Abstract
In this paper, we investigated high-resolution IR absorption and reflection spectra in one-sided periodical 2D macroporous silicon structures with nano-coatings of SiO2 and CdS, ZnO nanoparticles, as well as two-sided structures of macroporous silicon without nano-coatings. After changing the resolution of spectra measurements from 2 to 1 cm–1, the oscillation period of Wannier-Stark electro-optical effect decreases by 3 times, and absorption increases by 60–100 times; and for two-sided structures the oscillation period decreases by 1.5 times and absorption increases by 25–30 %. In addition, giant absorption oscillations with positive and negative amplitudes of 107 arb. un. were evaluated in spectral regions of Si–Si–bonds and Pb centers. Similar oscillations in the reflection spectra have much less amplitudes up to 4·104 arb. un. In the spectral area of the transverse phonon ωTO (Si–Si–bonds) absorption spectra of 2D macroporous silicon structures consistent fully with data for phonon polaritons in microresonators as a result of resonance interaction of dipole-active vibrations with the frequency of ωTO in thin films with the surface modes of microresonator. In addition, microresonators interact both with each other in one-sided macroporous silicon structures and in the system of two-sided macroporous silicon. The giant absorption oscillations testify the strong interaction of surface polaritons with photons. The coherence of oscillations and large-scale spatial correlation are а result of exciton-polariton condensation on macropores as microresonators. In 2D macroporous silicon structures with nano-coatings band bending on the surface of the macropores are significant. Therefore, the generated photoelectrons link with holes, forming electron-hole pairs named as exciton-polaritons according to phenomenon of Bose-Einstein condensation.
Highlights
One of the promising materials for the development of 2D photonic structures is macroporous silicon prepared by photoanodic etching
For one-sided structures of macroporous silicon after changing the resolution of spectra measurements from 2 cm–1 to 1 cm–1, the oscillation period decreases by 3 times: from 10–12 cm–1 to 3.5–4 cm–1, and absorption increases by 60–100 times (Fig. 5 a–c)
Two-sided structures of macroporous silicon with arbitrary macropore distribution were formed by photoelectrochemical etching of one side of silicon substrate and after that etching of an other side of silicon substrate
Summary
One of the promising materials for the development of 2D photonic structures is macroporous silicon prepared by photoanodic etching It is connected with formation of structures with necessary geometry and high ratio between the cylindrical macropore depth and diameter [1, 2]. In the wavelengths, compared with the optical period of the macroporous silicon structures for the normal fall of light, the measured IR absorption is by two orders of magnitude higher than the absorption of the silicon single crystal; the formation of steps was found [8]. The change in optical absorption by the 3/2 law correlates with the frequency dependence of the dielectric permeability between the surface levels and the forbidden zones in the crystal under the influence of an electric field, which is characteristic of the impurity effect of Franz-Keldysh.
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
