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Polymer Memory


Published on Dec 06, 2015

Abstract

Polymers are organic materials consisting of long chains of single molecules. Polymers are highly adaptable materials, suitable for myriad applications. Until the 1970s and the work of Nobel laureates Alan J. Heeger, Alan G. MacDiarmid and Hideki Shirakawa, polymers were only considered to be insulators. Heeger et al showed that polymers could be conductive.

Electrons were removed, or introduced, into a polymer consisting of alternately single and double bonds between the carbon atoms. As these holes or extra electrons are able to move along the molecule, the structure becomes electrically conductive.

Thin Film Electronics has developed a specific group of polymers that are bistable and thus can be used as the active material in a non-volatile memory. In other words, the Thin Film polymers can be switched from one state to the other and maintain that state even when the electrical field is turned off. This polymer is "smart", to the extent that functionality is built into the material itself, like switchability, addressability and charge store.

This is different from silicon and other electronic materials, where such functions typically are only achieved by complex circuitry. "Smart" materials can be produced from scratch, molecule by molecule, allowing them to be built according to design. This opens up tremendous opportunities in the electronics world, where "tailor-made" memory materials represent unknown territory

Polymers are essentially electronic materials that can be processed as liquids. With Thin Film's memory technology, polymer solutions can be deposited on flexible substrates with industry standard processes like spin coating in ultra thin layers. Digital memory is an essential component of many electronic devices, and memory that takes up little space and electricity is in high demand as electronic devices continue to shrink Researchers from the Indian Association for the Cultivation of Science and the Italian National used positive and negative electric charges, or space charges, contained within plastic to store binary numbers Research Council. A polymer retains space charges near a metal interface when there is a bias, or electrical current, running across the surface.

These charges come either from electrons, which are negatively charged, or the positively-charged holes vacated by electrons. We can store space charges in a polymer layer, and conveniently check the presence of the space charges to know the state of the polymer layer. Space charges are essentially differences in electrical charge in a given region. They can be read using an electrical pulse because they change the way the devices conduct electricity.

Space charge and Polymers

Making a digital memory device means finding a way to represent the ones and zeros of computer logic, devising a relatively convenient way to retrieve these binary patterns from storage, and making sure the information remain stable.

Digital memory is an essential component of many electronic devices, and memory that takes up little space and electricity is in high demand as electronic devices continue to shrink Researchers from the Indian Association for the Cultivation of Science and the Italian National used positive and negative electric charges, or space charges, contained within plastic to store binary numbers Research Council.

A polymer retains space charges near a metal interface when there is a bias, or electrical current, running across the surface. These charges come either from electrons, which are negatively charged, or the positively-charged holes vacated by electrons. We can store space charges in a polymer layer, and conveniently check the presence of the space charges to know the state of the polymer layer. Space charges are essentially differences in electrical charge in a given region. They can be read using an electrical pulse because they change the way the devices conduct electricity.

The researchers made the storage device by spreading a 50-nanometer layer of the polymer regioregularpoly on glass, then topping it with an aluminum electrode. To write a space charge to the device, they applied a positive 20-second, 3-volt pulse. To read the state, they used a 0.2-volt, one minute pulse. Any kind of negative electrical pulse erased this high state, or charge, replacing it with the default low state. The space charges remain stable for about an hour and also can be refreshed by another 3-volt positive pulse. The researchers intend to increase the memory retention ability of their device beyond an hour. Researchers are looking forward to increasing it into days or more. Once this is achieved, polymer devices can be used in data storage devices [and] also as a switch whose state can be changed externally by a voltage pulse.

FEATURES OF POLYMER MEMORY

1. Data stored by changing the polarization of the polymer between metal lines.

2. Zero transistors per bit of storage

3. Memory is Nonvolatile

4. Microsecond initial reads. Write speed faster than NAND and NOR Flash.

5. Simple processing, easy to integrate with other CMOS

6. No cell standby power or refresh required

7. Operational temperature between -40 and 110°C.

How does Polymer Memory work?

Making a digital memory device means finding a way to represent the ones and zeros of computer logic, devising a relatively convenient way to retrieve these binary patterns from storage, and making sure the information remains stable. Polymer memory stores information in an entirely different manner than silicon devices. Rather than encoding zeroes and ones as the amount of charge stored in a cell, Coatue’s chips store data based on the polymer’s electrical resistance. Using technology licensed from the University of California, Los Angeles, and the Russian Academy of Sciences in Novosibirsk, Coatue fabricates each memory cell as a polymer sandwiched between two electrodes. To activate this cell structure, a voltage is applied between the top and bottom electrodes, modifying the organic material. Different voltage polarities are used to write and read the cells.

Application of an electric field to a cell lowers the polymer’s resistance, thus increasing its ability to conduct current; the polymer maintains its state until a field of opposite polarity is applied to raise its resistance back to its original level. The different conductivity States represent bits of information. A polymer retains space charges near a metal interface when there is a bias, or electrical current, running across the surface.

These charges come either from electrons, which are negatively charged, or the positively-charged holes vacated by electrons. We can store space charges in a polymer layer, and conveniently check the presence of the space charges to know the state of the polymer layer. Space charges are essentially differences in electrical charge in a given region. They can be read using an electrical pulse because they change the way the device conducts electricity.

The basic principle of Polymer based memory is the dipole moment possessed by polymer chains. It is the reason by which polymers show difference in electrical conductivity. As explained earlier implementing a digital memory means setting up away to represent logic one and logic zero. Here polarizations of polymers are changed up or down to represent logic one and zero. Now let’s see what are a dipole and a dipole moment.














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