Sitall Substrates Research Articles

MAGNETO-OPTICAL KERR SPECTROSCOPY OF (СD 3 AS 2)100-X (MNAS) X COMPOSITES

Composite Films (Сd3As2)100-X(MnAs)X on silicon and sitall substrates with a concentration of Mn 5.8-16.4 at.% were obtained by vacuum-thermal evaporation. The structural properties of the films were investigated by X-ray phase analysis and scanning electron microscopy. Magneto-optical properties were studied by the method of the equatorial Kerr e ect (EEC) in the energy range of 0.5-4.0 eV in magnetic elds with a strength of up to 3 kE at a temperature of 20-300 K. In the geometry of the equatorial Kerr effect, spectral, field and temperature dependences of the EEC are obtained. The analysis of experimental data showed that with a Mn content of more than 12.9 at.% of the films contain the α′′-phase of the topological Dirac semimetal Cd3As2 in the form of large granules, as well as ferromagnetic MNAs granules. The Curie temperature of lms depends on the Mn content in them and is less than the temperature of bulk samples ofMPas. When the Mp content in the lm is 5.8 at.% and 6.4 at.%, the magneto-optical response is not detected, which indicates the formation of a superparamagnetic state or a spin glass state at low concentrations of Mn. With a film content of Mn 9.9 at%. A signi cant change in magneto-optical spectra was detected, which indicates the formation of MNAs nanoclusters and partial dissolution of Mn in the Cd3As2 matrix.

PRACTICAL APPLICATION OF A FRACTIONAL FACTOR EXPERIMENT FOR ASSESSING THE INFLUENCE OF FACTORS ON THE SENSITIVITY OF A CAPACITIVE HUMIDITY SENSOR OF A TWO-LAYER STRUCTURE

The work uses a fractional factorial experiment in order to reduce the number of experiments. Capacitive humidity sensors of a two-layer structure made on a sitall substrate served as experimental samples. Hygroscopic salt NaCl was used to create a moisture-sensitive layer that would perform the function of a dielectric. Solutions of this salt with concentrations of 0,89 mol/l and 5,33 mol/l were applied by spraying on the surface of capacitive humidity sensors with thicknesses of 5,0 μm and 10.0 μm. In order to prevent the drop of the dew point, a protective layer was created − it is a moisture-absorbing polymethyl methacrylate film with thicknesses of 40 μm and 80 μm. According to the Cochrane’s test, it is proved that the fractional factorial experiment is reproducible. Using regression analysis, a quantitative assessment of the influence of factors on the sensitivity of the capacitive humidity sensor of the two-layer structure was carried out. Based on the developed regression equation, it was established that the concentration of the NaCl salt solution significantly affects the sensitivity of the capacitive humidity sensor of the two-layer structure. Significant coefficients of the regression equation were determined using the Student's test. Adequacy of the adjusted regression equation to the results of the factorial experiment was proved using Fisher's test. Based on the regression equation on the scale of real factors, which contributes to the optimization of the humidity sensor manufacturing parameters, it was established that the sensitivity of the capacitive humidity sensor of the two-layer structure depends on such factors as the thickness of the protective layer and the concentration of the NaCl salt solution. However, the sensitivity of the capacitive humidity sensor of the two-layer structure is significantly affected by the concentration of the hygroscopic NaCl salt solution. The highest sensitivity of 2,46 nF/% is provided with the following optimal parameters of the manufacturing process of the capacitive humidity sensor of the two-layer structure: the concentration of the hygroscopic NaCl salt solution is 5,33 mol/l, the thickness of the protective layer is 80 μm. Considering that the thickness of the moisture-sensitive layer does not significantly affect the sensitivity of the capacitive humidity sensor, the thickness of this layer can be taken in the range from 5,0 μm to 10,0 μm.

Synthesis of silicon-carbon films by induction-assisted plasma-chemical deposition

Silicon-carbon films are of great interest as diamond-like materials combining unique properties, e.g. high hardness, adhesion to a wide range of materials, abrasion resistance, chemical resistance, low friction coefficient and biocompatibility. The presence of silicon in the films significantly reduces their inner mechanical stress as compared to diamond films. Currently, the films are used in industry, primarily, as solid lubricants and protective coatings. There are a large number of silicon-carbon film synthesis methods the most widely used of which are various options of chemical vapor deposition. A new silicon-carbon film synthesis technique has been suggested and tested. The technique is based on the use of high-frequency induction for obtaining plasma of silicon and carbon vapors supplied to the reaction chamber from an external source. Impurity-free silicon-carbon films containing 63–65 % carbon atoms with sp3 orbital hybridization have been synthesized on Sitall substrates. The composition, surface roughness and friction coefficient of the impurity-free silicon-carbon films synthesized using the suggested technology have been studied. The possibility of implementing resistive switching in thin silicon-carbon films in cross-bar structures with metallic electrodes has been analyzed.

Creattion of silicon-carbon films by induction assisted plasma chemical deposition

Silicon-carbon films are of great interest as diamond-like materials combining unique properties – high hardness, adhesion to a wide class of materials, abrasion resistance, as well as chemical resistance, low coefficient of friction and biocompatibility. The presence of silicon in the composition makes it possible to significantly reduce the internal mechanical stresses in such coatings compared to diamond ones. In modern production, films have been used primarily as solid lubricants and protective coatings. There are a large number of methods for producing silicon-carbon films, the most widespread among which are various variants of vapor-phase chemical deposition. In this paper, a method for the synthesis of silicon-carbon films was proposed and tested, based on the use of a high-frequency inductor to produce a plasma of vapors of silicon-carbon liquid injected into the chamber from an external source. Pure silicon-carbon films with a carbon atom content with sp3-hybridized orbitals of 63–65 % were obtained on sitall substrates. The composition, surface roughness and coefficient of friction of unalloyed silicon-carbon films obtained by the proposed method were studied. The possibility of resistive switching in thin silicon carbon films in crossbar structures with metal electrodes was studied.

Morphological Features of Polycrystalline CdS1−xSex Films Obtained by Screen-Printing Method

The results of studying the morphological peculiarities of polycrystalline CdS1−xSex films, obtained by screen printing, with well-formed grain boundaries of high structural quality are presented here. The developed method for screen printing provides the formation of polycrystalline films of a specified area per cycle, provided that there is a possibility for varying their thickness from tens of microns to units, which allows reducing the solar cell’s thickness and facilitating the process of its connection with the substrate. Therefore, the application of the films to a sitall substrate by screen printing contributes to reducing the product weight and facilitating the process of joining sheet materials intended for solar panels, namely attaching the lasing element to the substrate. The purpose of this work is to study the morphological peculiarities of polycrystalline CdS1−xSex films obtained by an optimized screen-printing method and to create a model of their formation process. The structural and morphological peculiarities of the samples were studied using electron microscopy, AFM, XPA, and XFS. As a result of the work, based on the obtained experimental data, a model of the film formation process was developed. The model validity is justified by the conformity of the data of the experiment performed on its basis.

DETERMINATION OF THE QUALITATIVE INFLUENCE OF FACTORS ON THE SENSITIVITY OF THE CAPACITIVE HUMIDITY SENSOR OF A TWO-LAYER STRUCTURE BASED ON MULTIFACTOR DISPERSION ANALYSIS

A multifactorial dispersion analysis was applied in order to qualitatively assess the influence of the following factors: thickness of the moisture-sensitive layer; the thickness of the polymer coating as a protective layer; the concentration of the NaCl salt solution as an adsorbent material and their combined effect on the sensitivity of the capacitive humidity sensor of the two-layer structure. Capacitive humidity sensors of a two-layer structure, made on a sitall substrate, served as experimental samples. The copper film, which forms the covers of the capacitive humidity sensors, is applied to the surface of the sitall substrate in the form of a meander. In the developed design, the moisture-sensitive layer is hygroscopic salt, which performs the function of a dielectric. A moisture-absorbing film of polymethylmethacrylate serves as a protective layer. A multifactorial plan is developed for the case of three qualitative factors. Using multifactorial dispersion analysis, it was proved that the response of the model, that is, the sensitivity of the capacitive humidity sensor of the two-layer structure, is influenced by such factors as the thickness of the protective layer, the concentration of the NaCl salt solution, as well as the combined effect of factors such as the thickness of the moisture-sensitive layer + the concentration of the salt solution; the thickness of the protective layer + concentration of the salt solution. That is, the difference in the response values of the model is related to the change in the value of the factor and cannot be caused only by its random nature. However, the response of the model is significantly affected by the combined effect of the factor − the thickness of the protective layer + the concentration of the salt solution. In this case, the value of Fisher’s criterion, which is observed in the experiment, significantly exceeds the critical value of Fisher’s criterion F >Fkr (13.01>4.49). The influence of such factors as the thickness of the moisture-sensitive layer; the thickness of the moisture-sensitive layer + the thickness of the protective layer; the thickness of the moisture-sensitive layer + the thickness of the protective layer + the concentration of the salt solution is insignificant, that is, the difference in the response values of the model is due to its random nature. Using the dispersion analysis of the influence of the factor, it was proved that the sensitivity of capacitive humidity sensors is affected not only by the concentration of the NaCl salt solution, which was used to create a moisture-sensitive layer, but also by the design of the sensor.

Effect of the morphology of films of polyaniline derivatives poly-2-[(2E)-1‑methyl-2‑butene-1‑yl]aniline and poly-2-(cyclohex-2‑en-1‑yl)aniline on sensory sensitivity to humidity and ammonia vapors

The influence of the morphology of polyaniline derivatives on the electrical conductivity, sensory sensitivity to air humidity of thin-film structures based on them, and the reaction to ammonia vapors has been investigated. Aniline derivatives, as well as polymers based on them, poly-2-[(2E)-1‑methyl-2‑butene-1‑yl]aniline and poly-2-(cyclohex-2‑en-1‑yl), were synthesized. Using a scanning electron microscope, the morphology of the surface of thin films obtained from a solution of synthesized polymers by centrifugation on sitall substrates was studied. Studying the nature of morphology is extremely important when creating sensory devices. On the basis of these polymers, samples of resistive thin-film structures were prepared, the dependence of their electrical conductivity on the relative humidity of the air and the dependence of the current passing through the sample with a change in the concentration of ammonia vapors were measured. The influence of the morphology of the surface of the films on the sensitivity of sensors to air humidity has been experimentally revealed and the prospects of using the studied films in humidity sensors have been shown. According to the experimental data, it can be seen that poly-2-[(2E)-1‑methyl-2‑butene-1‑yl] aniline film has the highest conductivity at the same values of relative humidity.

APPLICATION OF MULTIFACTOR DISPERSION ANALYSIS WITH THE PURPOSE OF QUALITATIVE ASSESSMENT OF THE INFLUENCE OF FACTORS ON THE SENSITIVITY OF THE CAPACITIVE HUMIDITY SENSOR

In order to qualitatively assess the influence of such factors as the thickness of the moisture-sensitive layer, the concentration of the NaCl salt solution as an adsorbing material and their combined effect on the sensitivity of the capacitive humidity sensor, a multivariate dispersion analysis was used. Capacitive humidity sensors served as experimental samples. Capacitive humidity sensors are made on a 0.7×0.9 mm sitall substrate. A copper film is applied to the surface of the sitall substrate, which forms the covers of the capacitive humidity sensors in the form of a meander with the appropriate geometry of 7.85·10-2×150·10-6×1.2·10-6 m. In such a design, the moisture-sensitive layer is hygroscopic salt, which serves as a dielectric. To create a moisture-sensitive film, solutions of hygroscopic salt NaCl with concentrations of 0.89 mol/l and 5.33 mol/l were used. They were applied to the surface of capacitive humidity sensors with a spray gun at a distance of 40-50 cm with thicknesses of 5.0 μm and 10.0 μm. A multifactor plan was developed in the case of two qualitative factors. The research results were obtained on the basis of the comparison of the factor variance, which is due to the influence of the factor, and the residual variance, which is due to the influence of random causes. Factorial and residual variance were compared using the value of Fisher’s test. Using multivariate dispersion analysis, it was found that the concentration of the NaCl salt solution has a significant influence on the response of the model, namely the sensitivity of the capacitive humidity sensor. In this case, the value of Fisher’s criterion observed in the experiment significantly exceeds the critical value of Fisher’s criterion, namely 22.77>4.75 (F>Fck). The influence of such factors as the thickness of the moisture-sensitive layer and the combined effect of the thickness of the moisture-sensitive layer and the concentration of the salt solution is insignificant, i.e. the difference in the response values ​​of the model is related to its random nature rather than to the change in the value of the factor. Using the dispersion analysis of the influence of the factor, it was proved that regardless of the design of the capacitive humidity sensors, the concentration of the salt solution used to create the moisture-sensitive layer significantly affects the sensitivity of the capacitive humidity sensor.

Algorithm for determining the structural characteristics of amorphous nanogranulated composites from the microwave waves reflection or conductivity

We present an algorithm for calculating structural characteristics of amorphous nanogranular composites (mean free path of electron, average sizes of granules and gaps between them) by the measured reflection coefficients of microwave waves or conductivity. The algorithm was tested with amorphous granular composite films with thickness of 2.2–5.8 μm, deposited on a sitall substrate. We showed that the mean free path of electrons fully corresponded to the average size of the granules at certain contents of the metal phase and reflection coefficients of microwave waves. The results were obtained with the usage of atomic force and scanning electron microscopy.

APPLICATION OF REGRESSION ANALYSIS DURING THE ASSESSMENT PROCESS OF FACTOR IMPACT ON THE SENSITIVITY OF THE CAPACITIVE HUMIDITY SENSOR

In order to optimize the parameters of creating a moisture-sensitive layer of the capacitive humidity sensor, a multifactorial experiment plan was used in combination with regression analysis of the factor influence. Capacitive humidity sensors are made on a sitall substrate with size 0.7×0.9 mm, on the surface of which is applied a copper film, which forms the plates of the capacitive elements in the form of a meander with the appropriate geometry 7.85·10-2×150·10-6×1.2·10-6 m. Hygroscopic salt is a moisture-sensitive film that serves as a dielectric. Solutions of hygroscopic salt NaCl with concentrations 0.89 mol/l and 5.33 mol/l were used to create a moisture-sensitive film, which were applied to the surface of capacitive humidity sensors by spraying at a distance of 40–50 cm with thicknesses of 5.0 μm and 10.0 μm. Statistical processing of the results of the factor experiment by the Cochran test proved that the factor experiment is reproducible. Using the planning matrix of the full-factor experiment, a regression equation has been developed and on the basis of which it has been found that the concentration of salt solution used to create a moisture-sensitive layer significantly affects the sensitivity of the capacitive humidity sensor. According to Student criteria it has been established that all the coefficients of the regression equation are significant. Sensitivity has been chosen as criteria for parameters optimization of creation a moisture-sensitive layer of such a capacitive humidity sensor. The final regression equation on the scale of real factors makes it possible to optimize the parameters of creation a moisture-sensitive layer of the capacitive humidity sensor with the maximum values of the response function – “sensitivity”. It has been found that the highest sensitivity of 36.32 pF/% is provided by the following optimal parameters of the process of creating a moisture-sensitive layer: the concentration of salt solution, which serves as an adsorbent material, namely hygroscopic salt NaCl – 5.33 mol/l and thickness of moisture-sensitive layer 10.0 μm.

Structure and morphology effects on sensing properties Cd-=SUB=-x-=/SUB=-Pb-=SUB=-1-x-=/SUB=-S films

Polycrystalline films of CdxPb1-xS (0.021≤x≤0.090) supersaturated substitutional solid solutions with a cubic structure B1 (Fm3m space group) have been obtained with varying cadmium acetate salt Cd(CH3COO)2 in the reaction mixture within 0.01-0.10 mol/l on the sitall substrates. Their thickness changed from ~0.4 to ~1.0 microns. A correlation has been established between the structural-morphological and functional properties of CdxPb1-xS thin-film layers. The extreme character of the voltage sensitivity dependence on the cadmium salt concentration in the reaction bath is associated with the nonmonotonic introduction of cadmium into the PbS crystal lattice. It is shown that the maximum photocurrent is possessed by CdxPb1-xS thin-film layers formed from crystallites with pronounced faceting. We have found the surface sensitivity of the CdxPb1-xS films to the presence of ~0.02 mg/m3 NO2 in the air, which is significantly lower than the maximum allowable concentration. Keywords: chemical bath deposition, film morphology, structural properties, CdxPb1-xS solid solution, photosensitivity, sensing properties.

Investigation of the dynamics of heating metal-dielectric structures with nanometer conductive film under the influence of microwave fields

The paper presents the results of experimental studies and analysis of the dynamics of heating of metal-dielectric structures (MDS) with aluminum conducting films on glass or sitall substrates when exposed to powerful microwave fields, as well as when exposed to direct and alternating currents.

Asymmetric magnetization reversal processes in amorphous composites (Fe40Co40B20)x(AL2O3)100-x

The amorphous composite films (Co40Fe40B20)x(Al2O3)100-x with different content of the metal (Co40Fe40B20)x “(CoFeB)x” and the dielectric (Al2O3)100-x components were obtained in the original ion-beam deposition unit. Sputtering of a composite target from an amorphous Co40Fe40B20 alloy plate with dielectric Al2O3 inserts was carried out in the argon atmosphere at an operating pressure of ∼5.10–4 Torr on glass-ceramic Sitall substrates. The presence of two regions in the IR spectra of composites with different values of х confirms the existence of the metal and dielectric components during the ion-plasma deposition of composites on a sitall substrate as a result of self-arrangement. The magnetic hysteresis was measured at room temperature for (CoFeB)x(Al2O3)100-x thin film samples for x = 1, 75 and from 9 to 69 with the step x = 10 at different angles (φ) when magnetic field applied out of a plane (φ = 90°) and in-plane (φ = 0°) of the films. The obtained results show that at low alloy (CoFeB)x contents the film composites with nominal x = 1, 9, and 19 behave as paramagnetic from the first glance. With an increase of the alloy (CoFeB)x content to nominal x = 29–75 amorphous composites films seems as superparamagnetic and ferromagnetic materials that are characterized as reversal magnetization with no coercivity and remanence. The existence of a magnetic vortex in the samples with x = 59–75 opens different remarkable applications like data storage.

Peculiarity of the low temperature magnetoresistive effect in the Corbino disk with magnetic ordering

The transverse magnetoresistance (MR) hysteresis loops of a magnetically ordered Corbino disk have been studied in the temperature range 300–2 K in an external magnetic field with induction up to 1 T oriented in the plane of the disk (ϕ = 0°) and perpendicularly to its plane (ϕ = 90°). The Corbino disk is made of a thin permalloy film obtained on an insulating sitall substrate by ion-beam sputtering. Independently of the temperature and measurement geometry, the field dependences of MR in the range of weak magnetic fields up to the magnetisation saturation exhibit sharp peaks of the negative MR caused by the domain walls motion during the magnetisation reversal of the sample. The position of the peak in the magnetic field (Bp) is determined by the temperature as well as the angle between magnetic field direction and the disk plane. It was found that a temperature change in the range of T = 300–2 K leads to a change in its position in the range of 0.2–6.0 mT and 8–22 mT at ϕ = 0° and ϕ = 90°, respectively. The magnetic field direction reorientation from in-plane to out-of-pane at T = 2 K leads to the Bp change from 6 to 22 mT. In the range of strong magnetic fields above the magnetization saturation field at ϕ = 0° the positive MR component decreases with induction and has a linear non-saturable dependence down to T ≈ 40–50 K due to the magnon MR component dominance. The complete freezing of magnons at T = 2 K leads to the absence of high-field magnetoresistive effect. At ϕ = 90° in weak fields, the MR changes its sign from positive to negative due to the anisotropic MR component dominance because of the disk magnetisation reorientation perpendicular to the current lines. In a strong field it changes the slope due to the saturation of negative anisotropic MR component, as well as possible additional contribution of the positive geometric Lorentzian MR.

Synthesis of bulk crystals and thin films of the ferromagnetic MnSb

High-temperature ferromagnets are widely used on a practical level. Based on them, magnetic memory for computers and various types of magnetic field sensors are created. Therefore, bulk ingots and thin-film samples of ferromagnet manganese antimonide (MnSb) with a high Curie point are of great interest, both from the practical and fundamental sides. Manganese antimonide films are obtained in hybrid structures using molecular-beam epitaxy. The thickness of the films does not exceed tens of nanometers. Despite their high sensitivity to magnetic fields, their small thickness prevents them from being used as magnetic field sensors. The aim of this work was to synthesise thick bulk ingots of manganese antimonide crystalsand films with a thickness of ~ 400 nm on sitall and silicon substrates. MnSb crystals were synthesised using the vacuum-ampoule method and identified using XRD, DTA, and microstructural analysis. The results of studies of bulk samples indicated the presence of an insignificant amount of antimony in additionto the MnSb phase. According to the DTA thermogram of the MnSb alloy, a small endothermic effect was observed at 572 °C, which corresponds to the melting of the eutectic on the part of antimony in the Mn-Sb system. Such composition, according to previous studies, guaranteed the production of manganese antimonide with the maximum Curie temperature. A study of the magnetic properties showed that the synthesised MnSb crystals were a soft ferromagnet with the Curie point ~ 587 K. Thin MnSb films were obtained by an original method using separate sequential deposition in a high vacuum of the Mnand Sb metals with their subsequent annealing. To optimise the process of obtaining films with stoichiometric composition, the dependences of the thickness of metal films on the parameters of the deposition process were calculated. The temperature range of annealing at which the metals interact with the formation of ferromagnetic MnSb films was established, the films were identified, and their electrical and magnetic properties were measured

Development of Enzyme Conductometric Biosensor for Dopamine Determination in Aqueous Samples

AbstractDopamine is a biologically active chemical that performs a number of vital functions as a hormone and neurotransmitter. Therefore, the determination of dopamine concentration in the human body is important for biomedical research. The content of dopamine in the blood varies depending on the age of a healthy person and can serve as a prognostic marker of many diseases. The aim of this work was to develop a new enzyme conductometric biosensor for the determination of dopamine in aqueous samples and to study the biosensor's analytical characteristics. The conductometric method of analysis with differential measurement mode was used in the work. Two pairs of gold interdigitated electrodes deposited on a sitall substrate were used as a conductometric transducer. The biorecognition element of the biosensor was based on laccase immobilized by glutaraldehyde cross‐linking. The optimal conditions of laccase immobilization were selected. The influence of solution parameters (ionic strength, pH, buffer capacity) on the biosensor work was investigated. The biosensors demonstrated high sensitivity to dopamine (minimum limit of detection −7.8 μM) with the linear range up to 1 mM. The biosensor was highly selective and reusable. The proposed biosensor was tested regarding the possibility of its long‐term storage under different conditions. The developed conductometric biosensor was proven to be suitable for measuring dopamine concentration in biological and pharmaceutical samples.

In English

In this work, a nanoscale structure consisting of contacting layers of a metal of the iron subgroup and a rare earth metal oxide (REM) is considered. Such nanostructures have an interesting feature, which is that as a result of the contact of these layers, an increase in the galvanomagnetic, magneto-optical and kinetic properties of ferromagnetic metals are observed. Presumably, the enhancement is due to an increase in the magnetization of these metals, caused by the exchange f - d interaction between the unfilled f- and d-electron shells of the atoms that make up the contacting layers. The aim of this work is to find the possibility of such f - d exchange interaction by the EPR method. To compose the studied nanostructure, Fe used as it has the strongest magnetic properties in its subgroup. Gd2O3 was used as an REM oxide as one of the few oxides giving a significant signal in the EPR region. The Gd2O3/Fe nanostructure created by sequential electron-beam deposition of Gd2O3 and Fe layers on a sitall substrate. The thickness of the oxide and metal layers was 68 and 112 nm, respectively. EPR spectra were recorded at room temperature on a computerized spectrometer Radiopan 2547 SE / X at the frequency of 9.3 GHz. The set of the obtained spectra was processed using the OriginPro and MatLab programs, which confirmed their compliance with the Lorentz model. From the experimentally obtained EPR linewidth, the parameter of the exchange f - d interaction is determined under the condition of a number of assumptions. The value of the g-factor is also found. Comparison of the EPR parameters of the spectra of individual layers of Gd2O3 and Fe with the spectra of the Gd2O3/Fe nanostructure composed of them, including the value of the g factor and the exchange interaction parameter, suggests that the presence of an iron layer affects the EPR spectrum of the REM oxide layer Gd2O3. The exchange interaction parameter increases from 985 to 4685 (rel. units), the g-factor decreases from 3.5 to 2.4. The most probable reason for the change in the spectrum is the exchange f - d interaction between atoms with unfilled f- and d-electron shells that are parts of the contacting layers.

Influence of technological regimes of plasma chemical deposition on texture formation in aluminum nitride films

Textured polycrystalline aluminum nitride films were grown by magnetron sputtering of an aluminum target in a mixture of argon and nitrogen, followed by the formation of a film on sitall substrates. The influence of the pressure of the working gases, the power dissipated on the target, and the ratio of the Ar / N2 gas fluxes on the texture of the aluminum nitride films are investigated. The phase composition and degree of crystallinity of the obtained films were determined using scanning electron microscopy and X-ray diffraction. The results of studies of the phase composition and parameters of the crystal structure of aluminum nitride films are presented: the size of the coherent scattering regions, the predominant orientation of the crystallites in the growing film, and the degree of crystallinity. It is noted that the films are predominantly oriented along the (111) and (002) planes. The degree of crystallinity of the A1N films varied from 10 to 30% depending on the conditions of the deposition process. The relative microdeformation of the lattice (Δd/d), depending on the parameters, ranged from 1.7·10−3 to 6.9·10−3. The size of the crystallites is affected by the microdeformation of the lattice, with its increase by 4 times, the size of the crystallites decreased by 3.6 times from 29 to 8 nm.

Electrical properties of Na0.5Bi0.5TiO3 thin films deposited on sitall substrates

We report some special features of Na0.5Bi0.5TiO3 (NBT) thin films growth process, as well as structural and electrical properties of these films. The films were grown on Pt/sitall substrates by high-frequency (13.56 MHz) magnetron deposition method. To crystallize the films the NBT/Pt/sitall structure was annealed at a temperature around 500 °C ÷ 700 °C in air. Results of X-ray diffraction showed that annealing at 700 °C led to the crystallization of the NBT films in the perovskite phase with minor inclusions of the pyrochlore phase. Temperature dependences of dielectric hysteresis loops (P-E) and current density-electrical field (J-E) characteristics were investigated. A tendency of narrowing of the hysteresis loops with an increase of the temperature to 180 °C was detected, which can be probably associated with the features of the diffuse rhombohedral/tetragonal phase transition. The remanent polarization (Pr) and the coercive field (Ec) values measured at room temperature were 9 μC/cm2 and 40 kV/cm, respectively. It was found that with an increase of the temperature the leakage currents increased in the entire investigated range of applied electrical fields. Charge transfer mechanisms responsible for the leakage currents in NBT thin films are discussed.

Investigation of gas-sensitive properties of cobalt oxide films

This paper presents a study of the gas-sensitive properties of cobalt oxide films formed by rapid thermal annealing on a sitall substrate. Cobalt films were formed on a pre-cleaned sitall substrate by vacuum thermal evaporation. The thickness of the deposited films was 470 nm. Rapid thermal annealing (RTA) was used to form cobalt oxide films. RTA of cobalt films was carried out at temperatures of 500°C, 600°C and 700°C. The resistivity of the films after RTA at 500°C, 600°C and 700°C was 3.6 × 10–2 Ohm·cm, 1.2 × 103 Ohm·cm and 5.8 × 103 Ohm·cm, respectively. The surface morphology of the obtained films was investigated by the AFM method. The gas sensitivity of cobalt oxide films was studied for gases like CO, NO2, CH4, C3H6O (vapors of acetone), C3H8O (vapors of isopropyl) and NH3·H2O (vapors of ammonium hydroxide 25%). The gas sensitivity was measured at 300°C. The results of gas sensitivity measurements showed significantly lower sensitivity to gases such as CO, NO2 and CH4. It was found that cobalt oxide films have good sensitivity to gases such as C3H6O, NH3·H2O and C3H8O. Sensitive elements based on cobalt oxide films are interesting as gas sensor elements for the detection of C3H6O, NH3·H2O and C3H8O.