PbSnS thin films were prepared by hot-wall vacuum evaporation. The Rutherford backscattering technique was employed for the investigation of Pb_{x}Sn_{1 - x}S thin films composition. With a help of atomic force microscopy the main stages in the development of the thin films were characterized. Contact angle measurements of water drop on Pb_{x}Sn_{1 - x}S thin films have been conducted on our original setup.
The paper presents the results of investigation of element composition of CuInSe₂ (CIS) compounds obtained by vertical Bridgman technique and on a glass substrate by the thermal deposition of Cu-In thin films with the subsequent annealing in selenium vapour. The depth profile distribution of elements in these samples using the Rutherford backscattering spectrometry/channeling technique in conjunction with the RUMP code simulation is also discussed.
The paper presents our recent investigations of the early stage growth of titanium silicides on a modified Si(100) substrate. The substrate was modified by deposition of a minute amount of Ni atoms, and the subsequent flash annealing. This process led to the creation of parallel defect lines on the Si(100) surface. We expected TiSi_2 to form elongated structures on top and/or between the defect lines. Though this idea failed, stable nanostructures were observed and characterized using scanning probe microscopy (scanning tunneling microscopy and atomic force microscopy) methods.
In that report we observe the initial stages in the process of film growth at different irradiation doses. Investigations of influence of Mo deposition on glass substrates by means of self-ion-assisted deposition on its topography (atomic force microscopy) and wettability (sessile-drop method) were carried out. It was found out that with an increase of the irradiation dose, the average roughness and the contact angle increases rapidly at first and then decrease. 2.45-2.77 increase in the contact angle of water when Mo-based coating was deposited on the glass was observed.
We show that post growth annealing of GaMnAs under As capping at temperatures in the range of 180-210ºC leads to significant surface modifications. Depending on GaMnAs layer thickness and composition, we obtain either a smooth continuous reacted (MnAs) surface layer or 3D islands (quantum dots). The surface modifications are due to a solid phase epitaxial process, in which Mn interstitials diffusing to the GaMnAs surface are bound with the As.
Epitaxial manganite La_{0.67}Sr_{0.33}MnO₃ (LSMO) layers, with a thickness of 20-50 nm, are prepared on single crystal (001) SrTiO₃ (STO) substrates by pulsed laser deposition technique. Structural characterization (composition analysis, surface morphology), investigated by the Rutherford backscattering spectroscopy and atomic force microscopy, reveals the growth of stoichiometric LSMO films with a smooth surface (root-mean-square value of 0.21-1.6 nm). The prepared LSMO films possess high Curie temperature ( ≈ 412 K), low room temperature resistivity (1-2 mΩ cm) and maximum of temperature coefficient of resistivity TCR = 2.7% K¯¹ at 321 K.
Titanium dioxide (TiO_2) thin films having different thicknesses of 220, 260, and 300 nm were deposited onto well-cleaned n-type silicon substrates by reactive DC magnetron sputtering and annealed in the range of 200-1000C in steps of 200°C. The effects of thermal annealing and thickness variation on the crystalline quality and surface morphology of the films were investigated by X-ray diffraction and atomic force microscopy measurements. It was found that the film quality and morphology depend on the annealing temperature. TiO_2 films exhibit a grain-like surface morphology. The root-mean-square roughness and grain size on the surface increase as a result of increasing film thickness.
Thin obalt films, 40 nm and 100 nm in thickness, were evaporated at an incidence angle of 45° in a vacuum of about 10^{-5} mbar, simultaneously on unheated glass substrates and NaCl crystals. The magnetic microstructure of these films was investigated in a previous paper. In the present paper, to obtain an insight into relation between the magnetic microstructure and the morphological structure, we studied the latter structure with atomic force microscopy and transmission electron microscopy. For the films 40 nm as well as 100 nm thick, the presence of contribution of the shape anisotropy (related to the geometric alignment of the grains of the film) to the magnetic anisotropy of the film was found. Nevertheless, for the films investigated, we could not detect crystallographic texture.
The influence of the size of crystalline regions on mechanical properties of irradiated oxides has been studied using a magnesium aluminate spinel MgAl_2O_4. The samples characterized by different dimensions of crystalline domains, varying from sintered ceramics with grains of few micrometers in size up to single crystals, were used in the experiments. The samples were irradiated at room temperature with 320 keV Ar^{2+} ions up to fluences reaching 5 × 10^{16} cm^{-2}. Nanomechanical properties (nanohardness and Young's modulus) were measured by using a nanoindentation technique and the resistance to crack formation by measurement of the total crack lengths made by the Vickers indenter. The results revealed several effects: correlation of nanohardness evolution with the level of accumulated damage, radiation-induced hardness increase in grain-boundary region and significant improvement of material resistance to crack formation. This last effect is especially surprising as the typical depth of cracks formed by Vickers indenter in unirradiated material exceeds several tens of micrometers, i.e. is more than hundred times larger than the thickness of the modified layer.
This paper presents a comparative study between the microstructural features of two water-ferrofluids intended for biological applications. In both cases the ferrophase was prepared by auto-catalytic reaction between ferrous and ferric salts and resulted in magnetite and some maghemite precipitates. The difference is given by the stabilizer molecule: tetramethylammonium hydroxide and, respectively, citric acid. Transmission electron microscopy and atomic force microscopy were utilized for ferrophase size investigation. The evidence of short chains and large aggregates was obtained mainly by atomic force microscopy analysis (the tip diameter being equal to 5 nm). Their role in the ferrofluid rheological properties was studied by carrying out comparative measurements of viscosity and surface tension. Complementary investigation of the ferrofluid composition was done by means of IR absorption spectra. The suitability of the prepared ferrofluids for biological goals was proved by their convenient ferrophase diameter as well as by their stability in time.
The investigation of influence of Xe^{+} ions irradiation of graphite on its surface topography and wettability was conducted. With the increase of the irradiation dose, the roughness average increases rapidly at first (when the sample was irradiated at the dose of 1 × 10^{14} cm^{-2}) and then decreases slowly. The atomic force microscopy three-dimensional pictures showed that after irradiation of graphite of Xe^{+} ions with a dose of 3 × 10^{15} cm^{-2} hemispherical grains (from 0.2 to 0.8 μm in diameter) appear on its surface. Surface water contact angle measurement showed that irradiation of graphite by Xe^{+} ions leads to a hydrophobic surface of graphite. We have observed that irradiation of graphite by Xe^{+} ions can be used for obtaining graphite surface with desirable topography and water wettability.
Crystalline nanocomposite KDP/Al₂O₃ was obtained by growth of KDP nanocrystals inside nanopores of amorphous alumina matrix (Al₂O₃) with pores diameter of 35 nm. Performed atomic force microscopy and X-ray diffraction analysis confirmed that Al₂O₃ matrix is filled up with a tetragonal phase KDP nanocrystals in preferred crystallographic orientation [100]. The nonlinear optical response was studied by means of second harmonic generation via the Maker fringe technique employing picosecond laser pulses at wavelength of 1064 nm. The polarization dependent second harmonic generation response was observed mainly due to the macroscopic crystalline structure anisotropy of KDP/Al₂O₃ nanocomposite. The investigation of such type of nanocomposites which combine nanoscale nonlinear optical materials has a great importance since they may improve the performance of entire system.
The article presents the experimental results of the investigation of the absorption spectra and nonlinear refraction of the metal-dielectric nanocomposite that contains the lithium niobate pyroelectric crystal coated with the silver nanofilms on its surface. The atomic force microscopy surface research of these crystals with and without films are also provided. The nanowidth silver films impact on optical spectra and nonlinear refraction of LiNbO₃-Ag nanocomposite was analyzed depending on the sign of the side charge of the crystal, that contain nanofilms.
The influence of InAs coverage on the formation of self-assembled quantum dots grown by molecular-beam epitaxy was investigated by atomic force microscopy and photoluminescence measurements. As the InAs coverage increased from 2.0 to 3.0 monolayers, the quantum dot density decreased from 1.1 × 10^{11} to 1.36 × 10^{10} cm^{-2}. This result could be attributed to the coalescence of neighboring small InAs quantum dots resulting in the formation of much larger InAs quantum dots with lower quantum dot density. Atomic force microscopy results revealed that as the InAs quantum dot coverage increased, the transition of size distribution of InAs quantum dots from single-modal to multimodal occurred. The temperature-dependent photoluminescence spectra showed that the photoluminescence spectra red shifted and the photoluminescence peak intensity decreased as the InAs coverage increased. The thermal activation energy was strongly dependent on the InAs coverage, and for InAs quantum dots with 3.0 ML thick InAs coverage, this energy was estimated to be 147 meV.
Magnesium and its alloys are interesting materials for biodegradable implant applications. Magnesium alloys have very good strength properties, they are lightweight, but their main disadvantage is a low corrosion resistance in the physiological environment. Various modifications of a Mg alloys surface by deposition of different coatings are used to prevent untimely dissolution. The article presents the investigation results of a thin ZnO coating deposited on a MgCa2Zn1Gd3 alloy by means of the magnetron sputtering method. The studies include: scanning electron microscope observation of the ZnO surface, X-ray phase analysis, surface roughness measurement in atomic force microscopy, the microhardness test and potentiodynamic corrosion resistance test in the Ringer solution at 37°C. It was found that the ZnO coating is compact and continuous. It increases the hardness of the MgCa2Zn1Gd3 alloy and also improves its corrosion resistance. The corrosion potential is shifted slightly towards the positive values from -1.52 V to -1.50 V for the alloy with the ZnO coating.
Thermally stimulated luminescence of X-ray irradiated β -Ga₂O₃ thin films was investigated. An analysis of the form of the elementary contours making the thermally stimulated luminescence curves shows that recombination processes at the thermally stimulated luminescence peaks with maxima at 77, 135, 178, and 235 K in thin films of β -Ga₂O₃ are described in terms of linear kinetics. The spectral composition of the thermally stimulated luminescence of the thin films was studied. Some methods are employed to determine the activation energies and frequency factors corresponding to the thermally stimulated luminescence peaks. It is established that the recombination processes occurring upon release of the trapping centers in thin films β -Ga₂O₃ are conditioned by diffusion-controlled tunneling recombination due to thermally-stimulated migration of V_{k}-centers.
Crystallization of Li₂O-7GeO₂ glass was carried out on heating, simultaneously differential scanning calorimetry and electric properties were studied. Morphology of the phase states obtained at glass devitrification was examined by atomic force microscopy. It was shown that amorphous phase of Li₂O-7GeO₂ was crystallized in stages through the intermediate state with increased conductivity σ . In the intermediate state the sample volume was occupied by nanometer-sized nuclei with ordered structure surrounded by internuclear amorphous medium. Complete glass crystallization occurred through transformation of nanometer-sized nuclei into micrometer-sized crystallites and was accompanied by a sharp and irreversible decrease of conductivity. Atomic force microscopy of the samples heat-treated in different ways showed that Li₂O-7GeO₂ glass crystallization was suppressed near the surface and mainly proceeded within the sample bulk. Charge transfer in amorphous, nanocrystalline intermediate and polycrystalline phases of Li₂O-7GeO₂ was associated with motion of the weakly bound Li ions.
The silver colloids and silver films are known for their signal enhancing properties in Raman spectroscopy. Surface enhanced raman spectroscopy is a very useful tool to detect molecules at low concentration or even single molecules in examined samples. Here we present a study on the preparation of silver colloidal solution and deposition of silver films on mica. The colloidal solutions were examined by two methods: the UV-VIS spectroscopy to determine their optical properties and atomic force microscopy to determine the size of the particles and structure of the deposited films. The crystal violet (tris(4-(dimethylamino)phenyl)methylium chloride) solution was used as a test sample for evaluation of enhancing properties of silver colloidal solutions and films. These experiments have shown that both colloidal solutions and films, are efficient surface enhanced raman spectroscopy substrates, therefore they can be used in further studies for enhancement of the Raman signal of biopolymers, f.e. polysaccharides and DNA.
Nowadays, it is well established that changes of cell stiffness observed by atomic force microscopy are linked with the cell cytoskeleton. Its structural and functional alterations are underlying major diseases such as cancer, inflammation or neurodegenerative disorders. So far, the use of atomic force microscopy is mostly focused on the determination of the Young modulus using the modified Hertz model. It can quantitatively describe the elastic properties of living cells, however, its value is burdened by the fact that cells are neither isotropic nor homogeneous material. Often, during the atomic force microscopy measurements, the hysteresis between the loading and unloading curves are observed which indicates the dissipation of an energy. In our studies, the index of plasticity was introduced to enumerate such effect during a single loading-unloading cycle. As the results show, such approach delivers an additional parameter describing the mechanical state of cell cytoskeleton. The analysis was performed on test samples where the mechanical properties of the melanoma cells were changed by glutaraldehyde and cytochalasin D treatments. The non-treated cells were compared with fibroblasts.
The structure of the surface and spectra of the cathodoluminescence of Y₂O₃:Eu thin films when changing the activator concentration in the range 1.0-7.5% by mole obtained by RF sputtering were investigated. On the base of the shape of the cathodoluminescence spectra at different concentrations of the activator, the possibility of irregular solutions creating of yttrium and europium oxides and the structural features of the small and large crystallites forming the film Y₂O₃:Eu is shown. The dependence of the cathodoluminescence intensity on the energy of the exited electrons and current density of electron irradiation was established.
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