• Journal of Environmental Science International
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• v.22 no.1
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• pp.83-89
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• 2013

Silicon carbide with aluminium oxide was used to remove the sulphur hexafluoride ($SF_6$) gas using microwave irradiation. The destruction and removal efficiencies (DREs) of $SF_6$ were studies as a function of various decomposition temperatures and microwave powers. The decomposition of $SF_6$ gas was analyzed using GC-TCD. XRD (X-ray powder diffraction) and XRF (X-ray Fluorescence Spectrometer) were used to characterize the properties of aluminum oxide. DREs of $SF_6$ were increased as the microwave powers were increased. Additive aluminium oxide on SiC increased the removal efficiencies and decreased the decomposition temperature. The XRD results show that the ${\gamma}-Al_2O_3$ was transformed to ${\alpha}-Al_2O_3$ during $SF_6$ decomposition by microwave irradiation. It was found that the best material to control $SF_6$ was SiC with $Al_2O_3$ 30 wt% in consideration of microwave energy consumption and $SF_6$ decomposition rate.

• Korean Journal of Materials Research
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• v.26 no.8
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• pp.430-437
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• 2016

Aluminum oxide ($Al_2O_3$) thin films were grown by atomic layer deposition (ALD) using a new Al metalorganic precursor, dimethyl aluminum sec-butoxide ($C_{12}H_{30}Al_2O_2$), and water vapor ($H_2O$) as the reactant at deposition temperatures ranging from 150 to $300^{\circ}C$. The ALD process showed typical self-limited film growth with precursor and reactant pulsing time at $250^{\circ}C$; the growth rate was 0.095 nm/cycle, with no incubation cycle. This is relatively lower and more controllable than the growth rate in the typical $ALD-Al_2O_3$ process, which uses trimethyl aluminum (TMA) and shows a growth rate of 0.11 nm/cycle. The as-deposited $ALD-Al_2O_3$ film was amorphous; X-ray diffraction and transmission electron microscopy confirmed that its amorphous state was maintained even after annealing at $1000^{\circ}C$. The refractive index of the $ALD-Al_2O_3$ films ranged from 1.45 to 1.67; these values were dependent on the deposition temperature. X-ray photoelectron spectroscopy showed that the $ALD-Al_2O_3$ films deposited at $250^{\circ}C$ were stoichiometric, with no carbon impurity. The step coverage of the $ALD-Al_2O_3$ film was perfect, at approximately 100%, at the dual trench structure, with an aspect ratio of approximately 6.3 (top opening size of 40 nm). With capacitance-voltage measurements of the $Al/ALD-Al_2O_3/p-Si$ structure, the dielectric constant of the $ALD-Al_2O_3$ films deposited at $250^{\circ}C$ was determined to be ~8.1, with a leakage current density on the order of $10^{-8}A/cm^2$ at 1 V.

• Journal of the Korean institute of surface engineering
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• v.55 no.5
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• pp.273-283
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• 2022

Al6061 aluminum alloy specimens were exposed to atmospheric conditions for maximum 24 months. 24-month exposure specimen showed some more frequent and larger size of corrosion products and pitting on the surface compared with the 12-month exposure specimens. The XRD examination revealed the dominant surface oxide phases of Al₂O₃ and Al(OH)₃. The oxide thickness at uniform oxidation (or non-pitting) region was not much changed over exposure time. The 1.2 ㎛ deep oxygen penetration area was found in the 12-months exposed specimen near the thin uniform aluminum oxide film. The line-EDS was conducted through the penetration regions and non-penetrated grain boundary. There were signs of O and Si concentration through the penetration region, whereas non-penetration region showed no concentration of O or Si. It was confirmed that pitting is a more severe degradation mode in Al6061 (max. >4 ㎛ deep) compared with the uniform oxidation (max. ~200 nm deep) up to 24-months exposure.

• Journal of the Semiconductor & Display Technology
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• v.21 no.2
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• pp.11-14
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• 2022

In this work, we evaluated the Al₂O₃ film, which was deposited by atomic layer deposition, degraded by exposure to harsh environments. The Al₂O₃ films deposited by atomic layer deposition have long been used as a gas diffusion barrier that satisfies barrier requirements for device reliability. To investigate the barrier and mechanical performance of the Al₂O₃ film with increasing temperature and relative humidity, the properties of the degraded Al₂O₃ film exposed to the harsh environment were evaluated using electrical calcium test and tensile test. As a result, the water vapor transmission rate of Al₂O₃ films stored in harsh environments has fallen to a level that is difficult to utilize as a barrier film. Through water vapor transmission rate measurements, it can be seen that the water vapor transmission rate changes can be significant, and the environment-induced degradation is fatal to the Al₂O₃ thin films. In addition, the surface roughness and porosity of the degraded Al₂O₃ are significantly increased as the environment becomes severer. the degradation of elongation is caused by the stress concentration at valleys of rough surface and pores generated by the harsh environment. Becaused the harsh envronment-induced degradation convert amorphous Al₂O₃ to crystalline structure, these encapsulation properties of the Al₂O₃ film was easily degraded.

• Korean Journal of Materials Research
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• v.31 no.6
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• pp.339-344
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• 2021

Composite materials offer distinct and unique properties that are not naturally inherited in the individual materials that make them. One of the most attractive composites to manufacture is the aluminum alloy matrix composite, because it usually combines easiness of availability, light weight, strength, and other favorable properties. In the current work, Powder Metallurgy Method (PMM) is used to prepare Al2024 matrix composites reinforced with different mixing ratios of yttrium oxide (Y₂O₃) particles. The tests performed on the composites include physical, mechanical, and tribological, as well as microstructure analysis via optical microscope. The results show that the experimental density slightly decreases while the porosity increases when the reinforcement ratio increases within the selected range of 0 ~ 20 wt%. Besides this, the yield strength, tensile strength, and Vickers hardness increase up to a 10 wt% Y₂O₃ ratio, after which they decline. Moreover, the wear results show that the composite follows the same paradigm for strength and hardness. It is concluded that this composite is ideal for application when higher strength is required from aluminum composites, as well as lighter weight up to certain values of Y₂O₃ ratio.

• Journal of the Korean Ceramic Society
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• v.50 no.6
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• pp.439-445
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• 2013

Both an unreinforced $Al_2O_3$/Al matrix and a ${\alpha}-Al_2O_3$ particulate reinforced composite have been produced by the oxidation of an Al surface doped with NaOH in the absence of any other dopant. Fabrication of the matrix was initiated by the formation of $NaAlO_2$, which provides a favorable surface structure for the matrix formation by breaking the protective $Al_2O_3$ layer on Al. During the matrix growth, the external surface of the growth front was covered with a very thin sodium-rich oxide. A cyclic formation process of the sodium-rich oxide on the growth surface was proposed for the sodium-induced directed metal oxidation process. This process involves dissolution of the sodium-rich oxide, motion of Na to the growth front, and re-formation of the oxide on the surface. Near-net-shape composites were fabricated by infiltrating an $Al_2O_3$/Al matrix into a ${\alpha}-Al_2O_3$ particulate preform, without growth barrier materials. The infiltration distance increased almost linearly in the NaOH-doped preform.

• Journal of Powder Materials
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• v.10 no.5
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• pp.337-343
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• 2003

Nanostructured Cu-$Al_2O_3$ composite powders were synthesized by thermochemical process. The synthesis procedures are 1) preparation of precursor powder by spray drying of solution made from water-soluble copper and aluminum nitrates, 2) air heat treatments to evaporate volatile components in the precursor powder and synthesis of nano-structured CuO + $Al_2O_3$, and 3) CuO reduction by hydrogen into pure Cu. The suggested procedures stimulated the formation of the gamma-$Al_2O_3$, and different alumina formation behaviors appeared with various heat treating temperatures. The mean particle size of the final Cu/$Al_2O_3$ composite powders produced was 20 nm, and the electrical conductivity and hardness in the hot-extruded bulk were competitive with Cu/$Al_2O_3$ composite by the conventional internal oxidation process.

• Journal of the Semiconductor & Display Technology
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• v.14 no.4
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• pp.45-49
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• 2015

Using a combined CVD and ALD equipment system, multi-layer quantum well structures of $Al_2O_3/a-Si/Al_2O_3$ were fabricated on silicon Schottky junction devices and implemented to quantum well solar cells, in which the 1~1.5 nm thicknesses of the aluminum oxide films and the a-Si thin film layers were deposited at $300^{\circ}C$ and $450^{\circ}C$, respectively. Fabricated solar cell was operated by tunneling phenomena through the inserted quantum well structure being generated electrons on the silicon surface. Efficiency of the fabricated solar cell inserted with multi-quantum well of 41 layers has been increased by about 10 times that of the solar cell of pure Schottky junction solar cell.

• Journal of the Korean Ceramic Society
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• v.44 no.3 s.298
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• pp.175-181
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• 2007

Molecular dynamics simulation (MD) of $(62-x)CaO{\cdot}38Al_{2}O_{3}{\cdot}xBaO$ glasses has been carried out using empirical potentials with the covalent term. The simulations closely reproduce the total neutron correlation functions of glass with 5 mol% BaO and physical properties of these glasses such as elastic constants. For these glasses, aluminum is tetrahedrally coordinated by oxygen, but there is a part of five-fold and six-fold coordination of aluminum. There are no major changes to the mid-range structure of glass, as barium is substituted for calcium. To predict the barium coordination number, we have used the bond valence (BV) theory and also compared the results of simulation with Bond valence. The coordination number for oxygen around barium atoms is close to 8 and the average distance of barium and oxygen is nearly 2.80 A. The viscosity of these glasses increases with the content of barium oxide substituted for calcium oxide.

• Journal of Sensor Science and Technology
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• v.29 no.4
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• pp.266-269
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• 2020

In this study, we investigated the effect of a sulfur passivation (S-passivation) process step on the electrical properties of surface-channel In_0.7Ga_0.3As quantum-well (QW) metal-oxide-semiconductor field-effect transistors (MOSFETs) with S/D regrowth contacts. We fabricated long-channel In_0.7Ga_0.3As QW MOSFETs with and without (NH₄)₂S treatment and then deposited 1/4 nm of Al₂O₃/HfO₂ through atomic layer deposition. The devices with S-passivation exhibited lower values of subthreshold swing (74 mV/decade) and drain-induced barrier lowering (19 mV/V) than the devices without S-passivation. A conductance method was applied, and a low value of interface trap density D_it (2.83×10¹² cm^-2eV^-1) was obtained for the devices with S-passivation. Based on these results, interface traps between InGaAs and high-κ are other defect sources that need to be considered in future studies to improve III-V microsensor sensing platforms.