Herein, we present indium tin oxide (ITO) as a promising candidate for developing adaptable standard resistors. The ITO thin-film device structures exhibit an average resistivity of approx. 1.5 × 10–4 Ω ⋅ cm, demonstrating remarkable stability in resistance values over time and showcasing temperature-independent magnetoresistance, making them reliable for various applications. ITO resistor structures were found to be optimal with an area ≥10–7 cm2, without observed additional series resistance. The temperature dependence of resistance values changes by approx. 10

A siliceous material in which a framework order was established with a surfactant with sixteen carbon atoms in alkyl chains, MCM-41-C16, was synthesised, surface-modified, and tested regarding the selected physical properties. The pristine material was extracted in an acidic aqueous alcohol and then lined with different surface groups. The properties of four adsorbents were investigated using XRD, X-ray photoelectron spectroscopy, and N2 physisorption techniques. The unit-cell constant was determined from X-ray diffractograms, being in fixed relation to the edge length of the hexagonal frame. The specific surface areas of mesopores and whole crystallites were determined from low-temperature N2-physisorption isotherms. The novelty of this work is a mathematical model of a crystalline microstructure explaining the sizes and shapes of crystalline grains in relation to adsorption features, proposed and successfully tested with the aforementioned experimental data. The roughness of the surface is different from one that is necessary to explain the experimental characteristics quantitatively.

In this article a complete procedure to investigate thin semiconductor plates (epitaxial layers), including high-resolution X-ray diffraction measurements, mathematical modelling of both crystalline structure and crystalline microstructure and computations to approximate solving inverse problems, is proposed and described in detail. The method is successfully applied to estimate crystalline homogeneity of a square indium-arsenide plate epitaxially-grown on gallium-arsenide substrate. To this end, the specimen is tested in nine areas around points forming a square grid. It is demonstrated that whole specimen may be regarded as a single large crystalline grain consisting of crystallites separated by small-angle boundaries. The crystallites occur as rode-like cuboids elongated in the direction perpendicular to the plate surface, with different areas of the sample and with base sizes not much differing. The mean-absolute second-order strain is very small and almost constant in the whole sample. The first-order strain also appears and, effectively, the structure of the crystalline layer is tetragonal with unit-cell parameters being smaller parallelly and larger perpendicularly to the layer surface and varying slightly in the layer. The results are presented in tables and figures and commented.

The main problem that arises in the mobility spectrum analysis (MSA) is the appearance of additional spectral lines, which are not related to real physical processes and transport mechanisms. The paper proposes a simple model of systematic errors occurring in magneto-transport measurements and investigates their impact on this adverse phenomenon. The analysis was carried out for typical mobility spectra characteristic of single- and dual-carrier transport. On the basis of numerical experiments, heuristic rules were formulated that can be helpful in distinguishing real spectral lines from false peaks caused by measurement errors.

Measurements of magnetotransport in SnTe/PbTe heterojunctions grown by the molecular beam epitaxy technique on (001) undoped CdTe substrates were performed. At low magnetic fields, quantum corrections to conductivity were observed that may be attributed to the presence of topological states at the junction interface. For a sample with a 5-nm-thick SnTe layer, the data analysis suggests that midgap states are actually gapped. However, the phase coherence effects in 10 and 20 nm SnTe/PbTe samples are fully explained assuming the existence of gapless Dirac cones. Magnetotransport at higher magnetic fields is described in the framework of mobility spectrum analysis (MSA). We demonstrate that the electron-and holelike peaks observed simul-taneously for all SnTe/PbTe heterojunctions may originate from the concave and convex parts of the energy isosurface for topological states-and not from the existence of quasiparticles both carrying negative and positive charges. This interpretation is supported by numerical calculations of conductivity tensor components for gapless (100) Dirac cones, performed within a classical model and based on the solutions of the Boltzmann transport equation. Our approach shows the feasibility of MSA in application to magnetotransport measurements on topological matter.

The paper highlights the need to develop techniques for the precise parameterization of multi-channel charge carrier transport, which are of fundamental importance for the effective design of semiconductor devices. The current state of development of these measurement techniques at the Military University of Technology is presented, as well as exemplary results for semiconductor structures obtained by molecular beam epitaxy (MBE).

Accurate determination of electronic transport properties of individual transparent conductive oxide layers, namely indium tin oxide (ITO), is essential for further development and design of photonic devices with ITO layer as a tunable ultrafast optoelectronic component. Precise magnetotransport measurements are here implemented to achieve carrier mobility distribution that gives insight into types and characteristics of carrier species. ITO thin films with various sheet resistance of ≈10, 75, and 350 Ω sq −1 , respectively, are examined at near‐room temperature. Unimodal mobility distribution is revealed in ITO films, independently on their resistivity, with no evidence of unseparated contributions from surface or interface states. The electron mobility varies depending on ITO's resistivity, ranging from 36.8 to 47.2 cm 2 V −1 s −1 at 300 K. Importantly, no minority hole conduction is present. The ITO thin films exhibit solely bulk‐like conduction with an absence of parallel conductions. In addition, the existence of single‐type electron population in ITO that can be viewed as an important validation of exclusively donor‐type defects and/or impurities contributing to total ITO conductivity is experimentally confirmed. These results indicate that ITO can be viewed as an integrated counterpart for photonic metadevices.

The purpose of this research was a study of selected physical properties of a class of absorbents with large specific surface area (some of them including self-assembled monolayers on mesoporous supports). A polycrystalline powder of silica-based material with crystalline honeycomb structure (of SBA-15 type) was synthesized. The primary material was calcined and then lined with N-[3-(tri-methoxy-silyl)propyl]ethylenediamine to coordinate to cations Ba2+, Sn2+, Fe2+ or Cu2+. All six specimens’ properties were investigated using X-ray diffraction, X-ray photoelectron spectroscopy and nitrogen adsorption techniques. The unit-cell constant being edge-length of the hexagonal frame was determined for each sample and occurred the largest one for the pure silica material, smaller for the ethylenediamine-covered silica support and the smallest one (and approximately the same) for immobilized specimens. The shrinkage of internal nanotubes resulted from subsequent treatment of the basic siliceous skeleton with N-[3-(tri-methoxy-silyl)propyl]ethylenediamine and creating the charge-transfer complexes with cations Ba2+, Sn2+, Fe2+ or Cu2+. The specific surface areas of mesopores and whole crystallites, together with the volume of mesopores, were determined from low-temperature N2-physisorption isotherms. A mathematical model of crystalline microstructure explaining the sizes and shapes of crystalline grains in relation to adsorption features was proposed and successfully confronted with the results following experimental data. The roughness of the surface is different from one that occurred to be necessary to explain the experimental characteristics quantitatively. The estimated silicon-organic layer thickness was close to the corresponding molecule length for hybrid specimens.

Narrow band-gap semiconductors, namely ternary InAsSb alloys, find substantial technological importance for mid-infrared application as photodetectors in medical diagnostics or environmental monitoring. Thus, it is crucial to develop electrical contacts for these materials because they are the fundamental blocks of all semiconductor devices. This study demonstrates that electroplated gold contacts can be considered as a simple and reliable metallization technology for the electrical-response examination of a test structure. Unalloyed electroplated Au contacts to InAsSb exhibit specific contact resistivity even lower than vacuum-deposited standard Ti–Au. Moreover, temperature-dependent transport properties, such as Hall carrier concentration and mobility, show similar trends, with a minor shift in the transition temperature. It can be associated with a difference in metallization technology, mainly the presence of a Ti interlayer in vacuum-deposited contacts. Such a transition may give insight into not only the gentle balance changes between conductivity channels but also an impression of changing the dominance of carrier type from p- to n-type. The magnetotransport experiments assisted with mobility spectrum analysis clearly show that such an interpretation is incorrect. InAsSb layers are strongly p-type dominant, with a clear contribution from valence band carriers observed at the whole analyzed temperature range. Furthermore, the presence of thermally activated band electrons is detected at temperatures higher than 220 K.

Triaxial porcelains were produced of two whiteware blends containing kaolin B (of "high-crystallinity" kaolinite) or halloysitic kaolin M (also with "low-crystallinity" kaolinite) in two different industrial firing cycles (fast or slow) with final temperatures 1270 degrees C, 1300 degrees C, 1320 degrees C and 1340 degrees C. The crystalline microstructure of mullite in all porcelain samples was studied by X-ray diffraction through analysing 110 and 001 reflections using the Voigt function method and by optical and electron microscopy. Mean crystallite sizes were determined independently for both 110 and 001 diffraction directions as principal semi-quantitative characteristics for all sixteen specimens. They illustrated well the influence of kaolin kind, firing cycle and processing temperature on crystalline microstructure. Significant differences were observed as functions of each of these three parameters for most pairs of specimens. The differences of mean crystallite sizes were significant for 110 diffraction direction and smaller for 001 (especially for samples fired in higher temperatures). Additionally, the influence of fluxes of a triaxial composition on growth of mullite crystallites was shown by comparing crystallite sizes of mullite in the studied industrial porcelains to those produced by firing a reference kaolin. In most samples positive correlation of mean crystallite size estimated for [001] direction with length of crystalline prism estimated from electron microscopy images was noted, and this can be considered relevant for the investigation of formulations and processing conditions, since microstructural observations by electron microscopy require much longer sample preparation times, and are less representative of the studied whole sample. These results are significant in formulation of industrial porcelains in order to select both raw materials and firing cycles for obtaining required mullite development. That will improve the technical properties of final industrial porcelain.

Physical and Technical Aspects of Measurements of Ordinary and Extraordinary Refraction Indices and Birefringence of Nematic Liquid Crystals J. Kędzierski, M.A. Kojdeckib,∗, K. Kowiorski, Z. Raszewski and E. Miszczyk Institute of Applied Physics, Military University of Technology, Warsaw, Poland Institute of Mathematics and Cryptology, Military University of Technology, Warsaw, Poland Institute of Electronic Materials Technology, Department of Chemical Technologies, Warsaw, Poland Institute of Physics, University of Technology and Humanities, Radom, Poland

ABSTRACT Compositional and microstructural analysis of mullites in porcelain whitewares obtained by the firing of two blends of identical triaxial composition using a kaolin B consisting of ‘higher-crystallinity’ kaolinite or a finer halloysitic kaolin M of lower crystal order was performed. No significant changes in the average Al2O3 contents (near the stoichiometric composition 3:2) of the mullites were observed. Fast and slow firing at the same temperature using B or M kaolin yielded different mullite contents. The Warren–Averbach method showed increase of the D110 mullite crystallite size and crystallite size distributions with small shifts to greater values with increasing firing temperature for the same type of firing (slow or fast) using the same kaolin, as well as significant differences between fast and slow firing of the same blend at different temperatures for each kaolin. The higher maximum frequency distribution of crystallite size observed at the same firing temperature using blends with M kaolin suggests a clearer crystallite growth of mullite in this blend. The agreement between thickening perpendicular to prism faces and mean crystallite sizes of mullite were not always observed because the direction perpendicular to 110 planes is not preferred for growth.

Nanocrystalline boehmite (gamma-aluminium-oxyhydroxide) is a material of industrial importance, the functionality of which follows from its crystalline microstructure. A procedure for preparing boehmite nanoparticles, comprising the formation of a precipitate by the alkalization of an aqueous solution of aluminium nitrate and subsequent hydrothermal aging, was previously elaborated. The application of an additive (maltitol or tartaric acid) to control the sizes and shapes of crystallites in the produced polycrystalline powder of boehmite was developed. The aim of this work is a study of the effect of the hydrothermal treatment time on nanocrystalline characteristics of boehmite, both in absence and in presence of the additive. The obtained materials were investigated by using X-ray diffraction (XRD) as principal technique and additionally by scanning and transmission electron microscopy. The multi-peak analysis of powder XRD patterns was applied to determine the prevalent crystallite shape, volume-weighted crystallite size distribution, and second-order crystalline lattice strain distribution being principal quantitative characteristics of the crystalline microstructure. Based on these characteristics, three types of the microstructure correlated with the production procedures were observed and discussed in detail. The nanoparticles of boehmites were found to be monocrystalline grains with characteristic habits and sizes of order of ten nanometers weakly dependent on the hydrothermal treatment time.

Kaolinite and montmorillonite are two clay minerals with different structures:dioctahedral 1:1 without layer charge and dioctahedral 2:1 with low layer charge. X-ray-diffraction microstructural analysis of two fractions of two reference clays (with kaolinite or montmorillonite) from the Clay Minerals Society Source Clay Repository were performed by the Voigt function method to provide microstructural data not available in the baseline studies of this Repository. A rough agreement was found between crystallite sizes determined from X-ray diffraction patterns and from images by field-emission scanning electron microscopy. In addition, the influence of swelling by ethyleneglycol on crystallite size was studied by the mentioned method. Two factors were found to affect the crystallite size variation in ethylene-glycol-treated clay minerals:(i) the increase of the unit cell in [001] direction due to the interlayer absorption of ethylene glycol molecules in the case of swelling minerals and (ii) the physisorption at the surfaces of the crystallites. Both effects operate in the case of montmorillonite, whereas just the latter one is expected in kaolinite.

Wedge cells of small apex angle, filled with liquid crystals, were used to determining optical characteristics as functions of temperature for three liquid crystalline mixtures recently produced and a reference nematic. The interference fringes appearing in polarised monochromatic light (of sodium yellow line) normally incident on the cell were exploited to measure the ordinary and extraordinary refractive indices in the reflection mode and birefringence in the transmission mode. The measurements were repeated using Abbe's refractometer for 6CHBT as the reference to verifying the precision. Additionally the order parameter was computed from birefringence as a function of temperature. The results confirm the usefulness of the method and provide the properties of two nematic liquid crystals of small and large birefringence and one smectic liquid crystal of medium birefringence, recently produced. The experimental systems served also to investigating phase transition between the liquid crystals and the isotropic liquid at near-clearing temperature.

X-ray-diffraction microstructural analysis was performed for corundum powders produced from Bayer aluminium hydroxides in different ways and for high purity corundum powders produced from other raw materials. Crystalline microstructure characterised by prevalent crystallite shape, volume-weighted crystallite size distribution and second-order crystalline lattice strain distribution was determined through modelling crystallite shapes as hexagonal prisms, with the resulting mean volume-weighted standardised crystallite size in the range 406-1941 angstrom, height-to-base-diagonal ratio in the range 0.68-0.94 and the mean-absolute second-order strain in the range 0.028-0.087%. Crystallite size distributions were found to be well approximated as bimodal logarithmic-normal ones and consequently four types of microstructure were recognized as depending on precursors and methods of production.

Liquid-crystalline perylene-3,4,9,10-tetra-(n-hexylester) forms characteristic dendritic or flower-like structures at room temperature when it is deposited on a hydrophilic glass substrate using the zone-casting technique. It was found that such unique structures were not possible to be created simply by recrystallisation of this dye from a liquid-crystalline columnar phase. On the basis of the observations using a confocal microscope and the study of wide angle X-ray scattering (WAXS) as well as the analysis of the absorption and fluorescence spectra, some conclusions, concerning the molecular organisation in the dendritic structure, are drawn. Based on the research, one can assume that the dendrites are formed by columnar molecular aggregates with the column axes parallel to the substrate. Such an organisation of the molecules can be interesting from the point of view of organic electronics.

Optical properties of a nematic liquid crystal with small refractive index and small birefringence were studied. The ordinary and extraordinary refractive indices and birefringence were measured as functions of temperature by using an Abbe refractometer and wedge nematic cells. From values of these indices the nematic orientational order parameter was calculated by using several methods and corresponding mathematical models. Kuczyński et al. method was found to be suitable for determining the order parameter also for materials featuring small ordinary refractive index, with unknown density.

Co(2+)-containing cordierite glasses, of nominal compositions (Mg(1-x)Co(x))2Al4Si5O18 (with x = 0, 0.2, 0.4, 0.6, 0.8 and 1), were prepared by melting colloidal gel precursors. After isothermal heating at 1273 K for around 28 h, a single-phase α-cordierite (high-temperature hexagonal polymorph) was synthesized. All materials were investigated using X-ray powder diffraction and field-emission scanning electron microscopy. The crystal structure and microstructure were determined from X-ray diffraction patterns. Rietveld refinement confirmed the formation of magnesium-cobalt cordierite solid solutions. The unit-cell volume increased with the increase of cobalt content in the starting glass. The crystalline microstructure of the cordierites was interpreted using a mathematical model of a polycrystalline material and characterized by prevalent crystallite shape, volume-weighted crystallite size distribution and second-order crystalline lattice-strain distribution. Hexagonal prismatic was the prevalent shape of α-cordierite crystallites. Bimodality in the size distribution was observed and interpreted as a consequence of two paths of the crystallization: the nucleation from glass of μ-cordierite, which transformed into α-cordierite with annealing, or the nucleation of α-cordierite directly from glass at high temperatures. Scanning electron microscopy images agreed well with crystalline microstructure characteristics determined from the X-ray diffraction line-profile analysis.

Second discrepancy principle was found as an effective rule for choosing the regularization parameter in Tikhonov’s method applied for solving linear operator equations of the first kind. The rule is formulated as an additional non-linear equation involving second discrepancy to be satisfied by the regularized solution and regularization parameter together. Two constant parameters appearing in the definition of this criterion may be chosen freely within some limits, preserving asymptotic convergence properties of the method when errors in data tend to zero. This work presents a heuristic approach to determining both constants: they are found on the basis of numerical simulations exploiting realistic model representations with inexact data of problems which are to be solved and accounting for appropriate error levels. The approach is expressed as an approximate optimization problem defined on a class of inverse problems studied. The formulation of the method is given together with a numerical illustration. A set of Fredholm’s integral equations of the first kind with convolution-type operators is taken as an example. Inexact data imitate peaks from X-ray diffraction patterns realistically. The effectiveness of Tikhonov’s regularization with this version of second discrepancy principle is demonstrated on further examples. Weak sensitivity of the method to over- or under-estimation of errors in data is observed. It is concluded that only random errors in data (while discretization errors are omitted) can be accounted for solving the analysed inverse problems effectively.