The electrokinetic possibilities of separation and concentration of S.aureus bacteria in human whole blood (test mixture) were studied using a new design of a four-electrode biosensor chip format with transparent microelectrodes. In the measurements, a closed cell was used, into which the test mixture was poured. The electrokinetic movement of bacteria during concentration was observed when AC voltage was applied to the first and second annular external electrodes, and DC voltage was applied to the third and fourth semicircular central electrodes. The process of separation of erythrocytes and concentration of bacteria was recorded by an optical method. It is shown that the concentration of bacteria appears after 8 minutes and increases by 30 minutes in the region of the central electrodes under model conditions. The measurements were carried out on two biosensor chip formats having almost identical electrophysical parameters of capacitance and conductivity at frequencies from 100 Hz to 1 MHz. It is determined that the amplitude-frequency mode and biosensor chip format can be used to develop methodological support for the identification of bacterial species, but only by optical methods. It is shown that in order to increase the number of bacteria on both of the central electrode in the concentration mode, it is necessary to increase the speed of the electroosmotic flow at alternating current, by optimizing the composition of the medium and the parameters of the electrical regime in order to equalize the rates of separation and concentration processes.

The paper analyzes the parameters of silicon avalanche LEDs and their use for electron-optical signal transmission systems. The advantages of silicon avalanche LEDs are shown, among which high speed and compatibility with silicon technology should be highlighted. Experimental avalanche LEDs based on nanostructured silicon were fabricated and studied. The results of controlling the electroluminescence spectrum of avalanche LEDs due to the choice of production conditions to form nanostructured silicon are presented. It was found that the temperature of the substrate during the deposition of the surface nanocomposite aluminum + silicon film affected the size of the formed silicon nanoparticles determining the spectral characteristics of avalanche LEDs. This allows shifting the maximum of their emission spectrum to a shorter wavelength region of the visible range due to the forming of smaller silicon nanoparticles. The authors have developed an optical interconnection system consisting of avalanche LEDs based on nanostructured silicon and a microchannel silicon wafer used to transmit a light signal. The study of various operating modes of the developed optoelectronic system was performed and an increase in the efficiency of optocouple based on avalanche LEDs to 0.2% due to the pulsed operating mode was achieved. It is shown that the efficiency of the optocouple increases with LED current and it is the pulsed mode of its operation that is characterized by the maximum current, which is due to more efficient removal of Joule heat in the intervals between pulses, ensuring stable operation of the entire system. The results obtained open up new opportunities for the development of optical interconnections between silicon chips and silicon optoelectronics in general.

The conditions for the formation of anodic titanium oxide with a tubular structure were studied. The mechanism for the formation of tubular titanium oxide based on the localization of the electrochemical oxidation of titanium in the places of the barrier layer at the bottom of the pore, where the density of the flowing anodic current is increased, as a result of which the temperature of these regions increases. With an increase in the temperature of the barrier layer above the threshold value, a transition from the traditional «honeycomb-like» porous structure to the tubular structure takes place. The proposed mechanism is confirmed by the results of experimental research.

Using the example of mixed suspensions of S.aureus bacteria and human erythrocytes, it was shown that regardless of the number of cells in the mixed suspension, all the studied bioprocessor chip formats, based on indium tin oxide (ITO) microelectrodes, demonstrate the same mechanisms of the electrokinetic bioprocesses occurring associated with separation and by concentrating cells of various sizes. The result obtained is in good agreement with the results of [6], from which it follows that with an appropriate electrical mode and a frequency of 800 Hz, blood cells experience a negative dielectrophoretic force, which pushes them out of the surface of the central electrode, because it is stronger than the electrohydrodynamic force responsible for dragging the cells account electroosmotic flow AC voltage. It has been shown that bacteria are transported to the central electrode area due to the electroosmotic flow, since the electrohydrodynamic force for bacteria is greater than their positive dielectrophoretic force, and the dielectrophoretic force pushing blood cells pulls bacteria to the middle of the central electrode, where electrohydrodynamic force is the weakest, and dielectrophoretic and electrophoretic force are the biggest.

The peculiarities of the phase composition and electronic structure of aluminum–silicon composite films near the Al 0.75 Si 0.25 composition obtained by the magnetron and ion-beam sputtering methods on a Si(100) silicon substrate are studied using the X-ray diffraction techniques and ultrasoft X-ray emission spectroscopy. In addition to silicon nanocrystals of about 25 nm in size, an ordered solid solution corresponding to the previously unknown Al 3 Si phase is formed in magnetron sputtering on a polycrystalline Al matrix. Films obtained by ion-beam sputtering of the composite target are found to be monophasic and contained only one phase of an ordered solid solution of aluminum silicide Al 3 Si of the Pm3m cubic system with the primitive cell parameter a = 4.085 Å. However, subsequent pulsed photon annealing of the composite with different radiation doses from 145 to 216 J/cm 2 gives rise to the partial decomposition of the Al 3 Si phase with the formation of free metallic aluminum and silicon nanocrystals with sizes in the range from 50 to 100 nm, depending on the pulsed photon radiation dose.

Исследованы фазовый состав и электронное строение композитных пленок Al-Si вблизи состава Al0.75Si0.25 на подложке Si(100), полученных магнетронным и ионно-лучевым напылением. При магнетронном напылении в поликристаллической Al матрице образуются нанокристаллы кремния размерами ~25 нм и упорядоченный твердый раствор Al3Si кубической сингонии Рm3m с параметром примитивной ячейки a = 4.085 Å. Пленки, полученные ионно-лучевым напылением, однофазны и содержат только упорядоченный твердый раствор Al3Si. При этом образование фазы Al3Si сопровождается изменением характера распределения плотности Al 3s-состояний. Вместо параболического характера роста плотности состояний в нижней и средней части валентной зоны (как в чистом металле) наблюдается почти линейный. Аналогичный эффект отмечается для Si 3s-состояний. Кроме того, взаимодействие атомов Al и Si приводит к уменьшению плотности Al 3s-состояний вблизи уровня Ферми в результате перехода части электронов на более электроотрицательные атомы кремния. Селективное вытравливание алюминия в случае магнетронной пленки приводит к формированию нанопористой губчатой структуры, а для ионно-лучевой пленки селективное травление не приводит к появлению развитой морфологии, что подтверждает ее однофазность. Последующий импульсный фотонный отжиг (ИФО) ионно-лучевых пленок дозами 145-216 Дж/см2 приводит к частичному распаду фазы Al3Si с формированием металлического алюминия и нанокристаллов кремния с размерами 50-100 нм в зависимости от дозы ИФО. Последующее травление образца, подвергнутого ИФО, ведет к получению развитой нанопористой структуры. Работа выполнена при поддержке Минобрнауки России в рамках государственного задания ВУЗам в сфере научной деятельности на 2017-2019 годы. Проект № 3.6263.2017/ВУ.

AbstractThe peculiarities of the phase composition and electronic structure of aluminum–silicon composite films near the Al_0.75Si_0.25 composition obtained by the magnetron and ion-beam sputtering methods on a Si(100) silicon substrate are studied using the X-ray diffraction techniques and ultrasoft X-ray emission spectroscopy. In addition to silicon nanocrystals of about 25 nm in size, an ordered solid solution corresponding to the previously unknown Al_3Si phase is formed in magnetron sputtering on a polycrystalline Al matrix. Films obtained by ion-beam sputtering of the composite target are found to be monophasic and contained only one phase of an ordered solid solution of aluminum silicide Al_3Si of the Pm3m cubic system with the primitive cell parameter a = 4.085 Å. However, subsequent pulsed photon annealing of the composite with different radiation doses from 145 to 216 J/cm^2 gives rise to the partial decomposition of the Al_3Si phase with the formation of free metallic aluminum and silicon nanocrystals with sizes in the range from 50 to 100 nm, depending on the pulsed photon radiation dose.

A comparative study of the magnetization curves of continuous and porous multilayered Pd 10 nm /[Co 0.3 nm ]/Pd 0.55 nm ]15/Pd 2 nm films deposited on an anodized TiO 2 template was performed by magnetometry. Based on the comparison of the dependences of coercive field H C on angle θ between the easy-magnetization axis and the direction of external magnetic field H with theoretical dependences H C (θ) for the magnetization reversal by domain walls motion (according to the Kondorski model) and the rotation of magnetic moments (by the Stoner–Wohlfarth model), the differences in the mechanisms of magnetization reversal for two mentioned types of the films were revealed. The correlation between the difference in the morphologies of the continuous and porous films and revealed change in the mechanisms of the magnetization reversal, as well as the changes in values of H C and calculated constants of the magnetic anisotropy, is discussed.

Методом магнитометрии проведено сравнительное исследование кривых намагниченности сплошной и пористой многослойной пленки Pd10nm/[Co0.3nm/Pd0.55nm]15/Pd2nm, осажденной на темплат анодного TiO2. На основании сопоставления зависимостей коэрцитивной силы HC от угла theta между осью легкого намагничивания и направлением внешнего магнитного поля H с теоретическими зависимостями HC(theta) для перемагничивания путем движения доменных стенок (по модели Кондорского) и вращения магнитных моментов (по модели Стонера-Вольфарта) выявлены различия в механизмах перемагничивания двух указанных типов пленок. Обсуждается взаимосвязь между различием в морфологии сплошной и пористой пленок и выявленной сменой механизма перемагничивания, а также изменениями значений HC и рассчитанных констант магнитной анизотропии. Работа выполнена в рамках Государственной программы научных исследований "Физическое материаловедение, новые материалы и технологии" (задание 2.44), договора Ф16В2-004 с БРФФИ (Беларусь), гранта 2014/13/N/ST8/00731 National Science Centre (NCN, Poland).

Films of Al-Si nanocomposites produced by magnetron evaporation of a complex target onto a silicon substrate have been investigated using scanning electron microscopy, X-ray diffraction, ultrasoft X-ray emission spectroscopy, and X-ray absorption near edge structure spectroscopy. It has been found that silicon inclusions are nanocrystals with the mean size of 20–25 nm, with the surface covered by an amorphous silicon layer. The presence of the aluminum matrix in the initial films changes their band structures, in particular, near the bottom of the valence band. After the removal of aluminum, the structure of the valence band becomes identical to that in the bulk material and the structure of the conduction band indicates the presence of a disordered surface layer with a thickness of ∼5 nm.