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Autowaves in Planar Molecular Structures

Y.B. Gaididei and V.Y. Chekh*

National Technical University of Ukraine

This is an abstract for a poster to be presented at the
Fifth Foresight Conference on Molecular Nanotechnology.
There will be a link from here to the full article when it is available on the web.

 

The problem of investigations of charge density dynamics in 2-D molecular structures is actual for the development of future molecular information processing devices. The model of the charge transport has been investigated for the structures which consists of such molecular chains: donor- mediator chain- acceptor organized in Langmuir-Blodgett films on the substrate. It is assumed that strong nonlinear charge carrier - conformation interaction is presented for molecular donor and acceptor.

The initial Hamiltonian of the system's model has been reduced to 3 nonlinear equations for homogenous systems (nonlinear diffusion equations for heterogeneous ones) with the formalism of density matrix. Their solutions were obtained by digital computer modeling and phase space method.

It is shown that it is possible to initiate by optic pump some dynamic effects of changing of charge density in the film with presence of external electric field. Particularly, in homogenous systems the following modes has been investigated:

  1. Bistable mode. The system tends to the non-equilibrium phase transition from the monostable to bistable modes at a well-defined pump level.
  2. Waiting mode. It is possible to discompose the monostable system for relatively long period of time by the momentary pump impulse.
  3. Relaxation oscillations are possible with the stable pump and external voltage level as well as transition to chaos accordingly to Feigenbaum scenario with the periodically modulated optic pump level or [and] voltage.

In heterogeneous systems with well-defined parameters the number of nonlinear waves (autowaves) and non-equilibrium structures are possible to be initiated by the external optic pump. Particularly, the following ones has been investigated:

  1. Stationary spatially heterogeneous structures are possible in the systems where the diffusion coefficients for charge carriers in the substrate are relatively greater when in molecular film.
  2. Autowave processes "switch waves" ("trigger waves") are possible for the heterogeneous systems with the parameters corresponds to bistable mode of homogenous ones.
  3. Autowaves "traveling impulse" and reverberators are possible to be initiated in the systems which corresponds to waiting mode in homogenous ones when the diffusion coefficients for the molecular film are greater then for the substrate in the parallel to the substrate (and film) plate direction.

All effects above could be demonstrated in a view of computer animation. Stability of numerical solutions of the model equations has been investigated as well.


*Corresponding Address:
Victor Yu. Chekh,16 Polytechnichna Str., Design Office "Storm", National Technical University of Ukraine 252056 Kiev, Ukraine, ph: +038-044-274-0295, fax : +038-044-274-1015, email : chekh@ntu-kpi.kiev.ua



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