Semiconductor structure having nanocrystalline core and nanocrystalline shell

• US 9,153,734 B2
• Filed: 05/28/2013
• Issued: 10/06/2015
• Est. Priority Date: 11/09/2011
• Status: Active Grant

• Current Assignee: Osram Opto Semiconductors GmbH (Ams-Osram AG)
• Original Assignee: Pacific Light Technologies Corp. (Ams-Osram AG)
• Inventors: Kurtin, Juanita N., Carillo, Matthew J., Hughes, Steven M.
• Primary Examiner(s): Le, Thao X
• Assistant Examiner(s): SWAN, GARDNER W.S
• Application Number:
  US13/903,875
• Publication Number:
  US 20130323872A1
• Time in Patent Office: 861 Days
• Field of Search: 257/13, 257/17, 257/22, 257/E21.09, 257/E29.071, 257/E29.082, 313/498, 313/499, 438/962, 252/301.6 R, 977/774
• US Class Current: 1/1
• CPC Class Codes: B01J 13/02 Making microcapsules or microballoons for medical preparations A61K9/50
• CPC Class Codes: B82Y 30/00 Nanotechnology for materials or surface science, e.g. nanocomposites
• CPC Class Codes: B82Y 40/00 Manufacture or treatment of nanostructures
• CPC Class Codes: B82Y 99/00 Subject matter not provided for in other groups of this subclass
• CPC Class Codes: C01B 19/007 Tellurides or selenides of metals C01B19/002 takes precedence
• CPC Class Codes: C01P 2002/84 by UV- or VIS- data
• CPC Class Codes: C01P 2004/04 obtained by TEM, STEM, STM or AFM
• CPC Class Codes: C01P 2004/10 extending in one dimension, e.g. needle-like
• CPC Class Codes: C01P 2004/54 Particles characterised by their aspect ratio, i.e. the ratio of sizes in the longest to the shortest dimension
• CPC Class Codes: C01P 2004/64 Nanometer sized, i.e. from 1-100 nanometer
• CPC Class Codes: C01P 2004/80 Particles consisting of a mixture of two or more inorganic phases
• CPC Class Codes: C09K 11/02 Use of particular materials as binders, particle coatings or suspension media therefor
• CPC Class Codes: C09K 11/025 non-luminescent particle coatings or suspension media
• CPC Class Codes: C09K 11/565 with zinc cadmium
• CPC Class Codes: C09K 11/883 with zinc or cadmium
• CPC Class Codes: H01L 21/02422 Non-crystalline insulating materials, e.g. glass, polymers
• CPC Class Codes: H01L 21/02557 Sulfides
• CPC Class Codes: H01L 21/0256 Selenides
• CPC Class Codes: H01L 21/02601 Nanoparticles fullerenes H10K85/211
• CPC Class Codes: H01L 21/02628 using solutions
• CPC Class Codes: H01L 33/002 : having heterojunctions or graded gap
• CPC Class Codes: H01L 33/005 : Processes
• CPC Class Codes: H01L 33/04 : with a quantum effect structure or superlattice, e.g. tunnel junction
• CPC Class Codes: H01L 33/06 : within the light emitting region, e.g. quantum confinement structure or tunnel barrier
• CPC Class Codes: H01L 33/502 : Wavelength conversion materials

Abstract

A method of fabricating a semiconductor structure involves forming an anisotropic nanocrystalline core from a first semiconductor material, the anisotropic nanocrystalline core having an aspect ratio between, but not including, 1.0 and 2.0, and forming a nanocrystalline shell from a second, different, semiconductor material to at least partially surround the anisotropic nanocrystalline core.

Claims

1. A method of fabricating a semiconductor structure, the method comprising:

forming an anisotropic nanocrystalline core from a first semiconductor material, the anisotropic nanocrystalline core having an aspect ratio between, but not including, 1.0 and 2.0; and

forming a nanocrystalline shell from a second, different, semiconductor material to completely surround the anisotropic nanocrystalline core, wherein the nanocrystalline shell has a center, wherein the nanocrystalline shell extends in a first direction along a first axis and extends in a second direction along a second axis perpendicular to the first axis, and wherein the anisotropic nanocrystalline core is formed off-center with respect to the nanocrystalline shell in the first direction along the first axis and off-center with respect to the nanocrystalline shell in the second direction along the second axis, and wherein the nanocrystalline shell is longer in the first direction than in the second direction.

2. The method of claim 1, further comprising:

prior to forming the nanocrystalline shell, stabilizing the anisotropic nanocrystalline core in solution with a surfactant.

3. The method of claim 2, wherein the surfactant is octadecylphosphonic acid (ODPA).

4. The method of claim 2, wherein the surfactant acts as a ligand for the anisotropic nanocrystalline core, the method further comprising:

prior to forming the nanocrystalline shell, replacing the surfactant ligand with a second ligand, the second ligand more labile than the surfactant ligand.

5. The method of claim 4, wherein the second ligand is selected from the group consisting of a primary amine and a secondary amine.

6. The method of claim 1, wherein forming the nanocrystalline shell comprises forming the second semiconductor material in the presence of a mixture of surfactants.

7. The method of claim 6, wherein the mixture of surfactants comprises a mixture of octadecylphosphonic acid (ODPA) and hexylphosphonic acid (HPA).

8. The method of claim 7, wherein forming the nanocrystalline shell comprises tuning the aspect ratio of the nanocrystalline shell by tuning the ratio of ODPA versus HPA.

9. The method of claim 7, wherein forming the second semiconductor material in the presence of the mixture of surfactants comprises using a solvent selected from the group consisting of trioctylphosphine oxide (TOPO) and trioctylphosphine (TOP).

10. The method of claim 1, wherein forming the anisotropic nanocrystalline core comprises forming at a temperature approximately in the range of 350-380 degrees Celsius.

11. The method of claim 1, wherein forming the anisotropic nanocrystalline core comprises forming a cadmium selenide (CdSe) nanocrystal from cadmium oxide (CdO) and selenium (Se) in the presence of a surfactant at a temperature approximately in the range of 300-400 degrees Celsius, and arresting the reaction prior to completion.

12. The method of claim 11, wherein forming the nanocrystalline shell comprises forming a cadmium sulfide (CdS) nanocrystalline layer on the CdSe nanocrystal from cadmium oxide (CdO) and sulfur (S) at a temperature approximately in the range of 120-380 degrees Celsius, and arresting the reaction prior to completion.

13. A method of fabricating a semiconductor structure, the method comprising:

forming an anisotropic nanocrystalline core from a first semiconductor material; and

forming a nanocrystalline shell from a second, different, semiconductor material to completely surround the anisotropic nanocrystalline core, wherein the nanocrystalline shell has a center, wherein the nanocrystalline shell extends in a first direction along a first axis and extends in a second direction along a second axis perpendicular to the first axis, and wherein the anisotropic nanocrystalline core is formed off-center with respect to the nanocrystalline shell in the first direction along the first axis and off-center with respect to the nanocrystalline shell in the second direction along the second axis, and wherein the nanocrystalline shell is longer in the first direction than in the second direction.

14. The method of claim 13, further comprising:

prior to forming the nanocrystalline shell, stabilizing the anisotropic nanocrystalline core in solution with a surfactant.

15. The method of claim 14, wherein the surfactant is octadecylphosphonic acid (ODPA).

16. The method of claim 14, wherein the surfactant acts as a ligand for the anisotropic nanocrystalline core, the method further comprising:

prior to forming the nanocrystalline shell, replacing the surfactant ligand with a second ligand, the second ligand more labile than the surfactant ligand.

17. The method of claim 16, wherein the second ligand is selected from the group consisting of a primary amine and a secondary amine.

18. The method of claim 13, wherein forming the nanocrystalline shell comprises forming the second semiconductor material in the presence of a mixture of surfactants.

19. The method of claim 18, wherein the mixture of surfactants comprises a mixture of octadecylphosphonic acid (ODPA) and hexylphosphonic acid (HPA).

20. The method of claim 19, wherein forming the nanocrystalline shell comprises tuning the aspect ratio of the nanocrystalline shell by tuning the ratio of ODPA versus HPA.

21. The method of claim 19, wherein forming the second semiconductor material in the presence of the mixture of surfactants comprises using a solvent selected from the group consisting of trioctylphosphine oxide (TOPO) and trioctylphosphine (TOP).

22. The method of claim 13, wherein forming the anisotropic nanocrystalline core comprises forming at a temperature approximately in the range of 350-380 degrees Celsius.

23. The method of claim 13, wherein forming the anisotropic nanocrystalline core comprises forming a cadmium selenide (CdSe) nanocrystal from cadmium oxide (CdO) and selenium (Se) in the presence of a surfactant at a temperature approximately in the range of 300-400 degrees Celsius, and arresting the reaction prior to completion.

24. The method of claim 23, wherein forming the nanocrystalline shell comprises forming a cadmium sulfide (CdS) nanocrystalline layer on the CdSe nanocrystal from cadmium oxide (CdO) and sulfur (S) at a temperature approximately in the range of 120-380 degrees Celsius, and arresting the reaction prior to completion.