# US 7,612,270 B1 · Nanoelectromechanical digital inverter

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- Number: US 7,612,270 B1
- Document ID: US7612270B1
- Status: Granted
- Kind: B1
- Application number: 12/099,989
- Filed: 2008-04-09
- Published: 2009-10-15
- Granted: 2009-11-03
- Earliest claimed: 2008-04-09
- Assignees: International Business Machines Corporation
- Inventors: Huilong Zhu
- Web page: https://patentgrep.com/patent/US7612270B1

## CPC

- H01H 1/0094: {Switches making use of nanoelectromechanical systems [NEMS]}
- H03K 19/20: characterised by logic function, e.g. AND, OR, NOR, NOT circuits (H03K19/003 - H03K19/01 take precedence)
- Y10S 977/724: Devices having flexible or movable element
- Y10S 977/742: Carbon nanotubes, CNTs
- H01H: ELECTRIC SWITCHES; RELAYS; SELECTORS; EMERGENCY PROTECTIVE DEVICES (contact cables H01B7/10; electrolytic self-interrupters H01G9/18; emergency protective circuit arrangements H02H; switching by electronic means without contact-making H03K17/00)
- H03K: PULSE TECHNIQUE (measuring pulse characteristics G01R; modulating sinusoidal oscillations with pulses H03C; transmission of digital information H04L; discriminator circuits detecting phase difference between two signals by counting or integrating cycles of oscillation H03D3/04; automatic control, starting, synchronisation or stabilisation of generators of electronic oscillations or pulses where the type of generator is irrelevant or unspecified H03L; coding, decoding or code conversion, in general H03M)
- Y10S: TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS

## Abstract

A digital inverter formed by three carbon nanotubes (CNTs) extending vertically from a substrate, one CNT functioning as first source (S1) and having a first logic signal applied to it, another CNT functioning as second source (S2) and having a second logic signal applied to it, a third CNT functioning as gate (G), and disposed between the two sources (S1, S2). A drain (D) contact is associated with the gate (G). A logic signal applied to the gate (G) causes one or the other of the sources (S1, S2) to deflect, contacting the drain (D) and transferring its logic signal thereto—such as logic “0” on the gate resulting in logic “1” (from one of the sources) being transferred to the drain (D), and logic “1” on the gate resulting in logic “0” (from the other of the sources) being transferred to the drain (D).

## Claims

### Claim 1

A digital inverter comprising:
a first carbon nanotube (CNT) extending from a substrate, and functioning as a first source (S1) for the digital inverter;
a second carbon nanotube (CNT) extending from the substrate, and functioning as a second source (S2) for the digital inverter;
a third carbon nanotube (CNT) extending from the substrate, and functioning as an input (G) of the digital inverter; and
a conductive structure disposed on the third CNT, and functioning as an output (D) of the digital inverter when either the first CNT or the second CNT are in contact with the conductive structure disposed on the third CNT.

### Claim 2 (depends on 1)

The digital inverter of claim 1, wherein:
the first CNT is disposed at a first distance from the third CNT; and
the second CNT is disposed at a second distance from the third CNT wherein said first and second distances are substantially the same.

### Claim 3 (depends on 2)

The digital inverter of claim 2, wherein:
the first and second CNTs are disposed on two sides of the third CNT.

### Claim 4 (depends on 1)

The digital inverter of claim 1, wherein:
the first, second, and third CNTs extend substantially vertically from the substrate.

### Claim 5 (depends on 1)

The digital inverter of claim 1, further comprising:
first, second, and third electrodes being disposed on a surface of the substrate,
wherein the first, second and third CNTs extend from corresponding said first, second and third electrodes.

### Claim 6 (depends on 5)

The digital inverter of claim 5, further comprising:
first, second, and third catalyst structures being disposed on the first, second, and third electrodes respectively,
wherein the first, second and third CNTs extend from corresponding said first, second and third catalyst structures.

### Claim 7 (depends on 1)

The digital inverter of claim 1, wherein:
the first, second and third CNTs have a height “H” of approximately 20-100 nm.

### Claim 8 (depends on 1)

The digital inverter of claim 1, wherein:
the first and second CNTs are sufficiently long to allow them to bend, and the third CNT (G) is sufficiently stiff to substantially prevent it from bending.

### Claim 9 (depends on 8)

The digital inverter of claim 8, wherein:
the first and second CNTs are selectively caused to bend and contact the third CNT (G).

### Claim 10 (depends on 1)

The digital inverter of claim 1, wherein:
in a first state, the first CNT deflects towards the third CNT and physically contacts the third CNT while the second CNT is isolated from the third CNT.

### Claim 11 (depends on 1)

The digital inverter of claim 1, wherein:
in a second state, the second CNT deflects towards the third CNT and physically contacts the third CNT while the first CNT is isolated from the third CNT.

### Claim 12 (depends on 1)

The digital inverter of claim 1, wherein:
said conductive structure is disposed near a top end of the third CNT (G).

### Claim 13

A method of for inverting a digital signal comprising:
providing a nanoelectromechanical digital inverter comprising first, second, and third elongated carbon nanotubes (CNTs) extending from a surface of a substrate;
providing a drain (d) for the digital inverter;
applying a first digital logic source signal to the first CNT which functions as a first source (S1) for of the digital inverter;
applying a second digital logic source signal to the second CNT which functions as a second source (S2) for of the digital inverter;
using the third CNT as a gate (G) for the digital inverter; and
applying a third digital logic signal to the gate (G) causing one of the first and second CNTs to deflect towards the third CNT and physically contact the third CNT whereby the drain outputs one of the first and second digital logic source signals which is the inverse of the third digital logic signal.

### Claim 14 (depends on 13)

The method of claim 13, further comprising:
disposing a conductive contact structure near a top end of the third CNT whereby:
when the first CNT deflects towards the third CNT, the first CNT physically contacts the conductive contact structure of the third CNT; and
when the second CNT deflects towards the third CNT, the second CNT physically contacts the conductive contact structure of the third CNT.

### Claim 15 (depends on 13)

The method of claim 13, including:
selecting the first and the second digital logic source signals to have a voltage difference ranging from 0.5 to 15 volts.

### Claim 16 (depends on 13)

The method of claim 13, including:
providing first and second CNTs that are sufficiently long to allow them to deflect; and
providing a sufficiently stiff third CNT (G) to substantially prevent it from deflecting.

### Claim 17 (depends on 16)

The method of claim 16, including:
disposing the first CNT at a first distance from the third CNT; and
disposing the second CNT at a second distance from the third CNT wherein said first and second distances are substantially the same.

### Claim 18 (depends on 17)

The method of claim 17, including:
disposing the first and second CNTs on two sides of the third CNT.

### Claim 19 (depends on 17)

The digital inverter of claim 17, including:
disposing first, second, and third electrodes on a surface of a substrate; and
extending the first, second and third CNTs from corresponding said first, second and third electrodes.

### Claim 20 (depends on 19)

The digital inverter of claim 19, including:
extending the first, second, and third CNTs substantially vertically from the substrate.