N. G. Galkin, I. M. Chernev, E. Yu. Subbotin, O. A. Goroshko, S. A. Dotsenko, A. M. Maslov, K. N. Galkin, O. V. Kropachev, D. L. Goroshko, A. Yu. Samardak, A. V. Gerasimenko, E. V. Argunov
{"title":"Structural, Transport, and Magnetic Properties of Ultrathin and Thin FeSi Films on Si(111)","authors":"N. G. Galkin, I. M. Chernev, E. Yu. Subbotin, O. A. Goroshko, S. A. Dotsenko, A. M. Maslov, K. N. Galkin, O. V. Kropachev, D. L. Goroshko, A. Yu. Samardak, A. V. Gerasimenko, E. V. Argunov","doi":"10.1134/s1027451024020265","DOIUrl":null,"url":null,"abstract":"<h3 data-test=\"abstract-sub-heading\">Abstract</h3><p>Polycrystalline and epitaxial iron silicide (FeSi) films with thicknesses of 3.2–20.35 nm are grown on a Si(111) substrate using solid-phase and molecular-beam epitaxy at 350°C, as confirmed by X-ray diffraction data. Morphological studies reveal that the films grown by solid-phase epitaxy are continuous and smooth with a root-mean-square roughness ranging from 0.4 to 1.1 nm, while those grown by molecular-beam epitaxy exhibit increased roughness and consist of coalesced grains with sizes up to 1 μm and a pit density of up to 1 × 10<sup>7</sup> cm<sup>–2</sup>. In the case of solid-phase epitaxy, an increase in the thickness leads to incomplete silicide formation and the emergence of a layer of disordered iron silicide with a thickness ranging from 10 to 20 nm, possibly with an excess of iron. This is confirmed by a change in the nature of the temperature dependence of the resistivity ρ from semiconductor to semimetallic, which leads to a decrease in the resistivity by 1.5–2 times. The nonmonotonic character of the temperature dependence of the resistivity ρ(<i>T</i>) for an ultrathin FeSi film with a thickness of 3.2 nm is identified, exhibiting a maximum around 230–240 K, a rising segment from 160 to 65 K with <i>E</i><sub>g</sub> = 14.8 meV, and further unsaturated growth down to 1.5 K. As the thickness of the FeSi films grown by molecular-beam epitaxy increases, the minimum and maximum are not observed, but the nonmonotonic trend of ρ(<i>T</i>) with decreasing temperature and the opening of the band gap <i>E</i><sub>g</sub> = 23 meV are preserved. The possible reasons for the observed effects in the ρ(<i>T</i>) dependences are considered. An anomalous Hall effect is detected in ultrathin and thin FeSi films grown by solid-phase and molecular-beam epitaxy, respectively, which confirms the weak ferromagnetic properties of the films. The results demonstrate the feasibility of growing and controlling the properties of ultrathin and thin FeSi films on silicon using methods of solid-phase and molecular-beam epitaxy, providing them with unique transport and magnetic properties not present in single crystals.</p>","PeriodicalId":671,"journal":{"name":"Journal of Surface Investigation: X-ray, Synchrotron and Neutron Techniques","volume":null,"pages":null},"PeriodicalIF":0.5000,"publicationDate":"2024-05-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":"0","resultStr":null,"platform":"Semanticscholar","paperid":null,"PeriodicalName":"Journal of Surface Investigation: X-ray, Synchrotron and Neutron Techniques","FirstCategoryId":"1085","ListUrlMain":"https://doi.org/10.1134/s1027451024020265","RegionNum":0,"RegionCategory":null,"ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"Q4","JCRName":"PHYSICS, CONDENSED MATTER","Score":null,"Total":0}
引用次数: 0
Abstract
Polycrystalline and epitaxial iron silicide (FeSi) films with thicknesses of 3.2–20.35 nm are grown on a Si(111) substrate using solid-phase and molecular-beam epitaxy at 350°C, as confirmed by X-ray diffraction data. Morphological studies reveal that the films grown by solid-phase epitaxy are continuous and smooth with a root-mean-square roughness ranging from 0.4 to 1.1 nm, while those grown by molecular-beam epitaxy exhibit increased roughness and consist of coalesced grains with sizes up to 1 μm and a pit density of up to 1 × 107 cm–2. In the case of solid-phase epitaxy, an increase in the thickness leads to incomplete silicide formation and the emergence of a layer of disordered iron silicide with a thickness ranging from 10 to 20 nm, possibly with an excess of iron. This is confirmed by a change in the nature of the temperature dependence of the resistivity ρ from semiconductor to semimetallic, which leads to a decrease in the resistivity by 1.5–2 times. The nonmonotonic character of the temperature dependence of the resistivity ρ(T) for an ultrathin FeSi film with a thickness of 3.2 nm is identified, exhibiting a maximum around 230–240 K, a rising segment from 160 to 65 K with Eg = 14.8 meV, and further unsaturated growth down to 1.5 K. As the thickness of the FeSi films grown by molecular-beam epitaxy increases, the minimum and maximum are not observed, but the nonmonotonic trend of ρ(T) with decreasing temperature and the opening of the band gap Eg = 23 meV are preserved. The possible reasons for the observed effects in the ρ(T) dependences are considered. An anomalous Hall effect is detected in ultrathin and thin FeSi films grown by solid-phase and molecular-beam epitaxy, respectively, which confirms the weak ferromagnetic properties of the films. The results demonstrate the feasibility of growing and controlling the properties of ultrathin and thin FeSi films on silicon using methods of solid-phase and molecular-beam epitaxy, providing them with unique transport and magnetic properties not present in single crystals.
期刊介绍：
Journal of Surface Investigation: X-ray, Synchrotron and Neutron Techniques publishes original articles on the topical problems of solid-state physics, materials science, experimental techniques, condensed media, nanostructures, surfaces of thin films, and phase boundaries: geometric and energetical structures of surfaces, the methods of computer simulations; physical and chemical properties and their changes upon radiation and other treatments; the methods of studies of films and surface layers of crystals (XRD, XPS, synchrotron radiation, neutron and electron diffraction, electron microscopic, scanning tunneling microscopic, atomic force microscopic studies, and other methods that provide data on the surfaces and thin films). Articles related to the methods and technics of structure studies are the focus of the journal. The journal accepts manuscripts of regular articles and reviews in English or Russian language from authors of all countries. All manuscripts are peer-reviewed.
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