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 MOSFETMain component:1. source (S), drain (D) and gate (G)2. dielectric layer3. 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 = 0VReading : 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 characteristicsON/OFF ratio of over 610

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Nonvolatile memory with grapheneFabrication:

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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 isomerso Gray curves closed isomerso 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 anode2. PEDOT:PSS hole-

injection layer3. Crosslinked

triphenylamine dimer (XTPD) derivatives as hole transport layers

4. XDTE phototransduction layer

5. Poly (spirofluorene) emission and electron transport layer

6. Ba cathode7. 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 nanoscalechallenges:switching and transport propertiesvalidation of transport properties the exclusion of electrode reactionsCharacteristics:Low costlow processing temperaturepotential 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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