Search

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. [ABSTRACT FROM AUTHOR]

Arrays of Ge quantum dot molecules were grown by molecular beam epitaxy using a template, composed of a multilayer structure with layers of vertically aligned three-dimensional (3D) Ge islands buried in an Si crystal matrix with the Si capping layer on top. Depending on preparation conditions, the molecules assume various configurations, including a square frame with [001]–[010]-oriented sides. It was shown by scanning tunneling microscopy that the 3D islands are located closer to the buried SiGe mound centers with the increase of the capping layer thickness. The mechanism of the quantum dot molecule formation is ascribed to strain relaxation. It was confirmed by Monte Carlo simulations of heteroepitaxial Ge growth on the template, containing the buried Ge mound. [ABSTRACT FROM AUTHOR]

The photoluminescence (PL) of Ge/Si nanostructures synthesized by using Ge + ion bombardment is studied. The structure represents a Si substrate with GeSi nanoclusters created by 80 keV Ge implantation with a fluence of ∼ 10 15 ions/cm 2 and subsequent thermal annealing. The PL measurements confirm the advantage of Ge/Si structures synthesized using Ge + ion bombardment over the usual epitaxial structures with GeSi quantum dots. The presence of defects produced by Ge implantation results in pronounced PL at telecom wavelengths up to room temperature. The results provide a basis for creating efficient light emitters compatible with the existing Si technology. [ABSTRACT FROM AUTHOR]

Hybrid structures containing Ag nanoparticles and GeSi quantum dots were developed using the self-organization of metal nanoislands on the surface of a strained semiconductor structure. The enhanced photoluminescence from GeSi quantum dots (QDs) coupled with Ag nanoislands was obtained. Ag nanoislands epitaxially grown on top of the multilayered structures with GeSi QDs support a surface plasmon resonance that can be tuned to the QD emission wavelength by changing Ag nanoparticle parameters. The numerical modeling of surface plasmon resonance allows attributing this effect to the increase of the recombination rate due to the coupling of QD emitters with Ag nanoislands. [ABSTRACT FROM AUTHOR]

Regular pit-patterned Si(001) substrates were prepared by electron-beam lithography followed by plasma chemical etching. The geometry of the pits was controlled by varying the etching conditions and the electron-beam exposure duration. It was shown that the location of three-dimensional (3D) Ge nanoislands subsequently grown on the pit-patterned Si substrates depends on the shape of the pit bottom. In the case of pits having a sharp bottom, 3D Ge islands nucleate inside the pits. For pits with a wide flat bottom, the 3D Ge island nucleation takes place at the pit periphery. This effect is attributed to the strain relaxation depending not only on the initial pit shape, but also on its evolution during the Ge wetting layer deposition. It was shown by Monte Carlo simulations that in the case of a pit with a pointed bottom, the relaxation is most effective inside the pit, while for a pit with a wide bottom, the most relaxed area migrates during Ge deposition from the pit bottom to its edges, where 3D Ge islands nucleate. [ABSTRACT FROM AUTHOR]

The possibility of fabricating two-dimensional Si layers on a CaF2/Si(111) film by molecular beam epitaxy is studied. The growth conditions, under which the regions of two-dimensional Si layers are formed, are found. Raman spectroscopy, transmission electron microscopy, photoluminescence, and electron paramagnetic resonance (EPR) studies have shown that regions of two-dimensional Si layers are formed in epitaxial structures prepared by the deposition of one to three biatomic Si layers on the CaF2/Si(111) film surface at a temperature of 550°С. The Raman spectra of these structures exhibit a narrow peak at 418 cm–1, which is due to light scattering on vibrations of Si atoms in the plane of a two-dimensional Si layer intercalated with calcium. The EPR spectra of multilayer structures with regions of two-dimensional Si layers embedded in CaF2 demonstrate an isotropic signal with an asymmetric Dyson shape and the g-factor under illumination. Consequently, this signal can be attributed to photoinduced conduction electrons in extended two-dimensional Si islands. These results may be useful for understanding the mechanisms of the formation of two-dimensional materials on CaF2/Si(111) substrates. [ABSTRACT FROM AUTHOR]

The specific features of growth and the structural and optical properties of GaSi2 layers formed by the successive deposition of Si and CaF2 onto a Si(111) substrate with simultaneous irradiation with a high-energy electron beam are studied. The Raman spectra recorded for the electron-beam-irradiated regions exhibit peaks characteristic of CaSi2 crystal layers. Studies of the surface morphology of the structures formed show that, under the conditions of synthesis chosen, the formation of CaSi2 layers upon electron irradiation proceeds by a two-dimensional layer mechanism. The photoluminescence spectra recorded for the regions modified by the electron beam greatly differ from the spectra recorded outside these regions. [ABSTRACT FROM AUTHOR]