Metastable TiO2-II in atomic layer deposited thin and ultrathin films: stabilization, properties and impact on film growth
Kuupäev
2024-07-09
Autorid
Ajakirja pealkiri
Ajakirja ISSN
Köite pealkiri
Kirjastaja
Abstrakt
Doktoritöös uuriti õhukeste titaandioksiidi (TiO₂) kilede struktuuri ja faasikoostist, et teha kindlaks metastabiilset TiO₂-II faasi sisaldavate kilede valmistamise võimalused ja omadused. Oma eriliste omaduste tõttu on TiO₂-l palju olulisi rakendusi. TiO₂ kasutatakse värvi-, paberi-, ravimi- ja kosmeetikatööstuses, aga see pakub suurt huvi ka mikro- ja nanoelektroonika tööstusele tänu oma suurele dielektrilisele konstandile ja optikatööstusele tänu suurele murdumisnäitajale ja läbipaistvusele nähtavas spektripiirkonnas. TiO₂ on samuti leidnud rakendust isepuhastuvates ja antibakteriaalsetes pinnakatetes, katalüsaatorites, gaasisensorites ja korrosioonivastastes katetes.
Üks vähemuuritud aga tähelepanuväärsemaid TiO₂ modifikatsioone on TiO₂-II. See faas on oma unikaalsete omaduste tõttu äratanud viimasel ajal suurt huvi erinevates tehnoloogiaharudes. Näiteks on teoreetiliste uuringute tulemusena leitud, et selle faasi fotokatalüütilised ja mehhaanilised omadused ületavad tunduvalt TiO₂ enimtuntud faaside, anataasi ja rutiili, vastavaid omadusi. Kuna aga TiO₂-II saamine enamuse tavapäraste materjalisünteesi meetoditega on vähetõenäoline, siis pole seni piisavalt andmeid selle faasi mitmete omaduste (näit murdumisnäitaja, keelutsooni laiuse ja kõvaduse) kohta, ega selle faasi moodustumise kohta tahkisekiledes. Seetõttu on doktoritöö peamiseks panuseks TiO₂-II faasi edukas stabiliseerimine sellisel kujul, mis võimaldas määrata TiO₂-II optilisi ja mehaanilisi omadusi. Selleks uuriti võimalusi TiO₂-II aatomkihtsadestamiseks, selgitati välja tehnoloogiliste protsesside parameetrid, mis soodustavad TiO₂-II teket ning õpiti tundma nende parameetrite mõju saadud kilede omadustele. Tulemusena saadi ülevaade TiO₂-II sisalduse mõjust seda faasi sisaldavate kilede optilistele ja mehhaanilistele omadustele. Saadud tulemused on hea lähtepunkt edasisteks uuringuteks ja TiO₂-II võimalikeks rakendusteks, näiteks fotokatalüüsis ja suure kõvadusega funktsionaalsetes pinnakatetes.
This study explores titanium dioxide (TiO₂) thin films, focusing on the structural properties of those, and particularly, on the deposition and characterization of films containing the metastable high-pressure TiO₂-II phase. TiO₂ is a material of great importance due to its unique properties. TiO₂ is used in the paint, paper, pharmaceutical, and cosmetics industries, and has attracted great interest in micro- and nanoelectronics because of its high permittivity and in optical applications because of high refractive index and transparency in the visible spectral range. TiO₂ has also been applied in self-cleaning and antibacterial coatings, photocatalysts, gas sensors, and anti-corrosion coatings. The TiO₂-II phase is one of the less explored but attractive modifications of TiO₂ that has garnered interest in various areas due to its unique properties. For instance, theoretical studies have predicted superior mechanical and photocatalytic properties of this phase compared with those of anatase and rutile phases of TiO₂. However, as the formation and stabilization of TiO₂-II is unlikely in the majority of conventional material synthesis processes, there is insufficient data on its properties (for instance, refractive index, hardness, and bandgap energy) and formation in thin films. Hence, one of the key contributions of this work is the successful stabilization of TiO₂-II in a form that allowed characterization of its optical and mechanical properties. For this purpose, atomic layer deposition processes allowing formation of TiO₂-II in thin films were investigated and the influence of the deposition process parameters on the material properties was thoroughly studied. As a result, this work provides insights into the effect of TiO₂-II content on optical and mechanical properties of TiO₂ thin films, offering a basis for further exploration and potential for applications, for instance, in photocatalysis and functional coatings with enhanced hardness.
This study explores titanium dioxide (TiO₂) thin films, focusing on the structural properties of those, and particularly, on the deposition and characterization of films containing the metastable high-pressure TiO₂-II phase. TiO₂ is a material of great importance due to its unique properties. TiO₂ is used in the paint, paper, pharmaceutical, and cosmetics industries, and has attracted great interest in micro- and nanoelectronics because of its high permittivity and in optical applications because of high refractive index and transparency in the visible spectral range. TiO₂ has also been applied in self-cleaning and antibacterial coatings, photocatalysts, gas sensors, and anti-corrosion coatings. The TiO₂-II phase is one of the less explored but attractive modifications of TiO₂ that has garnered interest in various areas due to its unique properties. For instance, theoretical studies have predicted superior mechanical and photocatalytic properties of this phase compared with those of anatase and rutile phases of TiO₂. However, as the formation and stabilization of TiO₂-II is unlikely in the majority of conventional material synthesis processes, there is insufficient data on its properties (for instance, refractive index, hardness, and bandgap energy) and formation in thin films. Hence, one of the key contributions of this work is the successful stabilization of TiO₂-II in a form that allowed characterization of its optical and mechanical properties. For this purpose, atomic layer deposition processes allowing formation of TiO₂-II in thin films were investigated and the influence of the deposition process parameters on the material properties was thoroughly studied. As a result, this work provides insights into the effect of TiO₂-II content on optical and mechanical properties of TiO₂ thin films, offering a basis for further exploration and potential for applications, for instance, in photocatalysis and functional coatings with enhanced hardness.
Kirjeldus
Väitekirja elektrooniline versioon ei sisalda publikatsioone