Bistable behaviour

First, the proper switching function of the device was verified. Both device parts were tested and each of them showed bistable behaviour as it can be seen for device part A11 in Figure 27.13. The NDR region and the threshold bias were shifted to higher voltages and appeared at 10-14 V as compared with a few volts in the stacked devices. Additionally, the current did not rise as fast and abruptly at the threshold voltage. 

Animal psychology Bistable behaviour of an animal under stress (flight or attack)... 

Seelig, F. F. (1971b). Mono- or bistable behaviour in a weakly or strongly open chemical reaction system. J. Theor. Biol., 32, 93-106. 

SINGH B.P. and PRASAD P.N., (1988), 0ptical Bistable Behaviour of a Planar Quasi-Waveguide Interferometer Made with a Conjugated Organic Polymer Film, J. Opt. Soc. Am., B5, 453-456. 

Another important reaction supporting nonlinear behaviour is the so-called FIS system, which involves a modification of the iodate-sulfite (Landolt) system by addition of ferrocyanide ion. The Landolt system alone supports bistability in a CSTR the addition of an extra feedback chaimel leads to an oscillatory system in a flow reactor. (This is a general and powerfiil technique, exploiting a feature known as the cross-shaped diagram , that has led to the design of the majority of known solution-phase oscillatory systems in flow... 

Figure C2.16.6. The energy states of a metastable and bistable muonium in Si are illustrated in a configuration diagram. It plots the defect energy as a function of a coordinate which combines position and all the relaxations and distortions of the crystal. The specific example, discussed in the text, illustrates acceptor and donor levels, metastability, bistability and negative- U [50] behaviour.

Ganapathisubramanian, N. and Showalter, K. (1986). Relaxation behaviour in a bistable chemical system near the critical point and hysteresis limits. J. Chem. Phys., 84, 5427-36. 

Positional changes of atoms in a molecule or supermolecule correspond on the molecular scale to mechanical processes at the macroscopic level. One may therefore imagine the engineering of molecular machines that would be thermally, photochem-ically or electrochemically activated [1.7,1.9,8.3,8.109,8.278]. Mechanical switching processes consist of the reversible conversion of a bistable (or multistable) entity between two (or more) structurally or conformationally different states. Hindered internal rotation, configurational changes (for instance, cis-trans isomerization in azobenzene derivatives), intercomponent reorientations in supramolecular species (see Section 4.5) embody mechanical aspects of molecular behaviour. 

In solid state all the 10 pyroelectric crystal groups allow in principle for bistable switching behaviour. This is the proper ferroelectricity. Under certain conditions ferroelectricity (improper) can be realized in liquid crystals. This was shown by Meyer and coworkers115 in 1975. Since that time intense activities have been initiated, applying this property for flat-panel devices, switches, light modulators etc. In principle, three effects can be observed and used ... 

Photochromic behaviour of salicylidene anilines incorporated in a Langmuir-Blodgettmultilayer shows that thermal decoloration is suppressed by the highly ordered densely packed environment Bistability has been observed with the triphenylimidazolyl radical dimer when irradiated at 350nm . A transition between two states is induced by changing either the flow rate or incoming light flux. This is believed to be the first example of chemical instability induced in an isothermal photochemical system. 

Szafrahski, M. and Katrusiak, A. (2000). Thermodynamic behaviour of bistable NH -N hydrogen bonds in monosalts of l,4-diazabicyclo[2.2.2]octane. Chem. Phys. Lett. 318,427-432. Katrusiak, A. and Szafrahski, M. (1999). Ferroelectricity in NH-N hydrogen-bonded crystals. Phys. Rev. Lett. 82, 576-579. 

One possible application for low complexity electronics is radio fi equency identification-tags (RFID) for example in the food or drug packaging industry. In addition, for economic reasons the low cost electronics system should be able to operate without a permanent power supply. Many organic materials not only show conducting or semi-conducting but also bistable switching behaviour. 

The peroxidase reaction provides another prototype for periodic behaviour and chaos in an enzyme reaction. As noted by Steinmetz et al. (1993), in view of its mechanism based on free radical intermediates, this reaction represents an important bridge between chemical oscillations of the Belousov-Zhabotinsky type, and biological oscillators. In view of the above discussion, it is noteworthy that the model proposed by Olsen (1983), and further analysed by Steinmetz et al. (1993), also contains two parallel routes for the autocatalytic production of a key intermediate species in the reaction mechanism. As shown by experiments and accounted for by theoretical studies, the peroxidase reaction possesses a particularly rich repertoire of dynamic behaviour (Barter et al, 1993) ranging from bistability (Degn, 1968 Degn et al, 1979) to periodic oscillations (Yamazaki et al, 1965 Nakamura et al, 1969 ... 

In the parallel investigation of systems where metal-ligand charge-transfer (MLCT) occurs, studies into transition metal complexes of the redox-active quinone ligand have unravelled crossover behaviour that accompanies electron transfer. This reversible process, known as valence tautomerism, has been observed with bistability in the solid state. ° Exotic photomechanical behaviours, such as the bending of crystals of ID chain materials with IR irradiation,have been attributed to the unique structural consequences of electron transfer within the solid. 

Heintz. R.A. Zhao. H. Ouyang, X. Grandinetti. G. Cowen, J. Dunbar, K.R. New insight into the nature of Cu(TCNQ) Solution routes to two distinct polymorphs and their relationship to crystalline films that display bistable switching behaviour. Inorg. Chem. 1999. 38 (1), 144-156. 

For all of the samples studied and for particle sizes down to the lowest studied, 150 nm, very similarly shaped SCO transition curves were observed and taken to imply that no significant size effect influenced the SCO process, at least in these particular nano-objects. Nanocrystals of the 3D coordination polymer [Fe(prazine)Pt(CN)4], which displays SCO properties in the bulk, also preserve the same magnetic, structural and optical bistability for particle sizes on the order of 50 nm. Recent evidence suggests however that this may not always be the case, as in the example of the 2D coordination polymer [Fe(3-fluoropyridine)2M(CN)4] where the bulk SCO properties were shown to be very markedly influenced by the nanoparticle dimen-sions. Detailed discussion of this topic falls outside the scope of this review but we refer to it here because it is an aspect of spin crossover studies that bears fundamentally" " on the practical application in device teehnology of nano-dimensioned SCO materials, which continue to display hysteretie behaviour at such dimensions. 

Two types of EPR (electron paramagnetic resonance) detectable bistability have been detected during recent years. The first is related to the EPR spectrometer itself and not to the sample. The physical cause of the phenomenon is the non-linear behaviour of the sample to cavity coupling [26]. The width of the hysteresis loop was found to vary with the filling factor of the cavity. This type was detected by Giordano et al. [26] during studies on polypyrrole radical. 

It is also worth to mention here that the bistability phenomena can be easily understood in animal behaviour and social behaviour as mentioned in Section 8.6. 

As the external environment changes due to age and drastic changes in the environment itself, individual has to change his behavioural patterns. Bistability as discussed in Chapter 8 is expected to be a common phenomena under such circumstances. 

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