Electrical bistability property

The results shown graphically in Hgs. 19 and 20 are noteworthy. The conduction through voltages were 0.65 and 3.8 V, respectively, for Ag-PPCN and Ag-PTDCN. Before conduction though, the thin film was an insulator with a resistivity of about 10 ft m, and after conduction through the thin film had metallic conduction with a resistivity of only about 0.7 ft m. The resistance difference between the insulator state and the conductor state was up to about seven orders (10 ). Hence, the electrical bistability properties of these polymer thin films were quite evident, and the insulator phase and conductor phase could be defined as the O state and 1 state, respectively. Furthermore, this bistability property was stable... 

The electrical properties of the Ag-TDCN thin films were measured. As shown in Fig. 24, the I-V curve of the sample indicates that the films possess good electrical bistability. The Ag-TDCN thin film is initially insulating (we call it the 0 state) and a conductance of less than 10" ft" cm" within the voltage threshold 1.36 V. At this voltage threshold point the electron current increased abruptly, and... 

Of much interest are the electroluminescence properties of conjugated polymers that allow the development of electrically switched light-emitting devices [8.257]. Electric field activated bistable molecules are expected to switch at a critical field strength [8.258]. 

Such controlled motion might become even more important, if one realizes that a bistable, controllable rotaxane might be useful as a nanoscale electronic device. One state would then be the "0", the other would represent the 1" state of one bit of a computer memory. Even if we have a long way to go before using these molecules as reliable functional units in electrical circuits minimized to nanometer dimensions, it seems to be of great promise and such promise demands the intense study of ways to synthesize these molecules and the detailed examination of their properties. 

The simplest manifestation of self-organization in a reacting system is the occurrence of bistability, that is, the coexistence of two locally stable homogeneous states. In all electrical models, bistable behavior results from the interaction of an N-shaped stationary polarization curve with a sufficiently large ohmic resistor in the external circuit. These two features also represent the backbone for all more complex forms of self-organization where, owing to exactly these two properties of the system, the double-layer potential takes on the role of the autocatalytic variable. 

Tetracyanoquinodimethane (TCNQ) and related compounds [10], have been extensively investigated in the last decades. When combined with tetrathiafulvalene (TTF) and some metals such as Ag and Cu, it may show very useful properties such as electrical and optical bistability. However, to apply these organic thin films in electronic or photoelectric devices, it is of great importance that the films should exhibit few impurities and defects and it is also desired that the films crystallinity can be controlled. For these reasons, we explore an ionized cluster beam deposition method to fabricate organic crystalline thin films. 

The above devices inspired scientists to develop solid-state MSTJ devices made from a [2]pseudorotaxane and [2]rotaxane (Figure 76) in which hydrophobic and hydrophilic regions were directly incorporated into the molecular structure to allow self-organization. ° The electrical properties were found to be highly dependent on the supramolecular structure, the presence of bistability within the (super)molecule, and the organization of the Langmuir-Blodgett film. The devices exhibited a... 

Basic research to discover how smectic liquid crystals are affected by heat and electric fields has resulted in several effects being found, and a few of them have been extensively studied and developed into working display prototypes and early commercialization. The property of bistability is both useful and, at the same time, a problem. As yet a really long term application involving smectic liquid crystals has not been found. However, they continue to hold a fascination because they can offer many unique properties which are continually being reexplored for new applications. 

Figure 5. Response of polar dielectrics (containing local permanent dipoles) to an applied electric field from top to bottom paraelectric, ferroelectric, ferrielectric, antiferroelectric, and helielectric (helical anti-ferroelectric). A pyroelectric in the strict sense hardly responds to a field at all. A paraelectric, antiferro-electric, or helieletric phase shows normal, i.e., linear dielectric behavior and has only one stable, i.e., equilibrium, state for E=0. A ferroelectric as well as a ferrielectric (a subclass of ferroelectric) phase shows the peculiarity of two stable states. These states are polarized in opposite directions ( P) in the absence of an applied field ( =0). The property in a material of having two stable states is called bistability. A single substance may exhibit several of these phases, and temperature changes will provoke observable phase transitions between phases with different polar characteristics.

T. Carlsson, F.M. Leslie and J.S. Laverty, Biaxial Nematic Liquid Crystals -Flow Properties and Evidence of Bistability in the Presence of Electric and Magnetic Fields, Mol. Cryst Liq. Cryst, 212, 189-196 (1992). 

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