Papers by Dmitry Goloshchapov
Конденсированные среды и межфазные границы
Конденсированные среды и межфазные границы
Semiconductors, 2019
The possibility of synthesizing integrated GaN/por-Si heterostructures by plasma-assisted molecul... more The possibility of synthesizing integrated GaN/por-Si heterostructures by plasma-assisted molecular beam epitaxy without an A1N/Si buffer layer is demonstrated. The beneficial effect of the high-temperature nitridation of a silicon substrate before GaN growth on the crystal quality of the GaN/Si layers is shown. It is established that, to obtain two-dimensional GaN layers on Si(111), it is reasonable to use compliant por-Si substrates and low-temperature GaN seed layers with a 3D morphology synthesized by plasma-assisted molecular beam epitaxy at relatively low substrate temperatures under stoichiometric conditions and upon enrichment with nitrogen. In this case, a self-assembled array of GaN seed nanocolumns with a fairly uniform diameter distribution forms on the por-Si substrate surface. The basic GaN layers, in turn, should be grown at a high temperature under stoichiometric conditions upon enrichment with gallium, upon which the coalescence of nucleated GaN nanocolumns and growth of a continuous two-dimensional GaN layer are observed. The use of compliant Si substrates is a relevant approach for forming GaN-based semiconductor device heterostructures by plasma-assisted molecular beam epitaxy.
Semiconductors, 2019
Integrated heterostructures exhibiting a nanocolumnar morphology of the In x Ga 1-x N film are gr... more Integrated heterostructures exhibiting a nanocolumnar morphology of the In x Ga 1-x N film are grown on a single-crystal silicon substrate (c-Si(111)) and a substrate with a nanoporous buffer sublayer (por-Si) by molecular-beam epitaxy with the plasma activation of nitrogen. Using a complex of spectroscopic methods of analysis, it is shown that the growth of In x Ga 1-x N nanocolumns on the por-Si buffer layer offer a number of advantages over growth on the c-Si substrate. Raman and ultraviolet spectroscopy data support the inference about the growth of a nanocolumn structure and agree with the previously obtained X-ray diffraction (XRD) data indicative of the strained, unrelaxed state of the In x Ga 1-x N layer. The growth of In x Ga 1-x N nanocolumns on the por-Si layer positively influences the optical properties of the heterostructures. At the same half-width of the emission line in the photoluminescence spectrum, the emission intensity for the heterostructure sample grown on the por-Si buffer layer is ~25% higher than the emission intensity for the film grown on the c-Si substrate.
Photonics
In our work, the effect of a dental Er:YAG pulsed laser and a diamond cylindrical drill with a tu... more In our work, the effect of a dental Er:YAG pulsed laser and a diamond cylindrical drill with a turbine handpiece on dentin tissue was studied using spectral imaging. The combination of spectral imaging of FTIR microspectroscopy data and subsequent multivariate analysis (hierarchical cluster analysis (HCA) and principal component analysis (PCA)) was shown to unambiguously detect visually indistinguishable structural changes occurring in the hard dental tissue (dentin) depending on the method used for their pre-processing, and to classify and differentiate the identified features at the submicron level with high spatial resolution. The detectable spectral transformations indicate that the preparation of dental tissue with a dental laser leads to significant changes in the organic components of dentin, which may affect adhesion. The use of a diamond cylindrical drill with a turbine handpiece is characterized by a larger area (depth) of the altered hard tissue than in the case of a dent...
International Journal of Molecular Sciences
Using a biomimetic strategy and bioinspired materials, our work proposed a new technological appr... more Using a biomimetic strategy and bioinspired materials, our work proposed a new technological approach to create a hybrid transitional layer between enamel and dental biocomposite. For this purpose, an amino acid booster conditioner based on a set of polar amino acids (lysine, arginine, hyaluronic acid), calcium alkali, and a modified adhesive based on BisGMA and nanocrystalline carbonate-substituted hydroxyapatite are used during dental enamel restoration. The molecular properties of the hybrid interface formed using the proposed strategy were understood using methods of multivariate statistical analysis of spectral information collected using the technique of synchrotron infrared microspectroscopy. The results obtained indicate the possibility of forming a bonding that mimics the properties of natural tissue with controlled molecular properties in the hybrid layer. The diffusion of the amino acid booster conditioner component, the calcium alkali, and the modified adhesive with nano...
Stomatologiâ, 2022
OBJECTIVE The aim of the studyis the peculiarities of the molecular composition of the biointerfa... more OBJECTIVE The aim of the studyis the peculiarities of the molecular composition of the biointerface between the native human dental tissue and the dental composite, created in an alkaline environment, based on synchrotron chemical infrared micro-mapping. MATERIAL AND METHODS When creating a biomimetic interface under alkaline conditions, we used an original bioprimer, dentin conditioner, nanofilled universal adhesive, and a light-curing compomer based on BIS-GMA. RESULTS Biointerface analysis was carried out on the basis of chemical infrared micro-mapping, implemented using the equipment of the Australian Synchrotron, and subsequent multivariate cluster analysis of the collected spectral data array. It was shown that the use of a primer modified with a set of polar amino acids additionally facilitated the opening of dentinal tubules and the penetration of the bioprimer components into the dentin with the formation of a deeper transitional hybrid layer. At the same time, modification of the Bis-GMA adhesive using nanocrystalline carbonate-substituted hydroxyapatite, which has a structural and morphological organization similar to natural dental tissue apatite, led to an increase in the degree of conversion of the used adhesive material during polymerization. CONCLUSION Using a biomimetic strategy and nanocrystals of carbonate-substituted hydroxyapatite as a filler of a universal adhesive, the necessary conjugation at the interface with dentin can be achieved without disrupting the polymerization processes, as well as preserving the natural structural complexity of the intact tissue, which makes it possible to take into account the individual characteristics of the patient.
Coatings, May 3, 2022
This article is an open access article distributed under the terms and conditions of the Creative... more This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY
Results in Engineering
The problem of engineering a biomimetic mineralized layer on the surface of native dental tissue ... more The problem of engineering a biomimetic mineralized layer on the surface of native dental tissue (bio-template) was considered in our work. The formation of the mineralized layer on a biotemplate is achieved with the use of nanocrystalline carbonatesubstituted calcium hydroxyapatite (HAp), calcium alkali, and a complex of polyfunctional organic and polar amino acids. By applying the set of structural and spectroscopic methods of analysis we have confirmed the formation of a mineralized biomimetic HAp layer on the surface of bio-template with properties resembling those of natural hard tissue. The thickness of the biomimetic mineralized layer varies from 300 to 500 nm, while the direction of some ncHAp nanocrystals coincides with that of the apatite crystals in the enamel. We also demonstrated that the engineered mineralized HAp layer was characterized by homogeneous micromorphology and enhanced nanohardness in the region of the enamel rods exceeding those of native enamel. The development of a strategy for biomimetic engineering and a technique for enamel surface pre-treatment to enable tissue mineralization has huge potential in dental applications.
Pharmaceutics
This article is an open access article distributed under the terms and conditions of the Creative... more This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY
Biomimetics
The application of biomimetic strategies and nanotechnologies (nanodentology) has led to numerous... more The application of biomimetic strategies and nanotechnologies (nanodentology) has led to numerous innovations and provided a considerable impetus by creating a new class of modern adhesion restoration materials, including different nanofillers. An analysis of the molecular properties of biomimetic adhesives was performed in this work to find the optimal composition that provides high polymerisation and mechanical hardness. Nanocrystalline carbonate-substituted calcium hydroxyapatite (nano-cHAp) was used as the filler of the light-cured adhesive Bis-GMA (bisphenol A-glycidyl methacrylate). The characteristics of this substance correspond to the apatite of human enamel and dentin, as well as to the biogenic source of calcium: avian eggshells. The introduction and distribution of nano-cHAp fillers in the adhesive matrix resulted in changes in chemical bonding, which were observed using Fourier transform infrared (FTIR) spectroscopy. As a result of the chemical bonding, the Vickers hard...
Journal of Imaging
This pilot study presents a practical approach to detecting and visualising the initial forms of ... more This pilot study presents a practical approach to detecting and visualising the initial forms of caries that are not clinically registered. The use of a laser-induced contrast visualisation (LICV) technique was shown to provide detection of the originating caries based on the separation of emissions from sound tissue, areas with destroyed tissue and regions of bacterial invasion. Adding microRaman spectroscopy to the measuring system enables reliable detection of the transformation of the organic–mineral component in the dental tissue and the spread of bacterial microflora in the affected region. Further laboratory and clinical studies of the comprehensive use of LICV and microRaman spectroscopy enable data extension on the application of this approach for accurate determination of the boundaries in the changed dental tissue as a result of initial caries. The obtained data has the potential to develop an effective preventive medical diagnostic approach and as a result, further perso...
Optical Materials
Abstract This study examines the effect of etching modes and their combination on the design, mic... more Abstract This study examines the effect of etching modes and their combination on the design, microstructure and optical properties of compliant substrates based on porous silicon. Data obtained from microstructural and spectroscopic methods of analysis showed that, under invariable parameters of the crystal lattice, the value of residual stresses, size of the crystallites, volume of crystalline fraction, and the reflectivity and energy of direct transitions in the porous layer of silicon all depend on the combination of the etching modes. However, they do not always correlate with the value of the layer porosity calculated from an analysis of SEM images. Competent selection of these parameters can provide additional advantages in case of monolithic integration of AIIIBV layers and the obtained compliant silicon substrate. Proper selection also ensures an efficient solution to problems concerning the control of deformation and residual stresses in the epitaxial layer. As an outcome, this will open up new methods of design and development for effective devices related to silicon-based electronics.
Journal of Physics: Conference Series, 2021
360 nm and 700 nm thick GaAs layers were grown by MO MOCVD growth technique directly on compliant... more 360 nm and 700 nm thick GaAs layers were grown by MO MOCVD growth technique directly on compliant Si (100) substrate and on supper-lattice (SL) AlGaAs buffer layer. The XRD study revealed better structural quality for the sample grown on SL / por-Si buffer. AFM study revealed a smoother sample surface with blocks of more regular rectangular shape and larger size as well. Photoluminescence spectra of the samples revealed an energy shift of PL maximum intensity for both samples. Sample grown on SL buffer also showed higher PL intensity corresponding to better crystalline perfection.
Semiconductors, 2018
The properties of porous GaAs samples produced by the electrochemical etching of single-crystal n... more The properties of porous GaAs samples produced by the electrochemical etching of single-crystal n-GaAs(100) wafers are studied by X-ray diffraction analysis, electron microscopy, and infrared and ultraviolet spectroscopy. It is possible to show that, by choosing the composition of the electrolyte and the conditions of etching, samples can be produced not only with different degrees of porosity and pore sizes (nanopores/micropores), but with another type of sample surface as well. The etching of n-GaAs(100) wafers under the conditions chosen in the study does not change the orientation of the porous layer with respect to the orientation of the single-crystal GaAs(100) substrate. At the same time, etching induces a decrease in the half-width of the diffraction peak compared to that for the initial wafer, a splitting of the phonon mode in the infrared spectra and a partial shift of the components in accordance with the parameters of anodic etching, and a change in the optical properties in the ultraviolet region.
Semiconductors, 2017
The properties of epitaxial Ga x In 1-x P alloys with an ordered arrangement of atoms in the crys... more The properties of epitaxial Ga x In 1-x P alloys with an ordered arrangement of atoms in the crystal lattice are studied by a number of spectroscopic methods. The alloys are grown by metal-organic chemical vapor deposition onto single-crystal GaAs(100) substrates. It is shown that, under conditions of the coherent growth of an ordered Ga x In 1-x P alloy on a GaAs(100) substrate, atomic ordering results in radical modifications of the optical properties of the semiconductor compared to the properties of disordered alloys. Among these modifications are a decrease in the band gap and an increase in the luminescence intensity. From the data of dispersion analysis of the infrared dispersion spectra and from ultraviolet spectroscopy data obtained in the transmittance-reflection mode of measurements, the basic optical characteristics, specifically, the dispersion of the refractive index and the high-frequency permittivity of Ga x In 1-x P alloys with ordering are determined. All of the experimental data are in good agreement with the developed theoretical concepts.
Journal of Physics: Conference Series, 2021
The aim of the study is the problem of formation of the biomimetic interface between the dental p... more The aim of the study is the problem of formation of the biomimetic interface between the dental product and dentin of the human tooth as well as the investigations of molecular-chemical features in biointerface with the use of molecular multivariate IR-visualization. The data on synchrotron IR-mapping made enabled to differentiate the regions of sound dentin tissue and biomimetic transition layer and also to determine molecular groups responsible for the process of integration.
Semiconductors
Social background and planning objectives differentiate two kinds of development modes for new to... more Social background and planning objectives differentiate two kinds of development modes for new towns. One starts in the period of post-urbanization and post-industrialization and is committed to improving living conditions and dispersing urban central areas. The other begins in the stage of pre-urbanization and pre-industrialization with the purpose of promoting the development of urbanization and industrialization. However, academics have not given enough attention to researching the relationship between the different modes and their respective social backgrounds. This paper first proposes these two kinds of development modes and analyses how their different social contexts and institutional backgrounds lead to different planning and construction characteristics. Then, taking Beijing as an example, this paper presents a complete review of the development and transformation history of the planning and construction of China's new towns with different urbanization levels and in an institutional context. The whole history and transformation process can be considered a demonstration and evolution of the two different development modes. Accordingly, by analyzing the respective characteristics and transformation processes in different periods, this study reveals the impact of social background on the new towns' development and the problems caused by different development modes.
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Papers by Dmitry Goloshchapov