• The Transactions of the Korean Institute of Electrical Engineers C
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• v.48 no.1
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• pp.1-11
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• 1999

Hyrdogenated amorphous silicon thin film transistors are used as a pixel switching device of TFT-LCDs and very active research works on a-Si:H TFTs are in progress. Further development of the technology based on a-Si:H TFTs depends on the increased understanding of the device physics and the ability to accurately simulate the characteristics of them. A two-dimensional device simulator based on the realistic and flexible physical models can guide the device designs and their optimizations. A non-uniform finite-difference TFT Simulation Program, TFT2DS has been developed to solve the electronic transport equations for a-Si:H TFTs. In TFT2DS, many of the simplifying assumptions are removed. The developed simulator was used to calculate the transfer and output characteristics of a-Si:H TFTs. The measured data were compared with the simulated ones for verifying the validity of TFT2DS. Also the transient behaviors of a-Si:H TFTs were calculated even if the values of the related parameters are not accurately specified.

• Journal of the Korean institute of surface engineering
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• v.29 no.6
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• pp.797-802
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• 1996

Hydrogenated amorphous silicon carbide (a-SiC:H) films have been deposited on unheated substrates by low frequency (50Hz) plasma using $SiH_4+CH_4+H_2$ gas mixtures. Deposition rate, refractive index, optical band gap, Vickers hardness and IR spectrum of the deposited a -SiC:H films have been measured for various rations of gas flow rates k(=$CH_4/SiH_4$, 0.5k4) with a constant $H_2$ flow rate (100sccm). As k increases, the deposition rate of the a-SiC:H films increases up to the maximum value of about 220nm/h at k=2.5, and then it decreases. The refractive index of the films was 2.6 for k=2.5, while the optical band gap of the films was 3.3eV for k=2.2. The maximum value of Vickers hardness of the films was 1500Hv at k=1. The infrared transmission measurement shows that the films contain both Si-C and Si-$CH_3$ bonds.

• Journal of Powder Materials
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• v.17 no.5
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• pp.359-364
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• 2010

In an attempt to optimize the magnetic properties of (Nd, Dy)-Fe-B sintered magnets, hydrogenation and post-sintering heat treatment processes were investigated at various hydrogenation temperatures and heat treatment temperatures. The coercivity of (Nd, Dy)-Fe-B sintered magnets hydrogenated at $400^{\circ}C$ increased to about 1.2 kOe without any detrimental effect on the remanence. Moreover, the coercivity of the magnets was enhanced further by a consecutive $2^{nd}$ and $3^{rd}$ step heat treatment. These results eventually leaded to the reduction of the Dy content in a high coercive (> 30 kOe) (Nd, Dy)-Fe-B sintered magnets, as much as 10%.

• Tribology and Lubricants
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• v.15 no.4
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• pp.335-342
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• 1999

Corrosion of the disk has been an ongoing concern for the manufacturers of hard disk drives. With the advent of magnetoresistive (MR) head, very low levels of corrosion and contamination become more critical since the raised defects and corrosion products on the disk surface-anything that heats the MR sensor due to the contact-can distort the output signal of the head. This phenomenon is called as thermal asperity. In this paper, the effect of corrosion as a form of Co migration on the occurrence of thermal asperity in MR drives was investigated. The corrosion test at high temperature (60$^{\circ}C$) and high relative humidity (80%) was emphasized in this study and the testing results at ambient condition were compared. The corrosion on the disks was characterized as the amount of Co ion migration using an ion chromatography (IC) and a time-of-flight secondary ion mass spectroscopy (TOF-SIMS). It is proved that corrosion on the disk surface after storage testing is closely correlated to the amount of Co ions migration from the magnetic layer to disk surfaces and higher Co migration causes more thermal asperities in the drive. In order to reduce Co migration, several methods such as burnishing process and structure of the carbon overcoat were investigated. It is found that the hydrogenated carbon overcoat shows the least Co migration among different types of overcoat layer. However, the most effective way to reduce Co migration is the application of Cr layer between the overcoat and the magnetic alloy layer.

• Proceedings of the Korean Vacuum Society Conference
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• 2012.02a
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• pp.204-204
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• 2012

Peierls instability and spin ordering of zigzag graphene nanoribbons (GNR) created on a fully hydrogenated graphene (graphane) are investigated as a function of their width using first-principles density-functional calculations within the generalized-gradient approximation. For the width containing a single zigzag C chain (N=1), we find the presence of a Peierls instability with a bond alternated structure. However, for width greater than N=1, the Peierls distortion is weakened or disappears because of the incommensurate feature of Fermi surface nesting due to the interaction of C chains. Instead, there exists the antiferromagnetic (AFM) spin ordering in which the edge states are ferromagnetically ordered but the two ferromagnetic (FM) edges are antiferromagnetically coupled with each other, showing that electron-lattice coupling and spin ordering in GNR are delicately competing at an extremely thin width of N=2. It is found that, as the width of GNR increases, the energy gain arising from spin ordering is enhanced, but the energy difference between the AFM and FM (where two edge states are ferromagnetically coupled with each other) orderings decreases.

• 한국정보디스플레이학회:학술대회논문집
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• 2005.07a
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• pp.272-275
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• 2005

The high stability of a-Si:H TFTs device is studied with different deposited conditions of $SiN_x$ films by PECVD. The process parameters of $N_2$, $NH_3$ gas flow rate, RF power, and pressure s of hydrogenated amorphous silicon nitride are taken into account and analyzed by Taguchi experimental design method. The $NH_3$ gas flow rate and RF power are two major factors on the average threshold voltage and the a-SiNx:H film's structure. The hydrogen contents in $SiN_x$ films were measured by FTIR using the related Si-H/N-H bonds ratio in $a-SiN_x:H$ films. After the 330,000 sec gate bias stress is applied, the threshold voltages ($V_th$) shift less than 10%. This result indicates that the highly stable a-Si:H TFTs device can be fabricated with optimum gate $SiN_x$ insulator.

• Journal of Magnetics
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• v.4 no.2
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• pp.46-51
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• 1999

A solid-HDDR characteristics of the Nd-Fe-B-type alloys magnetic properties of the solid-HDDR treated materials have been investigated using three types of alloys; $Nd_{15}Fe_{77}B_8 (alloy A), Nd_{16}Fe_{75.9}B_8Zr_{0.1}(alloy B), and Nd_{12.6}Fe_{68.7}Co_{11.6}B_8Ga_{1.0}Zr_{0.1} $(alloy C). It has been found that the four-components alloy B and six-components alloy C have showed higher hydrogenation temperatures than the ternary alloy A. The alloys A and B appeared to absorb more hydrogen gas more rapidly as well compared to the alloy C. The disproportionation temperature of hydrogenated materials was exhibited no significant difference among the alloys. The thermal stability of the hydrided materials of the three types of alloys was found to become more stable in order of number of components. The disproportionation and the recombination kinetics were significantly sluggish in the solid-HDDR manner with respect to the conventional manner. Some degree of anisotropic nature was found to exist in the ingot and this anisotropic nature was retained even after the solid-HDDR treatment. It was suggested the solid-HDDR treatment may possibly be used for a preparation of an isotropic or anisotropic Nd-Fe-B-type cast magnets.

• Solar Energy
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• v.5 no.2
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• pp.46-53
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• 1985

Hydrogenated amorphous silicon solar cells which are fabricated by photo-chemical vapor deposition (photo-CVD) system has been investigated. In the photo-CVD system which consists of three separate reaction chambers, low-pressure mercury lamp has been used as a light source. The main reactant ($Si_2H_6/He$) gases which are premixed with a small amount of mercury vapor in a mercury-vaporizer kept at $50^{\circ}C$ have been used. Using $C_2H_2$ and $SiH_2(CH_3)_2$ as the carbon source, p-type wide band gap a-SiC:H films have been obtained. The result has been found that the undoped layers of the pin/substrate solar cells are influenced by the residual impurities, such as phosphorus and boron during the deposition process. By minimizing the effect of the impurities in the i-layer and optimizing conditions at the p-layer and p/i interface, the energy conversion efficiency of 9.61 % under AM-1 ($100mW/Cm^2$) has been achieved for pin/substrate solar cells illuminated through their p-layers, using the three separate reaction chamber apparatus. It is expected that a-SiC:H solar cells with the energy conversion efficiency over 10% have been fabricated by Photo-CVD method.

• Current Photovoltaic Research
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• v.5 no.4
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• pp.113-121
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• 2017

The researches on the silicon-based thin films are being actively carried out. The silicon-based thin films can be made as amorphous, microcrystalline and mixed phase and it is known that the optical bandgap can be controlled accordingly. They are suitable materials for the fabrication of single junction, tandem and triple junction solar cells. It can be used as a doping layer through the bonding of boron and phosphorus. The carbon and oxygen can bond with silicon to form a wide range of optical gap. Also, The optical gap of hydrogenated amorphous silicon germanium can be lower than that of silicon. By controlling the optical gaps, it is possible to fabricate multi-junction thin film silicon solar cells with high efficiencies which can be promising photovoltaic devices.

• Journal of the Korean Applied Science and Technology
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• v.10 no.2
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• pp.57-63
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• 1993

This study investigated the reaction and variation of fatty acid composition of soybean oil when it is partially hydrogenated until its iodine value(IV) shifts from 134 to 110. Experment was conducted under he outlined reactiion conditions of temperatures(170, 190 and $210^{\circ}C$), pressure(1.3, 2.8 and 4.2atm) and nickel(Ni) catalyst concentraons(0.005, 0.01, 0.05, and 0.1%) with a fixed agitation(350rpm). Further investigation was also made to see the effect of added lecithin on hydrogenation. When reaction temperature was gradually raised and catalyst concentration increased, the content of linolenic acid progressively decreased while the increase amount of stearic acid reduced(P<0.05). On he other hand when pressure gradually increased, the contents of stearic acid and linolenic acid increased(P<0.05). Meanwhile when lecithin was added, reaction time increased by two to six times more than when no addition was made.