Search

It is demonstrated that it is possible to use the ammonia molecular beam epitaxy for growing structurally perfect high-ohmic GaN layers which allow generating SiN/Al(Ga)N/GaN heterostructures for transistors with a high mobility of electrons. The growth conditions are determined for GaN layers with smooth surface morphology (with a mean-squared deviation of $${\sim}$$ 2 nm) appropriate for creating sharp heteroboundaries. The possibility of improving the crystalline perfection of GaN layer due to the use of buffer high-temperature AlN layer (with the growth temperature above 940 $${}^{\circ}$$ C) is demonstrated. It was shown that in situ surface passivation of Al(Ga)N/GaN heterostructures by the ultrathin SiN layer allows generating normally closed transistors with unprecedented low values of the current collapse ( $${\sim}1\%$$ ).

The article presents how the understanding of the fundamental processes of self-organization and morphological transformations of the atomically clean Si(111) surface as a result of the study using in situ ultrahigh vacuum reflection electron microscopy can be applied to metrology. The method of high-resolution transmission electron microscopy is used to show that the native oxide formed on the Si(111) surface in atmospheric conditions replicates the atomic step height with high accuracy. The techniques for creating vertical measures in the range 0.31–31 nm with an error of less than 0.05 nm in the entire measurement range are developed on this basis. It is shown that it is possible to create extremely wide atomically smooth surfaces (up to 230 $$\mu$$ m) and use them as reference mirrors in interferometric microscopes. Crystal samples containing a certain number of monoatomic steps and atomically smooth surface areas are included in the State Secondary Reference Standard as a measure of angstrom height and angstrom flatness.

The aim – to determine the prevalence and major risk factors of intramyocardial hemorrhage (IMH) in timely revascularized patients with ST elevation myocardial infarction (STEMI), and to evaluate its importance for the development of postinfarction left ventricular (LV) dilatation. Materials and methods. We examined 24 patients with acute first anterior STEMI, who were admitted in the first six (on average 2.8±1.4) hours from symptoms development. The presence of IMH was assessed by cardiovascular magnetic resonance examination 3-4 days after primary percutaneous coronary intervention (pPCI). Echocardiography was performed during the first 24 hours and day 90 after acute myocardial infarction. LV dilatation was defined as at least 20 % increase of end-diastolic volume at 90 days. Endothelium-dependent flow-mediated brachial artery dilatation (FMD) was measured using high-resolution ultrasound at admission. Results and discussion. More than a third (37.5 %) of patients with anterior STEMI who underwent pPCI had signs of IMH. Hemorrhagic transformation of acute myocardial infarction was more often manifested in patients who were prescribed enoxaparin at the prehospital stage (RR = 3.75; 95 % CI 1.47–9.56) and less often in patients with multivessel (≥3) coronary artery disease (RR = 0.21; 95 % CI 0.03–1.00). There is a tendency to a more frequent detection of IMH in patients with endothelial dysfunction. Impaired reactive hyperemia (FMD ≤ 4.9 %) was associated with IMH development (RR 3.5; 95 % CI 0.9–13.5). The patients with IMH had a greater extent of myocardial damage according to CK-MB AUC and LGE at MRI and a more frequent development of postinfarction LV dilatation (RR 5.0; 95 % CI 1.3–19.7). The addition of intravenous quercetin started before pPCI to the standard basic treatment of acute myocardial infarction was associated with a significant decrease in the probability of hemorrhagic transformation (RR 0.21; 95 % CI 0.03–1.00). Conclusions. Pre-hospital administration of enoxaparin and endothelial dysfunction were the main predictors of IMH after pPCI in STEMI patients, whereas it was detected much less frequently in patients with multivessel (≥3) coronary artery disease. The presence of IMG has been associated with a greater extent of necrotized myocardium and more frequent development of postinfarction dilatation and dysfunction of the LV.

Background Cardio-vascular death (CVD) in patients with acute myocardial infarction (AMI) significantly decreased due to reperfusion and advances in pharmacotherapy. Acute heart failure (AHF) remains a common and unfavorable AMI-related complication. Aim To determine the incidence and prognostic value of Killip Class II–IV of AHF in long term follow-up of patients with ST-elevation myocardial infarction (STEMI). Methods All patients with STEMI were admitted to our emergency cardiology department during 1995–2011. CVD up to ten years after STEMI was the main outcome endpoint. We compared CVD in patients with and without AHF, and revascularization. Survival curve was generated by the Kaplan-Meier method. Predictors of mortality after STEMI were determined by multivariable Cox regression. Results Prospective cohort study includes 1625 STEMI patients; the mean age of the patients was 54.4±0.3 years, time from symptom onset was 5.0±0.2 hour, 1497 were men (92.1%), and 899 patients (55.5%) were revascularized (TLT – 632 (38.9%), PCI – 267 (16.4%), including 159 patients with stent implantation (9.8%). 412 patients had AHF - Killip Class II–IV (25.4%) during first 24 hours. Ten-year survival after STEMI was 85%; survival exceeded 88% in patients without AHF, but was 75% for those with AHF. Among patients who underwent revascularisation ten-year survival was 82.9% for patients in group with AHF, and was 87.1% for those without AHF. In multivariable Cox regression, age ≥65 years, female gender and HF were the predictive factors for CVD. Kaplan-Meier survival curves demonstrated higher incidence of CVD in AHF patients in compare with those without AHF in long-term follow-up (Figure 1). Conclusion According to the study AMI care is associated with high rates of long term survival, ten-year rates exceed 85%. AHF during first 24 hour in patients with STEMI worsens the prognosis, but reperfusion therapy increases survival. Further efforts to improve survival should be directed to patients with AHF and low revascularization rate that are associated with poor survival after AMI. Funding Acknowledgement Type of funding sources: None.

An association between high serum calcium/phosphate and cardiovascular events or death is well-established. However, a mechanistic explanation of this correlation is lacking. Here, we examined the role of calciprotein particles (CPPs), nanoscale bodies forming in the human blood upon its supersaturation with calcium and phosphate, in cardiovascular disease. The serum of patients with coronary artery disease or cerebrovascular disease displayed an increased propensity to form CPPs in combination with elevated ionised calcium as well as reduced albumin levels, altogether indicative of reduced Ca2+-binding capacity. Intravenous administration of CPPs to normolipidemic and normotensive Wistar rats provoked intimal hyperplasia and adventitial/perivascular inflammation in both balloon-injured and intact aortas in the absence of other cardiovascular risk factors. Upon the addition to primary human arterial endothelial cells, CPPs induced lysosome-dependent cell death, promoted the release of pro-inflammatory cytokines, stimulated leukocyte adhesion, and triggered endothelial-to-mesenchymal transition. We concluded that CPPs, which are formed in the blood as a result of altered mineral homeostasis, cause endothelial dysfunction and vascular inflammation, thereby contributing to the development of cardiovascular disease.

Objective ACE Insertion/deletion (I/D) polymorphism has been reported to be associated with various cardiovascular conditions, however its impact in patients with AHF remains controversial. This study aimed to analyze ACE I/D distribution, rate of acute heart failure (AHF) and survival in ST segment elevation myocardial infarction (STEMI) patients. Methods Genomic DNA from 245 STEMI patients and 87 healthy control subjects were analyzed by single polymerase chain reaction method. Based on the ACE I/D genotype STEMI patients were divided with AHF/no AHF, and then - for preserved/reduced ≤40% left ventricle (LV) ejection fraction (EF) to investigate the frequency of the mutant allele D. Results ACE gene polymorphism analyses revealed that D allele had been found more often in STEMI patients than in controls (84.1 vs. 72.4%). The frequency of II, ID, and DD genotypes in STEMI patients was 27.6%, 52.9% and 19.5% compared to 15.9%, 54.3% and 29.8%, respectively in controls with a significant difference in mutant homozygous genotype. Distribution of I/D ACE gene variants among AHF cases vs no AHF, showed similar frequency of II allele (15.8 vs 13.5%), ID allele (54.9 vs 52.8%) and DD allele (29.3 vs 33.7% respectively). In patients with preserved EF there was not statistical significance among different alleles with and without AHF. However, ACE DD polymorphism has been found in AHF patients with reduced EF significantly more often (50.0 vs 30.5%; p Conclusion Presented results confirmed ACE DD polymorphism to be associated with higher rate of cardiovascular death and presence of AHF with reduced LV EF in STEMI patients. Future studies are needed to evaluate importance of ACE DD polymorphism in order to find optimal treatment strategies and to prevent negative outcomes in those patients. Funding Acknowledgement Type of funding sources: None.

The formation of GaN nanocrystals on the graphene-like AlN (g-AlN) modification and graphene-like (g-Si3N3) silicon nitride by ammonia molecular beam epitaxy has been investigated. It has been found that the GaN growth on the g-Si3N3 surface leads to the formation of misoriented nanocrystals. During the GaN growth on the g-AlN surface, the epitaxial growth of similarly oriented GaN quantum dots of the graphite-like modification has been observed. The lattice parameters and energy structure of two graphite-like GaN modifications with the alternating AB (graphite structure) and AA+ (hexagonal boron nitride structure) layers have been calculated.

It is shown that intentionally undoped high-resistance GaN buffer layers in AlGaN/GaN heterostructures with high electron mobility for transistors can be formed by ammonia molecular beam epitaxy. The GaN growth conditions have been optimized using calculations of the background impurity and point defect concentrations at different ratios of the gallium and ammonia fluxes.

The InAs areas formation on the surface of InP (001) substrates annealed in an arsenic flux in an ultra-high vacuum was determined by scanning electron microscopy and atomic force microscopy. It is shown that the InAs areas are distributed non-uniformly over the surface and have an elongated shape predominantly along the $[1 \overline{1} 0]$ direction. The height and density of InAs areas increases with an increase in the annealing temperature.

In the present work, the low-fluence nonablating femtosecond laser irradiation (λ = 800 nm) of the GeO2 layer with Ge nanoclusters protected by SiO2 layers is studied by different types of microscopy (optical microscopy, atomic force microscopy, and scanning and transmittance electron microscopy) and Raman spectroscopy. After the laser modification, the multilayer thickness increased by 6%–29% depending on the laser fluence. It was found that the laser fluence of ∼40 mJ/cm2 was the optimal value for observing the swelling effect and was below the ablation threshold. Irradiation at this fluence led the Ge nanoclusters to decrease in size from 5–8 to ∼2 nm and crystallize, while the GeO2 matrix expanded due to the formation of GeO bubbles. The fabrication mechanism of the novel type of nanofoam consisting of a glassy matrix, cavities filled with gas, and semiconductor nanocrystals with reduced size dispersion is discussed. Presumably, this effect is associated with the selective absorption of IR (800 nm) laser radiation by Ge nanoclusters.

Metastable germanium monoxide (GeO) thin-insulating films have been investigated as a new promising material for atomic force microscope (AFM) oxidation lithography. The kinetics of GeO layer oxidation performed in the tapping mode of AFM was found to have a logarithmic relationship to oxide height versus pulse duration. Effect of humidity on oxidation of germanium monoxide thin films was studied at relative humidity 40, 60, 80%. When local anodic oxidation of GeO layer was carried out by AFM operating in the contact mode in high voltage (≥9 V) regime and at high relative humidity (RH = 80%), the size and shape of fabricated oxide was changed drastically.

00-The kinetics of the formation and thermal decomposition of a two-dimensional SiN-(8 × 8) nitride layer on a Si(111) surface is studied. The SiN-(8 × 8) structure is a metastable intermediate phase formed during the nitridation of silicon before the formation of a stable amorphous Si3N4 phase. Studying the SiN-(8 × 8) structure by scanning tunneling microscopy shows its complex structure: it consists of an adsorption (8/3 × 8/3) phase, with the lateral period 10.2 A, and a honeycomb structure with a ~6 A side of a hexagon that is turned 30° with respect the adsorption phase. The band gap of the SiN-(8 × 8) phase is measured and found to be ~2.8 eV, which is smaller compared to the band gap of the β-Si3N4 crystal phase 5.3 eV. The interplanar spacings in the (AlN3)/(SiN)2 structure on the Si(111) surface are measured. The spacings are 3.3 and 2.86 A in SiN and AlN, respectively. Such interplanar spacings are indicative of weak van der Waals interaction between the layers. A model of the SiN-(8 × 8) structure as a flat graphene-like layer is suggested. The model is consistent with the diffraction and microscopy data.

This paper demonstrates the applicability of nanoindentation technique using atomic-force microscope cantilever for studying the elastic properties of suspended semiconductor structures on the basis of relatively thick GaAs/AlGaAs membranes in the case when their stiffness significantly exceeds that of the cantilever of atomic-force microscope, which is confirmed by the agreement between the experimentally determined values of both relative and absolute stiffness measured at different points of the investigated structure with theoretical predictions.

The dislocation structure of diamond crystals grown in the Mg-Si-C system at pressure of 7.0–7.5 GPa and temperature of 1800 °C was studied by selective etching. We determined the dislocation density and identified individual features of etching for the growth sectors of {111} and {100} faces. On the {111} faces, all etch pits formed at the outcrops of different dislocations were found to be identical. The feature of grown diamond crystals is the presence of numerous large dislocation loops in the {100} growth sectors. The identified patterns of crystals etching and the internal crystal structure features are associated with the presence of a silicon impurity in the grown diamonds.

This article reports a study of the morphology of diamond crystals grown at 7.0 GPa and 1800 °C in the Mg-C system with the addition of silicon in an amount of 0.5 wt%. Step patterns on {111} and {100} faces were studied in a wide range of magnifications using optical microscopy (DIC), scanning electron microscopy (SEM), and atomic force microscopy (AFM). Morphological studies revealed that a reduction in the growth rate and a change in the morphological significance of the {100} and {111} faces were associated with adsorption of a mobile impurity (silicon) leading to poisoning of kinks and (or) steps. This leads to roughing of the faces and formation of macrosteps as well as 2D and 3D nucleation islands. At a silicon concentration of 1.0 wt% or more, immobile impurity particles are apparently formed on macrostep terraces, and growth inhibition occurs according to the Cabrera-Vermilyea model.

The process of local anodic oxidation of thin GeO films has been studied using an atomic force microscope. The electron-probe microanalysis showed that oxidized areas of a GeO film were germanium dioxide. The effect of the voltage pulse duration applied to the probe–substrate system and the atmospheric humidity on the height of the oxide structures has been studied. The kinetics of the local anodic oxidation (LAO) in a semi-contact mode obeys the Cabrera–Mott model for large times. The initial growth rate of the oxide (R0) significantly increases and the time of starting the oxidation (t0) decreases as the atmospheric humidity increases by 20%, which is related to an increase in the concentration of oxygen-containing ions at the surface of the oxidized GeO film. It was shown that nanostructures in thin GeO layers can be formed by the LAO method.

Titanium oxynitride (TiOxNy) coatings increase the bio- and hemocompatibility of stainless steel and Co-Cr vascular stents, possibly by directly releasing NO. Herein, to examine the applicability of this approach to nitinol (NiTi) devices, we coated NiTi samples with TiOx or TiOxNy by reactive magnetron sputtering using different reaction gas compositions and bias voltages. One side of the samples was preliminarily abraded, while the other remained in its original state. Samples morphology, composition and structure were studied by atomic force microscopy (AFM), X-ray diffraction (XRD) and field emission scanning electron microscopy (FE SEM). We investigated how various types of TiOx and TiOxNy coatings interact with EA.hy926 endothelial cells. None of the tested samples exhibited cytotoxicity, and an N2:O2 ratio of 3:1 regardless of the bias voltage was found to be optimal for NO production and cell adhesion, spreading, and viability, which was ascribed to a cumulative positive effect of the composition and nanoroughness of TiOxNy coatings formed under these conditions. Thus, the deposition of TiOxNy coatings was concluded to be a promising strategy of increasing the biocompatibility of NiTi stents.

The phase transitions during the oxidation of polycrystalline tin (β-Sn) were studied. The intense photoluminescence from SnO was observed in the annealing temperature range of 300–400 °C. An increase in the annealing temperature led to a sharp decrease in photoluminescence. It is associated with the phase transition of SnO to SnO2. Two approaches were proposed for obtaining the dual-band material based on tin oxides and GeSiSn compounds. Using the Sn-rich nanoislands grown on the vapor–liquid-solid (VLS) mechanism, the nanoislands having SnO(x) in their upper part, and the SiSn solid solution under SnO(x) were obtained after annealing. Furthermore, the growth technology of the dual-band material, which included tin oxides on top of a GeSiSn/Si multiple quantum well (MQW) structure, was developed. Tin oxides demonstrated the photoluminescence signal in the visible region, whereas the SiSn solid solution in nanoislands and GeSiSn/Si multiple quantum well structure showed the photoluminescence signal in the infrared range.

A system of quantum dots based on Al x In1−xAs/Al y Ga1−yAs solid solutions is investigated. The use of Al x In1−xAs wide-gap solid solutions as the basis of quantum dots substantially extends the spectral emission range to the short-wavelength region, including the wavelength region near 770 nm, which is of interest for the development of aerospace systems of quantum cryptography. The optical characteristics of Al x In1−xAs single quantum dots grown by the Stranski–Krastanov mechanism were studied by cryogenic microphotoluminescence. The statistics of the emission of single quantum dot excitons was studied using a Hanbury Brown–Twiss interferometer. The pair photon correlation function indicates the sub-Poissonian nature of the emission statistics, which directly confirms the possibility of developing single-photon emitters based on Al x In1−xAs quantum dots. The fine structure of quantum dot exciton states was investigated at wavelengths near 770 nm. The splitting of the exciton states is found to be similar to the natural width of exciton lines, which is of great interest for the development of entangled photon pair emitters based on Al x In1−xAs quantum dots.

In this article, we report the unusual growth of diamond crystals produced in Mg–C and Mg–Ge–C systems at high-pressure, high-temperature conditions. We have found that the growth of the habit {100} faces occurs by deposition of a substance (carbon) on two nonequivalent {100} and {111} surfaces. Precipitation of carbon atoms on the (100) plane occurs by elementary layers with a thickness of about 0.1 and 0.2 nm. The change in the density of elementary steps leads to the formation of step bunches that transform into faceted macrostates with an increase in their thickness of more than 400 nm. The maximum inclination angle of macrostep ends corresponds to the {111} faces position. As a result, singular stable {111} microfacets are formed at the ends of the macrosteps, which themselves grow layer by layer. The deposition of carbon on {100} and {111} surfaces of one simple form of diamond crystals leads to the zonal structure of {100} growth sectors.

Objectives Reperfusion may cause no-reflow phenomenon. Both microvascular obstruction (MVO) and intramyocardial hemorrhage (IMH) have been recognized as poor prognostic factors in myocardial infarction (MI) patients. The aim of the study was to evaluate hypothesis whether cardioprotective strategy prevent IMH in MI patients after primary percutaneous coronary intervention (PCI). Methods This multicenter open-label randomized clinical trial enrolled 143 patients with first acute anterior ST-elevation MI (STEMI) reperfused within 6 h after symptoms onset. Cardiac magnetic resonance (CMR) was performed to assess left ventricular (LV) function and microvascular injury in 23 patients within the first week (3.5±1.2 days) after STEMI. Nine patients were randomized into soluble intravenous form of quercetin (Q) group and 14 - to the control group. Q infusions were started before PCI and used during the next 5 days. MVO was visualized using early gadolinium enhancement (EGE) and IMH was detected by using T2-WI. Results The study groups did not differ in terms of demographic characteristics, time to admission and main clinical data. Initially, the number of LV myocardial segments with edema was similar - 7.8±1.7 in patients of Q subgroup versus 6.8±1.8 in patients of the control subgroup (p=0.245). However, patients of the Q subgroup tended to have greater number of segments with gadolinium accumulation and higher value of the transmural index (7.7±1.2 compared to 6.2±1.5; p Conclusion Detection of MVO and IMH by CMR can accurately demonstrate the severity of myocardial injury. Intravenous Q can decrease the rate of IMH additionally to infarct size limitation. Further investigations are needed to confirm our results and to determine whether prevention of IMH can impact on better prognosis. Funding Acknowledgement Type of funding source: None

A system of quantum dots on the basis of AlxIn1-xAs/AlyGa1-y As solid solutions has been studied. The usage of broadband AlxIn1-x solid solutions as the basis of quantum dots makes it possible to expand considerably the spectral emission range into the short-wave region, including the wavelength region near 770 nm being of interest for the design of aerospace systems of quantum cryptography. The optical characteristics of single AlxIn1-xAs quantum dots grown according to the Stranski–Krastanov mechanism are studied by the cryogenic microphotoluminescence method. The fine structure of exciton states of quantum dots is studied in the wavelength region near 770 nm. It is shown that the splitting of exciton states is comparable with the natural width of exciton lines, which is of great interest for the design of emitters of pairs of entangled photons on the basis of AlxAs1-x quantum dots.

A technique for reversible surface modification with an atomic-force-microscope (AFM) probe is suggested. In this method, no significant mechanical or topographic changes occur upon a local variation in the surface potential of a sample under the AFM probe. The method allows a controlled relative change in the ohmic resistance of a channel in a Hall bridge within the range 20–25%.

The atomic structure of GaSb/GaP quantum dots grown via molecular beam epitaxy on a (100) GaP surface at epitaxy temperatures of 420–470°C is investigated. It is established that, depending on morphology of the GaP growth surface, the deposition of 1 ML of GaSb leads to the formation of strained Ga(Sb, P)/GaP or fully relaxed GaSb/GaP quantum dots. The obtained heterostructures exhibit high photoluminescence efficiency.

The electrical and optical properties of silicon nanopillars (Si NPs) are studied. Electron-beam lithography and reactive ion etching are used for the formation of ordered Si-NP arrays. The Si NPs with a diameter from 60 to 340 nm and a height from 218 to 685 nm are formed. The Si NPs are coated with a TiONx layer with a thickness of 8 nm for chemical and electrical passivation of the surface. Scanning electron microscopy and atomic-force microscopy are used to characterize the obtained structures. The Si-NP arrays acquire various colors when exposed to “bright-field” illumination. The spectra of reflection from the Si-NP arrays in the wavelength range 500–1150 nm are obtained.

Background— The aim of this study is to examine the relationship between time in the therapeutic range (TTR) and clinical outcomes in heart failure patients in sinus rhythm treated with warfarin. Methods and Results— We used data from the Warfarin versus Aspirin in Reduced Cardiac Ejection Fraction (WARCEF) trial to assess the relationship of TTR with the WARCEF primary outcome (ischemic stroke, intracerebral hemorrhage, or death), with death alone, ischemic stroke alone, major hemorrhage alone, and net clinical benefit (primary outcome and major hemorrhage combined). Multivariable Cox models were used to examine how the event risk changed with TTR and to compare the high TTR, low TTR, and aspirin-treated patients, with TTR being treated as a time-dependent covariate. A total of 2217 patients were included in the analyses; among whom 1067 were randomized to warfarin and 1150 were randomized to aspirin. The median (interquartile range) follow-up duration was 3.6 (2.0–5.0) years. Mean (±SD) age was 61±11.3 years, with 80% being men. The mean (±SD) TTR was 57% (±28.5%). Increasing TTR was significantly associated with reduction in primary outcome (adjusted P P =0.001), and improved net clinical benefit (adjusted P P =0.082 for ischemic stroke and adjusted P =0.109 for major hemorrhage). Conclusions— In patients with heart failure in sinus rhythm, increasing TTR is associated with better outcome and improved net clinical benefit. Patients in whom good quality anticoagulation can be achieved may benefit from the use of anticoagulants. Clinical Trial Registration— URL: http://www.clinicaltrials.gov . Unique identifier: NCT00041938.

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 100 nm 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 0.8 eV, whereas the bandgap of unstrained Si0.5Ge0.5 is about 1 eV. 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.

The possibility of using AlN/Al2O3 substrates to grow AlGaN/GaN hetero-epitaxial structures with a two-dimensional electron gas is studied. A method of calibrating the temperature of the substrates by measuring the thermal radiation spectrum is proposed. Differences between AlN/Al2O3 substrates that lead to differences in the electrophysical parameters of the grown structures are determined. AlN/Al2O3 substrates were used to grow AlGaN/GaN samples with a two-dimensional electron gas mobility in excess of 1300 cm2/(V · s) at an electron concentration in the channel higher than 1013 cm−2.

Modern lithographical methods used to create linear measures for nanometer-range dimensions and the main factors which limit the applications of such gages have been analyzed in the paper. Prospects for developing high-precision measures based on an atomically structured crystalline surface (containing monoatomic steps) whose parameters are bound to the crystallographic parameters of the crystal (traceable to the length measure) are shown. A method which can be used to create such measures based on controlling the surface morphology of monocrystalline silicon at an atomic level due to the effects of self-organization arising at the atomically clean surface as a result of annealing in ultrahigh vacuum is proposed. A description of the set of high-precision gages of vertical dimensions STEPP-IFP-1 in a size range of 0.31–31 nm with an error in the whole interval of gages of less than 0.05 nm is presented. The set of high-precision gages after carrying out state testing is included into the state registry of measuring means as measuring type no. 48115-11 (Federal Agency on Technical Regulating and Metrology order no. 6290 of October 31, 2011).

The effect of the electrolyte composition on the surface morphology and the dispersion dependences of the refractive index and extinction coefficient of ∼20-nm-thick anodic layers on InAs (111)III substrates is studied by atomic force microscopy and spectral ellipsometry. It is shown that oxidation in electrolytes with different acidities does not modify the surface morphology of the initial InAs substrates. The films formed upon oxidation exhibit close dispersion dependences, despite the difference in the chemical composition between the films. This makes possible the high-precision monitoring of the thickness of anodic layers on InAs substrates by means of ellipsometry with the optical model of a single-layer isotropic film on an absorbing substrate.

“Step-and-terrace” surface morphology, with regular arrays of atomically flat terraces separated by monatomic steps was obtained by annealing GaAs(001) substrates in conditions close to equilibrium. The closeness of annealing conditions to equilibrium was determined by experiments on samples with lithographic marks. The annealing kinetics are characterized by full-length monatomic steps, and also by Fourier and autocorrelation analyses. A comparison of the experiment with Monte Carlo simulation enabled us to elucidate the main stages and microscopic mechanisms of the step-terraced morphology formation, and to evaluate the effective parameters which determined this process. The formation of straight dislocation-induced steps of monatomic height were studied under thermo-mechanical stress relaxation in GaAs/AlGaAs heterostructures bonded to glass.

The operating principles of subminiature semiconductor emitters are formulated in this chapter, and the research results of the performance for those emitters that have been developed and manufactured at the SB RAS Institute of Semiconductor Physics for the last 5 years are given. The results of developing single-mode vertical cavity surface emitting lasers with a wavelength of 795 nm future-oriented for application in a chip scale atomic clock operating at a transition of 5S1/2→5P1/2 of Rb87 atoms are reported, as well as the results of developing a fully semiconductor Bragg microcavity for single-photon emitters. The latter combines current pumping selectively positioned InAs quantum dots, high external quantum efficiency, and a low level of output radiation divergence.

Layers of Si crystals grown on SiO2 surfaces are investigated by scanning tunneling and atomic force microscopy. The deposition of an array of Ge islands on SiO2 surfaces prior to Si growth is found to significantly decrease the concentration of Si crystals and make them more uniform in size. The Si crystals grown at temperatures from 430 to 550 °C have a rounded shape of the growing surface. This indicates the presence of a high concentration of threading dislocations and that is confirmed by the observation of dislocation-related photoluminescence in the 1.5 μm region. Layers of Si crystals grown on SiO2 are of interest for the fabrication of optical resonant structures for the near-infrared region.

The inertness of the cleaved (0001) surface of a Bi2Se3 single crystal to oxidation has been demonstrated using X-ray photoelectron spectroscopy, as well as atomic-force and scanning tunneling microscopy and spectroscopy. No intrinsic bismuth and selenium oxides are formed on the surface after a month of storage in air. Atomically flat surfaces with macroscopic sizes (∼1 cm2) and rms roughness less than 0.1 nm have been prepared, and (1 × 1)-(0001) Bi2Se3 atomic structure has been resolved. The tunneling conductance measurements have shown that the energy dependence of the surface density of states is quasilinear in the band gap of Bi2Se3.

A high-quality inclusion-free ZnWO4 crystal 90 mm in diameter and with a mass of up to 8 kg was grown by the low thermal gradient Czochralski technique. Crystallographic properties of ZnWO4(010) cleaved surfaces were evaluated with reflection high energy electron diffraction (RHEED), and the electronic structure of the surface was studied using X-ray photoelectron spectroscopy (XPS). A system of Kikuchi lines was observed for cleaved ZnWO4(010) by RHEED confirming the high crystallographic state of the surface. The XPS valence-band and core-level spectra of ZnWO4(010) have been measured. The XPS measurements reveal that tungsten and zinc atoms are in the formal valences +6 and +2, respectively, on cleaved ZnWO4(010) surface. The 3.0 keV Ar+ bombardment of the surface causes partial transformation of tungsten ions from W6+ to lower valence states; however, no partial loss of oxygen atoms belonging to ZnO6 octahedra occurs due to this bombardment of the ZnWO4(010) surface because after this treatment zinc r...

The evolution of surface band bending and the probabilities of electron emission in a vacuum are studied under cesium and oxygen deposition on atomically flat and rough As-rich and Ga-rich GaAs (001) surfaces by means of photoreflectance spectroscopy and photoemission quantum-yield spectroscopy. On the rough surface, as compared to the flat one, the suppression of non-monotonic Cs-induced band bending variations is observed, along with the overall band bending increase. Multiple repeated activations of the GaAs (001) surface by cesium and oxygen followed by vacuum anneals led to an increase in the root-mean-square roughness from Rq ˜ 0.1-0.2 nm up to ˜ 3 nm. As a result, the probability of electron escape into vacuum decreased by half.

In this paper, the initial stages of local anodic oxidation (LAO) process initiated by AFM probe are studied on the wide (∼100μm) terraces of the atomic-smooth Si (111) surface when creating dense array of local oxidation points. The dependence of LAO points height on the value of voltage initiating the oxidation is found to have a pronounced step-like feature with a characteristic period of 0.7 ± 0.1 nm. The presented analysis shows for the first time the realization of the step-layer mechanism of anodic oxide growth on the Si (111) surface.

AbstractGaAs thermal smoothing at temperatures T ≤ 650°C in the conditions close to equilibrium yields surfaces with atomically smooth terraces separated by steps of monatomic height. At higher temperatures surface smoothing is changed to roughening. Possible reasons of surface roughening at elevated temperatures are studied by means of Monte Carlo simulation and compared with the experimental results on GaAs. It is proved that GaAs roughening at elevated temperatures is caused by kinetic instabilities due to deviations from equilibrium towards growth or sublimation. The microscopic mechanisms of kinetic-driven roughening are discussed.

Efficiently exploiting SIMD vector units is one of the most important aspects in achieving high performance of the application code running on Intel Xeon Phi coprocessors. In this paper, we present several effective SIMD vectorization techniques such as less-than-full-vector loop vectorization, Intel MIC specific alignment optimization, and small matrix transpose/multiplication 2D vectorization implemented in the Intel C/C++ and Fortran production compilers for Intel Xeon Phi coprocessors. A set of workloads from several application domains is employed to conduct the performance study of our SIMD vectorization techniques. The performance results show that we achieved up to 12.5x performance gain on the Intel Xeon Phi coprocessor. We also demonstrate a 2000x performance speedup from the seamless integration of SIMD vectorization and parallelization.

Conductive indium nanowires up to 50 nm in width and up to 10 μm in length are fabricated on the surface of silicon by local resputtering from the probe of an atomic-force microscope. To accomplish this, indium was transferred from an atomic force microscopy tip to the surface by applying a potential difference between the tip and substrate. The fabricated indium nanowires were several micrometers in length. Unlike thermal DPN, our DPN method hardly oxidized the indium, producing nanowires with conductivities from 5.7 10−3 to 4 10−2 Ωcm.