• Journal of the Microelectronics and Packaging Society
• /
• v.25 no.4
• /
• pp.137-142
• /
• 2018

Room temperature ferromagnetism of Co doped ZnO was studied using (ZnO/Co) multilayer structure, and the effects of ZnO sub-layer thickness on the RT ferromagnetism was investigated. As for the as-deposited state, the diamagnetism was observed for ($ZnO\;20{\AA}/Co\;x{\AA}$) while the ferromagnetism was observed for ($ZnO\;40{\AA}/Co\;x{\AA}$). After vacuum-annealed, both showed the RT ferromagnetism and ($ZnO\;40{\AA}/Co\;x{\AA}$) structure interestingly showed negative remanence magnetization behavior. UV-Vis spectrometer revealed that Co atoms were substituted with Zn in ZnO and Co cluster was not found in XPS and HRTEM EDS analysis.

• Proceedings of the Korean Magnestics Society Conference
• /
• 2007.05a
• /
• pp.141.1-141.1
• /
• 2007

• Proceedings of the Korean Society of Precision Engineering Conference
• /
• 2011.06a
• /
• pp.1237-1238
• /
• 2011

• Proceedings of the Korean Magnestics Society Conference
• /
• 1995.10a
• /
• pp.98-99
• /
• 1995

• Proceedings of the Materials Research Society of Korea Conference
• /
• 2002.05a
• /
• pp.124-124
• /
• 2002

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.25 no.5B
• /
• pp.985-991
• /
• 2000

In this paper, the optimum structure of 2GHz magnetic thin film planar inductor were designed and fabricated to reduce the inductor area and to maximize the inductance L and quality factor Q of the inductor. The optimum design was performed utilizing Co90Fe10 layer multilayered with SiO2 layers to avoid the eddy-current skin effect and considering new lumped element model. New magnetic thin film inductors operating at 2GHz were fabricated on a Si substrate utilizing photo-lithography and lift-off techniques. The frequency characteristics of L, Q, and impedance in more than fifty identical inductors were measured using an RF Impedance Analyzer(HP4291B with HP16193A test fixture). The self-resonant frequencies(SRF) of the inductors were measured by a Vector Network Analyzer(HP8510). The developed inductors have SRF of 1.8 to 2.3GHz, L of 47 to 68nH, and Q of 70 to 80 near 1GHz. Finally, high frequency, high performance, planar micro-inductor(area=30.8 x 30.8il$^2$) with maximized L and Q were fabricated succefully.

• Transactions on Electrical and Electronic Materials
• /
• v.12 no.5
• /
• pp.193-196
• /
• 2011

Lead zirconate titanate (PZT)/ bismuth ferrite (BFO) multilayer thin films have been fabricated by the spin-coating method on Pt(200 nm)/Ti(10 nm)/$SiO_2$(100 nm)/p-Si(100) substrates using $BiFeO_3$ and $Pb(Zr_{0.52}Ti_{0.48})O_3$ metal alkoxide solutions. The PZT/BFO multilayer thin films show a uniform and void-free grain structure, and the grain size is smaller than that of PZT single films. The reason for this is assumed to be that the lower BFO layers play an important role as a nucleation site or seed layer for the formation of homogeneous and uniform upper PZT layers. The dielectric constant and dielectric losses decreased with increasing number of coatings, and the six-layer PZT/BFO thin film has good properties of 162 (dielectric constant) and 0.017 (dielectric losses) at 1 kHz. The remnant polarization and coercive field of three-layer PZT/BFO thin films were 13.86 ${\mu}C/cm^2$ and 37 kV/cm respectively.

• Macromolecular Research
• /
• v.15 no.7
• /
• pp.688-692
• /
• 2007

The hydrogen-bonding induced alternating multilayer thin films of dendrimers and block copolymer micelles were demonstrated. The block copolymer micelles derived from amphiphilic poly(2-ethyl-2-oxazoline)block-$poly({\varepsilon}-carprolactone)$ (PEtOz-PCL) in aqueous phase have a core-shell structure with a mean hydrodynamic diameter of 26 nm. The hydrogen bonding between the PEtOz outer shell of micelle and the carboxyl unit of poly(amidoamine) dendrimer of generation 4.5 (PAMAM-4.5G) at pH 3 was utilized as a driving force for the layerby-layer alternating deposition. The multilayer thin film was fabricated on the poly(methyl methacrylate) (PMMA) thin film spin-coated on silicon wafer or glass substrate by the alternate dipping of PEtOz-PCL micelles and PAMAM dendrimers in aqueous solution at pH 3. The formation of multilayer thin film was characterized by using ellipsometry, UV-vis spectroscopy, and atomic force microscopy. The PEtOz outer shell of PEtOz-PCL micelle provided the pH-responsive hydrogen bonding sites with peripheral carboxylic acids of PAM AM dendrimer. The multilayer thin film was reversibly removed after dipping in aqueous solution at $pH{\geq}5.6$ due to dissociation of the hydrogen bonding between PEtOz shell of PEtOz-PCL micelle and peripheral carboxyl units of PAMAM dendrimer.

• Polymer(Korea)
• /
• v.35 no.2
• /
• pp.130-135
• /
• 2011

Along with the fast development of electronics, the demands of portable electronics and wireless sensors are growing rapidly. The need for self-powering materials capable of powering the electrical devices attached to them is increasing, The piezoelectric effect of polyvinylidene fluoride (PVDF) can be used for this purpose. PVDF has a special crystal structure consisting of a ${\beta}$-phase that can produce piezoelectricity. In this paper, multilayer PVDF films were fabricated to increase the ${\beta}$-phase content. A solution of 10% concentration N;N-dimethylacetamide (DMAc) in PVDF (PVDF/DMAc) was used to fabricate the films via spin coating technique with the following optimum process parameters: a spin rate of 850 rpm, spin time of 60 s, drying temperature of $60^{\circ}C$, and drying time of 30 min, Compared with single-layer PVDF films, the multilayer films exhibited higher ${\beta}$-phase content. The ${\beta}$-phase content of the films increased gradually with increasing number of layers until 4, Maximum ratio of ${\beta}$-phase content was 7.72.

• Journal of the Korean institute of surface engineering
• /
• v.45 no.3
• /
• pp.111-116
• /
• 2012

Oblique angle deposition (OAD) is a physical vapor deposition method which utilizes non-normal angles between the substrate and the vaporizing source. It has been known that tilting the substrate changes the properties of the film deposited on it, which was thought to be a result of morphological change of the film. In this study, OAD has been applied to prepare single and multilayer Al films by magnetron sputtering. The magnetron sputtering source of 4 inch diameter was used to deposit the films. Al films have been deposited on Si wafers and cold-rolled steel sheets. The multilayer films were prepared by changing the tilting angle upside down at each layer interval, which means that when the first layer was deposited at an angle of $+45^{\circ}$, the second layer was deposited at an angle of $-45^{\circ}$, and vice versa. The microstructure, surface roughness and reflectance of the films were investigated using a scanning electron microscope, a surface profiler and a spectrophotometer, respectively. The corrosion resistance was measured and compared using the salt spray test. The single layer film prepared at an oblique angle of $60^{\circ}$ prepared at other angles. However, for the multilayer films, the film prepared at an oblique angle of $45^{\circ}$ showed the most compact and featureless structure. The multilayer films were found to exhibit higher corrosion resistance than the single layer films.