• Journal of the Korea Academia-Industrial cooperation Society
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• v.13 no.5
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• pp.2319-2324
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• 2012

In this paper, the design of asymmetric branch line couplers using artificial dielectric substrate (ADS) is described. The effective permittivity and permeability increase in ADS because of the lots of the inserted via-holes. So the physical length and width of transmission lines realized on ADS are reduced compared to the standard lines. This enables one to design size-reduced microwave circuits. As an instance in this work, an asymmetric branch line coupler with the ratio of 3:1 is designed at 2GHz. The designed coupler has a small size of 53.4% compared to the normal circuit while the same performances are preserved. A good agreement between the simulated and measured asymmetric power dividing ratio is shown. The measured loss is only less than 0.2dB, which is a very small value.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.27 no.2
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• pp.123-130
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• 2016

In this paper, a novel flexible microfluidic metamaterial absorber is proposed for remote chemical sensor applications. The proposed metamaterial absorber consists of a periodic of split-ring-cross resonators(SRCRs) and a microfluidic channel. The SRCR patterns are inkjet-printed using silver nanoparticle inks on paper. The microfluidic channels are laser-etched on polydimethylsiloxane(PDMS) material. The proposed absorber can detect change of the effective permittivity at different liquids. Therefore, the absorber can be used for a remote chemical sensor by detecting change of the resonant frequencies. The performance of the proposed absorber is demonstrated with full-wave simulation and measurement results. The experimental results shows that the resonant frequency is 10.49 GHz at the empty channel. When ethanol and DI-water are injected into the channel, the resonant frequencies are 10.04 GHz and 8.9 GHz, respectively.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.15 no.9
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• pp.783-787
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• 2002

In recent year, B $i_{4-}$x L $a_{x}$ $Ti_3$ $O_{12(BLT)}$ is one of promising substitute materials for the ferroelectric random access memory(FRAM) applications. But the systematic composition is still insufficient, so this experiment was carried out in ceramic ambient sintering process which has the very excellent ferroelectric property. Samples were prepared by a bulk and the purpose which was estimated with a suitability of thin films applications. The density of B $i_{3.75}$ L $a_{0.25}$ $Ti_3$ $O_{12}$ was high and the XRD pattern showed that the intensity of main peak (117) was increased at the argon ambient sintering. Controlling the quantity of oxygen, crystallization showed a thin, long plate like type, and we obtained the excellent dielectric and polarization properties at the argon atmosphere sintering. Also this sintering process was effective at the bulk sample. Argon ambient sintered sample produced higher permittivity of 154, the remanent polarization(2Pr) of 6.8 uC/$\textrm{cm}^2$ compared with that sintered in air and oxygen ambient. And this sintering process showed a possibility which could be applied to thin films process..

• Transactions on Electrical and Electronic Materials
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• v.16 no.3
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• pp.142-145
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• 2015

In this work, open stubs were fabricated on a polyether sulfone (PES) substrate, and their basic radio frequency (RF) characteristics were investigated for application to RF matching components of a flexible monolithic microwave integrated circuit (MMIC). According to the results, an open stub employing coplanar waveguide (OSCPW) on PES exhibited much lower loss than that on silicon substrate. The OSCPW with a length of $500{\mu}m$ on PES showed capacitance values of 0.031 ~ 0.044 pF from 0.5 to 50 GHz. For application to a relatively high-value capacitive matching, an open stub employing a fishbone-type transmission line (OSFTTL) was fabricated on PES, and its characteristics were investigated. The OSFTTL showed much higher capacitance values than the OSCPW due to the high effective permittivity value. Specifically, the OSFTTL on PES showed capacitance values of 0.066 ~ 0.24 pF from 0.5 to 50 GHz, which are higher than those for the open stub on silicon substrate. The above results indicate that the OSCPW and OSFTTL on PES can be effectively used for application to low/high-value capacitive matching components on microwave and millimeter wave flexible MMIC. To the best of the authors' knowledge, this work is the first report of the investigation of RF capacitive matching components on PES substrate.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.9 no.3
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• pp.296-304
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• 1998

A design method of an electromagnetic wave absorber with ferrite fins in the second layer, which has very wide band frequency characteristics and is used for single-polarized wave absorption such as TV wave etc, has been designed. To examine the effectiveness of the Equivalent Material Constants Method$(EMCM)^{[1]}$ which is approximate method, the effective complex permittivity calculated by the Hashin-Strikman formulas and the EMCM are compared. Since, furthermore, the reflectivities by the EMCM in space and the FDTD method in an rectangular waveguide agreed well each other, it has been confirmed that the proposed electromagnetic wave absorber has excellent absorption characteristics in the frequency range of 30 MHz to 5830 MHz. Thus, it can be concluded that the EMCM is usefull to design and analyze the electro-magnetic wave absorber proposed here.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2008.11a
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• pp.145-145
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• 2008

High-k materials have been paid much more attention for their characteristics with high permittivity to reduce the leakage current through the scaled gate oxide. Among the high-k materials, $ZrO_2$ is one of the most attractive ones combing such favorable properties as a high dielectric constant (k= 20 ~ 25), wide band gap (5 ~ 7 eV) as well as a close thermal expansion coefficient with Si that results in good thermal stability of the $ZrO_2$/Si structure. During the etching process, plasma etching has been widely used to define fine-line patterns, selectively remove materials over topography, planarize surfaces, and trip photoresist. About the high-k materials etching, the relation between the etch characteristics of high-k dielectric materials and plasma properties is required to be studied more to match standard processing procedure with low damaged removal process. Among several etching techniques, we chose the inductively coupled plasma (ICP) for high-density plasma, easy control of ion energy and flux, low ownership and simple structure. And the $BCl_3$ was included in the gas due to the effective extraction of oxygen in the form of $BCl_xO_y$ compounds. During the etching process, the wafer surface temperature is an important parameter, until now, there is less study on temperature parameter. In this study, the etch mechanism of $ZrO_2$ thin film was investigated in function of $Cl_2$ addition to $BCl_3$/Ar gas mixture ratio, RF power and DC-bias power based on substrate temperature increased from $10^{\circ}C$ to $80^{\circ}C$. The variations of relative volume densities for the particles were measured with optical emission spectroscopy (OES). The surface imagination was measured by scanning emission spectroscope (SEM). The chemical state of film was investigated using energy dispersive X-ray (EDX).

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.16 no.10 s.101
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• pp.1050-1058
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• 2005

This paper presents how to design and implement a very compact, cost effective and broad band receiver module for IEEE 802.16 FWA(Fixed Wireless Access) in the 40 GHz band. The presented receiver module is fabricated in a multi-layer LTCC(Low Temperature Cofired Ceramic) technology with cavity process to achieve excellent electrical performances. The receiver consists of two MMICs, low noise amplifier and sub-harmonic mixer, an embedded image rejection filter and an IF amplifier. CB-CPW, stripline, several bond wires and various transitions to connect each element are optimally designed to keep transmission loss low and module compact in size. The LTCC is composed of 6 layers of Dupont DP-943 with relative permittivity of 7.1. The thickness of each layer is 100 um. The implemented module is $20{\times}7.5{\times}1.5\;mm^3$ in size and shows an overall noise figure of 4.8 dB, an overall down conversion gain of 19.83 dB, input P1 dB of -22.8 dBm and image rejection value of 36.6 dBc. Furthermore, experimental results demonstrate that the receiver module is suitable for detection of Digital TV signal transmitted after up-conversion of $560\~590\;MHz$ band to 40 GHz.

• Proceedings of the Korean Vacuum Society Conference
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• 2014.02a
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• pp.493-493
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• 2014

The manufacturing cost of thin-film photovoltics can potentially be lowered by minimizing the amount of a semiconductor material used to fabricate devices. Thin-film solar cells are typically only a few micrometers thick, whereas crystalline silicon (c-Si) wafer solar cells are $180{\sim}300\mu}m$ thick. As such, thin-film layers do not fully absorb incident light and their energy conversion efficiency is lower compared with that of c-Si wafer solar cells. Therefore, effective light trapping is required to realize commercially viable thin-film cells, particularly for indirect-band-gap semiconductors such as c-Si. An emerging method for light trapping in thin film solar cells is the use of metallic nanostructures that support surface plasmons. Plasmon-enhanced light absorption is shown to increase the cell photocurrent in many types of solar cells, specifically, in c-Si thin-film solar cells and in poly-Si thin film solar cell. By proper engineering of these structures, light can be concentrated and coupled into a thin semiconductor layer to increase light absorption. In many cases, silver (Ag) nanoparticles (NP) are formed either on the front surface or on the rear surface on the cells. In case of poly-Si thin film solar cells, Ag NPs are formed on the rear surface of the cells due to longer wavelengths are not perfectly absorbed in the active layer on the first path. In our cells, shorter wavelengths typically 300~500 nm are also not effectively absorbed. For this reason, a new concept of plasmonic nanostructure which is NPs formed both the front - and the rear - surface is worth testing. In this simulation Al NPs were located onto glass because Al has much lower parasitic absorption than other metal NPs. In case of Ag NP, it features parasitic absorption in the optical frequency range. On the other hand, Al NP, which is non-resonant metal NP, is characterized with a higher density of conduction electrons, resulting in highly negative dielectric permittivity. It makes them more suitable for the forward scattering configuration. In addition to this, Ag NP is located on the rear surface of the cell. Ag NPs showed good performance enhancement when they are located on the rear surface of our cells. In this simulation, Al NPs are located on glass and Ag NP is located on the rear Si surface. The structure for the simulation is shown in figure 1. Figure 2 shows FDTD-simulated absorption graphs of the proposed and reference structures. In the simulation, the front of the cell has Al NPs with 70 nm radius and 12.5% coverage; and the rear of the cell has Ag NPs with 157 nm in radius and 41.5% coverage. Such a structure shows better light absorption in 300~550 nm than that of the reference cell without any NPs and the structure with Ag NP on rear only. Therefore, it can be expected that enhanced light absorption of the structure with Al NP on front at 300~550 nm can contribute to the photocurrent enhancement.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2008.06a
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• pp.169-169
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• 2008

To keep pace with scaling trends of CMOS technologies, high-k metal oxides are to be introduced. Due to their high permittivity, high-k materials can achieve the required capacitance with stacks of higher physical thickness to reduce the leakage current through the scaled gate oxide, which make it become much more promising materials to instead of $SiO_2$. As further studying on high-k, an understanding of the relation between the etch characteristics of high-k dielectric materials and plasma properties is required for the low damaged removal process to match standard processing procedure. There are some reports on the dry etching of different high-k materials in ICP and ECR plasma with various plasma parameters, such as different gas combinations ($Cl_2$, $Cl_2/BCl_3$, $Cl_2$/Ar, $SF_6$/Ar, and $CH_4/H_2$/Ar etc). Understanding of the complex behavior of particles at surfaces requires detailed knowledge of both macroscopic and microscopic processes that take place; also certain processes depend critically on temperature and gas pressure. The choice of $BCl_3$ as the chemically active gas results from the fact that it is widely used for the etching o the materials covered by the native oxides due to the effective extraction of oxygen in the form of $BCl_xO_y$ compounds. In this study, the surface reactions and the etch rate of $Al_2O_3$ films in $BCl_3/Cl_2$/Ar plasma were investigated in an inductively coupled plasma(ICP) reactor in terms of the gas mixing ratio, RF power, DC bias and chamber pressure. The variations of relative volume densities for the particles were measured with optical emission spectroscopy (OES). The surface imagination was measured by AFM and SEM. The chemical states of film was investigated using X-ray photoelectron spectroscopy (XPS), which confirmed the existence of nonvolatile etch byproducts.