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Teys S.A.,RAS Semiconductor Physics Institute
Applied Surface Science | Year: 2017

Structural and morphological features of the wetting layer formation and the transition to the three-dimensional Ge growth on (111) and (100) Si surfaces under quasi-equilibrium growth conditions were studied by means of scanning tunneling microscopy. The mechanism of the transition from the wetting layer to the three-dimensional Ge growth on Si was demonstrated. The principal differences and general trends of the atomic processes involved in the wetting layers formation on substrates with different orientations were demonstrated. The Ge growth is accompanied by the Ge atom redistribution and partial strain relaxation due to the formation of new surfaces, vacancies and surface structures of a decreased density. The analysis of three-dimensional Ge islands sites nucleation of after the wetting layer formation was carried out on the (111) surface. The transition to the three-dimensional growth at the Si(100) surface begins with single {105} facets nucleation on the rough Ge(100) surface. © 2016 Elsevier B.V.

Tsarev A.V.,RAS Semiconductor Physics Institute
Optics Letters | Year: 2010

A compact acousto-optic (AO) filter with multireflector (MR) beam expanders constituted by 32 photonic crystal rows of airholes in LiNbO3 waveguide has been proposed and numerically studied by the two-dimensional finitedifference- time-domain method. The diameter and position of every row of holes are gradually varied along MR beam expanders in order to provide high efficiency and good sidelobe suppression. Device sizes are 70 μ m × 150 μ m, with an FWHM bandwidth of 4:4 nm, a tuning range of 110 nm, internal loss of-3 dB, and sidelobes of-20 dB, thus providing a unique value of 0:6 μ m2 for the productFWHMbandwidth by an AO length. It is intended for use in fiber optics telecommunications and sensing. © 2010 Optical Society of America.

Tsarev A.V.,RAS Semiconductor Physics Institute
Optics Letters | Year: 2010

This Letter presents a beam splitter in a silicon-on-insulator (SOI) ridge waveguide loaded by a photonic crystal row of holes close to the Brewster angle. The propagation of the fundamental guided mode in this structure has been examined by the three-dimensional finite-difference time-domain method. It is shown that a TE-polarized optical beam exhibits the Brewster effect at an incident angle of about 39°, giving a small splitting ratio (<0.04) in a wide spectral range for silica-filled holes with a typical diameter of 200 nm and a spacing of 300 nm. The row of holes close to the Brewster angle is the perspective to be used in developing complementary metal-oxide semiconductor-compatible tunable devices based on multireflector filtering technology. © 2010 Optical Society of America.

Korotkov A.S.,RAS Semiconductor Physics Institute
Journal of Solid State Chemistry | Year: 2014

Space formations of GeO polyhedra have been analyzed for 114 noncentrosymmetric germanates. The type of GeO polyhedra space formations is dependent on the stoichiometric ratio SR=n(O)/n(Ge), where n(O) is the number of oxygen and n(Ge) is the number of germanium atoms in formal composition of the compound. Individual (GeO) polyhedra are found for SR≥3 chains of the polyhedra that exist in the range of SR=3-5. Only framework formations are possible at SR≤2.7. © 2014 Elsevier Inc.

Tsarev A.,RAS Semiconductor Physics Institute
Proceedings of SPIE - The International Society for Optical Engineering | Year: 2013

Paper present results of numerical investigation by finite difference time domain (FDTD) method of new tunable optical filter which utilized multiple coupled silicon wire waveguides on SOI structures. In order to improve simulation accuracy we introduce modified effective index method (MEIM) which correctly describes in 2d case both the phase and the group indexes in 3d strip waveguide, typically used in silicon photonics in thin SOI structures. MEIM utilizes the combined index profile containing two spatial parameters as in actual 3d waveguide. Namely, the central part with refractive index of Si has the width w around waveguide height h and it is mainly responsible for the group index. The base part has the same width W as in 3d waveguide and refractive index Nb which is mainly responsible for the phase index. As a results, MEIM provides typical error about 1%-2% for the filter free spectral range (FSR) instead of about 30% for EIM. Numerical simulation of novel filter proves its general conception and demonstrates that a short 360 mkm structure with 32 couplers has spectral resolutions 1.5 nm, loss -1 dB and sidelobes below -26 dB. It provides wavelength tuning (without Vernier principle) within total FSR 36 nm at central optical wavelength 1.55 mkm by temperature change up to 100 C in four sets of thermo optic phase shifters. Device of 1 cm size provides 0.05 nm filter linewidth. Filter can be manufactured by CMOS compatible technology and very promising for applications in photonics.

The intermediate stages of the formation of a Ge wetting layer on Si(111) and Si(100) surfaces under quasiequilibrium grow conditions have been studied by means of scanning tunneling microscopy. The redistribution of Ge atoms and relaxation of mismatch stresses through the formation of surface structures of decreased density and faces different from the substrate orientation have been revealed. The sites of the nucleation of new three-dimensional Ge islands after the formation of the wetting layer have been analyzed. Both fundamental differences and common tendencies of atomic processes at the formation of wetting layers on Si(111) and Si(100) surfaces have been demonstrated. The density of three-dimensional nuclei on the Si(111) surface is determined by changed conditions for the surface diffusion of Ge adatoms after change in the surface structure. Transition to three-dimensional growth on the Si(100) surface is determined by the nucleation of single {105} faces on the rough Ge(100) surface. © 2012 Pleiades Publishing, Ltd.

Tsarev A.V.,RAS Semiconductor Physics Institute
Optics Express | Year: 2011

Multiple optical elements utilize crossing of channel optical waveguides. This paper introduces efficient silicon wire waveguide crossing by means of vertical coupling of tapered Si wire with upper polymer wide strip waveguide through a silica buffer. Numerical simulations by 3D FDTD prove that optimal structure of 70 μm length can provide 98% efficiency for through pass and 99.9% efficiency for cross pass, as well as negligible back reflection (-50 dB) and cross talk (-70 dB). Proposed waveguide crossing on thin silicon-on-insulator CMOS compatible structures could find multiple applications in Photonics. © 2011 Optical Society of America.

Tsarev A.,RAS Semiconductor Physics Institute
Optics Letters | Year: 2013

A modified effective index method (MEIM), which correctly describes, in a 2D case, both the phase and the group indexes in a 3D photonic wire waveguide, is introduced in the Letter. The MEIM utilizes the combined index profile with two spatial parameters. The central part with wire index has the width of nearly a wire height, and it is responsible for the group index. The basic part has the width of 3D wire and the smaller refractive index Nb. Numerical experiments by finite-difference time-domain method of Fabry-Perot and asymmetric Mach-Zehnder interferometers constructed by silicon wires prove that the MEIM gives an excellent agreement (about 2%) with test 3D simulation in comparison with an about 40% error for the effective index method. © 2013 Optical Society of America.

Gritsenko V.A.,RAS Semiconductor Physics Institute
Physics-Uspekhi | Year: 2012

Amorphous oxide SiO 2, oxynitride SiOxNy, and silicon nitride Si 3N 4 are the three key dielectric materials of silicon device technology. Silicon nitride is currently finding use in a variety of applications, in particular, as a storage medium in next-generation flash memory devices. Varying the chemical composition of nonstoichiometric silicon-rich SiN x allows a wide-range control of its optical and electrical properties. In this review, an analysis of the electronic structure of silicon nitride of varying composition is presented. ©2012 Uspekhi Fizicheskikh Nauk, Russian Academy of Sciences.

The fluctuations of the microwave electromotive force in the magnetic field state with an extremely low conductivity have been revealed in 2D electronic Corbino disks prepared based on GaAs/AlAs heterostructures. The experimental data are attributed to the spatial inhomogeneity and time instability of the electronic states that have zero conductivity and are induced by microwave radiation in the 2D Corbino disks at high filling factors. © 2010 Pleiades Publishing, Ltd.

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