원자층 증착 기술과 자기 조립 단분자막을 이용한 새로운 나노제조 기술의 개발에 관한 연구

Abstract

This thesis describes five main subjects: in the part I, a vapor-phase molecular layer deposition (MLD) of self-assembled multilayer thin films, in the part II, ZrO2-based organic-inorganic nanohybrid thin film fabricated by using MLD method combined with ALD, in the part III, a low-temperature fabrication of mixed-organic-inorganic nanohybrid superlattices for applying to flexible devices, in the part IV, high-resolution patterning of Al thin films using water-mediated nTP, and in the part V, thin-film transfer printing (TFTP) technique with atomic layer deposition (ALD). These subjects are novel fusion nanofabrication technologies grfted into atomic layer deposition and self-assembled monolayers. The part I introduces a vapor-phase molecular layer deposition of self-assembled multilayer thin films for organic thin-film transistor. In the present MLD process, alkylsiloxane self-assembled multilayers (SAMs) are grown under vacuum by repeated sequential adsorptions of C=C-terminated alkylsilane and aluminum hydroxide with ozone activation. The MLD method is a self-controlled layer-by-layer growth process, and is perfectly compatible with the atomic layer deposition (ALD) method. The prepared SAMs films exhibited good mechanical flexibility and stability, excellent insulating properties, and relatively high dielectric capacitances of 374 nF/cm2 with a high dielectric strength of 4 MV/cm. They were then used as a 12 nm-thick dielectric for pentacene-based thin-film transistors (TFTs), which showed a maximum field effect mobility of 0.57 cm2/V s, operating at -4 V with an on/off current ratio of ∼103. Part II shows ZrO2-based organic-inorganic nanohybrid thin film using MLD method combined with ALD. The prepared SAOL-ZrO2 organic-inorganic nanohybrid films exhibited good mechanical stability, excellent insulating properties, and relatively high dielectric constant k (~16). They were then used as a 23 nm-thick dielectric for low voltage pentacene-based thin film transistors, which showed a maximum field effect mobility of 0.63 cm2/V s, operating at -1 V with an on/off current ratio of ∼103. The part III describes a low-temperature fabrication of mixed-organic-inorganic nanohybrid superlattices for high-k thin stable gate dielectrics on flexible substrates. The self-assembled organic layers (SAOLs) are grown by repeated sequential adsorptions of C=C-terminated alkylsilane and metal (Al or Ti) hydroxyl with ozone activation. The TiO2 and Al2O3 inorganic layers are grown by ALD, which relies on sequential saturated surface reactions resulting in the formation of a monolayer in each sequence and is a potentially powerful method for preparing high quality multicomponent superlattices. The MLD method combined with ALD (MLD-ALD) was applied to fabricate SAOLs-Al2O3-SAOLs-TiO2 nanohybrid superlattices on polycarbonate substrates with accurate control of film thickness, large-scale uniformity, excellent conformality, good reproducibility, multilayer processing capability, sharp interfaces, and excellent film qualities at relatively low temperature. The prepared ultrathin nanohybrid films exhibited good thermal and mechanical stability, good flexibility, excellent insulating properties, and relatively high dielectric constant k (6~11). The MLD-ALD method is an ideal fabrication technique for various flexible electronic devices. Part IV indroduces a new nano-transfer printing (nTP) method that uses a water-mediated transfer process. Water-mediated nTP is based on the direct transfer of a metal thin film from a stamp to a substrate via water-mediated surface bonding between the stamp and the substrate. This procedure can generate aluminum (Al) patterns with micrometer and nanometer-scale feature sizes. Furthermore, an array of Al nanochannels is fabricated by using this method. The transferred Al patterns chemically bound to the substrate surface and thus exhibit strong adhesion. Finally, the part V describes a new patterning technique of inorganic materials by using thin-film transfer printing (TFTP) with atomic layer deposition. This method consists of the atomic layer deposition (ALD) of inorganic thin film and a nanotransfer printing (nTP) that is based on a water-mediated transfer process. In the TFTP method, the Al2O3 ALD growth occurs on FTS-coated PDMS stamp without specific chemical species, such as hydroxyl group. The CF3-terminated alkylsiloxane monolayer, which is coated on PDMS stamp, provides a weak adhesion between the deposited Al2O3 and stamp, and promotes the easy and complete release of Al2O3 film from the stamp. The water layer serves as an adhesion layer to provide good conformal contact and form strong covalent bonding between the Al2O3 layer and Si substrate. Thus, the TFTP technique is potentially useful for making nanochannels of various inorganic materials.