We discuss the feasibility of absolute negative conductivity (ANC) in two-dimensional electron systems (2DES) stimulated by microwave radiation in transverse magnetic field. The mechanism of ANC under consideration is associated with the electron scattering on acoustic piezoelectric phonons accompanied by the absorption of microwave photons. It is demonstrated that the dissipative components of the 2DES dc conductivity can be negative (σxx = σyy < 0) when the microwave frequency Ω is somewhat higher than the electron cyclotron frequency Ωc or its harmonics. The concept of ANC associated with such a scattering mechanism can be invoked to explain the nature of the occurrence of zero-resistance "dissipationless" states observed in recent experiments.

We present a model which provides a plausible explanation of the effect of zero-resistance and zeroconductance states in two-dimensional electron systems subjected to a magnetic field and irradiated with microwaves observed in a number of experiments and of the effect main features. The model is based on the concept of absolute negative conductivity associated with photon-assisted scattering of electrons on impurities. It is shown that the main features of the effect can be attributed to the interplay of different electron scattering mechanisms.

The finite element method is used for modelling of self-positioning microstructures and nanostructures. The geometrically nonlinear problem with large rotations and large displacements is solved using a step procedure with coordinate updating after each step. It is shown that the real shape of the self-positioning structures is rather complicated and the analytical formulae have limited applicability in the estimation of such parameters as the curvature radius and/or angle of elevation.

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