This document provides an overview of organic memories, including transistor-type polymer memories, nonvolatile memory using graphene, and photochromic transduction layers in memory. Transistor-type polymer memories can be fabricated through a simple process using organic thin-film transistors and offer benefits like low cost, light weight, and mechanical flexibility. Nonvolatile memory devices have been demonstrated using a multilayer graphene film as an interlayer between insulating polyimide layers, exhibiting write-once-read-many characteristics. Photochromic materials can also be used as switching layers in light-emitting organic memories, where the materials have two stable isomeric forms switched by light.

1. Spring 2015
Organic Memories
Dr. Farhad Akbari Boroumand
By:
Atiyeh Koohi Saadi

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Outline
• Electronic Memory
• Types of electronic memory
• Transistor-type polymer memories
– Device structures
– Operating principle
• Nonvolatile memory with graphene
• One Diode-One Resistor Cell Array for Memory
• Photochromic Transduction Layers in Memory
– Light-emitting organic memory
• Conclusion

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Electronic Memory
Electronic storage devices:
• retains retrievable digital data over a time interval
• fast in response
• compact in size
• read and write feasible when connected to a central processing unit
Mechanical storage devices:
• CD
• DVD
• floppy disk
• hard disk
• video/audio tape

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Types of electronic memory
Types of memory
Non-volatile memory
ROM
EPROM WORM
Hybrid
Flash EEPROM FeROM
Volatile memory
(RAM)
DRAM SRAM

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Transistor-type polymer memories
• Application of organic transistors in memories
• Simple fabrication process of OTFTs
• Low cost
• Light weight
• mechanical flexibility of organic materials

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Device structures
• Design features similar to MOSFET
Main component:
1. source (S), drain (D) and gate (G)
2. dielectric layer
3. active semiconductor layer

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Device structures
• Electrodes : Au for polymer-based FETs  ohmic
contact with conjugated polymers
• Dielectric : inorganic or polymeric insulator
• Semiconductor : conjugated molecule or polymer
• Substrate : glass, wafer, or plastic

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Operating principle
• Control over the source–drain current in OFETs via a
third terminal  applications in switches, shift
registers and logic elements  volatile
• An additional voltage, between the gate and the
semiconductor channel to alter the charge
distribution  nonvolatile
Writing : VG = 200V and VD = 0V
Reading : VG =0V and VD =−30V
Erasing : VG =−100V and VD =0V

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Operating principle

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Nonvolatile memory with graphene
• Graphene :
– Transparency
– Conduction properties
– Solution possibility
Multilayer graphene film (MLG) as interlayer
between insulating polyimide (PI) layers
WORM type characteristics
ON/OFF ratio of over 6
10

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Nonvolatile memory with graphene
Fabrication:

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Nonvolatile memory with graphene
80 nm
3 nm

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Nonvolatile memory with graphene
WORM memory type

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One Diode-One Resistor Cell Array for Memory

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Photochromic Transduction Layers in Memory
 utilization of photochromic materials (PCM), as
switching/transduction layers
Closed molecular
Open isomer
•The open isomer is converted to the
closed form via a UV-induced reaction
•The closed structure can be returned to
the open configuration via visible light
excitation

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o Black curve  open isomers
o Gray curves  closed isomers
o red-shift in absorption bands by the identity of the R and R’ moieties
 Minimum barriers from HTM (and ETM) into the PCM in the ON state (closed)
 Maximum barriers from HTM (and ETM) into the PCM in the OFF state (open)
Photochromic Transduction Layers in Memory

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1. ITO anode
2. PEDOT:PSS hole-
injection layer
3. Crosslinked
triphenylamine dimer
(XTPD) derivatives as
hole transport layers
4. XDTE
phototransduction
layer
5. Poly (spirofluorene)
emission and electron
transport layer
6. Ba cathode
7. Al top contact
Light-emitting organic memory

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Light-emitting organic memory

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Conclusion
 polymer memories, an alternative to the conventional
memory technologies due to miniaturizing from micro to
nanoscale
challenges:
switching and transport properties
validation of transport properties
 the exclusion of electrode reactions
Characteristics:
Low cost
low processing temperature
potential for flexible devices

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Organic Memristor

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References
[1]. Qi-Dan Linga, Der-Jang Liawb, Chunxiang Zhuc, Daniel Siu-Hung Chanc,
En-Tang Kanga, Koon-Gee Neoha, “Polymer electronic memories:
Materials, devices and mechanisms” , 2008
[2]. Yongsung Ji, Minhyeok Choe, Byungjin Cho, Sunghoon Song,
Jongwon Yoon, Heung Cho Ko and Takhee Lee, “Organic nonvolatile memory
devices with charge trapping multilayer graphene film” , 2012
[3]. Tae-Wook Kim, David F. Zeigler, Orb Acton, Hin-Lap Yip, Hong Ma, and
Alex K.-Y. Jen, “All-Organic Photopatterned One Diode-One Resistor Cell
Array for Advanced Organic Nonvolatile Memory Applications” , 2012
[4]. R. Clayton Shallcross, Philipp Zacharias, Anne Köhnen, Peter O.Körner,
Eduard Maibach , and Klaus Meerholz, “Photochromic Transduction Layers
in Organic Memory Elements” , 2013

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