22. The process of claim 21 wherein said nucleation temperature is lowered to a crystal growth temperature during said step of adding said solution of Group III and Group V semiconductor nanocrystal precursors to said heated binary mixture of surfactants by adding to said binary mixture of surfactants said solution of Group III and Group V semiconductor nanocrystal precursors at a temperature sufficiently lower than the temperature of said binary surfactant mixture to thereby cool said binary mixture of surfactants down to said crystal growth temperature as said solution of Group III and Group V semiconductor nanocrystal precursors is added to said heated binary mixture.

23. The process of claim 20 wherein said Group III metal is selected from the group consisting of:

Al, Ga, and In; and

said Group V element is selected from the group consisting of P, As, and Sb.

24. The process of claim 20 wherein said liquid which is a solvent for said first and second precursors comprises a polar organic solvent.

25. The process of claim 23 wherein said solvent comprises a trialkyl phosphine.

26. The process of claim 20 wherein said first surfactant in said binary mixture of surfactants is selected from the group consisting of a 3-18 carbon tri-alkyl phosphine and a 3-18 carbon tri-alkyl phosphine oxide.

27. The process of claim 20 wherein said phosphorus-containing organic acid second surfactant in said binary mixture comprises phosphonic acid having the formula ROP(OH)₂, where R is a 3-18 carbon organic group.

28. The process of claim 20 wherein said phosphonic acid second surfactant comprises hexyl-phosphonic acid.

29. The process of claim 20 wherein said phosphorus-containing organic acid second surfactant is a phosphinic acid having the formula R′

R_xH<sub>(1−

x)</sub>POOH, where R and R′

are the same or different 3-18 carbon organic groups and x is 0-1.

30. A Group III-V semiconductor nanocrystal having a rod-like shape formed by reacting together a precursor containing one or more Group III metals selected from the group consisting of Al, Ga, and In with a precursor containing one or more Group V elements selected from the group consisting of P, As, and Sb in a binary mixture of surfactants including a phosphorus-containing organic acid surfactant capable of promoting growth of rod-like semiconductor nanocrystals when a sufficient amount of said surfactant is present in said binary mixture of surfactants.