A novel approach for the preparation of ferroelectric composite films has been successfully developed by combining sol-gel evaporation-induced self-assembly (EISA) of porous lead zirconate titanate (PZT) films with atomic layer deposition (ALD) of titania. The EISA process, which utilizes a Brij-type surfactant, facilitates the formation of large columnar perovskite grains with narrow (similar to 20 nm) interconnected pores. ALD, employing the thermal reaction of titanium isopropoxide with water, ensures uniform titania growth within the pores throughout the film thickness, as demonstrated by transmission electron microscopy and ellipsometric porosimetry. The resulting PZT-TiOx composite films exhibit a pronounced photovoltaic current under visible light illumination, attributed to electron excitation from the valence band to Ti3+ states, followed by movement via a hopping conduction mechanism. The photocurrent value varies with the direction of polarization. This behavior presents a potential method for controlling photoconductivity through polarization, with possible applications in electronic and photonic devices.

The properties of graphene chips with low reproducibility (LR) after photolithography (PLG) and graphene functionalization have been studied. It is shown that the introduction of additional cleaning after PLG can significantly increase the reproducibility of the parameters of processed graphene in biosensors. The use of dilute PBS solutions for virus detection makes it possible to increase the relative concentration sensitivity of biosensors by several times.

Предложен метод определения аппаратной функции при измерениях поверхностного потенциала в режиме Кельвин-зонд-микроскопии. Метод основан на применении в качестве тестовой структуры поверхности политипов SiC, содержащих области однослойного и двухслойного графена. Измерение профилей потенциала вдоль различных направлений на такой поверхности позволяет определить аппаратную функцию для зондовых измерений потенциала. Используя аппаратную функцию, можно выполнять процедуру деконволюции и восстанавливать точный потенциал поверхности. Ключевые слова: сканирующая зондовая микроскопия, Кельвин-зонд-микроскопия, потенциал поверхности, тестовые структуры, графен, карбид кремния.

Porous ferroelectric lead zirconate titanate (PZT) films are a promising material for various electronic applications. This study focuses on understanding how the structure-directing agent, polyvinylpyrrolidone, can alter the structure and electrical properties of porous PZT films prepared through chemical solution deposition. Films with various porosities of up to ~40 vol.% and pore connectivities from 3-0 to 3-3 were prepared and studied by capacitance–voltage, dielectric hysteresis, transient current, photocurrent, and local current techniques. We have found that a linear decrease in material volume in a porous film is not the only factor that determines film properties. The creation of new internal grain boundaries plays a key role in changing electrical properties. This research expands the understanding of physical phenomena in porous ferroelectric films and may facilitate the development of new materials and devices.

The paper proposes a method for determining the instrumental function for measuring the surface potential in the Kelvin probe microscopy mode. The method is based on the use of SiC samples with regions of single-layer and double-layer graphene as a test structure. The measurement of potential profiles along different directions on such a surface makes it possible to determine the instrumental function for measurements of the potential. Using the instrumental function, one can perform a deconvolution procedure and restore the exact surface potential.

The optical properties of thin films and layers of Ag nanoparticles on a c-Si substrate are modeled by calculating the complex pseudo-dielectric function . The evolution of the imaginary part with an increase in the thickness of continuous layers from the dielectric function e of the substrate to e of bulk silver is studied, which demonstrates the appearance of optical characteristics of Ag and the suppression of c-Si features in the form of critical points. The data measured on the spectroscopic ellipsometer for Ag films produced by magnetron sputtering for several nominal thicknesses from 10 to 300 nm, and layers of Ag nanoparticles chemically deposited on a c-Si substrate, were interpreted using a pseudo-dielect ric function and by calculating the complex dielectric functions e using the Drude-Lorentz model. Morphological parameters obtained by atomic force microscopy and scanning electron microscopy were also used in the calculations. Since the Ag layers and films were deposited on the c-Si substrate without any additional layers (except for the native layer), the determined pseudo-dielectric functions for thicknesses in the range of 7-50 nm turned out to be close to the calculations of the dielectric functions using the Drude-Lorentz model. It was found that in the calculated and experimental spectra in the imaginary part of e2 and a peak appears at E -3.9 eV, which is interpreted as a plasmon resonance in the lon-gitudinal mode at oblique incidence of light. In the e2 spectrum of a layer of disordered Ag nanoparticles produced by chemical deposition, there is a broader localized surface plasmon resonance peak at E -2.5 eV, in contrast to thin films. Whereas, in a layer of larger nanoparticles, the peak is absent, and its e dependence is close to e for bulk Ag.

Scanning probe microscopy investigations of triboelectric charges on thin films of high-k dielectrics LaScO3, MoSe2 semiconductor “flakes”, PZT films are carried out. It is shown that the value of the accumulated triboelectric charge in these films depends on their thickness. The strongest effect is observed in the LaScO3 film 6 nm thick and the PZT film 100 nm thick. The dependence of the value of the measured triboelectric potential on the pressing force and the probe material is also experimentally found.

Abstract SPM studies of triboelectric charges on thin films of high-k dielectrics LaScO3, semiconductor ”flakes“ MoSe2, and ferroelectric PZT films have been carried out. It is shown that the value of the accumulated triboelectric charge in these films depends on their thickness. The strongest effect is observed in the LaScO3 film 6 nm thick and the PZT film 100 nm thick. The dependence of the value of the measured triboelectric potential on the loading force and the material of the probe was also experimentally found.

In this work, the modification of the surface parameters of graphene chips after electrolysis treatment in a NaClO 4 aqueous solution has been studied. Two electrolysis modes have been analysed. In the first one, a negative potential (-0.2 V) is applied to the graphene chips, while in the second one the potential is positive (0.8 V). Investigation using a number of techniques including atomic force microscopy, Kelvin probe force microscopy, Raman spectroscopy, measurements of current-voltage characteristics and low-frequency noise has shown that the electrolysis mode with application of a positive potential on graphene chips decreases the 1/ f noise and allows one to obtain a uniform surface potential distribution while leaving the graphene structure undamaged. The results of this study help to understand the efficiency and reproducibility of the procedure for electrolysis treatment of graphene chips.

The local polarization processes in thin BaTi1-xZrxO3 films were investigated by contact conducting scanning probe microscopy and piezoresponse microscopy. A relationship between the direction of the created domains and the magnitude of the flowing currents is established. The value of the residual polarization is found, and the hysteresis loop is measured using scanning probe microscopy as well as the values ​​of the piezomodule dzz and the value of the coercive field Ec for these films are determined.

The surface topography, local current distribution and piezoresponse signal in porous ferroelectric PZT films are studied using conductive atomic force microscopy (c-AFM) and piezoforce microscopy (PFM). The PZT films were formed from solutions with the addition of 0–20 wt% polyvinylpyrrolidon (PVP) as a porogen with the molecular weight of 360000. Applying c-AFM, the topography images and distribution maps of the local current of the same surface area are obtained, which made it possible to compare the profiles of the topography and current signals. It is shown that in PZT films prepared without PVP addition, the local currents flow inside the grains forming the columnar structure with nonconductive grain-boundaries. At PVP content of 1-3 wt%, separate current peaks are observed on the analyzed profiles, but starting from 6 wt% PVP and higher, the local current flowing in the pore regions exceeds the current recorded in the grain area.

Local polarization processes in BaTi 1 – x Zr x O 3 thin films are studied using contact conductive scanning probe microscopy and piezoelectric response microscopy. The relationship between the direction of the created domains and the magnitude of the flowing currents is established. The value of the residual polarization is found. Using scanning probe microscopy, the hysteresis loop is measured and the values of the piezoelectric modulus d zz and coercive field E c for these films are determined.

Thin films of two-component H2Pc, PdPc, PbPc, CuPc phthalocyanines were studied by scanning probe microscopy methods. Young's modulus values of the phthalocyanines films were measured, which made it possible to optimize the regimes for studying soft phthalocyanine films and to select suitable probes with proper stiffness and the magnitude of the force acting onto the surface. For all films, the electric field induced reversible local conductivity switching effect was studied. It is shown that under room conditions it is possible to reversibly change the value of the local conductivity of a copper phthalocyanine film approximately by an order of magnitude. When conducting the experiment under vacuum conditions, a significant weakening of this effect occurs. It has been established that for a CuPc film, a pressure of 20 mbar is the lower boundary value for creating regions of increased conductivity. The observed effect is explained by the penetration of OH- ions (from the surface adsorbed water film) into the phthalocyanine film with the subsequent formation of oxygen-containing complexes that increase conductivity.

AbstractSynthesis of AlN and GaN layers on a Si(100) substrate by chloride vapor-phase epitaxy has been considered. The process includes sulfidizing of the silicon surface, nucleation and growth of an AlN layer, and then formation of a GaN/AlN structure. It has been found that in the case of a (100)Si substrate, GaN nucleates on buffer AlN layers that may have two crystallographic orientations in contrast to a Si(111) substrate, on which a buffer layer may have only one orientation. It has been shown that the treatment of the Si(100) substrate in an aqueous solution of (NH_4)_2S decreases the FWHM of the rocking curve for GaN(0002) by a factor of 1.5.

Synthesis of AlN and GaN layers on a Si(100) substrate by chloride vapor-phase epitaxy has been considered. The process includes sulfidizing of the silicon surface, nucleation and growth of an AlN layer, and then formation of a GaN/AlN structure. It has been found that in the case of a (100)Si substrate, GaN nucleates on buffer AlN layers that may have two crystallographic orientations in contrast to a Si(111) substrate, on which a buffer layer may have only one orientation. It has been shown that the treatment of the Si(100) substrate in an aqueous solution of (NH 4 ) 2 S decreases the FWHM of the rocking curve for GaN(0002) by a factor of 1.5.

Regions of single-layer- and bilayer graphene on the surface of thermally processed 4H-SiC substrates are studied using Kelvin probe force microscopy and Raman spectroscopy. We establish experimentally the key parameters of the adopted graphene growth technique which enables the fraction of bilayer graphene to be reduced to a minimum, while samples with a fraction of single-layer graphene as high as 95% are obtained.

The local current distribution across the grains and their boundaries in ferroelectric PZT films are studied using conductive AFM. The films were formed with various grain structures and different lead excess content by chemical solution deposition. C-AFM measurements have shown the influence of the lead excess and seed sublayer crystallization conditions on the grain-boundary conductivity. PZT films with fixed 0-15 wt% Pb excess demonstrate non-conductive grain boundaries, whereas in films with fixed 30 wt% Pb excess the grain-boundary conductivity is found to be much higher than that of the grains themselves. Conductive grain-boundaries was also found in PZT films without lead excess in crystallized sublayer. A study of the transient current at varied preliminary polarization revealed the current peaks in the current-voltage curves. The appearance conditions and magnitude of these peaks depend on the grain-boundary conductivity. The correlation between the grain-boundary conduction and the current polarization dependences is confirmed.

It is established that the magnetron sputtered thin PbZr54Ti46O3 (PZT) films contain a certain amount of pores, which makes it impossible to investigate their properties by traditional methods. It is shown that the boundaries of polycrystalline blocks in PZT films have an increased values of appearing transient currents associated with grain boundaries traps recharging. It is also found that the values of transient currents differ for oppositely polarized domains in the PZT films. The thickness of studied films was determined by the ellipsometry method as well as the dielectric function epsilon in the energy range E = 1.4-5 eV.

AFM study of surface morphology in green LED structures and multifractal analysis allowed us to reveal a relationship between step-meandering morphology quantitatively characterized by a multifractal parameter, the degree of disorder, and features of In incorporation in InGaN/GaN MQW structures. These features manifest themselves in a shape of the distribution of peak external quantum efficiency values with wavelengths (DPEW) in the current range of 0.1–1000 mA. High values of degree of disorder result in spinodal alloy decomposition and/or local In enriched regions in InGaN alloy and in a twofold decrease in EQE values in green LEDs.