Synthesis of metal oxide surfaces and interfaces with crystallographic control using solid-liquid-vapor etching and vapor-liquid-solid growth

• US 10,312,081 B2
• Filed: 12/06/2016
• Issued: 06/04/2019
• Est. Priority Date: 07/15/2016
• Status: Active Grant

• Current Assignee: University Of Kentucky Research Foundation (University of Kentucky)
• Original Assignee: University Of Kentucky Research Foundation (University of Kentucky)
• Inventors: Guiton, Beth S., Yu, Lei
• Primary Examiner(s): Deo, Duy Vu N
• Application Number:
  US15/370,041
• Publication Number:
  US 20180019122A1
• Time in Patent Office: 910 Days
• CPC Class Codes: C30B 1/00 Single-crystal growth directly from the solid state unidirectional demixing of eutectoid materials C30B3/00; under a protective fluid C30B27/00
• CPC Class Codes: C30B 11/12 Vaporous components, e.g. vapour-liquid-solid-growth
• CPC Class Codes: C30B 29/16 Oxides
• CPC Class Codes: C30B 29/60 characterised by shape
• CPC Class Codes: H01L 21/02381 Silicon, silicon germanium, germanium
• CPC Class Codes: H01L 21/02414 Oxide semiconducting materials not being Group 12/16 materials, e.g. ternary compounds
• CPC Class Codes: H01L 21/0242 Crystalline insulating materials
• CPC Class Codes: H01L 21/0243 Surface structure
• CPC Class Codes: H01L 21/02433 Crystal orientation
• CPC Class Codes: H01L 21/02521 Materials
• CPC Class Codes: H01L 21/02554 Oxides
• CPC Class Codes: H01L 21/02603 Nanowires
• CPC Class Codes: H01L 21/02639 Preparation of substrate for selective deposition
• CPC Class Codes: H01L 21/02645 Seed materials
• CPC Class Codes: H01L 21/02653 Vapour-liquid-solid growth
• CPC Class Codes: H01L 31/18 Processes or apparatus specially adapted for the manufacture or treatment of these devices or of parts thereof

Abstract

The present invention provides integrated nanostructures comprising a single-crystalline matrix of a material A containing aligned, single-crystalline nanowires of a material B, with well-defined crystallographic interfaces are disclosed. The nanocomposite is fabricated by utilizing metal nanodroplets in two subsequent catalytic steps: solid-liquid-vapor etching, followed by vapor-liquid-solid growth. The first etching step produces pores, or “negative nanowires” within a single-crystalline matrix, which share a unique crystallographic direction, and are therefore aligned with respect to one another. Further, since they are contained within a single, crystalline, matrix, their size and spacing can be controlled by their interacting strain fields, and the array is easily manipulated as a single entity—addressing a great challenge to the integration of freestanding nanowires into functional materials. In the second, growth, step, the same metal nanoparticles are used to fill the pores with single-crystalline nanowires, which similarly to the negative nanowires have unique growth directions, and well-defined sizes and spacings. The two parts of this composite behave synergistically, since this nanowire-filled matrix contains a dense array of well-defined crystallographic interfaces, in which both the matrix and nanowire materials convey functionality to the material. The material of either one of these components may be chosen from a vast library of any material able to form a eutectic alloy with the metal in question, including but not limited to every material thus far grown in nanowire form using the ubiquitous vapor-liquid-solid approach. This has profound implications for the fabrication of any material intended to contain a functional interface, since high interfacial areas and high quality interfacial structure should be expected. Technologies to which this simple approach could be applied include but are not limited to p-n junctions of solar cells, battery electrode arrays, multiferroic materials, and plasmonic materials.

Claims

1. A method for synthesizing a nanocomposite of aligned nanowires within a crystalline matrix comprising:

(a) depositing at least two metal nanodroplets on a surface of a metal oxide single crystalline matrix;

(b) etching negative nanowires into the surface of the crystalline matrix by solid-liquid-vapor etching with the metal nanodroplets; and

(c) filling the negative nanowires from (b) by vapor-liquid-solid growth with a metal oxide reactant vapor and the metal nanodroplets to form nanowires within the crystalline matrix, wherein the reactant vapor is a second material to the metal oxide of the crystalline matrix.

2. The method of claim 1, further comprising removing the metal nanodroplets after step (c).

3. The method of claim 1, wherein the crystalline matrix is selected from the group consisting of SnO₂, ZnO, MgO, Ga₂O₃, TiO₂, In₂O₃, Fe₂O₃, Fe₃O₄, CdO, γ

-Al₂O₃, CaO, NiO, MnO, Eu₂O₃, and Sm₂O₃.

4. The method of claim 1, wherein the metal nanodroplets comprise a metal selected from the group consisting of gold, gallium, silver, copper and platinum.

5. The method of claim 1, wherein the reactant vapor is selected from the group consisting of SnO₂, ZnO, MgO, Ga₂O₃, TiO₂, In₂O₃, Fe₂O₃, Fe₃O₄, CdO, γ

-Al₂O₃, CaO, NiO, MnO, Eu₂O₃, Sm₂O₃ and elements contained therein.

6. The method of claim 1, wherein the reactant vapor comprises a group IV or group 14 element, a III-V material or a II-VI material.

7. The method of claim 1, wherein the etched negative nanowire is etched vertically with respect to the surface of the crystalline matrix.

8. The method of claim 1, wherein the etched negative nanowire is etched horizontally along the surface of the crystalline matrix.

9. The method of claim 1, wherein the etched negative nanowire is etched at an angle with respect to the surface of the crystalline matrix.

10. The method of claim 1, further comprising continuing growth of the nanowire such that it protrudes above the surface of the crystalline matrix.

11. The method of claim 1, wherein growth of the nanowire is discontinued such that the nanowire only partially fills the negative nanowire.

12. The method of claim 1, wherein the metal nanodroplets are embedded into the crystalline matrix in (b) at the base of the etched negative nanowire.

13. The method of claim 1, wherein the negative nanowire in (b) is etched to a depth to provide an adhesive force between the metal nanodroplet and walls of the negative nanowire.

14. The method of claim 1, wherein the formed nanowires are contained within the crystalline matrix.

15. The method of claim 1, wherein the formed nanowires extend beyond the surface of the crystalline matrix.

16. The method of claim 1, wherein the nanodroplets reside at the tip of the formed nanowires.