# US 8,771,822 B2 · Methods for the growth of three-dimensional nanorod networks

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- Number: US 8,771,822 B2
- Document ID: US8771822B2
- Status: Granted
- Kind: B2
- Application number: 13/008,170
- Filed: 2011-01-18
- Published: 2012-07-19
- Granted: 2014-07-08
- Earliest claimed: 2011-01-18
- Assignees: Wisconsin Alumni Research Foundation
- Applicants: Xudong Wang; Jian Shi
- Inventors: Xudong Wang; Jian Shi
- Web page: https://patentgrep.com/patent/US8771822B2

## CPC

- C30B 25/005: {Growth of whiskers or needles}
- B82Y 30/00: Nanotechnology for materials or surface science, e.g. nanocomposites
- B82Y 40/00: Manufacture or treatment of nanostructures
- C30B 25/18: characterised by the substrate
- C30B 29/16: Oxides
- C30B 29/60: characterised by shape
- Y10T 428/24355: Continuous and nonuniform or irregular surface on layer or component [e.g., roofing, etc.]
- Y10T 428/24612: Composite web or sheet
- Y10T 428/2918: including free carbon or carbide or therewith [not as steel]
- C30B: SINGLE-CRYSTAL GROWTH (by using ultra-high pressure, e.g. for the formation of diamonds, B01J3/06); UNIDIRECTIONAL SOLIDIFICATION OF EUTECTIC MATERIAL OR UNIDIRECTIONAL DEMIXING OF EUTECTOID MATERIAL; REFINING BY ZONE-MELTING OF MATERIAL (zone-refining of metals or alloys C22B); PRODUCTION OF A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE (casting of metals, casting of other substances by the same processes or devices B22D; working of plastics B29; modifying the physical structure of metals or alloys C21D, C22F); SINGLE CRYSTALS OR HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; AFTER-TREATMENT OF SINGLE CRYSTALS OR A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE (for producing semiconductor devices or parts thereof H10); APPARATUS THEREFOR
- B82Y: SPECIFIC USES OR APPLICATIONS OF NANOSTRUCTURES; MEASUREMENT OR ANALYSIS OF NANOSTRUCTURES; MANUFACTURE OR TREATMENT OF NANOSTRUCTURES
- Y10T: TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION

## Abstract

Methods for growing a three-dimensional nanorod network in three-dimensional growth spaces, including highly confined spaces, are provided. The methods are derived from atomic layer deposition (ALD) processes, but use higher temperatures and extended pulsing and/or purging times. Through these methods, networks of nanorods can be grown uniformly along the entire inner surfaces of confined growth spaces.

## Claims

### Claim 1

A three-dimensional nanorod network comprising:
(a) a substrate that defines at least one three-dimensional growth space having at least one nanoscale dimension; and
(b) a plurality of nanorods extending outwardly from the substrate surface and into the at least one three-dimensional growth space, wherein the plurality of nanorods are uniformly distributed on the substrate surface in the at least one growth space, and wherein the nanorods are metal oxide nanorods, and wherein the metal oxide is TiO2.

### Claim 2

A three-dimensional nanorod network comprising:
(a) a substrate that defines one or more three-dimensional growth spaces having at least one nanoscale dimension; and
(b) a plurality of single-crystalline nanorods extending outwardly from the substrate surface and into the three-dimensional growth spaces, wherein the plurality of nanorods are uniformly distributed on the substrate surface in the growth spaces, the nanorod network having a roughness factor of at least 3000.

### Claim 3

A three-dimensional nanorod network comprising:
(a) a substrate that defines at least one three-dimensional growth space having at least one nanoscale dimension; and
(b) a plurality of single-crystalline nanorods extending outwardly from the substrate surface and into the at least one three-dimensional growth space, the nanorods having a solid cross-section along their lengths, wherein the plurality of nanorods are uniformly distributed on the substrate surface in the at least one growth space, further wherein the substrate defines a plurality of three-dimensional growth spaces comprising elongated channels having nanoscale diameters and the nanorods extend inwardly from the walls of the elongated channels, and further wherein at least some of the nanorods are merged at their roots.

### Claim 4 (depends on 3)

The nanorod network of claim 3, wherein the substrate is an anodized aluminum oxide membrane.

### Claim 5

A three-dimensional nanorod network comprising:
(a) a substrate that defines at least one three-dimensional growth space having at least one nanoscale dimension; and
(b) a plurality of single-crystalline nanorods extending outwardly from the substrate surface and into the at least one three-dimensional growth space, the nanorods having a solid cross-section along their lengths, wherein the plurality of nanorods are uniformly distributed on the substrate surface in the at least one growth space, the nanorod network characterized in that the nanorods are sufficiently dense and interlinked that they are able to provide a free-standing, nanorod network upon the removal of the substrate, wherein the free-standing, nanorod network is in the form of a tubular assemblage in which nanorods are merged at their roots.

### Claim 6

A three-dimensional nanorod network comprising:
(a) a substrate that defines at least one three-dimensional growth space having at least one nanoscale dimension; and
(b) a plurality of single-crystalline nanorods extending outwardly from the substrate surface and into the at least one three-dimensional growth space, the nanorods having a solid cross-section along their lengths, wherein the plurality of nanorods are uniformly distributed on the substrate surface in the at least one growth space, and further wherein the at least one three-dimensional growth space comprises the inter-nanostructure volume defined by a matrix of nanostructures, wherein the average center-to-center distance between the nanostructures in the matrix is no greater than about 2 μm.

### Claim 7 (depends on 6)

The nanorod network of claim 6, wherein the longest nanorods have lengths that are at least as long as the smallest dimension of the at least one growth space.

### Claim 8 (depends on 6)

The nanorod network of claim 6, wherein the substrate and the nanorods are formed from different materials.

### Claim 9 (depends on 6)

The nanorod network of claim 6, wherein the nanorods form a continuous coating on the surface of the substrate within the at least one growth space.

### Claim 10 (depends on 6)

The nanorod network of claim 6 wherein the substrate defines a plurality of three-dimensional growth spaces comprising elongated channels having nanoscale diameters and the nanorods extend inwardly from the walls of the elongated channels.

### Claim 11 (depends on 10)

The nanorod network of claim 10, wherein at least some of the nanorods are sufficiently long to extend across the diameter of the elongated channels.

### Claim 12 (depends on 10)

The nanorod network of claim 10, wherein the average length of the nanorods within the channels does not change as a function of nanorod position along the length of the channels.

### Claim 13 (depends on 6)

The nanorod network of claim 6, wherein at least some of the nanorods within the inter-nanostructure volume are sufficiently long to extend from one nanostructure of the matrix to another nanostructure of the matrix.

### Claim 14 (depends on 6)

The nanorod network of claim 6, wherein the matrix of nanostructures comprises a matrix of aligned nanoscale pillars.

### Claim 15 (depends on 6)

The nanorod network of claim 6, wherein the matrix of nanostructures comprises a matrix of nanoscale particles.

### Claim 16 (depends on 6)

The nanorod network of claim 6, characterized in that the nanorods are sufficiently dense and interlinked that they are able to provide a free-standing, nanorod network upon the removal of the substrate.

### Claim 17 (depends on 6)

The nanorod network of claim 6, wherein the at least one three-dimensional growth space comprises the inter-nanostructure volume defined by a regular array of pillars having nanoscale diameters.

### Claim 18 (depends on 6)

The nanorod network of claim 6, wherein the at least one three-dimensional growth space comprises the inter-nanostructure volume defined by a regular array of nanospheres having nanoscale diameters.

### Claim 19 (depends on 6)

The nanorod network of claim 6, wherein the substrate defines a plurality of three-dimensional growth spaces, the majority of the three-dimensional growth spaces having at least one nanoscale dimension.

### Claim 20 (depends on 6)

The nanorod network of claim 6, wherein the average center-to-center distance between the nanostructures in the matrix is no greater than about 1 μm.