• Korean Journal of Materials Research
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• v.7 no.1
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• pp.69-75
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• 1997

Thin films of $Si0_2(1000{\AA})/CoNiCr(400{\AA})/Cr$ were fabricated as a function of Cr thickness by KF magnetron sputtering. The saturation magnetization, coercive force and squareness with annealing temperature for these films were investigated. The values of saturation magnetization of $SiO_2/CoNiCr/Cr$ thin films decreased as the thickness of Cr underlayer increased, whereas coercive force increased as the thickness of Cr underlayer increased. The value of Ms was 600 emu/cc and the maximum value of Hc was 550 Oe. Especially, the value of saturation magnetization was rapidly decreased $SiO_2/CoNiCr/Cr(1700{\AA})$ thin films as the annealing temperature increased And the coercive force increased as the annealing temperature increased When annealing temperature was $650^{\circ}C$, the Ms was reduced to 90 % of the as-deposited film. And the Hc was showed maximum 1600 Oe. It was thought that Cr diffusion into CoNiCr layer reduced the magnetic moment of CoKiCr layer. In addition. Hc might he increased due to grain growth perpendicular to the film plane.

• Journal of the Korean Magnetics Society
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• v.14 no.3
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• pp.99-104
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• 2004

We have studied to understand the barrier and interface qualities and structural changes through measuring temperature dependent spin-polarization as functions of plasma oxidation time and annealing time. Magnetic tunnel junctions consisting of SiO2$_2$/Ta 5/CoFe 17/IrMn 7.5/CoFe 5/Al 1.6-Ox/CoFe 5/Ta 5 (numbers in nm) were deposited and annealed when necessary. A 30 s,40 s oxidized sample showed the lowest spin-polarization values. It is presumed that tunneling electrons were depolarized and scattered by residual paramagnetic Al due to under-oxidation. On the contrary, a 60s, 70 s oxidized sample might have experienced over-oxidation, where partially oxidized magnetic dead layer was formed on top of the bottom CoFe electrode. The magnetic dead layer is known to increase the probability of spin-flip scattering. Therefore it showed a higher temperature dependence than that of the optimum sample (50 s oxidation). temperature dependence of 450 K annealed samples was improved when the as-deposited one compared. But the sample underwent 475 K and 500 K annealing exhibits inferior temperature dependence of spin-polarization, indicating that the over-annealed sample became microstucturally degraded.

• Journal of the Korean earth science society
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• v.30 no.4
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• pp.409-426
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• 2009

In the four sedimentary cores from Yeoja Bay, the analyses of grain size, benthic foraminiferal species compositions, assemblages and statistics were carried out to investigate the effects of late Holocene sea-level change on benthic foraminifera. The core sediments were mainly composed of fine-grained silt and clay. The benthic foraminifera were classified into 27 species of 16 genera, 30 species of 21 genera, 50 species of 29 genera and 52 species of 29 genera in Core YC-1 to 4, respectively. In the result of cluster analysis, it seemed that Group 1 (Core YC-1 and 2) of representative A. beccarii assemblages was deposited in upper bay environment and Group 2 (Core YC-3 and 4) of representative E. clavatum-A. beccarii assemblages was deposited in inner bay environment affected by offshore water. In the result of species composition analysis, the production frequency of A. beccarii was gradually decreased from low layer to upper layer, whereas production frequency of E. clavatum and P.F./T.F. was gradually increased to upward. These change patterns appeared in benthic and planktonic foraminifera seemed to reflect the late Holocene sea-level rise in Yeoja Bay.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.37 no.2
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• pp.208-214
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• 2024

This reports the electrical properties of single-crystal β-gallium oxide (β-Ga₂O₃) vertical Schottky barrier diodes (SBDs) with a different guard ring structure. The vertical Schottky barrier diodes (V-SBDs) were fabricated with two types guard ring structures, one is with metal deposited on the Al₂O₃ passivation layer (film guard ring: FGR) and the other is with vias formed in the Al₂O₃ passivation layer to allow the metal to contact the Ga₂O₃ surface (metal guard ring: MGR). The forward current values of FGR and MGR V-SBD are 955 mA and 666 mA at 9 V, respectively, and the specific on-resistance (R_on,sp) is 5.9 mΩ·cm² and 29 mΩ·cm². The series resistance (R_s) in the nonlinear section extracted using Cheung's formula was 6 Ω, 4.8 Ω for FGR V-SBD, 10.7 Ω, 6.7 Ω for MGR V-SBD, respectively, and the breakdown voltage was 528 V for FGR V-SBD and 358 V for MGR V-SBD. Degradation of electrical characteristics of the MGR V-SBD can be attributed to the increased reverse leakage current caused by the guard ring structure, and it is expected that the electrical performance can be improved by preventing premature leakage current when an appropriate reverse voltage is applied to the guard ring area. On the other hand, FGR V-SBD shows overall better electrical properties than MGR V-SBD because Al₂O₃ was widely deposited on the Ga₂O₃ surface, which prevent leakage current on the Ga₂O₃ surface.

• Proceedings of the IEEK Conference
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• 2000.06b
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• pp.80-83
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• 2000

In this work we deposited Pentacene thin film by OMBD at the various substrate temperatures, deposition rate and the various annealing temperatures for the fabrication of organic TFT and investigated the electrical and film surface characteristics such as sheet resistance, contact resistance and conductance Film thickness were measured by $\alpha$-step and the sheet resistance, contact resistance and conductance were extracted from the relation between the distance of the contacts and the resistance. During the film deposition the substrate temperature was held at 3$0^{\circ}C$, 4$0^{\circ}C$, 5$0^{\circ}C$, 6$0^{\circ}C$, 8$0^{\circ}C$ and 10$0^{\circ}C$, respectively. After the film deposition, Au contact was deposited by thermal evaporation. For the effect of annealing, the thin film was annealed in the nitrogen environment at 10$0^{\circ}C$ and 14$0^{\circ}C$ for 10 seconds, respectively. Film surface characteristics at the vatious substrate temperatures were measured by AFM. The crystallization of thin film was improved as the substrate temperatures were increased and the maximum gram size was 4${\mu}{\textrm}{m}$. The conductivity of thin film was found to be 7.40 $\times$10$^{-7}$ ~ 7.78$\times$10$^{-6}$ S/cm and the minimum contact resistance was 2.5324 ㏁.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.9 no.3
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• pp.576-581
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• 2005

In this paper. the a-Si:H TFT using ferroelectric of $SrTiO_3$ as a gate insulator is fabricated on glass. High k gate dielectric is required for on-current, threshold voltage and breakdown characteristics of TFT Dielectric characteristics of ferroelectric are superior to $SiO_2$ and $Si_3N_4$. Ferroelectric increases on-current and decreases threshold voltage of TFT and also ran improve breakdown characteristics.$SrTiO_4$ thin film is deposited by e-beam evaporation. Deposited films are annealed for 1 hour in N2 ambient at $150^{\circ}C\~600^{\circ}C$. Dielectric constant of ferroelectric is about 60-100 and breakdown field is about IMV/cm. In this paper, the TFT using ferroelectric consisted of double layer gate insulator to minimize the leakage current. a-SiN:H, a-Si:H (n-type a-Si:H) are deposited onto $SrTiO_3$ film to make MFNS(Metal/ferroelectric/a-SiN:H/a-Si:H) by PECVD. In this paper, TFR using ferroelectric has channel length of$8~20{\mu}m$ and channel width of $80~200{\mu}m$. And it shows that drain current is $3.4{\mu}A$at 20 gate voltage, $I_{on}/I_{off}$ is a ratio of $10^5\~10^8,\;and\;V_{th}$ is$4\~5\;volts$, respectively. In the case of TFT without having ferroelectric, it indicates that the drain current is $1.5{\mu}A$ at 20gate voltage and $V_{th}$ is $5\~6$ volts. If properties of the ferroelectric thin film are improved, the performance of TFT using this ferroelectric thin film can be advanced.

• Korean Journal of Materials Research
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• v.11 no.1
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• pp.20-26
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• 2001

The deposition characteristics of MOCVO Cu using the (hfac)Cu(I) (1,5-DMCOD)(1,1,1,5,5,5-hexafluoro-2,4-pentanedionato Cu(I) 1,5-dimethyl-cyclooctadine) as a precursor have been investigated in terms of the effects of hydrogen and H(hfac) ligand addition with He carrier gas. MOCVD Cu using a Helium carrier gas showed a low deposition rate (20~$125{\AA}/min$) at the substrate temperature range of 180~$230^{\circ}C$. Moreover, the Cu film deposited at 19$0^{\circ}C$ was very thin (~$700{\AA}$) and showed the lowest resistivity value of $2.8{\mu}{\Omega}-cm$. The deposition rate of MOCVD Cu using $H_2$or H(hfac) addition was significantly enhanced especially at the low temperature region (180~$190^{\circ}C$). Furthermore, thinner Cu films (~$500{\AA}$) provided low resistivity (3.6~$2.86{\mu}{\Omega}-cm$). From surface reflectance measurement, very thin films deposited by using different gas system revealed good surface morphology comparable with sputtered Cu film ($300^{\circ}C$, vacuum-anneal). Hence, Cu film using (hfac)Cu(1,5-DMCOD) as a precursor is expected as a good seed layer in the electrochemical deposition process for Cu metallization.

• Korean Journal of Materials Research
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• v.5 no.7
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• pp.835-841
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• 1995

The deposition properties of Si$_3$N$_4$ deposited by low pressure chemical vapor deposition were studied to evaluate Si$_3$N$_4$as part of multi-layer coatings for anti-oxidation and anti-wear coating of graphite in the propellant-burning environment. Si$_3$N$_4$was deposited on the pack-SiC coated graphite and the tendencies of deposition rate and surface morphology changes with temperatures and reaction gas ratios were investigated. In low deposition temperatures the deposition rate increased tilth increasing temperature but in high temperatures the deposition rate decreased with increasing temperature. The grain size of Si$_3$N$_4$decreased with increasing temperature. In condition that the range of reaction gas ratios is 20$\leq$NH$_3$/SiH$_4$$\leq$40, the deposition rate and surface morphology did not change. The Si$_3$N$_4$deposited at 800~130$0^{\circ}C$ was amorphous, and by post-annealing at 130$0^{\circ}C$ in a $N_2$ambient, the Si$_3$N$_4$crystalized.

• Analytical Science and Technology
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• v.30 no.5
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• pp.270-278
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• 2017

The absorption of blood onto the surfaces of white cotton, polyester, rayon, and nylon fabrics was studied. Different categories of fabrics (woven and knitted) with diverse thickness, were manually folded twice to obtain four fabric layers, and $100{\mu}L$ of human blood was dropped onto the surface of the fabrics. The amount of blood that penetrated the fabric layer and the shape of bloodstain observed on the fabrics were influenced by the chemistry, thickness, and texture of the fabric. The blood bearing fabrics were left to dry for 3 days, washed by hand using tap water, and Lumiscene was then sprayed onto the fabrics to enhance the latent bloodstain for comparison of the shape of the bloodstain before and after washing by hand. The features of the bloodstain after washing varied greatly with the recipient fabrics. Additionally, stronger luminescence was observed at the surface where the blood was deposited compared to the background. However, it was confirmed that physical contact during the washing can deform the original shape of the bloodstain. The effect of the drying time on the bloodstain after hand washing was also studied. $100{\mu}L$ of blood was dropped on the surfaces of the fabrics and dried for 0, 1, 12, 24, 72 h, and 7 days, then washed by hand, before the bloodstain was enhanced with Lumiscene. The results of this experiment indicated that the increased drying time induces stronger chemiluminescence of Lumiscene. However, after drying of the bloodstain for 7 days, the luminescence of the bloodstain was decreased at the blood deposited site and increased around the blood deposited site.

• Korean Journal of Materials Research
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• v.10 no.12
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• pp.807-811
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• 2000

CeO$_2$ and SrBi$_2$Ta$_2$O$_{9}$ (SBT) thin films for MFISFET (Metal-ferroelectric-insulator-semiconductor-field effect transistor) were deposited by r.f. sputtering and pulsed laser ablation method, respectively. The effects of sputtering gas ratio(Ar:O$_2$) during deposition for CeO$_2$ films were investigated. The CeO$_2$ thin films deposited on Si(100) substrate at $600^{\circ}C$ exhibited (200) preferred orientation. The preferred orientation, Brain size and surface roughness of films decreased with increasing oxygen to argon gas ratio. The films deposited under the condition of Ar:O$_2$= 1 : 1 showed the best C- V characteristics. The leakage current of films showed the order of 10$^{-7}$ ~10$^{-8}$ A at 100kV/cm. The SBT thin films on CeO$_2$/Si substrate showed dense microstructure of polycrystalline phase. From the C-V characteristics of MFIS structure with SBT film annealed at 80$0^{\circ}C$, the memory window width was 0.9V at 5V The leakage current density of Pt/SBT/CeO$_2$/Si structure annealed at 80$0^{\circ}C$ was 4$\times$10$^{-7}$ /$\textrm{cm}^2$ at 5V.