<p>U poslednjih nekoliko decenija, feroelektrici su prepoznati kao dobri kandidati<br />za širok spektar primene. Barijum titanat je jedan od najčešće istraživanih<br />perovskitnih materijala usled tipičnog feroelektričnog ponašanja na sobnoj<br />temperaturi, sa histerezisnom zavisnosti između polarizacije i električnog polja.<br />Specifična svojstva BaTiO<sub>3</sub> čine ovaj materijal veoma korisnim u proizvodnji<br />kondenzatora, memorija, senzora i dr. Pored toga, paraelektrična faza BaTiO<sub>3</sub><br />ima primenu u proizvodnji mikrotalasnih tunabilnih uređaja. BaTiO<sub>3</sub> pokazuje<br />paralaketrično ponašanje iznad Kirijeve temperature (120°C) i veliki je izazov<br />modifikovati materijal da bude paraelektričan na sobnoj temperaturi. Delimičnom<br />supstitucijom Ba<sup>2+</sup> ili Ti<sup>4+</sup> jona, jonima Sr<sup>2+</sup> ili Zr<sup>4+</sup>, respektivno, snižava<br />se Kirijeva temperatura i dolazi do pomeranja fazne transformacije feroelektri<br />čno/paraelektrično na niže temperature. Monolitna keramika na bazi bazi<br />BaTiO<sub>3</sub> je često istraživana kako bi se ispitale promene u strukturi i svojstvima<br />uzrokovane dodatkom dopanata, međutim ne postoji praktična primena ovih<br />materijala u mikrotalasnim tunabilnim tehnologijama. S druge strane, u trendu<br />sveopšte minijaturizacije elektronskih komponenti, tanki filmovi su prepoznati<br />kao dobri kandidati za proizvodnju tunabilnih uređaja. Jedan od ciljeva ovog<br />istraživanja bio je ispitivanje strukturnih i funkcinalnih svojstava tankih filmova na<br />bazi barijum titanata, BaTiO<sub>3</sub>, Ba<sub>1-x</sub>Sr<sub>x</sub>TiO<sub>3</sub> (x=0,1, 0,2, 0,3 i 0,4) i BaTi<sub>1-x</sub>Zr<sub>x</sub>O<sub>3</sub><br />(x=0,1 i 0,2), pripremljenih hemijskom depozicijom iz tečne faze. Metalne<br />soli BaCO<sub>3</sub>, C<sub>4</sub>H<sub>6</sub>O<sub>4</sub>Sr i ZrOCl<sub>2</sub> H<sub>2</sub>O i Ti(OCH<sub>2</sub>CH<sub>2</sub>CH<sub>2</sub>CH<sub>3</sub>)<sub>4</sub> rastvorene su<br />odvojeno u kiseloj sredini i pomešane u transparentne solove. Inkdžet štampa<br />i spin tehnika koršćene su za depoziciju funkcionalnih filmova na bazi BaTiO<sub>3</sub>.<br />Nakon deponovanja, pripremljeni filmovi su termički tretirani na različitim<br />temperaturama do 1000°C. U zavisnosti od koncentracije pripremljeni su filmovi<br />debljine od 100 do 700 nm,sa veličinom zrna od nekoliko desetina nanometara. Strukturna karakterizacija potvrdila je promene u strukturi BaTiO<sub>3</sub> tankih filmova<br />sa dodatkom Sr<sup>2+</sup> i Zr<sup>4+</sup>. Tetragonalna (feroelektrična) faza BaTiO<sub>3</sub> je potvrđena<br />rentgenostrukturnom analizom i Ramanovom spektroskopijom. S druge strane,<br />smanjenje tetragonalnosti je primećeno kod dopiranih uzoraka. Promene u<br />funkcionalnosti dopiranih BaTiO<sub>3</sub> filmova analizirane su na osnovu dielektričnih<br />i feroelektričnih merenja. Izvršene analize su potvrdile feroelektrično ponašanje<br />kod BaTiO<sub>3</sub>, dok se feroelektrični odgovor u tankim filmovima smanjuje sa<br />dopiranjem. Priprema elektroda specifičnih geometrija pogodnih za tunabilna<br />merenja različitim tehnikama depozicije bio je drugi cilj istraživanja. Tehnika spaterovanja u kombinaciji sa laserskim uklanjanjem, inkdžet štampa i fotolitografija<br />su korišćene za pripremu kružnih i koplanarnih elektroda na površini barijum<br />titanatnih tankih filmova. Uticaj procesnih parametara svake od pomenutih<br />metoda na dimenzionalnu preciznost pripremljenih elektroda je bio predmet istraživanja<br />u okviru teze. Odabrani laser se pokazao kao neprikladan za pripremu<br />elektroda na pripremljenim barijum titanatnim tankim filmovima. Inkdžet štampa<br />se pokazala kao korisna u pripremi elektroda mikrometarskih fimenzija, dok je za<br />pripremu sofisticiranijih geometrija fotolitografija pokazala najbolje performanse.</p> / <p>In past few decades, ferroelectrics are recognized as good candidates for wide<br />range of applications. Barium titanate is one of the most investigated perovskite<br />materials due to typical ferroelectric behavior at room temperature, with hysteresis<br />dependence of the polarization and electric field. Specified properties<br />of BaTiO<sub>3</sub> make this material useful in production of capacitors, memories,<br />sensors, etc. Nevertheless, paraelectric phase of BaTiO<sub>3</sub> may have application<br />in production of microwave tunable devices. Barium titanate shows paraelectric<br />behavior at temperatures above the Currie temperature (120 °C) and it is great<br />challenge to make material paraelectric at room temperature. Partial substitution<br />of Ba<sup>2+</sup> or Ti<sup>4+</sup> ions, by Sr<sup>2+</sup> or Zr<sup>4+</sup>, respectively, decreases the Currie temperature<br />of barium titanate and moves phase transition ferroelectric/paraelectric<br />to lower temperatures. Bulk BaTiO<sub>3 </sub>was often investigated in order to improve<br />structure and functionality by addition of dopant, but do not have practical<br />application in microwave tunable technologies. On the other hand, with the<br />trend of overall miniaturization of electronic devices, thin films are recognized<br />as good candidates for production of tunable devices. One of the aims in this<br />research was investigation of structural and functional properties of barium<br />titanate based thin films, BaTiO<sub>3</sub>, Ba<sub>1-x</sub>SrxTiO<sub>3</sub> (x=0,1, 0,2, 0,3 i 0,4) and<br />BaTi<sub>1-x</sub>ZrxO<sub>3</sub> (x=0,1 i 0,2), prepared by chemical solution deposition. Metal<br />salts of BaCO<sub>3</sub>, C<sub>4</sub>H<sub>6</sub>O<sub>4</sub>Sr and ZrOCl<sub>2</sub> H<sub>2</sub>O and Ti(OCH<sub>2</sub>CH<sub>2</sub>CH<sub>2</sub>CH<sub>3</sub>)<sub>4 </sub>were<br />separetly disolved in acetic environment and mixed in clear transparent sols.<br />Inkjet printing and spin coating were used for deposition of functional BaTiO3<br />based fims. After deposition prepared films were thermally treated at different<br />temperatures up to 1000 °C. In dependence of sol concentration thickness of<br />obtained films is from 100 to 700 nm and grain size is few tens of nanometers. Structural characterization confirmed changes in structure of barium titanate thin<br />films by addition of Sr<sup><sub>2+</sub></sup> i Zr<sup>4+</sup>. Tetragonal (ferroelectric) phase of BaTiO<sub>3</sub> is<br />confirmed by X-ray diffraction and Raman spectroscopy. On the other hand, decreasing<br />of tetragonality was noticed in doped samples. Changes in functionality<br />of doped BaTiO<sub>3</sub> thin films were analyzed by dielectric and ferroelectric measurements.<br />Performed analysis confirmed ferroelectric behavior of barium titanate<br />thin films, and decrease in ferroelectric answer of doped films. Investigation of<br />possibility of complex shaped electrodes preparation,suitable for tunability measurements, by different deposition techniques was the second goal of this research.<br />Sputtering technique in combination with laser removal, inkjet printing and photolithography were used for preparation of complex circular and coplanar electrodes<br />on the surface of barium titanate based thin films. Influence of processing<br />parameters for the each of mentioned technique on dimensional precision of prepared<br />electrodes was investigated. Selected laser was not appropriate for production<br />of electrodes on prepared barium titanate based thin films. Inkjet printing<br />was useful for production of electrodes in micrometer range, but for more sophisticated<br />geometries photolithography shows the best performance.</p>
Identifer | oai:union.ndltd.org:uns.ac.rs/oai:CRISUNS:(BISIS)110058 |
Date | 15 March 2019 |
Creators | Vukmirović Jelena |
Contributors | Srdić Vladimir, Stojanović Goran, Milanović Marija, Bobic Jelena, Stijepović Ivan |
Publisher | Univerzitet u Novom Sadu, Tehnološki fakultet Novi Sad, University of Novi Sad, Faculty of Technology at Novi Sad |
Source Sets | University of Novi Sad |
Language | Serbian |
Detected Language | English |
Type | PhD thesis |
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