Self-assembly of synthesized 4-pentynoic acid functionalized magnetite-maghemite nanoparticles on silicon dioxide/n-type silicon substrate / Aainaa Aqilah Baharuddin
This study is divided into two parts; i) synthesis of the functionalized magnetite-maghemite (Fe3O4-γ-Fe2O3) nanoparticles (FNPs) and ii) self-assembly of the FNPs on silicon substrate which serves as metal-oxide-semiconductor capacitor. Bare iron oxide nanoparticles (NPs) were synthesized by co-pre...
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| Format: | Thesis |
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2017
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| Online Access: | http://studentsrepo.um.edu.my/8441/7/aaina.pdf http://studentsrepo.um.edu.my/8441/ |
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| Summary: | This study is divided into two parts; i) synthesis of the functionalized magnetite-maghemite (Fe3O4-γ-Fe2O3) nanoparticles (FNPs) and ii) self-assembly of the FNPs on silicon substrate which serves as metal-oxide-semiconductor capacitor. Bare iron oxide nanoparticles (NPs) were synthesized by co-precipitation method and were altered to pH 12 (optimum pH) using NH4OH to promote dispersity right before ex-situ modification with oleic acid (0.2-0.8 g/g oleic acid to iron oxide) and subsequent 4-pentynoic acid (1.63 mmol) functionalization. In the first part, X-ray-diffraction (XRD) showed that lattice constants of the iron oxides co-exist as Fe3O4-γ-Fe2O3. Transmission electron microscopy showed that the particle size (10.94 ± 0.24 nm) of sample P-0.4 is complementary to the mean crystallite size (10 ± 1 nm) attained from XRD. Thermogravimetric-differential thermal analysis indicated that monolayer oleic acid FNPs was produced for ex-situ modification of 0.2 g/g oleic acid to iron oxide. Whereas higher concentrations of oleic acid ex-situ modifications generated bilayer oleic acid-coated FNPs to which, functionalization of 4-pentynoic acid was only successfully performed as indicated by Fourier transform infrared spectroscopy. Zetasizer affirmed the highly stabilized dispersion of FNPs at pH 12 with zeta potentials at relatively -47 to -75 mV and mean hydrodynamic particle size distributions of ~35-48 nm. Sample 0.4 g/g oleic acid to iron oxide, functionalized with 4-pentynoic acid, with the most stabilized nanoparticles in an aqueous medium was chosen for self-assembly in the second part. In the second part, investigation on the relation between temperature-influential self-assembly (70-300 ˚C) of the samples on SiO2/n-Si structure with their electrical characteristics was conducted. XRD analysis revealed that 8 ± 1 nm of FNPs which aggregated non-uniformly into film of 12.6 μm thickness was self-assembled via Si-O-C linkages. Besides, increasing temperature of heat treatments induced growth of native oxide, SiO2 on the Si substrate. Other implications of increasing heating
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temperature disclosed by attenuated total reflectance infrared analysis are breakdowns of Si-O-C linkages and formations of Si-OH defects. Atomic force microscopy implied that sample with more physisorbed surfactants exhibited the highest root-mean-square roughness (18.12 ± 7.13 nm) and vice versa (12.99 ± 4.39 nm). The increased saturation magnetization (71.527 A·m2/kg) and coercivity (929.942 A/m) acquired by vibrating sample magnetometer of the sample heated at 300 ˚C verified the surfactants’ disintegration. Leakage current density-electric field characteristics signified that sample heated at 150 ˚C with the most aggregated FNPs as well as the most developed Si-O-C linkages demonstrated the highest breakdown field and barrier height at 2.58 x 10-3 MV/cm and 0.38 eV respectively. Whereas sample heated at 300 ˚C with the least Si-O-C linkages and more Si-OH defects as well as lesser aggregated NPs showed the lowest breakdown field and barrier height at 1.08 x 10-3 MV/cm and 0.19 eV respectively. |
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