Wannier-Stark effect and electron-phonon interaction in macroporous silicon structures with SiO2 nanocoatings

Abstract

We investigated the contribution of electron-phonon interaction to the broadening parameter Γ of the Wannier-Stark ladder levels in oxidized macroporous silicon structures with different concentration of Si-O-Si states (TO and LO phonons). The obtained value of the Wannier-Stark ladder parameter Γ is much less than the djacent level energy evaluated from giant oscillations of resonance electron scattering on the surface states. We determined the influence of broadening on the oscillation amplitude in IR absorption spectra as interaction of the surface multi-phonon polaritons with scattered electrons. This interaction transforms the resonance electron scattering in samples with low concentration of Si-O-Si states into ordinary scattering on ionized impurities for samples with high concentration of Si-O-Si states. The transformation takes place at the scattering lifetime coinciding with the period of electron oscillations in the surface electric field.

Light Emitting “Polymer-Nanoparticles” Coatings on Macroporous Silicon Substrates

“…4 a and [23]). The obtained values of the broadening parameter  correspond to those for surface phonon polaritons measured in thin films of IIVI semiconductors [16].…”

“…IR absorption for substrates of oxidized macroporous silicon and macroporous silicon with microporous silicon layer (curves 3, 4) is lower and comparable. Thus, nanocoatings of polyethyleneimine with carbon multiwall nanotubes increase surface depletion [27] and IR absorption of macroporous silicon without nanocoatings and decrease surface accumulation [15,16] for SiO 2 coatings and microporous silicon layer. The Raman spectra of macroporous silicon structures with nanocoatings of polyethyleneimine with carbon multiwall nanotubes (Fig.…”

“…The oscillations of IR absorption result from electron resonance scattering in a strong electric field by impurity states on the surface of macropores, with the difference between two resonance energies E = Fa = 810 cm -1 equal to the WannierStark step [16]. The oscillations have small amplitudes of IR absorption and nearly the same period for samples with surface cleaning and those of macroporous silicon without preliminary surface cleaning.…”

“…Local electric fields at the "macroporenanocoating" interface [15] increase the resulted electron flow from the silicon matrix toward the nanocrystal layer and reduce the non-radiative recombination in light-emitting nanocoatings. The strength of a local electric field can be determined from the WannierStark effect [16].…”

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

“…The interband interaction has been studied and demonstrated that it does not break the Wannier-Stark ladder [18]. The electron-phonon interaction was considered in [21]. According to [18], the phonon damping effect leads to an additional shift towards the phase behavior.…”