# US 7,687,876 B2 · Controlled growth of a nanostructure on a substrate

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- Number: US 7,687,876 B2
- Document ID: US7687876B2
- Status: Granted
- Kind: B2
- Application number: 11/412,060
- Filed: 2006-04-25
- Published: 2009-04-30
- Granted: 2010-03-30
- Earliest claimed: 2005-04-25
- Assignees: Smoltek AB
- Inventors: Mohammad Shafiqul Kabir
- Web page: https://patentgrep.com/patent/US7687876B2

## CPC

- C23C 16/04: Coating on selected surface areas, e.g. using masks
- B82Y 10/00: Nanotechnology for information processing, storage or transmission, e.g. quantum computing or single electron logic
- B82Y 30/00: Nanotechnology for materials or surface science, e.g. nanocomposites
- B82Y 40/00: Manufacture or treatment of nanostructures
- C01B 32/162: characterised by catalysts
- C23C 16/26: Deposition of carbon only
- D01F 9/08: of inorganic material (working or processing of metal wire B21F; from softened glass, minerals or slags C03B37/00)
- D01F 9/127: by thermal decomposition of hydrocarbon gases or vapours {or other carbon-containing compounds in the form of gas or vapour, e.g. carbon monoxide, alcohols}
- H01J 1/304: Field-emissive cathodes
- H01J 3/022: {with microengineered cathode, e.g. Spindt-type}
- H01J 9/025: {of field emission cathodes}
- H10K 71/12: using liquid deposition, e.g. spin coating
- H10K 85/221: {Carbon nanotubes}
- C01B 2202/34: Length
- C01B 2202/36: Diameter
- H01J 2201/30469: Carbon nanotubes (CNTs)
- H01J 2237/31786: Field-emitting cathode
- H10K 10/462: {Insulated gate field-effect transistors [IGFETs]}
- Y10S 977/813: Of specified inorganic semiconductor composition, e.g. periodic table group IV-VI compositions
- Y10S 977/827: formed from hybrid organic/inorganic semiconductor compositions
- Y10S 977/832: having specified property, e.g. lattice-constant, thermal expansion coefficient
- Y10S 977/932: for electronic or optoelectronic application
- Y10S 977/939: Electron emitter, e.g. spindt emitter tip coated with nanoparticles
- C23C: COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL (making metal-coated products by extrusion B21C23/22; covering with metal by connecting pre-existing layers to articles, see the relevant places, e.g. B21D39/00, B23K; metallising of glass C03C; metallising mortars, concrete, artificial stone, ceramics or natural stone C04B41/00; enamelling of, or applying a vitreous layer to, metals C23D; treating metal surfaces or coating of metals by electrolysis or electrophoresis C25D; single-crystal film growth C30B; by metallising textiles D06M11/83; decorating textiles by locally metallising D06Q1/04)
- B82Y: SPECIFIC USES OR APPLICATIONS OF NANOSTRUCTURES; MEASUREMENT OR ANALYSIS OF NANOSTRUCTURES; MANUFACTURE OR TREATMENT OF NANOSTRUCTURES
- C01B: NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; {METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C}
- D01F: CHEMICAL FEATURES IN THE MANUFACTURE OF ARTIFICIAL FILAMENTS, THREADS, FIBRES, BRISTLES OR RIBBONS; APPARATUS SPECIALLY ADAPTED FOR THE MANUFACTURE OF CARBON FILAMENTS
- H01J: ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS (spark-gaps H01T; electric arc lamps H05B31/00; particle accelerators H05H)
- H10K: ORGANIC ELECTRIC SOLID-STATE DEVICES
- Y10S: TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS

## Abstract

The present invention provides for nanostructures grown on a conducting substrate, and a method of making the same. The nanostructures grown according to the claimed method are suitable for manufacturing electronic devices such as an electron beam writer, and a field emission display.

## Claims

### Claim 1

A nanostructure assembly comprising:
a conducting substrate;
a nanostructure supported by the conducting substrate; and
a plurality of intermediate layers between the conducting substrate and the nanostructure,
wherein at least two of the plurality of intermediate layers are interdiffused, and
wherein material of the at least two of the plurality of intermediate layers that are interdiffused are present in the nanostructure, the plurality of intermediate layers including at least one layer that affects a morphology of the nanostructure and at least one layer to affect an electrical property of an interface between the conducting substrate and the nanostructure, and
wherein at least one of the plurality of intermediate layers comprises material selected from the group consisting of amorphous silicon and germanium.

### Claim 2 (depends on 1)

The nanostructure of claim 1 wherein the conducting substrate comprises a metal.

### Claim 3 (depends on 2)

The nanostructure of claim 2 wherein the metal is selected from the group consisting of tungsten, molybdenum, niobium, platinum and palladium.

### Claim 4 (depends on 1)

The nanostructure assembly of claim 1 wherein the plurality of intermediate layers comprises a metal layer and a layer of semiconducting material.

### Claim 5 (depends on 4)

The nanostructure of claim 4 wherein the layer of semiconducting material is amorphous silicon.

### Claim 6 (depends on 1)

The nanostructure assembly of claim 1, wherein the nanostructure is a carbon nanotube.

### Claim 7 (depends on 1)

The nanostructure assembly of claim 1, wherein the nanostructure is a carbon nanofiber.

### Claim 8 (depends on 7)

The nanostructure assembly of claim 7, wherein the nanostructure has a conical angle less than 2°.

### Claim 9 (depends on 1)

The nanostructure assembly of claim 1, wherein the nanostructure is made from a compound selected from the group consisting of: InP, GaAs, and AlGaAs.

### Claim 10 (depends on 1)

The nanostructure assembly of claim 1, wherein the plurality of intermediate layers form an Ohmic contact.

### Claim 11 (depends on 1)

The nanostructure assembly of claim 1, wherein the plurality of intermediate layers form a Schottky barrier.

### Claim 12 (depends on 1)

An array of nanostructure assemblies according to claim 1, wherein the conducting substrate is directly on a wafer of silicon, or oxidized silicon.

### Claim 13 (depends on 1)

The nanostructure assembly of claim 1, wherein the plurality of intermediate layers is between 1 nm and 1 μm thick.

### Claim 14 (depends on 1)

The nanostructure assembly of claim 1, wherein the intermediate layer adjacent to the nanostructure is a layer of catalyst, and wherein the catalyst is selected from the group consisting of Ni, Fe, Mo, NiCr, and Pd.

### Claim 15

A carbon nanostructure assembly comprising:
a conducting substrate;
a layer of amorphous silicon on the conducting substrate; and
a layer of catalyst on the layer of amorphous silicon,
wherein the carbon nanostructure is disposed on the catalyst, and
wherein the layer of catalyst and the layer of amorphous silicon are interdiffused, and wherein material of the layer of catalyst and the layer of amorphous silicon that are interdiffused are present in the carbon nanostructure.

### Claim 16

A method of forming a nanostructure, comprising:
depositing a layer of semiconducting material on a conducting substrate;
depositing one or more intermediate layers, wherein at least one of the one or more intermediate layers comprises material selected from the group consisting of amorphous silicon and germanium;
depositing a catalyst layer on the one or more intermediate layers;
without first annealing the substrate, causing the substrate to be heated to a temperature at which the nanostructure can form; and
growing the nanostructure on the catalyst layer at the temperature, wherein at least one of the one or more intermediate layers are interdiffused with the catalyst layer, and wherein material of the catalyst layer and the at least one of the one or more intermediate layers that are interdiffused are present in the nanostructure.

### Claim 17 (depends on 1)

The nanostructure assembly of claim 1, additionally comprising a catalyst layer adjacent to the nanostructure, wherein the plurality of intermediate layers are not the same material as the catalyst.

### Claim 18 (depends on 17)

The nanostructure assembly of claim 17, wherein the catalyst layer is supporting or supported by the nanostructure, and the plurality of intermediate layers lies between the conducting substrate and whichever of the nanostructure and the catalyst layer is closer to the conducting substrate.

### Claim 19 (depends on 17)

The nanostructure assembly of claim 17, wherein the catalyst in the catalyst layer is selected from Ni, Fe, Mo, NiCr, and Pd.

### Claim 20 (depends on 17)

The nanostructure assembly of claim 17, wherein the catalyst layer is supporting the nanostructure, and further comprising a second catalyst layer supported by the nanostructure.

### Claim 21 (depends on 1)

An array of carbon nanostructures supported on a substrate, wherein each carbon nanostructure in the array comprises a nanostructure assembly according to claim 1, and wherein said each carbon nanostructure is spaced apart from any other carbon nanostructure in the array by between 15 nm and 200 nm.

### Claim 22 (depends on 16)

The method of claim 16, wherein the method further comprises depositing a metal layer on the layer of semiconducting material, and wherein the catalyst layer is deposited on the metal layer, and wherein, during the growing, the metal layer interdiffuses with the catalyst layer, and wherein material of the metal layer and the catalyst layer that are interdiffused become present in the nanostructure.

### Claim 23 (depends on 5)

The nanostructure assembly of claim 5, wherein the plurality of intermediate layers include a catalyst layer, wherein the layer of amorphous silicon, the layer of catalyst, and at least one of the plurality of intermediate layers have interdiffused with each other, and wherein material of the layer of amorphous silicon, the layer of catalyst, and the at least one of the plurality of intermediate layers that are interdiffused are present in the nanostructure.

### Claim 24 (depends on 23)

The nanostructure assembly of claim 23, wherein the nanostructure has a tip and a base, and wherein material of the layer of amorphous silicon, the layer of catalyst, and the at least one of the plurality of intermediate layers that are interdiffused are present both at the tip and at the base of the nanostructure.

### Claim 25 (depends on 14)

The nanostructure assembly of claim 14, wherein the layer of catalyst has interdiffused with at least one of the plurality of intermediate layers, and wherein material of the layer of catalyst and the at least one of the plurality of intermediate layers that are interdiffused are present in the nanostructure.

### Claim 26 (depends on 25)

The nanostructure assembly of claim 25, wherein the nanostructure has a tip and a base, and wherein material of the layer of catalyst and the at least one of the plurality of intermediate layers that are interdiffused are present both at the tip and at the base of the nanostructure.

### Claim 27 (depends on 4)

The nanostructure assembly of claim 4, wherein the plurality of intermediate layers include a layer of catalyst, and wherein at least one of the plurality of intermediate layers has interdiffused into the metal layer and into the semiconducting layer, and wherein material of the layer of catalyst, the metal layer, and the semiconducting layer that are interdiffused are present in the nanostructure.

### Claim 28 (depends on 27)

The nanostructure assembly of claim 27, wherein the nanostructure has a tip and a base, and wherein material of the layer of catalyst, the metal layer, and the semiconducting layer that are interdiffused are present both at the tip and at the base of the nanostructure.

### Claim 29 (depends on 1)

The nanostructure assembly of claim 1 wherein the plurality of intermediate layers comprises:
a first control layer disposed on the conducting substrate;
a metal/semi-metal layer disposed on the first control layer, wherein the first control layer controls diffusion from the metal/semi-metal layer into the conducting substrate;
a second control layer disposed on the metal/semi-metal layer; and
one or more layers disposed on the second control layer.

### Claim 30 (depends on 29)

The nanostructure assembly of claim 29 wherein the first control layer comprises material selected from the group consisting of Ta, Ti, TiN, SiNx, SiOx, and Al2O3.

### Claim 31 (depends on 29)

The nanostructure assembly of claim 29 wherein the second control layer comprises high k dielectric material.

### Claim 32 (depends on 31)

The nanostructure assembly of claim 31 wherein the second control layer comprises material selected from the group consisting of ZrOx, HfOx, SiNx, Ta2O5, Al2O3, and TiO2.