nanoelectronics final

Presented by:- Shikha Gupta (UE6558)

NANOELECTRONICS Branch of Engineering which uses

nanometer scale elements in design of integrated circuits such that one of the three dimensions of the electronic component is in nm.

Generally, Nanometer scale refers to electronic circuits less than 100nm.

1 nm= 10-9 metres

MOORE’S LAW

According to Moore’s Law, the number of transistors that will fit on a silicon chip doubles every eighteen months. Presently, microprocessors have

more than forty million transistors By the year 2020, the trend line of

Moore’s law states that there should be a one nanometer feature size. .

SCALING PRINCIPLES

For designing nano FET apart from channel length, other parameters like doping, voltages etc. are to be also scaled.

Original Device

Scaled Device

EJ MOSFET (Electrically variable shallow junction MOSFET)

NANO MOSFET

SCALING LIMITS OF MOSFET

Technical problem: For channel length<30nm , insulating SiO2 is expected to be less than 2nm thick. This thin layer causes gate dielectric tunneling

Physical problem: For channel length<10nm, direct source-drain tunneling occurs.

Schematic representation of Gate –dielectric tunneling and Direct source-drain tunneling

EJ- MOSFET

Construction

It consists of 2 gates :Upper gate and a lower gate. Gates are insulated from each other by an integrate oxide layer

Working

Upper layer electrically induces the inversion layers that are self aligned to the lower gate and the lower gate controls the current between the inversion layer.

Presence of two gates helps in suppressing short channel effects

QUANTUM EFFECTS IN ULTRASHORT CHANNEL MOSFET Mobility enhancement due to

decrease in scattering Threshold voltage increases with

decrease in channel width

THRESHOLD VOLTAGE ADJUSTMENT USING QUANTUM EFFECTS

For <110> oriented device n type has greater VT shift than p type

For <100> oriented device p type has greater VT shift than n type

To keep VT same for both square scaling i.e. width = height is used.

BASIC PHENOMENON OBSERVED IN NANO

DEVICES

BALLISTIC TRANSPORT IN NANO STRUCTURES

At room temperature mean free path of electron is around 10nm.So, at ultrashort channel length electron scattering decreases considerably.

At channel length less than 10nm,scattering approaches zero. It is called ballistic transport.

With decrease in temperature mean free path can be increased & ballistic transport can be obtained at larger channel length.

RESONANT TUNNELING IN NANO DEVICES RT is observed in hetero-structure

semiconductor devices made from pairs of different alloys III-V alloys..

Eg. AlGaAs/GaAs/AlGaAs diodes

MISCELLANEOUSNANO-STRUCTURES

Carbon nanotubes & nanowires

CARBON NANOTUBES

Single-wall carbon nanotubes are a new form of carbon made by rolling up a single graphite sheet to a narrow but long tube closed at both sides by fullerene-like end caps..

PROPERTIES

Exhibit electrical conductivity as high as copper, thermal conductivity as high as diamond

Strength 100 times greater than steel at one sixth the weight

Electrical conductivity depends on their helicity.

CURRENT APPLICATIONS

In field of electronics & communication

In solar cells to trap electrons Touch screens and flexible displays nanoradio, a radio receiver consisting

of a single nanotube, was demonstrated in 2007

In fabrication of ultracapacitors (which have high energy density)

NANOWIRES

Electrons in nanowires are quantum confined laterally and thus occupy energy levels that are different from that in bulk materials.

Aspect ratios (length-to-width ratio) of 1000 or more

Poor conductivity (edge effect)

APPLICATIONSCurrent Create active electronic devices like logic gates etc.Potential use As photon ballistic waveguides For connecting molecular-scale

entities in a molecular computer For flexible flat-screen displays

RECENT DEVELOPMENTS IN

FIELD OF NANOELECTRONICS

WORLD’S SMALLEST TRANSISTOR

Graphene Transistor

WORLD’S smallest transistor

quantum dot with a tiny circular cage at the center known as the central island. Voltage can change the conductivity of thesequantum dots, allowing them to store logic states

Ability to retain conductivity when only one atom thick.a small sheet of graphene is taken & channels are carved into it using electron beam lithography. What remains is a

Graphene Sheets

Schematic diagram of graphene transistor

NANO RADIO

First Radio at nano-scale

NANO RADIO

A nanoradio is a radio receiver or transmitter constructed on a nanometer scale.

Currently only receivers have been

developed( October 2007)

WORKING The nanotube, is contained in a

vacuum and one of its ends is connected to an electrode of a battery. The other electrode is placed a short distance from the nanotube's other end. The tube will vibrate in tune with any external electromagnetic signal, effectively acting as an antenna. The vibration frequency can be adjusted by changing the applied voltage.

NANO RADIO

NANO EMISSIVE DISPLAY

NANO EMISSIVE DISPLAY Launched in May,2005 by motorola

Works by moving electrons through its driver electronics and into the nanotubes, which then direct the electrons at groups of phosphors (pixels) on the interior surface of the display. When the phosphors are bombarded with electrons, they glow, giving off color—similar to the operation of a traditional CRT

ADVANTAGES

Light in weight and more slim

Saves 20% to 30% more power than other flat panel displays

Manufacturing cost is estimated to be a half to a third the cost of LCD and plasma displays

APPLICATION

Laptop screen due to better power saving & size

Screens in fighter planes due to better brightness & resolution

Automotive and aeronautical purposes

TV displays