Transparent Electronics Seminarx - 123SeminarsOnly

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2 Νοε 2013 (πριν από 3 χρόνια και 10 μήνες)

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Guided by


Miss. Shahida

Submitted by,


Sajas

K.K.


Roll no: 18


S5 EC

Introduction


What is transparent electronics?





In transparent electronics the usual opaque
semiconductor materials forming the basis for
electronic device fabrication is replaced with
transparent materials.






There are two technologies which preceded
and underlie transparent electronics:


1.
Transparent Conducting Oxides (TCOs)

2.
Thin Film Transistors (TFTs)

Transparent Conducting Oxides TCOs)




TCOs constitute an unusual class of materials
possessing two physical properties (generally
considered mutually exclusive):


1.
High optical transparency. (
Eg
>3.1eV)

2.
High electrical conductivity.





Transparent electronic
devices

Transparent Passive devices

Transparent Active devices

Transparent Passive devices




Transparent Thin Film Resistors



Transparent Thin Film Capacitors



Transparent Thin Film Inductors


Transparent Thin Film Resistors




Resistive
material: ITO (Indium Tin Oxide)



Typical sheet resistance ~ 10
-
10
5



Conductivity of TCO’s depends on number of
oxygen vacancies (
𝑉
𝑂
)

and metal atoms
occupying interstitial sites.

Transparent
T
hin Film Capacitors




Most insulators are transparent.




Contact layer is made of highly conducting
TCOs (ITO).



𝐶
=
𝜀
𝑖

𝑑
.



Transparent Thin Film Inductors




Hard to realize due to poor conductivity of
TCO’s compared to metals.

=
2
𝜋𝑓𝐿
/






High L requires larger number of turns which
in turn results in increased parasitic resistance.


Schottky Barriers



Formed from metal (anode)
-
semiconductor
(cathode) junction.



Space charge region (depletion region) and
potential barrier formation due to difference in
work function of metal and semiconductor.



Schottky barrier height

𝑛
=



𝜒


, where
𝜙
𝑛

Schottky barrier height





work function of
metal


𝜒


Electron affinity of semiconductor



Energy band in a Schottky barrier

Transparent Thin Film Transistors


Constitutes the heart of transparent
electronics



Channel is formed from highly insulating, wide
band gap transparent semiconductor(
ZnO
).



Source, drain and gate contacts are made
from highly conductive TCO (ITO).



Two possible configurations are:

a)
Bottom gate

b)
Top gate

Possible structure, (a) Bottom gate, and



(b) Top gate.

Operation of a bottom gate TFT

Strengths and Weaknesses


Strengths

Weaknesses

Visible transparency

High resistance of TCO’s

Large area

Lack of complementary devices

Low
cost (solution based
deposition and printing)

Low frequency of operation.(KHz

to few MHz).

f
T
=
𝜇
(
𝑉
𝐺

𝑉

)
/
2𝜋
𝐿
2

Low temperature processing

Technological immaturity

Free real estate



Passive availability (R & C)



Robust stable inorganic materials



Safe, nontoxic materials



Applications



Active Matrix LCD (AMLCD).



Active Matrix Organic Light Emitting Device
display backplane (AMOLED).



Value added glass.



Transparent electronics on opaque substrates.





UV
detectors and
arrays



Transparent solar cells



UV detectors for spectrally resolved imaging.



Security applications:



Invisible cameras and



Invisible RFID’s

Conclusion


Started as a mere electrical device technology
during world war 2, transparent electronics
now holds the key for many future
advancements in security, entertainment
efficient utilization of energy.




Reference


‘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