Itsekantavien hiilinanoputkivahvisteisten alumiinioksidikalvojen valmistus ja karakterisointi

Abstract

Tässä pro gradu -tutkielmassa pyrittiin valmistamaan hiilinanoputkilla vahvistettuja itsekantavia Al2O3-ohutkalvoja. Ohutkalvot kasvatettiin märkäetsauksella ja atomikerroskasvatuksella ja niitä vahvistettiin levittämällä hiilinanoputkia Al2O3-kerrosten väliin. Hiilinanoputkia linkitettiin verkostomaiseksi rakenteeksi ionisäteilytyksellä. Kalvoja karakterisoitiin valmistuksen aikana ja sen jälkeen elektronimikroskopialla, atomivoimamikroskopialla, profilometrialla ja ramanspektroskopialla. Käytettyjen karakterisointimenetelmien perusteella hiilinanoputkien linkittymistä saattoi olla havaittavissa. Hiilinanoputkilla vahvistettujen itsekantavien Al2O3-kalvojen Youngin moduulin arvoksi saatiin 300 GPa:a ja vahvistamattomille kalvoille saatiin Youngin moduulin arvoksi 790 GPa:a. Tulosten perusteella Al2O3-kalvojen mekaaninen kestävyys heikkeni. Tuloksista ei voida tehdä varmoja johtopäätöksiä lukuisten optimoimattomien vaiheiden takia, mutta niitä voidaan pitää suuntaa antavina.

On the market of free-standing thin films there is demand for new innovative products. The goal of this master's thesis was to find out if the mechanical properties of free-standing Al2O3 thin films can be enhanced with carbon nanotubes because in earlier studies it has been possible to reinforce Al2O3 films by utilising graphene. The motivation was the easy growth process of Al2O3 by atomic layer deposition and earlier results that show that carbon nanotubes can be linked with ion irradiation. In this study experimental methods from University of Jyväskylä's Nanoscience center and Accelerator laboratory are combined. The main focus of the study was in the creation of a manifacturing process for the Al2O3 thin films, but characterisation was also performed in several steps of the process. The free-standing Al2O3 thin films were manifactured by wet etching silicon from SiN-coated substrate and growing Al2O3 by atomic layer deposition on top. The Al2O3 films were attempted to reinforce by spreading ion irradiated carbon nanotube networks in between of two Al2O3 layers. On the characterisation of the thin films atomic force microscopy, electronmicroscopy, profilometry, and ramanspectroscopy were used. Based on the characterisation methods used, carbon nanotube linking might have been observed. The value of Young's modulus for carbon naotube reinforced Al2O3 films was found to be 300 GPa, which is in the same order of magnitude as other studies utilising graphene have found. For the non-reinforced films the value of Young's modulus was found to be 790 GPa. According to the results the carbon nanotube layer works to actually weaken the Al2O3 thin films. But due to many unknown parameters in the manufacturing process and low amount of repetitions these results can't be considered too trustworthy but directional instead.