In the present work, water-based gold nanofluids were synthesized by the solution plasma processing (SPP). The size distribution and the shape of gold nanoparticles in the nanofluids were investigated using high resolution transmission electron microscopy (HR-TEM). The dispersion stability of gold nanofluids was characterized using zeta potential, as well. The thermal properties of gold nanofluids were measured by utilizing lambda measurement device. Nanofluids containing nanoparticles with in diameter were successfully synthesized. As diameter of nanoparticles decreased, dispersion stability of nanofluids increased and the enhanced ratio of thermal conductivity increased. The nanofluid with nanoparticles of in diameter showed approximately 3% improvement in thermal conductivity measurement and this could be due to the enhanced Brownian movement.

본 논문에서는 용액 공정을 이용한 고분자 절연층을 갖는 top-gate 구조의 펜타센 박막 트랜지스터(Thin Film Transistor, TFT)의 특성을 연구하였다. Top-gate 구조의 펜타센 TFT 제작에 앞서 유기 반도체인 펜타센의 결정성 성장을 돕기 위해서 가교된 PVP (cross-linked poly(4-vinylphenol))를 유리 기판 상에 스핀 코팅을 이용하여 형성한 후, 노광 공정을 통해 니켈/은 구조를 갖는 채널 길이 10μm의 소오스, 드레인 전극을 형성하였다. 그리고 열 증착을 이용하여 60 nm 두께의 펜타센 층을 성막하였고, 고분자 절연체로서 PVA(polyvinyl alchol) 또는 가교된 PVA를 용액공정인 스핀 코팅을 이용하여 형성한 후 열 증착으로 알루미늄 게이트 전극을 성막하였다. 이로써 제작된 소자들의 전기적 특성을 확인한 결과 가교된 PVA를 사용한 펜타센 TFT 보다 PVA를 게이트 절연체로 사용한 소자가 전기적 특성이 우수한 것으로 관찰되었다. 이는 PVA의 가교 공정에 의한 펜타센 박막의 성능 퇴화에 기인한 것으로 사료된다. 실험 결과 0.9μm 두께의 PVA 게이트 절연막을 사용한 top-gate 구조의 펜타센 TFT의 전계 효과 이동도와 문턱전압, 그리고 전류 점멸비는 각각, 약 3.9×10-3 cm2/Vs, -11.5 V, 3×105으로써 본 연구에서 제안된 소자가 용액 공정형 top-gate 유기 TFT 소자로서 우수한 성능을 나타냄을 알 수 있었다.

Nano-sized Ni-ferrite powder was fabricated by spray pyrolysis process using the waste solution resulting from shadow mask processing. The average particle size of the powder was below 100 nm. The effects of the concentration of raw material solution, the nozzle tip size and air pressure on the properties of powder were studied. As the concentration increased, the average particle size of the powder gradually increased and its specific surface area decreased, but size distribution was much wider and the fraction of the Ni-ferrite phase greatly increased as the concentration increasing. As the nozzle tip size increased from 1 mm to 2 mm, the average particle size of the powder decreased. In case of 3 mm nozzle tip size, the average particle size of the powder increased slightly. On the other hand, in case of 5 mm nozzle tip size, average particle size of the powder decreased. Size distribution of the powder was unhomogeneous, and the fraction of the Ni-ferrite phase decreased as the nozzle tip size increasing. As air pressure increased up to 1 kg/, the average particle size of the powder decreased slightly, on the other hand, the fraction of the Ni-ferrite phase was almost constant. In case of 3kg/ air pressure, average particle size of the powder and the fraction of the Ni-ferrite phase remarkably decreased, but size distribution was narrow.