Coherent oscillations in IR spectra of 2d macroporous silicon structures with surface nanocoatings

Abstract

One of the promising materials for the development of 2D photonic structures is macroporous silicon obtained using photoanodic etching. Presence of periodically located cylindrical pores divided by silicon columns provides large effective surface of samples and enhanced optical and photo-physical characteristics of macroporous silicon structures. In this paper, the near-IR light absorption oscillations of 2D macroporous silicon structures with microporous silicon layers, SiO 2 nanocoatings and CdTe, ZnO surface nanocrystals are studded taking into account the Wannier-Stark electro-optical effect. An analysis of the experimental absorption spectra was carried out within the model of the resonant electron scattering with infinite amplitude on impurity states in strong electric field, with difference between two resonant energies equaled to the step of Wannier-Stark ladder. The constant oscillation period specifies the realization of Wannier-Stark effect on the randomly distributed surface bonds on siliconnanocoating interface. We compared the IR absorption oscillations in 2D macroporous silicon with surface nanocoatings, analyzed shifts and deviations of oscillation peaks. The coherence of the IR spectra oscillations increases with the decrease of surface state concentration and with the optimal area of contact of nanocrystals to the macropore surface. Thus, the shift of oscillations for ZnO nanoparticles with optimal size of nanocrystals (3.7-4.4 nm) leads to deviations of the oscillation peaks within 0.26-0.42 meV, the oscillation coherence reaches 0.25-0.4 %. The small broadening parameter of the Wannier-Stark ladder levels  = 0.30.8 cm -1 equals to that for surface phonon polaritons measured in thin films of II-VI semiconductors. Controllability and coherence of the investigated system are determined by forming of coherent Wannier levels in a narrow triangular potential well formed by an electric field at the silicon-nanocoating interface. In addition, we have proposed a high coherent optical quantum computer based on the quantum Wannier-Stark electro-optical effect on a silicon matrix with macropores and a layer of nanocrystals on the macropore surface.