Mechanical properties of nanocomposites with artificial periodic structure
Date
2024-07-12
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Abstract
Mikroelektromehaanilised süsteemid (MEMS) on vajalikud komponendid elektroonikaseadmetes nagu nutitelefonid ja nutikellad. MEMS-andurid ja -täiturid koosnevad mikrostruktuuridest ja nanomaterjalidest, mis peavad mehaaniliselt vastu pidama deformatsioonile ja kulumisele. Antud töö raames uuriti, kuidas on võimalik mõjutada nanomaterjali mehaanilisi omadusi luues kihilise struktuuriga nanokomposiite, edasise võimaliku perspektiiviga hakata uurima ka nende funktsionaalsust MEMS-seadmetes.
Valmistati kahe – ja kolmekihilised üksikutest Al₂O₃ ja Ta₂O₅ komponentkihtidest koosnevad õhukesed tahkiskiled. Kasutati aatomkihtsadestamise meetodit, mis võimaldas täpselt kontrollida Al₂O₃ ja Ta₂O₅ kihtide paksusi 70 nm kogupaksusega komposiitkiledes. Komponentkihtide paksus ja sadestamise järjekord mõjutasid komposiitkile mehaanilist kõvadust, mis korreleerub materjali kulumiskindlusega. Uurimistöö jooksul sadestatud komposiitkiled kõvenesid veelgi peale lõõmutamist Ta₂O₅ kihtide kristalliseerumise järel. Mehaanilisi omadusi mõjutas kristalliseerumiseks kasutatud temperatuur, 700 ja 800 ºC, ja kristalliitide orientatsioon. Orientatsioon sõltus samuti komponentkihtide paksusest ja järjekorrast.
Teiste uuritud ja sadestatud materjalikihtide kohta saab öelda, et ainult 20 nm kogupaksustega kahekihiliste SnO₂/ZrO₂ komposiitkilede kõvadus ja elastsusmoodul, mis kirjeldab materjali vastupidavust deformatsioonile, sõltusid oluliselt kihtide sadestamise järjekorrast. Al₂O₃ lisamisel ZrO₂ kilesse tihendati ZrO₂ struktuuri, kõvendades materjali. Al₂O₃ kihtide sadestamisel polükristallilisele grafeenile kompenseeriti grafeeniliblede vahelisi joondefekte, parandades süsinikkihi pidevust ja mehhaanilist elastsust.
Uuringud näitasid, et õhukeste oksiidkilede mehaanilisi omadusi on võimalik mõjutada kunstliku perioodilise kihilise struktuuriga. Mehaaniliselt vastupidavate komposiitkilede väljatöötamine võiks võimaldada arendada vastupidavamaid, võimsamaid ja väiksemaid MEMS seadeldisi.
Microelectromechanical systems (MEMS) are important components in electronic devices like smart phones and watches. MEMS sensors and actuators consist of microstructures and nanomaterials, that must resist deformation and wear. In the present work, the possibility of modifying the mechanical properties of nanomaterials by fabricating nanocomposites with layered structures was investigated. Double and triple layered Al₂O₃/Ta₂O₅ thin films were fabricated by atomic layer deposition, accurately controlling the thickness of Al₂O₃ and Ta₂O₅ components in 70 nm thick composite films. The thickness of the oxide layers and their deposition order influenced the mechanical hardness, i.e., material’s resistance to wear. The Al₂O₃/Ta₂O₅ composite films were hardened after annealing, that caused the crystallization of Ta₂O₅ layers. The mechanical properties were influenced by crystallization temperature and orientation of crystallites that depended on the thickness and order of the Al₂O₃ and Ta₂O₅ layers. In regard with alternatives to the abovementioned compounds, the hardness and elastic modulus, describing material’s resistance to deformation, of 20 nm thick double layered SnO₂/ZrO₂ composite films depended significantly on the deposition order of the component layers. Further, regarding metal oxides with mixed structure as alternative to multilayered films, the phase composition of ZrO₂ films was dependent on the content of Al₂O₃, used as dopant. The addition of Al₂O₃ densified the crystal lattice and hardened the host material. In addition, the continuity of polycrystalline graphene, and consequently the elasticity of carbon-based materials could be improved, growing Al₂O₃ on graphene. The research indicated, that it is possible to modify the mechanical properties of thin metal oxide films with an artificial periodic layered structure. Development of mechanically resilient composite films could promote the production of more reliable, powerful and smaller MEMS devices.
Microelectromechanical systems (MEMS) are important components in electronic devices like smart phones and watches. MEMS sensors and actuators consist of microstructures and nanomaterials, that must resist deformation and wear. In the present work, the possibility of modifying the mechanical properties of nanomaterials by fabricating nanocomposites with layered structures was investigated. Double and triple layered Al₂O₃/Ta₂O₅ thin films were fabricated by atomic layer deposition, accurately controlling the thickness of Al₂O₃ and Ta₂O₅ components in 70 nm thick composite films. The thickness of the oxide layers and their deposition order influenced the mechanical hardness, i.e., material’s resistance to wear. The Al₂O₃/Ta₂O₅ composite films were hardened after annealing, that caused the crystallization of Ta₂O₅ layers. The mechanical properties were influenced by crystallization temperature and orientation of crystallites that depended on the thickness and order of the Al₂O₃ and Ta₂O₅ layers. In regard with alternatives to the abovementioned compounds, the hardness and elastic modulus, describing material’s resistance to deformation, of 20 nm thick double layered SnO₂/ZrO₂ composite films depended significantly on the deposition order of the component layers. Further, regarding metal oxides with mixed structure as alternative to multilayered films, the phase composition of ZrO₂ films was dependent on the content of Al₂O₃, used as dopant. The addition of Al₂O₃ densified the crystal lattice and hardened the host material. In addition, the continuity of polycrystalline graphene, and consequently the elasticity of carbon-based materials could be improved, growing Al₂O₃ on graphene. The research indicated, that it is possible to modify the mechanical properties of thin metal oxide films with an artificial periodic layered structure. Development of mechanically resilient composite films could promote the production of more reliable, powerful and smaller MEMS devices.
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Väitekirja elektrooniline versioon ei sisalda publikatsioone