This document discusses organic flash memory, which functions similarly to traditional flash memory but uses organic materials. It can be written to and erased over 1,000 times with writing and erasing voltages as low as 6V and 1V, respectively. The memory is constructed on a flexible polyethylene naphthalate substrate with an array of floating-gate transistors made of organic materials like pentacene. This allows the memory to be integrated into flexible electronics. However, the organic flash memory currently only maintains memory for one day, though this retention time could be improved through design modifications. The document provides details on the construction and operating principles of organic flash memory.

1. Organic Flash Memory
Gizem MERCAN 2009510051

3.  The demand on memory
device elements based on
organic materials grows
rapidly
 Since they require low-cost
for manufacturing
 Yield high perfomance in
technological applications.
 There are many organic
materials that are being
used as memory device
elements that provide fast.
Information About Organic Memory Devices

4. Information About Organic Memory Devices
 Non-volatile memory which should retain for at least 10 years.
 It should provide high density data storage.
 High writing/reading stability.
 Long retention time.

5. What are principles of design?
 A typical organic memory device is based
on deposition of a low cost polymer film
on an active organic material.
 The organic memory devices are made
using organic bistability materials employ
ideal on/off ratio,
 Moderate read/write voltage,
 Quicker response time have potential
applications in RAM,ROM and flash
memory.

6. Types of Organic Memory Devices
 Generation of memory in organic devices can be
achieved by charge storage in terms of charge trapping,
charge separation, and change transfer within the active
components of the organic layer.
 Thus the material used should provide an energy barrier
to prevent recombination of negative and positive
charges.
 Then after the materials are polarized, conductance of
the device changes, where the low conductance state is
the OFF state and the high-conductance state is the ON
state.

7. Types of Organic Memory Devices
 This process where the electrically bistable materials are switched
from low conductive state (0) to high conductive state (1) by the
applied voltage is called writing.
 When the process is reversed by applying a reverse bias voltage as
from high conductive state to low conductive state, device performs
erasing.
 Roughly, Organic Memory Devices can be investigated under three
categories :
1. Resistive switch and write once, read many times (WORM) devices,
2. Molecular Memory Devices.
3. Polymer Memory Devices (PMDs).

8. Resistive switch&Worm and Moleculer
Memory Device
 A resistive material
which is an active thin
film is sandwiched
between these
electrodes.
 Highly ordered
monolayer of molecules
is placed between the
electrodes.

9. Polymer Memory Device
 An organic material layer
consisting of mixture of
molecules and
nanoparticles in an organic
polymer matrix is placed
between the electrodes
instead of a molecular
monolayer.

10. Flash Memory
 Flash memory is a non volatile computer storage chip
that can be electrically erased and programmed.
 It was developed eeprom and must be erased in fairly
large blocks before these can be rewritten with new data.
 The high density NAND type must also be programmed
and read in (smaller) blocks, or pages, while the NOR
type allows a single machine word (byte) to be written or
read independently.
 The NAND type is primarily used in memory cards, Usb
drives, solid-state drives, and similar products, for
general storage and transfer of data.

11. Principle of Operations
 Flash memory stores information in an array of memory cells made
from floating-gate transistors. In traditional single-level cell (SLC)
devices, each cell stores only one bit of information. Some newer
flash memory, known as multi-level cell (MLC) devices
 NOR flash: Each cell has one end connected directly to ground, and
the other end connected directly to a bit line.
 Default state is logically equivalent to a binary "1" value.
 A NOR flash cell can be programmed, or set to a binary "0" value.
 NAND flash: NAND flash also uses floating-gate transistors, but
they are connected in a way that resembles a Nand-gate.
 NAND flash uses tunnel injection for writing and tunnel release for
erasing. NAND flash memory forms the core of the
removable Usb storage devices known as Usb Flash Drives, as well
as most memory card formats and ssd available today.

12. Floating-gate transistors
• In flash memory, each
memory cell resembles a
standard MOSFET, except the
transistor has two gates
instead of one. On top is the
control gate (CG), as in other
MOS transistors, but below
this there is a floating gate
(FG) insulated all around by
an oxide layer. The FG is
interposed between the CG
and the MOSFET channel.

13. Organic Flash Memory
 The University of Tokyo developed the
‘organic flash memory’ a non volatile
memory(gecici olmayan bellek) that has
the same basic structure as a flash
memory and is made with organic
materials.(group led by Takeo Someya
and Tsuyoshi Sekitani)
 The erasing and reading voltages of the
new flash memory are as low as 6V and
1V,respectively.Data can be written in
and erased from the memory more than
1000 times.

14. Organic Flash Memory
 With its flexibility,the
flash memory can be
used for large area
sensors.
 electronic paper and
other large-area
electronic devices if
its memory retention
time can be extended.

15. Organic Flash Memory

16. Organic Flash Memory
 The research group used a polyethylene
naphthalate(PEN) resin sheet as a
substrate and arranged 26x26 2T
memory cells in an array structure on it.
 The sheet is flexible.the university
comfirmed that it can be bent until its
curvature radius 6mm without causing
mechanical or electrical degradation.
 Also comfirmed that the sheet can be
used as a non volatile memory.
The memory array.The white
parts are control gates and
watery blue parts under three
electrodes are pentacene(is
a polycyclic aromatic hydrocarbon consisting of
five linearly-fused benzene rings.)

17. Organic Flash Memory
The structure of the
intelligent pressure
sensor.
 Furthermore,the research group made an
‘intelligent pressure sensor’,which can retain a
pressure image in the sheet, by integrating the
memory array and a pressure sensor.
 Why it is called ‘Organic Flash memory’?
 Because, it is equipped with floating-gate
transistors,which are also used for silicon-
based flash memories.Specially,the PEN
substrate is mounted with aluminum(Al)
control gate electrodes,insulating
films,aluminum floating gates,organic
semiconductor pentacene and source and
gate electrodes made of gold(Au).

18. Organic Flash Memory
 The insulating film was made
by using a self-assembled
monolayer(SAM),which is
made of kind of phosphoric
acid having an alkyl
chain(CH2-CH2…)in addition
AlOx.
 The SAM is as thin as 2nm.

19. Advantages of Organic Flash Memory
 There are non volatile memories developed past.One is made by
using ferroelectric materials, and the other has a floating-gate
structure like the latest non volatile memory.
 However,It is difficult to lower the writing and erasing voltages of the
previous memory than 20V.
 Also it becomes unstable when exposed to air because its memory
properties fluctuate due to the nonconstant thickness of the
insulating film.
 At this time, SAM whose insulating film does not require thickness
checking to reduce the variation in memory properties.
 Moreover, the SAM is stable in atmosphere.

20. Disadvantages
 The new organic flash memory has a memory retention time of only
one day.
 But this can be improved by reducing the size of element and
employing an SAM with a long molecular length.

21. References
• Chen Qi , Bai Hua, Shi GaoQuan, Memory devices based on organic electric bistable materials, Chinese Science
Bulletin, 200, 52(15), 2017-2023
• J C. Scott, Is there an immortal memory?, Science, 2004, 304(5667), 62-63
• DOI: 10.1126/science.1179963
• Science 326, 1516 (2009);
• Tsuyoshi Sekitani, et al.
• Sensor Arrays
• Organic Nonvolatile Memory Transistors for Flexible
• www.sciencemag.org (this information is current as of December 10, 2009 ):
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• http://www.sciencemag.org/cgi/content/full/326/5959/1516
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• This article cites 22 articles, 2 of which can be accessed for free:
• http://www.sciencemag.org/cgi/collection/app_physics
• Physics, Applied
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• http://www.sciencemag.org/about/permissions.dtl

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