transparent final

7/28/2019 Transparent Final

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GOVT. WOMEN ENGINEERING

COLLEGE AJMER


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1. Introduction

2. Combining transparency with electrical conductivity

3. Carrier generation in TCO

4. Transparent electronic devices

5. Strengths and weaknesses

6. Application

7. Future Scope

8. Conclusion

9. References


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What is transparent electronics?


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Transparent electronics is an emerging science andtechnology focused on producing invisible electroniccircuitry and opto-electronic devices.

In transparent electronics the usual opaque

semiconductor materials forming the basis for electronicdevice fabrication is replaced with transparent materials.

Dramatical change in the look and use of electronic

devices


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A transparent material is an insulator which possesses completely

filled valence and empty conduction bands.

Hence their is a need to combine transparency with electrical

conductivity.


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For this we use-

DEGENERATE Doping

Certain oxides like In2O3,SnO2,Zn0,CdO consist of sufficient

transmission within the visible spectral range and moderate electrical

conductivity.

In a undoped state these are insulators with a band gap of 3eV.

To become a TCO host these are degenerately doped which results

in the displacement of Fermi-level into the conduction band. It

provides high mobility of extra carriers and low optical absorption.


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The high energy dispersion of conduction band also ensures apronounced Fermi level displacement above the conduction band

is known as BM shift (Burstein-Mass Shift).

This shift helps to broaden the optical transparency window

and keep the intense optical transition from the valence band out

of visible spectrum


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Burstein Mass (BM) Shift
http://en.wikipedia.org/wiki/File:MBshift_for_wiki.jpg


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The optical and transport properties of a conventional TCO are

governed by the efficiency and the specifics of the carrier generation

mechanism employed. Even in the most favorable situation, i.e. when

the effects of dopant solubility, clustering ,secondary phase formation

and charge compensation can be avoided. Large concentrations of

electron donors (substitutional dopants and/or native point defects) not

only promote the charge scattering but also may significantly alter the

electronic band structure of the host oxide, leading to a non-rigid band

shift of the Fermi level.TWO METHODS:-

SUBSTITUTIONAL DOPING

OXYGEN REDUCTION


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Substitutional Doping

Substitutional doping with aliovalent ions is the most widely

used approach to generate free carriers in TCO hosts.Compared with native point defects, it allows a better control

over the resulting optical and transport properties as well as

better environmental stability of the TCO films.

For example ZnO films have been prepared by doping with

group III , IV and VII elements giving rise to a wide range of

electrical conductivities.


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Oxygen Reduction

Removal of an oxygen atom from a metal oxide leaves twoextra electrons in the crystal.

Whether one or both of these electrons become free carriers

or remain localized at the vacancy site correlates with the

oxide free energy of formation.


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Transparent electronicdevices

Transparent Passive devices

Transparent Active devices


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Transparent Passive Devices:-

Transparent Thin Film Resistors

Transparent Thin Film Capacitors

Transparent Thin Film Inductors


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Transparent Thin Film Resistors

Resistive material used is indium tinoxide

Fig (a) consist of sixteen path squares

Fig(b) consist of sixteen path squares

Greater the no of squares more is the

resistance


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Transparent Thin Film Capacitor

Dielectric are insulators and

hence transparent

So in case of capacitor the main

concern is contact layer

This layer is made with the help

of highly conducting oxide - ITO


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Transparent Thin Film Inductor

These are quite hard to design becauselarge inductance value require large no

turns which results in parasatic

resistance that is undesirable.

In this case also ITO is used due to

higher conductivity.


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Transparent Active Devices-Transparent Thin Film Transistor(TTFT)


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Transparent thin film transistor constitute the heart of

transparent electronics

The first transparent thin film transistor was made in 2003which uses zinc oxide as conductor

Channel is formed from highly insulating, wide band gap

transparent semiconductor(ZnO).

Source, drain and gate contacts are made from highly

conductive TCO (ITO).

N-type TFT are widely used as there are certain problems associated

with the doping of p-type TFT.

Efforts are being made to improve the performance of p-type TFT.


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Strengths

Weaknesses

Visible transparency High resistance of TCOsLarge area Lack of complementary devicesLow cost (solution based deposition

and printing)Technological immaturity

Low temperature processingFree real estateSafe, nontoxic materialsRobust stable inorganic materials


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1.Transparent Smart Window


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2.Transparent Cell-phones


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3.Transparent Laptops


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4.Transparent Oled

5.Transparent Batteries


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Transparent Smart Cards

Windowpanes with Transparent Solar Cell

Can be used for energy harvesting

Heads-Up Displays (HUD) showing driver support

information directly on a vehicle's windshield

Head-Mount Displays" where the lenses of goggles or

eyeglasses serve as displays


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Oxides a new class of material can be used for manufacturing

of transparent devices

These see-through devices can prove a boon to the to

technology

This will also help in development on flexible, non-breakable

electronics

It will be helpful in development of human machine

interaction in near future


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ZnO: From Transparent Conducting Oxide to

Transparent Electronics Fortunato E, Barquinha P, PimentelA, Pereira L, Goncalves G, Martins R 2007 Amorphous IZO

TTFTs with saturation mobilities exceeding 100cm2/Vs. Phys.

Stat. Sol. (RRL) 1 (1), R346.

Transparent Electronics , Springer publications, J.F.Wager,

D. A. Keszler, R. E.Presley.

Transparent electronics: from synthesis to applications,

Wiley publications: Antonio Facchetti, Tobin J. Marks.

www.sciencemag.org


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Queries?

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