Molecular memory devices

Studies devoted to create high-density molecular memory devices (ideally, it is hoped to find materials in which each bit of digital information might be stored on a single molecule) are very active89 and larger manganese-carboxylate assemblies have been obtained (up to... 

The immobilization of a photoisomerizable material that can be switched by light between redox-active and redox-inactive or conductive and insulating states offers an encouraging route toward integrated molecular memory devices. Figure 7.2 shows a photoisomer state A in which the molecular unit is redox-inactive and no electronic signal is transduced. Photoisomerization of the chemical component to state B generates a redox-active assembly, and the electron transfer between the electrode and the chemical modifier yields an amperometric (electrochemical) indicator of the state of the system. 

Electron transfer in molecular memory devices 01MI55. 

An example of this approach is represented by the growth of 3-D coordination polymers with SCO properties via stepwise adsorption reactions for multilayer films based entirely on intra- and interlayer coordination bonds Fe(pyrazine) [Pt(CN) ] [218, 219], Indeed, after functionalization of the surface with the appropriate anchoring layer the coordination polymer is built in a stepwise fashion, alternating the metal ion (Fe "), the platinum salt ([Pt(CN) ] ), and pyrazine. The polymer shows many interesting properties, with the SCO transition accompanied by a variation in the dielectric constant of the material accompanied by a room temperature hysteresis of the dielectric constants. This dielectric hysteretic property may be useful in building molecular memory devices that can store information by high- and low-capacitance states. What must be remarked here is that these appealing properties cannot be exploited in bulk materials, but only in thin films. 

Seminario, J. M.,Zacarias,A. G., Derosa, PA. (2001). Dreoretical analysis of complementary molecular memory devices. J. Phys. Chem. A 105(5), 791-795... 

Bousseksou, A Milnar, G., Demont, P and Menegotto, J. (2003) Observation of a thermal hysteresis loop in the dielectric constant of spin crossover complexes towards molecular memory devices. /. Mater. Chem., 13, 2069-2071. 

Fabrication of Three-Terminal Molecular Memory Devices.212... 

Redox-Mediated Solid-State Molecular Memory Devices.221... 

REDOX-MEDIATED SOLID-STATE MOLECULAR MEMORY DEVICES... 

New natural polymers based on synthesis from renewable resources, improved recyclability based on retrosynthesis to reusable precursors, and molecular suicide switches to initiate biodegradation on demand are the exciting areas in polymer science. In the area of biomolecular materials, new materials for implants with improved durability and biocompatibility, light-harvesting materials based on biomimicry of photosynthetic systems, and biosensors for analysis and artificial enzymes for bioremediation will present the breakthrough opportunities. Finally, in the field of electronics and photonics, the new challenges are molecular switches, transistors, and other electronic components molecular photoad-dressable memory devices and ferroelectrics and ferromagnets based on nonmetals. 

Recent developments in polymer chemistry have allowed for the synthesis of a remarkable range of well-defined block copolymers with a high degree of molecular, compositional, and structural homogeneity. These developments are mainly due to the improvement of known polymerization techniques and their combination. Parallel advancements in characterization methods have been critical for the identification of optimum conditions for the synthesis of such materials. The availability of these well-defined block copolymers will facilitate studies in many fields of polymer physics and will provide the opportunity to better explore structure-property relationships which are of fundamental importance for hi-tech applications, such as high temperature separation membranes, drug delivery systems, photonics, multifunctional sensors, nanoreactors, nanopatterning, memory devices etc. 

Kahn and Martinez (1998) Spin transition polymers from molecular materials toward memory devices [17]. 

For quite a few years we have been concerned with the use of molecular systems in memory devices. Whatever the final objective might be, a fundamental requirement for the system is to have an hysteresis effect with regard to a given perturbation. When it is so, a transition between two electronic states takes place for a certain value of the perturbation, /Vf, when the perturbation increases, and for another value of the perturbation, Pcl, when the perturbation decreases, with Pc[ < Pcf. Between those two critical values, the state of the system depends on its history or on the information which has been stored. It is of course well known that a hard magnetic material might be used for storing information. Our work provides evidence of the possibility that molecular chemistry might provide compounds of that kind. 

In principle any molecule able to exist in two reversible, switchable states can represents a molecular switch (bistable device) with potential to form part of molecular circuitry or act as molecular memory. An excellent component for switchable molecular devices is the 1,2-dithienylethene system, which has been exploited ingeniously by Lehn in a number of bistable systems.54 The core switching element is the transformation of the dithienylethene unit between two stable states as a function of the wavelength of incident radiation (Scheme 11.8). 

As discussed at the beginning of this chapter, photochromic systems represent potential molecular level memory devices. A number of problems, however, must be solved for practical applications. A challenge problem is to find systems with multiple storage and nondestructive readout capacity those in which the record can be... 

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