Ji Sun Yun

Structural Properties of Nickel Manganite Thin Films Fabricated by Metal Organic Decomposition

Thin thermistor films of solutions with nickel and manganese oxides were prepared by metal-organic decomposition (MOD). The structural properties of the thin films were investigated as a function of annealing temperature. Field emission scanning electron microscope (FE-SEM) results indicated that the thin films had a thin thickness, smooth and dense surface. The crystallization temperature of was confirmed from thermogavimetric-differential thermal analysis (TG-DTA) curve. A single phase of cubic spinel structure was obtained for the thin film annealed from to , which was confirmed from the X-ray diffraction (XRD). From the selected area electron diffraction (SAED) in high resolution transmission electron microscope (HRTEM), the nano grains (2~3 nm) of spinel phase with (311) and (222) planes were detected for the thin film annealed at , which could be applicable to read-out integrated circuit (ROIC) substrate of the uncooled microbolometer with low processing temperature.

The Study on the Improvement of Piezoelectric and Electrical Characteristics of Bi 0.5 (Na 0.78 K 0.22 ) 0.5 TiO 3 Ceramics Modified by the La-based ABO 3 Pervskite Structure

The 0.99Bi0.5(Na0.78K0.22)0.5TiO3–0.01LaAlO3, 0.01LaMnO3 or 0.01LaFeO3 (0.99BNKT–0.01LA, 0.01LM or 0.01LF) ceramics were prepared by a conventional mixed mothod. The structure and morphology of the lead free ceramics were characterized by XRD (X-ray diffraction) and FE-SEM (field emission scanning electron microscopy). XRD results indicated that the BNKT ceramics modified by LA, LM or LF induced a transition from a ferroelectric tetragonal to a non-polar pseudo-cubic phase, leading to decrease in the remnant polarization (Pr) and coercive field (Ec) in the P-E hysterisis loops. The effects of the BNKT ceramics modified by La-based ABO3 pervskite structure on the electric-field induced strain were investigated, and the largest normalized unipolar strain (Smax/Emax) was found in BNKT-0.01LF ceramic.

Spin Spray-Deposited Spinel Thin Films for Microbolometer Applications

Spinel thin films were prepared by the spin spray technique to develop new thermal imaging materials annealed at low temperature for uncooled microbolometer applications. The spinel thin films were deposited from [(Ni0.30Co0.33Mn0.37)1-xCux]3O4 (0.1≤x≤0.2) solutions and then annealed at 400°C for 1 h in argon. Effects of Cu content (x) and deposition time on the electrical properties of the annealed films were investigated. With increasing deposition time, the resistivity of the annealed films increased. For the annealed films deposited for 1 min, the resistivity of x=0.15 films was lower than that of x=0.1 films due to the different grain sizes. The high temperature coefficient of resistance (TCR) of the annealed films could be obtained at temperature below 50°C. Typically, the resistivity of 127 Ω·cm and TCR of -5.69%/K at 30°C were obtained for x=0.1 films with deposition time of 1 min annealed at 400°C for 1 h in argon.

Micro-structure and NTCR Characteristics of Copper Manganite Thin Films Fabricated by MOD Process

Copper manganite thin films were fabricated on substrate by metal organic decomposition (MOD) process. They were burned-out at and annealed at various temperatures () for 1h in ambient atmosphere. Their micro-structure and negative temperature coefficient of resistance (NTCR) characteristics were analyzed for micro-bolometer application. The copper manganite film with a cubic spinel structure was well developed at which confirmed by XRD and HRTEM analysis. It showed a low resistivity () at room temperature and high NTCR characteristics of and at room temperature and , implying a good thin film for micro-bolometer application. Furthermore, its crystallinity was enhanced with increasing temperature to . However, the appearance of secondary phase at temperatures higher than lead to deteriorate the NTCR characteristics.

Structural and Electrical Properties of [(Co 1-x Cu x ) 0.2 (Ni 0.3 Mn 0.7 ) 0.8 ] 3 O 4 Spinel Thin Films for Infrared Sensor Application

Co1-xCux)0.2(Ni0.3Mn0.7)0.8)3O4 (0≤x≤1) thin films prepared by metal organic decomposition process were fabricated on SiN/Si substrate for infrared sensor application. Their structural and electrical properties were investigated with variation of Cu dopant. The ((Co1-xCux)0.2(Ni0.3Mn0.7)0.8)3O4 (CCNMO) film annealed at 500℃ exhibited a dense microstructure and a homogeneous crystal structure with a cubic spinel phase. Their crystallinity was further enhanced with increasing doped Cu amount. The 120 nm-thick CCNMO (x=0.6) thin film had a low resistivity of 53 Ω·cm at room temperature while the Co-free film (x=1) showed a significantly decreased resistivity of 5.9 Ω·cm. Furthermore, the negative temperature coefficient of resistance (NTCR) characteristics were lower than -2%/℃ for all the specimens with x≥0.6. These results imply that the CCNMO (x≥0.6) thin films are a good candidate material for infrared sensor application.

Complex Permeability of 0-3 Polymer Magnetic Composites for Near-Field Communication

Magnetic properties of composite materials consisting of polymer filled with ferromagnetic powders (MnZn ferrite, Fe-Si alloy) were investigated in this study. The volume fraction of magnetic powders as fillers was varied from 70 % to 95 %. This paper presents the fabrication method of polymer magnetic composites in an effort to produce the 0-3 types of MnZn ferrite and FeSi as fillers with a proper complex permeability through the optimization of some experimental parameters. The polymer matrix composites were prepared by mixing the crushed ferrites and flaky FeSi powders homogenously with low-density resins (EPDM, epoxy). The relationships among the manufacturing technology of these materials, their filler volume fraction, as well as their complex permeability were measured and analyzed.