Aigul F. Zinovieva

The emission properties of a single Si microdisk resonator with a deterministically embedded GeSi quantum dot (QD) stack have been investigated. The results demonstrate selective excitation of different modes of the resonator depending on the position of QDs. The photoluminescence (PL) spectrum changes dramatically depending on the location of the QDs in the resonator. For the central QD position, the excitation of low Q-factor Mie modes with high field concentration in the center of resonator results in the appearance of a broad PL band. When the stack of QDs is shifted from the center to the edge of the Si resonator, the quenching of this PL band is observed and narrow PL peaks corresponding to whispering gallery modes (WGMs) appear in the PL spectrum. It is found that resonator modes can be excited not only by QDs but also by the radiation of the wetting layer. It is shown that a GeSi island on the top of the QD stack, not covered by silicon, can play the role of a nanoantenna, redirecting radiation to the upper half-space, which is especially important for WGMs that usually radiate sideways.

Впервые экспериментально продемонстрирована возможность получения силицена на модифицированных электронным облучением подложках CaF2/Si(111). Показано, что формирующиеся под электронным пучком участки планарной поверхности CaSi2 с гексагональной упаковкой могут быть использованы как естественная основа для последующего роста силицена. На таких поверхностях проведено осаждение кремния и методами атомно-силовой микроскопии и спектроскопии комбинационного рассеяния света получено подтверждение формирования островков силицена.

For the first time, the possibility of producing silicene on CaF₂/Si(111) substrates modified by electron irradiation is experimentally demonstrated. It is shown that areas of the planar surface of CaSi₂ with hexagonal packing formed under an electron beam can be used as a natural template for the subsequent growth of silicene. Silicon is deposited on such surfaces and the formation of silicene islands is confirmed by atomic force microscopy and Raman spectroscopy.

In this paper, we study the effects of GeSi quantum dot emission coupling with the collective modes in the linear chains of Si disk resonators positioned on an SiO₂ layer. The emission spectra as a function of the chain period and disk radius were investigated using micro-photoluminescence (micro-PL) spectroscopy. At optimal parameters of the disk chains, two narrow PL peaks, with quality factors of around 190 and 340, were observed in the range of the quantum dot emission. A numerical analysis of the mode composition allowed us to associate the observed peaks with two collective modes with different electric field polarization relative to the chain line. The theoretical study demonstrates the change of the far-field radiation pattern with increasing length of the disk chain. The intensive out-of-plane emission was explained by the appearance of the dipole mode contribution. The obtained results can be used for the development of Si-based near-infrared light sources.

The effects of resonance interaction of plasmonic and photonic modes in hybrid metal-dielectric structures with square Al nanodisk lattices coupled with a Si waveguide layer were investigated using micro-photoluminescence (micro-PL) spectroscopy. As radiation sources, GeSi quantum dots were embedded in the waveguide. A set of narrow PL peaks superimposed on the broad bands were observed in the range of quantum dot emissions. At optimal parameters of Al nanodisks lattices, almost one order increasing of PL intensity was obtained. The experimental PL spectra are in good agreement with results of theoretical calculations. The realization of high-quality bound states in the continuum was confirmed by a comparative analysis of the experimental spectra and theoretical dispersion dependences. The results demonstrated the perspectives of these type structures for a flat band realization and supporting the slow light.

The formation of CaSi₂ films on Si(111) with the molecular-beam epitaxy (MBE) of CaF₂ under fast electron-beam irradiation was investigated. The method of a high-planarity CaSi₂ film synthesis assisted by electron-beam irradiation was developed. We combined two approaches to reduce the film roughness: the post-growth electron irradiation and codeposition of additional Si during CaF₂ growth. The application of the solid-phase epitaxy technique at the initial stage of film growth allowed for us to reduce surface roughness down to 1–2 nm.

The formation of CaSi₂ polycrystalline structures under the postgrowth electron irradiation of epitaxial CaF₂/Si(111) films with embedded thin Si layers was studied. The dependence on the electron exposure time was investigated for two types of structures with different film thicknesses. The optimal conditions for the formation of two-dimensional CaSi₂ structures were found. Raman spectra of the structures after a 1 min electron irradiation demonstrated only one pronounced peak corresponding to the vibrations of Si atoms in the plane of the calcium-intercalated two-dimensional Si layer. An increase in the exposure time resulted in the transition from two- to three-dimensional CaSi₂ structures having more complex Raman spectra with additional peaks typical of bulk CaSi₂ crystals. Based on the results of microscopic studies and transport measurements, a model explaining the observed effects was proposed.

Structural and optical properties of two-dimensional Si and Ge layers formed by molecular beam epitaxy on CaF 2 /Si(111) substrates