Papers by Author: Jong Hyun Seo

Abstract: In order to prevent pitting corrosions in aluminum thin film, zirconium incorporated chemical conversion coating on sputtered aluminum film was studied. Several pretreatment methods for conversion coating on the thin film were examined. There existed the optimum pretreatment and coating condition for successful growing of anticorrosive conversion coating layer in a given aggressive environment. Pit densities of aluminum thin films were significantly decreased with conversion coating. Electrochemical behaviors of conversion coated aluminum thin film were also discussed.

Abstract: Bond coatings, CoNiCrAlY, are prepared on Inconel 738 substrate by vacuum plasma spray (VPS). Mechanical properties of VPSed CoNiCrAlY coatings are investigated via Taguchi method and L18(21×37)
orthogonal arrays to determine the optimal setting and the relationship of experimental variables. Seven parameters were considered as follows: (A) arc current; (B) primary gas flow rate; (C) secondary gas flow rate; (D) stand-off distance; (E) working pressure; (F) carrier gas flow rate (Ar); and (G) powder feeding rate.
The effect of carrier gas flow rate on the porosity is determined to be the highest among the parameters investigated. Higher microhardness values are observed for the VPSed coatings as compared to the coatings prepared by conventional high velocity oxygen fuel probably due to low amount of the porosity.

Abstract: In order to improve long term stability of a-Si:H TFT for AM-OLED application a new driving method compensating Vth shift requires a new device structure of which hole injection is enhanced. ITO film was investigated for the hole injection material because it is essential material for display devices and has high work function favorable for hole injection. From I-V characteristics of TFTs with two types of source and drain material, i.e. Cr and ITO, the contact properties were measured and compared. Although electron injection property of ITO was worse than Cr, hole injection property was comparable to that of Cr.

Abstract: Amorphous silicon thin films were deposited below 160oC on PES plastic films using PECVD. After thin film deposition using PECVD, thin film failures such as film delamination and cracking often occurred. For successful growth of thin films (about 2000 Å) without their failures, it is necessary to solve the critical problem related to the internal compressive stress (some GPa) leading to delamination at a threshold thickness value of the films. The Griffith’s theory explains the failure process by looking at the excess of elastic energy inside the film, which overcomes the cohesive energy between film and substrate. In this work, reducing a-Si layer film thickness and optimizing a barrier SiNx layer have produced stable a-Si films at 150oC, over PES substrates.