Publications by authors named "Jakub Pawlak"

4 Publications

  • Page 1 of 1

An Analysis of Kikuchi Lines Observed with a RHEED Apparatus for a TiO-Terminated SrTiO (001) Crystal.

Materials (Basel) 2021 Nov 22;14(22). Epub 2021 Nov 22.

Faculty of Metals Engineering and Industrial Computer Science, AGH University of Science and Technology, al. Mickiewicza 30, 30-059 Kraków, Poland.

In this study, electron diffraction patterns observed under high vacuum conditions for an SrTiO surface were interpreted in detail while paying special attention to the features of inelastic effects. The surface of the SrTiO was carefully prepared to enforce its termination with single domains of TiO layers at the top. The inelastic patterns were interpreted using analytical models. Two types of Kikuchi lines are recognized in this paper: those which can be described with the Bragg law and those which appear due to surface wave resonance effects. However, we also discuss that there exists a formal connection between the two types of the Kikuchi lines observed.
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http://dx.doi.org/10.3390/ma14227077DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8624205PMC
November 2021

Simplified Determination of RHEED Patterns and Its Explanation Shown with the Use of 3D Computer Graphics.

Materials (Basel) 2021 Jun 3;14(11). Epub 2021 Jun 3.

Faculty of Physics and Applied Computer Science, AGH University of Science and Technology, al. Mickiewicza 30, 30-059 Kraków, Poland.

The process of preparation of nanostructured thin films in high vacuum can be monitored with the help of reflection high energy diffraction (RHEED). However, RHEED patterns, both observed or recorded, need to be interpreted. The simplest approaches are based on carrying out the Ewald construction for a set of rods perpendicular to the crystal surface. This article describes how the utilization of computer graphics may be useful for realistic reproduction of experimental conditions, and then for carrying out the Ewald construction in a reciprocal 3D space. The computer software was prepared in the Java programing language. The software can be used to interpret real diffractions patterns for relatively flat surfaces, and thus it may be helpful in broad research practice.
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http://dx.doi.org/10.3390/ma14113056DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8199926PMC
June 2021

High-Entropy Perovskites as Multifunctional Metal Oxide Semiconductors: Synthesis and Characterization of (GdNdLaSmY)CoO.

ACS Appl Electron Mater 2020 Oct 18;2(10):3211-3220. Epub 2020 Sep 18.

Academic Centre for Materials and Nanotechnology, AGH University of Science and Technology, Al. Mickiewicza 30, 30059 Kraków, Poland.

Single-phase multicomponent perovskite-type cobalt oxide containing five cations in equiatomic amounts on the A-site, namely, (GdNdLaSmY)CoO, has been synthesized via the modified coprecipitation hydrothermal method. Using an original approach for heat treatment, which comprises quenching utilizing liquid nitrogen as a cooling medium, a single-phase ceramic with high configuration entropy, crystallizing in an orthorhombic distorted structure was obtained. It reveals the anomalous temperature dependence of the lattice expansion with two weak transitions at approx. 80 and 240 K that are assigned to gradual crossover from the low- via intermediate- to high-spin state of Co. The compound exhibits weak ferromagnetism at ≤ 10 K and signatures of antiferromagnetic correlations in the paramagnetic phase. Ab initio calculations predict a band gap Δ = 1.18 eV in the ground-state electronic structure with the dominant contribution of O_p and Co_d orbitals in the valence and conduction bands, respectively. Electronic transport measurements confirm the negative temperature coefficient of resistivity characteristic to a semiconducting material and reveal a sudden drop in activation energy at ∼ 240 K from ∼ 1 eV in the low-temperature phase to ∼ 0.3 eV at room temperature. The possibility of fine tuning of the semiconducting band gap via a subtle change in A-site stoichiometry is discussed.
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http://dx.doi.org/10.1021/acsaelm.0c00559DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7660934PMC
October 2020

Surface-Step-Induced Magnetic Anisotropy in Epitaxial LSMO Deposited on Engineered STO Surfaces.

Materials (Basel) 2020 Sep 17;13(18). Epub 2020 Sep 17.

Faculty of Physics and Applied Computer Science, AGH University of Science and Technology, 30-059 Kraków, Poland.

Changes in stoichiometry, temperature, strain and other parameters dramatically alter properties of LSMO perovskite. Thus, the sensitivity of LSMO may enable control of the magnetic properties of the film. This work demonstrates the capabilities of interface engineering to achieve the desired effects. Three methods of preparing STO substrates were conducted, i.e., using acid, buffer solution, and deionized water. The occurrence of terraces and their morphology depend on the preparation treatment. Terraces propagate on deposited layers and influence LSMO properties. The measurements show that anisotropy depends on the roughness of the substrate, the method of preparing the substrate, and oxygen treatment. The collected results suggest that the dipolar mechanism may be the source of LSMO anisotropy.
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http://dx.doi.org/10.3390/ma13184148DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7560275PMC
September 2020
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