Обсуждаются механизмы образования, кристаллическая структура, особенности дефектообразования и состав формируемой при пониженных (менее 900 °С) ростовых температурах на поверхности Si из углеводорода и гидридов сплошной карбидной пленки. Показано, что при выращивании в течение длительного времени толстых карбидных слоев под карбидным слоем образуется система макродефектов и подстилающая поверхность, подобная пористому кремнию. Присутствие переходного слоя твердого раствора между карбидным слоем и подложкой из кремния проявляется в положении линий люминесцентных спектров исследуемых структур в области ближнего ИК диапазона. Для установления наиболее вероятных механизмов наблюдаемых излучательных переходов проведен анализ температурного поведения спектральных линий и расчет характера распределения по слоям структуры возбуждаемых светом неравновесных носителей заряда.

The structure and luminescence properties of Czochralski-grown n-Si samples implanted with oxygen ions have been comprehensively analyzed using photoluminescence and transmission electron microscopy (TEM). A high oxygen concentration (5 × 1019 cm–3) in a layer at a depth of 0.3–0.8 µm was obtained in the implanted material. The samples have been annealed according to the multistage technique, including low-temperature (650/800°C) and high-temperature (1000°C) stages, to obtain oxygen precipitates and a system of various extended defects. The structure of the dislocation-photoluminescence spectrum is determined by the features of interaction of dislocations with oxygen during annealing. It is established that decoration of dislocations with oxygen precipitates leads to quenching the D1 and D2 lines. The strong D1 line is due to “pure” (without oxygen precipitates) dislocations. Free amorphous oxygen precipitates emit at a wavelength of 1476 nm.

As a result of in situ irradiation in a high-resolution electron microscope, structure modelling, and calculation of images, it is shown that the incorporation of self-interstitial atoms into the extension region of the core of any dislocation is accompanied by their ordering in the form of cluster-like {111}, {001}, and {113} defects, which provide core relaxation. This fact made it possible to visualize for the first time the core structure of undissociated 60° dislocations of two types, glide ( $$60_{{{\text{sh}}}}^{^\circ }$$ ) and sessile ( $$60_{{{\text{gl}}}}^{^\circ }$$ ), which coexist at plastic deformation of Si. It is shown that incorporation of self-interstitial atoms into the dislocation core correlates with an increase of only the D2 line in the photoluminescence spectrum, while perfect sessile a/2〈110〉 dislocations with a core, consisting of paired 5/7-link atomic rings without dangling bonds, are responsible for the rise of the D1 line. This universal core occurs at coalescence of two $$60_{{{\text{sh}}}}^{^\circ }$$ dislocations during their slip in intersecting planes {111}, $$60_{{{\text{sh}}}}^{^\circ }$$ → $$60_{{{\text{gl}}}}^{^\circ }$$ transition, and transformation of a Frank dislocation into a perfect one.

The work discusses mechanisms of formation, crystal structure, some features of defect formation, and composition of the solid carbide film formed from a hydrocarbon and hydrides on the Si surface at low (< 900 °C) growth temperatures. It is shown that a system of macrodefects and a subsurface structure similar to porous silicon are formed under a carbide layer as a result of long-term growth of thick carbide layers. The presence of a solid solution transition layer between the carbide layer and the silicon substrate is manifested in the structure of luminescence spectra of studied structures in the near IR region. The most probable mechanisms of observed radiative transitions were established by analysing the temperature behavior of spectral lines and calculating the layer distribution of structures of light-excited non-equilibrium charge carriers.

The crystal structure features and light-emitting properties of 3C–SiC island films grown at decreased temperatures on the Si(100) surface by vacuum chemical epitaxy with the use of hydrogen-containing compounds are studied. The nucleation character and growth mechanisms of the nanocrystalline texture of microislands and the effect of elastic stresses accumulated on the surface of a growing carbide film on the shape of nucleating islands are traced by the methods of microscopy. The cathodoluminescence spectra from the surface carbidized Si layer and different areas of an individual 3C–SiC island are compared. The possible mechanisms of the appearance of additional spectral lines shifted with respect to the major peak towards the red and ultraviolet spectral regions in the observed spectra of epitaxial structures are discussed. These emission bands were earlier revealed only in the luminescence spectra of SiC nanocrystallites embedded into different (most often SiO2) matrices. The comparative analysis of the behavior of lines in the observed luminescent spectra has not revealed any appreciable size effect of formed surface nanocrystallites on their positions, but demonstrated their evident dependence on the oxygen content at the 3C–SiC layer/silicon substrate interface.

PEALD-grown hafnia and alumina buried oxide (BOX) stacks in silicon-on-insulator (SOI) structures were produced and characterized by XTEM and pseudo-MOSFET techniques. The ferroelectric phases of hafnia were observed by XTEM and SAED. It was shown that the minimal interface states density (IFS) < 10(12) cm(-2) and the maximal one with a memory window MW similar to 1 V could be obtained by the right choice of high-k dielectric layer sequence in BOX stack and thermal processing.

AbstractStructural defects formed in epitaxial GaAs layers as a result of 250-keV N^+ ion implantation to doses within 5 × 10^14–5 × 10^16 cm^–2 have been studied by the X-ray diffraction (XRD) and transmission electron microscopy techniques. No amorphization of the ion-implanted layer took place in the entire dose range studied. The implantation to doses of 5 × 10^14 and 5 × 10^15 cm^–2 led to the appearance of an additional peak on XRD curves, which was related to the formation of a stressed GaAs layer with positive deformation arising due to the formation of point-defect clusters. The implantation to a dose of 5 × 10^16 cm^–2 led to the formation of a dense structure of extended defects in the implanted layer, which was accompanied by the relaxation of macrostresses to the initial state.

Structural defects formed in epitaxial GaAs layers as a result of 250-keV N+ ion implantation to doses within 5 × 1014–5 × 1016 cm–2 have been studied by the X-ray diffraction (XRD) and transmission electron microscopy techniques. No amorphization of the ion-implanted layer took place in the entire dose range studied. The implantation to doses of 5 × 1014 and 5 × 1015 cm–2 led to the appearance of an additional peak on XRD curves, which was related to the formation of a stressed GaAs layer with positive deformation arising due to the formation of point-defect clusters. The implantation to a dose of 5 × 1016 cm–2 led to the formation of a dense structure of extended defects in the implanted layer, which was accompanied by the relaxation of macrostresses to the initial state.

The continuous transfer of (001)Si layers 0.2–1.7 μm thick by implanted hydrogen to the c-sapphire surface during direct bonding at high temperatures of 300–500°C is demonstrated for the first time. The formation of an intermediate silicon-oxide layer SiOx during subsequent heat treatments at 800–1100°C, whose increase in thickness (up to 3 nm) correlates with an increase in the positive charge Qi at the heterointerface to ~1.5 × 1012 cm–2 in contrast to the negative charge at the SiOx/Al2O3 ALD heterointerface. During silicon-layer transfer to sapphire with a thermal silicon-dioxide layer, Qi decreases by more than an order of magnitude to 5 × 1010 cm–2 with an increase in the SiO2 thickness from 50 to 400 nm, while the electron and hole mobilities barely differ from the values in bulk silicon. Based on these results, a qualitative model of the formation of positively charged oxygen vacancies in a 5-nm sapphire layer near the bonding interface is proposed.

Electroluminescence (EL) from light-emitting diodes (LEDs) at wavelengths in the range 1000-1650 nm, current densities of up to 10 A/cm2, and temperature of 64 K has been studied. p-Cz-Si wafers were irradiated with low-energy electrons (a variant of the technique based on rapid thermal annealing) and annealed in a chlorine-containing atmosphere at 1100°C. To obtain p-n junctions and ohmic contacts, layers of polycrystalline silicon doped with phosphorus and boron were deposited by vapour-phase epitaxy onto the opposite sides of the wafers. The dislocation structure in the samples under study consists of gliding 60⁰-dislocations and perfect and faulted dipoles. An analysis showed that the transformation of EL spectra with current is precisely described by six Gaussian lines. The peak wavelengths are current-independent and equal to 1235, 1309, 1369, 1414, 1472, and 1515 nm. The current dependences of the intensity of the EL lines have been determined.

The dependences of photoluminescence (PL) and the structure of {113} defects induced in n‐Cz‐Si (100) wafers by implantation of 350 keV O+ ions at a dose of 3.7 × 1014 cm−2 on the annealing time at 700 °C for 0.5–2.0 h in a chlorine‐containing atmosphere have been studied in detail. Extended defects were examined by high‐resolution transmission electron microscopy (HRTEM) on cross‐sectional samples. HRTEM evidences that {113} defects dominate in all the samples under study. A shift of the PL band from 920 to 903 meV (“903” line, R‐line, or 1370 nm line) was observed with increasing annealing time, which suggests a strong change of the {113} defect structure. According to the Geometrical Phase Method used for the measurements of lattice deformations around the {113} defects observed by HRTEM, this change is related to a transformation of a vacancy‐type {113} defect to an interstitial one. The effect of the measurement temperature on the main parameters of R‐line has been studied, too. A sample annealed for 1 h has some characteristic features of the temperature dependence of the PL intensity: it increases with activation energy of 19.1 meV at low temperatures and decreases with deactivation energies of 32.2 and 175.5 meV at higher temperatures. With the increasing temperature, the luminescence peak shifts by the same energy as the forbidden gap width, while the FWHM of the line grows linearly.

Heterostructures prepared from graphene and fluorographene (FG) using the technology of 2D printing on solid and flexible substrates were fabricated and studied. Excellent stability of printed graphene layers and, to a lesser degree, composite graphene: PEDOT: PSS layers were shown. Extraordinary properties of FG as an insulating layer for graphene-based heterostructures at fluorination degree above 30% were demonstrated. It is shown that the leakage current in thin (20-40 nm) films is normally smaller than 10^-8 A/cm2, the breakdown field being greater than 108 V/cm. In hybrid structures with printed FG layers in which graphene was transferred onto, or capsulated with, an FG layer, an increase in charge-carrier mobility and material conductivity amounting to 5-6 times was observed. The spectrum of future applications of FG layers can be further extended due to the possibility of obtaining, from weakly fluorinated graphene (< 20%), functional layers exhibiting a negative differential resistance behavior and, at fluorination degrees of 20-23%, field-effect-transistor channels with current modulation reaching several orders. Composite or bilayer films based on fluorographene and V2O5 or polyvinyl alcohol exhibit a stable resistive switching behavior. On the whole, graphene/FG heterostructures enjoy huge potential for their use in a wide spectrum of application, including flexible electronics.

Structural and optical properties of films and particles prepared from partially fluorinated graphene suspensions were examined. Photoluminescence (PL) coming from partially fluorinated graphene suspensions (quantum dots with fluorinated edges) and films prepared from such suspensions was observed. The necessary conditions for excitation of photoluminescence and PL emission spectra consisting of one to three PL features with energies 2.65, 2.81, and 2.97 eV have been identified. The PL emission spectra were compared with the spectrum of the size quantization levels in partially fluorinated graphene and few-layer graphene films. The spectrum of levels was revealed from the charge deep-level transient spectroscopy measurements taken during studying the electron capture and the emission processes in such films. The PL emission spectra were interpreted with the assumption that fluorination of graphene suspensions leads to formation of quantum dots within graphene. A qualitative model was proposed to explain the observed correlation between the PL emission spectrum and the energy spectrum of graphene quantum dots embedded in a fluorinated graphene matrix.

The structural and optical properties of Ge and GeSi nanocrystals, formed by annealing of GeO/SiO2 multilayers have been investigated. According to Raman spectroscopy, the formation of pure Ge nanocrystals is observed after post growth annealing at 700 degrees C. Annealings at 800 degrees C-900 degrees C leads to the formation of intermixed GexSi1-x nanocrystals. High resolution transmission electron microscopy shows that the structure and the size of the nanocrystals strongly depend on annealing temperature. Spatial redistribution of Ge with the formation of large faceted clusters located near the Si substrate as well as GeSi intermixing at the substrate/film interface were observed. In the case of the sample containing 20 pairs of GeO/SiO2 layers annealed at 900 degrees C, some clusters exhibit a pyramid-like shape. FTIR absorption spectroscopy measurements demonstrate that intermixing between the GeO and SiO2 layers occurs leading to the formation of a SiGeO2 glass. Low temperature (10 K-100 K) photoluminescence was observed in the spectral range 1400-2000 nm for samples containing nanocrystals. The temperature dependence of the photoluminescence is studied.

The possibility to control the size of the flakes of graphene suspension in the course of their fluorination in an aqueous hydrofluoric acid solution was demonstrated. The effect of the suspension composition, the fluorination time, temperature and thermal stress on the fragmentation process was investigated. The corrugation of suspension flakes, which occurs at fluorination due to a difference in the constants of graphene and fluorographene lattices, leads to the appearance of nonuniform mechanical stresses. The fact that the flake size after fragmentation is determined by the size of corrugation allows the assumption that the driving force of fragmentation is this mechanical stress. This assumption is confirmed by the break of the corrugated layers from flakes under thermal stress. Moreover, fluorination treatment at elevated temperatures (∼70 °C) significantly accelerates the fragmentation process. Suspensions of fluorinated graphene with nanometer size flakes are of interest for the development of 2D ink-jet printing technologies and production of thermally and chemically stable dielectric films for nanoelectronics. The printed fluorinated graphene films on silicon and flexible substrates have been demonstrated and the charges in metal–insulator–semiconductor structures have been estimated as the ultra low values of (0.5–2) × 1010 cm−2.

The properties of thin Si and SiGe layers grown on SiO2 by chemical vapor deposition (CVD) were studied using transmission electron and atomic force microscopies, and Raman and photoluminescence (PL) spectroscopies. The layers with a composition of Si0.5Ge0.5 become composed of nanocrystals with an average size of about 100nm at growth temperatures of 550°C which is significantly lower than that for the pure Si layers. Moreover, the Si0.5Ge0.5 layers exhibit a broad PL peak centered at 0.8eV, whereas the bandgap of unstrained Si0.5Ge0.5 is about 1eV. This indicates that PL occurs through deep energy levels in the bandgap, which can be associated with crystal defects. The predominance of deep-level PL in radiative emission can be the result of a high concentration of defects that appear due to a low growth temperature.

We investigate the structural and optical properties of GeO/SiO2 multilayers obtained by evaporation of GeO2 and SiO2 powders under ultrahigh vacuum conditions on Si(001) substrates. Both Raman and infrared absorption spectroscopy measurements indicate the formation of GeSi nanocrystals after postgrowth annealing at 800°C. High-resolution transmission electron microscopy characterizations show that the average size of the nanocrystals is about 5 nm. For samples containing GeSi nanocrystals, photoluminescence is observed at 14 K in the spectral range 1500–1600 nm. The temperature dependence of the photoluminescence is studied.

In the present study, we have examined the interaction between a suspension of graphene in dimethylformamide and an aqueous solution of hydrofluoric acid, which was found to result in partial fluorination of suspension flakes. A considerable decrease in the thickness and lateral size of the graphene flakes (up to 1-5 monolayers in thickness and 100-300 nm in diameter) with increasing duration of fluorination treatment is found to be accompanied by a simultaneous transition of the flakes from the conducting to the insulating state. Smooth and uniform insulating films with a roughness of ∼2 nm and thicknesses down to 20 nm were deposited from the suspension on silicon. The electrical and structural properties of the films suggest their use as insulating elements in thin-film nano- and microelectronic device structures. In particular, it was found that the films prepared from the fluorinated suspension display rather high breakdown voltages (field strength of (1-3) × 10(6) V cm(-1)), ultralow densities of charges in the film and at the interface with the silicon substrate in metal-insulator-semiconductor structures (∼(1-5) × 10(10) cm(-2)). Such excellent characteristics of the dielectric film can be compared only to well-developed SiO2 layers. The films from the fluorinated suspension are cheap, practically feasible and easy to produce.