Nanowire arrays

• US 6,359,288 B1
• Filed: 04/22/1998
• Issued: 03/19/2002
• Est. Priority Date: 04/24/1997
• Status: Expired due to Fees

• Current Assignee: Massachusetts Institute of Technology
• Original Assignee: Massachusetts Institute of Technology
• Inventors: Zhang, Lei, Zhang, Zhibo, Ying, Jackie Y., Dresselhaus, Mildred S.
• Primary Examiner(s): Jackson, Jr., Jerome
• Assistant Examiner(s): BAUMEISTER, BRADLEY W
• Application Number:
  US09/064,242
• Time in Patent Office: 1,427 Days
• Field of Search: 257/9, 257/28, 257/30, 257/29, 257/14, 205/173, 205/174, 205/202, 428/606, 428/613, 428/614, 428/620, 428/629, 428/472.2, 438/962
• US Class Current: 257/14
• CPC Class Codes: B82B 1/00 Nanostructures formed by manipulation of individual atoms or molecules, or limited collections of atoms or molecules as discrete units
• CPC Class Codes: B82Y 30/00 Nanotechnology for materials or surface science, e.g. nanocomposites
• CPC Class Codes: C30B 11/00 Single-crystal growth by normal freezing or freezing under temperature gradient, e.g. Bridgman-Stockbarger method C30B13/00, C30B15/00, C30B17/00, C30B19/00 take precedence; under a protective fluid C30B27/00
• CPC Class Codes: C30B 29/02 Elements
• CPC Class Codes: C30B 29/605 Products containing multiple oriented crystallites, e.g. columnar crystallites
• CPC Class Codes: H01L 21/31111 by chemical means
• CPC Class Codes: H01L 21/76885 By forming conductive members before deposition of protective insulating material, e.g. pillars, studs
• CPC Class Codes: Y10S 977/762 Nanowire or quantum wire, i.e. axially elongated structure having two dimensions of 100 nm or less
• CPC Class Codes: Y10S 977/781 Possessing nonosized surface openings that extend partially into or completely through the host material
• CPC Class Codes: Y10S 977/888 Shaping or removal of materials, e.g. etching
• CPC Class Codes: Y10T 428/12431 Foil or filament smaller than 6 mils
• CPC Class Codes: Y10T 428/12486 Laterally noncoextensive components [e.g., embedded, etc.]
• CPC Class Codes: Y10T 428/1259 Oxide

Abstract

An array of nanowires having a relatively constant diameter and techniques and apparatus for fabrication thereof are described. In one embodiment, a technique for melting a material under vacuum and followed by pressure injection of the molten material into the pores of a porous substrate produces continuous nanowires. In another embodiment, a technique to systematically change the channel diameter and channel packing density of an anodic alumina substrate includes the steps of anodizing an aluminum substrate with an electrolyte to provide an anodic aluminum oxide film having a pore with a wall surface composition which is different than aluminum oxide and etching the pore wall surface with an acid to affect at least one of the surface properties of the pore wall and the pore wall composition.

Claims

1. An nanowire array comprising:

a substrate having a plurality of non-interconnected pores each of the plurality of pores having a mean pore diameter which does not vary by more than 100% along the length of the pore; and

a material continuously filled in each of the plurality of pores of the substrate such that the material in each of the plurality of non-interconnected pores corresponds to a single crystal quantum wire with each of the single crystal quantum wires having substantially the same crystal orientation.

2. The nanowire array of claim 1 wherein:

each of the a single crystal quantum wires is provided having a length not less than three microns; and

the diameters of each of the plurality of pores are in the range of about 1 nanometer to about 300 nanometers.

3. The nanowire array of claim 2 wherein the diameters of each of the plurality of pores are in the range of about 1 nanometer to about 100 nanometers.

4. The nanowire array of claim 2 wherein the diameters of each of the plurality of pores are in the range of about 1 nanometer to about 50 nanometers.

5. The nanowire array of claim 2 wherein the mean diameter of each of the pores do not vary by more than 50% along the length of the pore.

6. The nanowire array of claim 2 wherein the mean diameter of each of the pores do not vary by more than 20% along the length of the pore.

7. The nanowire array of claim 1 wherein each of the plurality of pores in said substrate have a pore wall surface exposed to an electrolyte solution selected from the group of:

(1) an H₂SO₄ solution;

(2) an solution of H₂C₂O₄; and

(3) an H₃PO₄ solution to thereby change the composition of the pore walls to reduce a contact angle between the pore walls and the material in the molten state.

8. The nanowire array of claim 1 wherein said material continuously filling each of the plurality of pores is solidified from a pressure injected metal in a molten state.

9. An array of nanowires comprising:

a substrate having a plurality of pores provided therein, with each of the pores having a pore wall surface composition provided by last exposing the pore walls to an H₂SO₄ electrolyte solution to provide the pore walls having a contact angle which reduces the amount of pressure needed to fill the pore using a pressure injection process; and

a nanowire disposed in each of the pores, each of the nanowires having a single crystal structure and each of the single crystal nanowires having substantially the same crystal orientation and a packing density greater than 4.6×

10¹⁰ cm<sup>−

2</sup>.

10. The array of nanowires as recited in claim 9 wherein said means for supporting comprises an anodic aluminum oxide film.

11. The array of nanowires as recited in claim 9 wherein said means for supporting comprises a substrate comprised of a mesoporous material.

12. The array of nanowires as recited in claim 11 wherein said mesoporous material is mesoporous siliceous MCM-41.

13. The array of nanowires as recited in claim 9 wherein each of the nanowires have an average wire diameter in the range of about 1 nm to about 20 nm.