Mechanical properties of atomic layer deposited thin films and nanocomposites
Date
2017-07-10
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Abstract
Käesolevas töös kasutati aatomkihtsadestamist koos teiste töövõtetega nano¬struk¬tuursete komposiitide valmistamiseks. Töö käigus valmistati kolme eri¬nevat tüüpi komposiite: kiud- või pulbertäitega ning laminaatsed komposiidid. Saadud materjalidel mõõdeti instrumentaalse nanoindenteerimisega elastsus¬moodulid ja kõvadused. Mõõtmistulemusi analüüsiti kasutades erinevaid teo¬reetilisi mudeleid.
Katsed näitasid, et tõenäoliselt on kõige lihtsam valmistada laminaat¬struk¬tuuriga komposiite, mille korral ettevalmistused olid lihtsamad ja lisatöövõtteid kompaktse näidise saamiseks ei olnud vaja kasutada. Ülejäänud tüüpi struk¬tuuride korral on tõenäoliselt vaja lisauuringuid ja optimeerimist parimate tule¬muste saavutamiseks.
Elastsusmoodulite mõõtmine näitas, et aatomkihtsadestatud kiled ei ole väga jäigad. Näiteks oli amorfse Al2O3 moodul umbes 3 korda väiksem korundi-tüüpi Al2O3-st (≈110 GPa vs ≈340 GPa). HfO2, Ta2O5, ZrO2 moodulid olid samuti väiksemad makroskoopiliste objektidega võrreldes.
Komposiitsetel laminaatidel jäid elastsusmoodulid puhaste oksiidide moo¬dulite väärtuste vahepeale, välja arvatud ZrO2-Ta2O5 nanolaminaatide korral, milledel olid elastsumoodulid suuremad võrreldes puhaste koostisoksiididega. Nähtuse täpsed põhjused on veel välja selgitamata.
Kõvaduse poolest olid puhtad Al2O3 ja HfO2 peaaegu 2 korda kõvemad klaasist alusest (vastavalt 11–12 GPa ja 6,7 GPa). Tsirkoonium- ja tantaaloksiid olid klaasile lähedase kõvadusega (≈7 GPa).
Tulemustest saab järeldada, et ALD kiled on suhteliselt kõvad materjalid ja neid saaks sobitada erinevate materjalide elastsusmoodulitega kasutades erine¬vaid komposiitseid kooslusi. Viimane võib olla kasulik näiteks juhul, kui soovi¬takse kasutada ALD kilesid metallide või sulamite kaitsmiseks (nt korrosiooni¬kaitse). Samuti võimaldaks ALD kilede kasutamine muuta materjalide pindade mehaanilisi omadusi, mis võib olla vajalik näiteks mikro- või nanoelektor¬mehaaniliste seadmete (NEMS/MEMS) korral.
In this study atomic layer deposition combined with several other techniques was used to produce nanostructured composites. Three structure types were realized: fiber or particle filled and laminated structures. Mechanical properties (modulus and hardness) of composites were tested using instrumented nanoindentation. The results were analyzed in the context of several theoretical models where reasonable. Tests have shown that it is probably the easiest to prepare ALD laminated composites, where preparations were simple and compact sample was obtained without additional work techniques. The remaining types of structures likely need further research and optimization for best results. The elastic modulus measurements showed that the ALD films were not very rigid. For example, an amorphous Al2O3 was about 3 times less than the modulus of corundum-type Al2O3 (i. e. about 110 GPa versus ≈340 GPa). HfO2, Ta2O5, ZrO2 modules were also lower compared to bulk objects in macroscale. Elastic moduli of the composite laminates were intermediate between the values of the pure oxides, with the exception of ZrO2-Ta2O5 nanolaminates, in which case the moduli were larger compared to pure oxides. The exact causes of the phenomenon are still unaccounted for. The hardness of pure Al2O3 and HfO2 were nearly two times harder than soda-lime-glass (11–12 GPa and 6.7 GPa, respectively). Zirconium, and tantalum oxide were close to the hardness of glass (≈7 GPa). Results suggest that ALD oxide films are relatively hard materials and they could be matched to the different elastic moduli of other materials using various composite structures. The latter may be useful, for example, if it is desired to use the ALD films on metals or alloys (e.g. for corrosion protection). ALD films also allow to change mechanical properties of material surfaces that may be necessary in, for example, micro- or nanoelectromechanical (NEMS/MEMS) devices.
In this study atomic layer deposition combined with several other techniques was used to produce nanostructured composites. Three structure types were realized: fiber or particle filled and laminated structures. Mechanical properties (modulus and hardness) of composites were tested using instrumented nanoindentation. The results were analyzed in the context of several theoretical models where reasonable. Tests have shown that it is probably the easiest to prepare ALD laminated composites, where preparations were simple and compact sample was obtained without additional work techniques. The remaining types of structures likely need further research and optimization for best results. The elastic modulus measurements showed that the ALD films were not very rigid. For example, an amorphous Al2O3 was about 3 times less than the modulus of corundum-type Al2O3 (i. e. about 110 GPa versus ≈340 GPa). HfO2, Ta2O5, ZrO2 modules were also lower compared to bulk objects in macroscale. Elastic moduli of the composite laminates were intermediate between the values of the pure oxides, with the exception of ZrO2-Ta2O5 nanolaminates, in which case the moduli were larger compared to pure oxides. The exact causes of the phenomenon are still unaccounted for. The hardness of pure Al2O3 and HfO2 were nearly two times harder than soda-lime-glass (11–12 GPa and 6.7 GPa, respectively). Zirconium, and tantalum oxide were close to the hardness of glass (≈7 GPa). Results suggest that ALD oxide films are relatively hard materials and they could be matched to the different elastic moduli of other materials using various composite structures. The latter may be useful, for example, if it is desired to use the ALD films on metals or alloys (e.g. for corrosion protection). ALD films also allow to change mechanical properties of material surfaces that may be necessary in, for example, micro- or nanoelectromechanical (NEMS/MEMS) devices.
Description
Väitekirja elektrooniline versioon ei sisalda publikatsioone
Keywords
aatomkihtsadestamine, õhukesed kiled, nanomaterjalid, komposiitmaterjalid, mehaanilised omadused, atomic layer deposition, thin films, nanomaterials, composite materials, mechanical properties