Computer Memory
“In computing, memory refers to the state information of a computing system, as it is kept active in some physical structure. The term "memory" is used for the information in physical systems which are fast (i.e. RAM), as a distinction from physical systems which are slow to access (i.e. data storage). By design, the term "memory" refers to temporary state devices, whereas the term "storage" is reserved for permanent data. Advances in storage technology have blurred the distinction a bit —memory kept on what is conventionally a storage system is called "virtual memory".”
“Colloquially, computer memory refers to the physical devices used to store data or programs (sequences of instructions) on a temporary or permanent basis for use in an electronic digital computer. Computers represent information in binary code, written as sequences of 0s and 1s. Each binary digit (or "bit") may be stored by any physical system that can be in either of two stable states, to represent 0 and 1. Such a system is called bistable. This could be an on-off switch, an electrical capacitor that can store or lose a charge, a magnet with its polarity up or down, or a surface that can have a pit or not. Today, capacitors and transistors, functioning as tiny electrical switches, are used for temporary storage, and either disks or tape with a magnetic coating, or plastic discs with patterns of pits are used for long-term storage.”
“Computer memory is usually meant to refer to the semiconductor technology that is used to store information in electronic devices. Current primary computer memory makes use of integrated circuits consisting of silicon-based transistors. There are two main types of memory: volatile and non-volatile.”
(Wikipedia, Computer Memory, 1/1/2011)
With the recent dramatic developments in digital communication technology, demand for a variety of memory devices has been increasing rapidly. Memory devices suitable for use in applications including, for example, portable computers and electronic devices, including mobile terminals, smart cards, electronic money, digital cameras, personal digital assistants (PDAs), digital audio players and/or multimedia players, are required for retaining data in memory even when no power is being applied to the memory device, thereby tending to reduce the memory-related power consumption of the device. “
”Conventional memory devices may include a bistable element that may be switched between a higher resistance state and a lower resistance state when a voltage is applied to the devices. Resistive memory devices are memories whose resistance is varied depending on an applied voltage and in which data is stored in response to changes in the resistance.”
“Chalcogenide materials, semiconductors and various types of oxides and nitrides are known to have resistive memory properties. Some organic materials are also found to have resistive memory properties. Of these resistive memory devices, organic memory devices may include an upper electrode, a lower electrode and a memory layer between the upper and lower electrodes, wherein the memory layer may be formed of an organic material and memory properties are realized by using bistability of resistance values obtained when a voltage is applied between the upper and lower electrodes. Next-generation organic memory devices ensure non-volatility, which is an advantage of conventional flash memories, and at the same time, overcome the disadvantages of undesirable processability, increased fabrication costs and decreased degree of integration. “
“Research has been done on various materials due to their potential use as materials for organic active layers of organic memory devices. One example of such an organic memory device utilizes an organic memory device including an upper electrode, a lower electrode and a selectively conductive media between the two electrodes wherein the selectively conductive media contains an organic layer and a passive layer and the organic layer is made of a conjugated organic material. Another example includes a molecular memory cell including a first electrode, a second electrode, and first and second charge storage molecules between the first and second electrodes and coupled to the electrodes by a molecular linkage. Other work has suggested a conductive polymeric composite for use as an electrode material of a secondary battery, the polymeric composite including a salt of a ferrocene derivative and a polypyrrole or its derivative.”
Recent US Patents
2/15/2011
7,888,453
Ferrocene-containing polymers and organic memory devices comprising the same
Choi et al of Samsung, South Korea, synthesized ferrocene-containing polymers in which ferrocene is conjugated to the backbone of conductive conjugated polymers. Further disclosed are organic memory devices comprising the ferrocene-containing polymers. Because the organic memory devices possess the advantages of decreased switching time, decreased operating voltage, decreased fabrication costs and increased reliability, they may be used as highly integrated large-capacity memory devices. (RDC 8/26/2011)
Recent Journal Articles
2/25/2011
Dynamic Random Access Memory Effect and Memory Device Derived from a Functional Polyimide Containing Electron Donor-Acceptor Pairs in the Main Chain
(384–389)Macromolecular Rapid Communications 32 #4 (2011)
Tian et al of Beijing University of Chemical Technology, China synthesized a functional polyimide, hexafluoroisopropyl bis(phthalic dianhydride)/3,6-diaminocarbazole (6FDA/DAC), in which DAC serves as electron donor and 6FDA as electron acceptor. Electrical characterization results on the sandwiched polyimide memory device (ITO/Thin polyimide Layer/Au) indicate that the polyimide possesses electrical bistability and the device exhibits two accessible conductivity states, which can be reversibly switched from the low-conductivity (OFF) state to the high-conductivity (ON) state with an ON/OFF current ratio of about 104. Different from the widely reported write-once-read-many-times (WORM) effects, the device with the 6FDA/DAC polyimide as the active layer shows dynamic random access memory (DRAM) behavior. The ON state of the device was lost immediately after removal of the applied voltage, while by applying a constant bias (e.g., 3 V) the ON state can be electrically sustained. (RDC 2/24/2011)
1/28/2011
Annealing effect upon chain orientation, crystalline morphology, and polarizability of ultra-thin P(VDF-TrFE) film for nonvolatile polymer memory device
(6319-6333) Polymer 51 #26 (2010)
Lee, Prabu and Kim of Kyung Hee University, South Korea found that annealing the as-cast sample at temperature (ca. 120 °C) above Curie transition, but below its melting temperature was found to be the most suitable condition to fabricate the NvFePoRAM and/or SPM-based storage device with a memory density of about 30 GB/in2. (RDC 1/27/2011)