V. G. Golubev

Phase transition-governed opal–VO2 photonic crystal

Three-dimensional opal–VO2 photonic crystals were prepared by the chemical bath deposition technique. The x-ray diffraction and Raman spectroscopic data confirm the crystalline perfection of VO2 impregnated into synthetic opal pores. It is shown from the optical reflectivity measurements that the photonic bandgap of the opal–VO2 composite is governed by the phase transition in VO2.

Fabrication and structural studies of opal-III nitride nanocomposites

In this paper, regular three-dimensional systems of GaN, InN and InGaN nanoclusters have been fabricated for the first time in a void sublattice of artificial opal. The opal consisted of 220 nm diameter close packed amorphous silica spheres and had a regular sublattice of voids accessible to filling by other substances. GaN, InN and InGaN were synthesized directly in the opal voids from precursors such as metal salts and nitrogen hydrides. The composites structures have been characterized using x-ray diffraction, Raman spectroscopy, atomic force microscopy and optical measurements.

Photonic Crystals with Tunable Band Gap Based on Infilled and Inverted Opal-Silicon Composites

Abstract : Three-dimensional opal-Si composites with both direct (a variable extent of filling of opal voids with Si) and inverted structures have been synthesized. A structural analysis of these fabricated systems is performed. Reflectance spectra from the surface (III) of the composites are measured. Observed spectral features are interpreted as a manifestation of the direction III photonic band gap that is tunable in position and width in the visible and near-infrared spectral ranges.

Fabrication and structure of an opal-gallium nitride nanocomposite

A three-dimensional gallium nitride lattice has been synthesized within the void sublattice of an artificial opal. The composite structure has been characterized using X-ray diffraction, Raman spectroscopy and transmission electron microscopy.

TEM and HREM study of 3D silicon and platinum nanoscale assemblies in dielectric opal matrix

In this paper, regular systems of silicon and platinum assemblies have been fabricated in a three-dimensional (3D) void sublattice of synthetic opal. Silicon was introduced into opal pores by thermal CVD. The filling of the opal pores was varied by changing the parameters of the CVD process. The samples were also filled with platinum from a solution of platinum tetrachloride in ethanol in order to fabricate metal contact to silicon. A detailed TEM and HREM structural study of opal-Si and opal-Pt-Si composites was carried out using JEM4000EXII and JEM2010 electron microscopes. It was found that silica spheres in regular opal-Si composites are uniformly covered with a nanocrystalline silicon layer up to 25-30 nm thick. To form the Pt-Si contact, the silica spheres were coated with platinum before being embedded in silicon. The presence of a substructure in the silica spheres ensures a uniform distribution of platinum over the sphere surface.

Optical properties of diamond films grown by MPCVD method with alternating nanodiamond injection

Transparent polycrystalline diamond films with grain size ranging from a few tens to hundreds of nanometres were prepared on fused silica substrate by Microwave Chemical Plasma Vapour Deposition method (MPCVD). The new technique, called alternating nanodiamonds injection, was applied for substrate pretreatment. It was demonstrated that nanodiamonds injected on fused silica substrate serve as nucleation centres and make possible an increase in nucleation density to 1010 cm-2. The influence of MPCVD parameters such as methane concentration, total pressure and substrate temperature on the crystalline structure and optical properties of diamond films were investigated by using micro-Raman spectroscopy and scanning electron microscopy, transmittance and reflectance measurements in the wavelength range of 400-1000 nm. Under appropriate MPCVD parameters, diamond films with optical transmission ~70% from 650 to 1000 nm and high content of diamond phase were fabricated.

The synthesis of clusters of iron oxides in mesopores of monodisperse spherical silica particles

The method of obtaining nanoclusters α-Fe2O3 in the pores of monodisperse spherical particles of mesoporous silica (mSiO2) by a single impregnation of the pores with a melt of crystalline hydrate of ferric nitrate and its subsequent thermal destruction has been proposed. Fe3O4 nanoclusters are synthesized from α-Fe2O3 in the pores by reducing in thermodynamically equilibrium conditions. Then particles containing Fe3O4 were annealed in oxygen for the conversion of Fe3O4 back to α-Fe2O3. In the result, the particles with the structure of the core-shell mSiO2/Fe3O4@mSiO2/α-Fe2O3 are obtained. The composition and structure of synthesized materials as well as the field dependence of the magnetic moment on the magnetic field strength have been investigated.

Low-strain heteroepitaxial nanodiamonds: fabrication and photoluminescence of silicon-vacancy colour centres

Nanodiamonds with the diamond 1332.5 cm(-1) Raman line as narrow as 1.8 cm(-1) have been produced by reactive ion etching in oxygen plasma of heteroepitaxial diamond particles grown by microwave plasma enhanced chemical vapour deposition (MWPECVD) on silicon. After the etching, a doublet is recorded in the zero-phonon line photoluminescence spectra of an ensemble of silicon-vacancy (SiV) centres at 10 K. Each line of the doublet is split into two lines corresponding to the optical transitions between the split excited and ground energy levels of the SiV centres. These Raman and photoluminescent features have been observed previously only in low-strain homoepitaxial diamond films and single-crystal diamond.

Nanodiamond Injection into the Gas-Phase During CVD Diamond Film Growth

We describe a way of combining, in the same technological cycle, the nanodiamond particle injection from a suspension and the growth of diamond films by microwave plasma chemical vapor deposition (MPCVD). The breaking of injected nanodiamond aggregates into particles of about 100 nm in size when they hit a substrate provides a nucleation density over 1010 cm−2. The films produced from a CH4+H2 mixture with a periodic injection of ND particles during the film growth are found to consist of diamond nanocrystallites with the traces of sp2 -hybridized carbon on them.

Emitting a-SiOx(Er) films and a-SiOx(Er)/a-Si:H microcavities doped with Er by remote magnetron sputtering technique

We have developed the technique of growing amorphous a-SiO(x)(Er) films and a-SiO(x)(Er)/a-Si:H multilayer structures based on spatially separating the processes of the decomposition of an oxygen-silane gas mixture in an rf glow discharge plasma and remote magnetron sputtering of an Er target. This approach allows us to control independently the film deposition rate, the Er-ion concentration and its depth distribution in the film. Time-resolved photoluminescence measurements have shown that films and planar microcavities with an Er-doped active layer exhibit internal quantum efficiency for Er ion emission of ∼75%. The method that we suggest is a way of producing effectively emitting microcavity structures, in which the distribution profile of emission centers coincides with that of the electromagnetic field in individual layers of the structure.