Papers by Author: Jin Seong Park

Abstract: Chemical mechanical polishing (CMP) of platinum thin films was performed for the improvement of surface morphology. Platinum thin films after CMP process with alumina slurry showed the increase of surface morphology without a remarkable difference of the thermal characteristics of as-annealed platinum thin films. The power consumption of platinum thin films micro-heater also became very low by improvement of surface morphology after CMP process. The similar or improved electrical and thermal characteristics of platinum thin films for micro-heater of sensor applications as well as evaluation possibility of sensing property by the improved surface morphology were obtained after CMP process.

Abstract: The effects of flash-heating and aging on the microstructure and transformation characteristics has been studied in Cu-Al-Ni based melt-spun ribbons. When the as-spun ribbon, stabilized due to higher Al content and fast cooling, is flash-heated at 750 °C, the β1 parent phase is partially retained. Even though flash-heating temperature is increased upto 850 °C, a little β1 parent phase with lager grains above 10 μm is still retained. The Ms temperature is increased with increasing flash-heating temperature due to the decrease of grain constraint within grown grains. However, the greater part of β1 parent phase with smaller grains of 2 ~ 3 μm is transformed to martensite in the initial stage of aging at 200 °C. The Ms temperature of the ribbon with smaller grains is higher than that of the ribbon with larger grains. It is considered that the increase of Ms temperature is caused to the disappearance of lattice defects introduced during melt spinning by aging at 200 °C rather than grain growth.

Abstract: Tin oxide thin films were deposited at 375 °C on α-alumina substrate by metal-organic chemical vapor deposition (MOCVD) process. A number of hillocks on the film were formed after air annealing at 500 °C for 30 min and few things in N2 annealing. The oxygen content and the binding energy after air annealing came to close the stoichiometric SnO2. The cauliflower hillocks of the film seem to be formed by the continuous migration of crystallites from a cauliflower grain on the substrate to release the stress due to the increase of oxygen content and volume.

Abstract: SnO2 thin films were prepared on SiO2/Si substrate by RF-Magentron Sputtering method, varying the deposition time and Ar-to-O2 flow ratio. The post-annealing was conducted at 500 oC and 700 oC in Ar and O2 atmosphere, respectively. Film characteristics were very sensitive to the gas flow ratio during the deposition and the conditions of post-annealing. The Film thickness decreased with decreasing of Ar flow ratio at a constant amount (50 sccm) of total gas flow. Especially, the film deposited under Ar-O2 mixture gas (Ar-to-O2 ratio of 50%) showed clearly aggregated morphology of small particles (cauliflower) in a wide range of area. In the annealed films, these cauliflowers separated some small grains, decreasing the film thickness.