• 한국초전도학회:학술대회논문집
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• v.9
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• pp.152-159
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• 1999

YBa$_2Cu_3O_{7-{\delta}}$ (YBCO) films grown on CeO$_2$-buffered r-cut sapphire substrates (CbS's) were prepared and their structural and electrical properties were measured. Post-annealed CeO$_2$ films were used as buffer layers for the experiments. It turned out that the YBCO films grown on post-annealed CbS's had the rms roughness of less than 20 ${\AA}$ and peak-to-peak roughness of about 30 ${\AA}$ when the YBCO film thickness was 3000 ${\AA}$. Meanwhile, YBCO films on in-situ grown CeO$_2$ buffer layers on r-cut sapphire substrates appeared to have the peak-to-peak roughness of more than 450 ${\AA}$. X-ray diffraction data revealed that the YBCO flms were epitaxially grown along the c-axis with the typical FWHM of(005) ${\theta}$ -2 ${\theta}$ peak about 0. 16 $^{\circ}$ and ${\Delta}$ ${\omega}$ of the (005) peak about 0.5 $^{\circ}$. T$_c$ > 87 K, ${\Delta}$T < 1 K and R(look)/R(100K) ${\ge}$3 were observed from the YBCO films. Applicability of the YBCO films for high-frequency applications was described.

• Korean Journal of Materials Research
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• v.10 no.6
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• pp.437-444
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• 2000

We investigated the effect of substrate temperature, chemical composition and post-deposition heat-treatment on the crystal structure and electrical transport of $La_{1-x}Sr_xMnO_{3-{\delta}}$(0.19${\leq}x{\leq}$0.31) thin films. As-prepared $La_{1-x}Sr_xMnO_{3-{\delta}}$ films grown at $500^{\circ}C$ by sputter techniques were found to have the pseudo-tetragonal system(a/c=0.97) and a highly preferential <001> orientation. The films were changed to be of the cubic system by post-deposition annealing at around $900^{\circ}C$. A main target of $La_{0.67}Sr_{0.33}MnO_3$ as well as auxliary targets of $La_{0.3}Sr_{0.7}MnO_3$ ceramics were co-sputtered to control the chemical composition of the film. The Sr content(x) of the film ranged from 0.19 to 0.31, depending on the number of the auxiliary target. When x increased from 0.19 to 0.31, the electrical resistivity of the film decreased and the transition temperature between metal and semiconductor shifted to higher temperature. With a magnetic field of 0.18 T, the magneto-resistance ratio (MR(%) = (${\rho}_o-{\rho}_H/{\rho}_H$) of the $La_{0.69}Sr_{0.31}MnO_3$ thin film was about 390%.

• Journal of the Microelectronics and Packaging Society
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• v.28 no.4
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• pp.41-45
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• 2021

In this study, in order to secure the high reliability of the memristor, we adopted a patterned lithium filament seed layer as the main agent for resistive switching (RS) characteristic on the 30 nm thick ZrO₂ thin film at the device manufacturing stage. Lithium filament seed layer with a thickness of 5 nm and an area of 5 ㎛ × 5 ㎛ were formed on the ZrO₂ thin film, and various electrode areas were applied to investigate the effect of capacitance on filament type memristive behavior in the parallel memristive circuit of memristor and capacitor. The RS characteristics were measured in the samples before and after 250℃ post-annealing for lithium metal diffusion. In the case of conductive filaments formed by thermal diffusion (post-annealed sample), it was not available to control the filament by applying voltage, and the other hand, the as-deposited sample showed the reversible RS characteristics by the formation and rupture of filaments. Finally, via the comparison of the RS characteristics according to the electrode area, it was confirmed that capacitance is an important factor for the formation and rupture of filaments.

• Journal of Magnetics
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• v.11 no.1
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• pp.16-19
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• 2006

$2-\mu{m}$ thick GaN epilayer was prepared, and 80 KeV $Co^{-}$ ions with a dose of $3X10^{16}\;cm^{-2}$ were implanted into GaN at $350^{\circ}C$. The implanted samples were post annealed at $700^{\circ}C$. We have investigated the magnetic and structural properties of Co ion-implanted GaN by various measurements. HRXRD results did not show any peaks associated with second phase formation and only the diffraction from the GaN layer and substrate structure were observed. SIMS profiles of Co implanted into GaN before and after annealing at $700^{\circ}C$ have shown a projected range of $\sim390\AA$ with 7.4% concentration and that there is little movement in Co. AFM measurement shows the form of surface craters for $700^{\circ}C$-annealed samples. The magnetization curve and temperature dependence of magnetization taken in zero-field-cooling (ZFC) and field-cooling (FC) conditions showed the features of superparamagnetic system in film. XPS measurement showed the metallic Co 2p core levels spectra for $700^{\circ}C$-annealed samples. From this, it could be explained that magnetic property of our films originated from Co magnetic clusters.

• Journal of the Korean Society for Heat Treatment
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• v.24 no.2
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• pp.87-91
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• 2011

Single layer Sn doped $In_2O_3$ (ITO) films and ITO 50 nm / Au 10 nm / ITO 40 nm (IAI) multilayer films were prepared with electron beam assisted magnetron sputtering on glass substrates. The effects of the Au interlayer, post-deposition atmosphere annealing and intense electron irradiation on the methanol gas sensitivity were investigated at room temperature. As deposited ITO films did not show any diffraction peaks in the XRD pattern, while the IAI films showed the diffraction peak for $In_2O_3$ (400). In this study, the gas sensitivity of ITO and IAI films increased proportionally with the methanol vapor concentration and an intense electron beam irradiated IAI film shows the higher sensitivity than the others film. From the XRD pattern, it is supposed that increased crystallization promotes the gas sensitivity. This approach is promising in gaining improvement in the performance of IAI gas sensors used for the detection of methanol vapor at room temperature.

• Proceedings of the Korean Vacuum Society Conference
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• 2012.08a
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• pp.376-376
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• 2012

Semiconductor nanowires (NWs) are future building block for nano-scale devices. Especially, Ge NWs are fascinated material due to the high electrical conductivity with high carrier mobility. It is strong candidate material for post-CMOS technology. However, thermal stability of Ge NWs are poor than conventional semiconductor material such as Si. Especially, when it reduced size as small as nano-scale it will be melted around CMOS process temperature due to the melting point depression. Recently, Graphene have been intensively interested since it has high carrier mobility with single atomic thickness. In addition, it is chemically very stable due to the $sp^2$ hybridization. Graphene films shows good protecting layer for oxidation resistance and corrosion resistance of metal surface using its chemical properties. Recently, we successfully demonstrated CVD growth of monolayer graphene using Ge catalyst. Using our growth method, we synthesized Ge/graphene core/shell (Ge@G) NW and conducted it for highly thermal stability required devices. We confirm the existence of graphene shell and morphology of NWs using SEM, TEM and Raman spectra. SEM and TEM images clearly show very thin graphene shell. We annealed NWs in vacuum at high temperature. Our results indicated that surface melting phenomena of Ge NWs due to the high surface energy from curvature of NWs start around $550^{\circ}C$ which is $270^{\circ}C$ lower than bulk melting point. When we increases annealing temperature, tip of Ge NWs start to make sphere shape in order to reduce its surface energy. On the contrary, Ge@G NWs prevent surface melting of Ge NWs and no Ge spheres generated. Furthermore, we fabricated filed emission devices using pure Ge NWs and Ge@G NWs. Compare with pure Ge NWs, graphene protected Ge NWs show enhancement of reliability. This growth approach serves a thermal stability enhancement of semiconductor NWs.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.30 no.5
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• pp.183-188
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• 2020

Lead zinc niobate (PZN)-added lead zirconate titanate (PZT) thick films with thickness of 5~10 ㎛ were fabricated on silicon and sapphire substrates using aerosol deposition method. The contents of PZN were varied from 0 %, 20 % and to 40 %. The PZN-added PZT film showed poorer electrical properties than pure PZT film when the films were coated on silicon substrate and annealed at 700℃. On the other hand, the PZN-added PZT film showed higher remanent polarization and dielectric constant values than pure PZT film when the films were coated on sapphire and annealed at 900℃. The ferroelectric and dielectric characteristics of 20 % PZN-added PZT films annealed at 900℃ were compared with the result values obtained from bulk ceramic specimen with same composition sintered at 1200℃. As annealing temperature increased, dielectric constant increased. These came from enhanced crystallization and grain growth by post heat treatment.

• Proceedings of the IEEK Conference
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• 2004.06b
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• pp.391-394
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• 2004

In this study, highly thermal stable Ni Germanosilicide has been utilized using NiPt alloy and novel NiPt/Co/TiN tri-layer. And, the Ni Germanosilicide Properties were characterized according to different Ge ratio (x) in $Si_{l-x}Ge_x$ for the next generation CMOS application. The sheet resistance of Ni Germanosilicide utilizing pure-Ni increased dramatically after the post-silicidation annealing at $600^{\circ}C$ for 30 min. Moreover, more degradation was found as the Ge fraction increases. However, using the proposed NiPt/Co/TiN tri-layer, low temperature silicidation and wide range of RTP process window were achieved as well as the improvement of the thermal stability according to different Ge fractions by the subsequent Co and TiN capping layer above NiPt on the $Si_{l-x}Ge_x$. Therefore, highly thermal immune Ni Germanosilicide up to $600^{\circ}C$ for 30 min is utilized using the NiPt/Co/TiN tri-layer promising for future SiGe based ULSI technology.

• Journal of the Microelectronics and Packaging Society
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• v.6 no.1
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• pp.31-37
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• 1999

In this study, the thermal property and adhesion of the electroless-deposited Cu thin film were investigated. The multilayered structure of Cu /TaN /Si was fabricated by electroless-depositing the Cu thin layer on the TaN diffusion barrier which was deposited by MOCVD on the Si substrate. The thermal stability was investigated by measuring the resistivity as post-annealing temperature for the multilayered Cu /TaN /Si specimen which was annealed at atmospheres of $H_2$and Ar gases, respectively. The adhesion strength of Cu films was evaluated by the scratch test. The adhesion of the electroless-deposited Cu film was compared with other deposition methods of thermal evaporation and sputtering. The scratch test showed that the adhesion of electroless plated Cu film on TaN was better than that of sputtered Cu film and evaporated Cu film.

• Journal of the Microelectronics and Packaging Society
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• v.22 no.4
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• pp.111-115
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• 2015

To improve the efficiency of the Si solar cell, high minority carrier life time is required. Therefore, the passivation technology is important to eliminate point defects on the silicon surface, causing the loss of minority carrier recombination. PECVD or post-annealing of thermally-grown $SiO_2$ is commonly used to form the passivation layer, but a high-temperature process and low thermal stability is a critical factor of low minority carrier lifetime. In this study, atomic layer deposition was used to grow the $Al_2O_3$ passivation layer at low temperature process. $Al_2O_3$ was selected as a passivation layer which has a low surface recombination velocity because of the fixed charge density. For the high charge density, an improved minority carrier lifetime, and a low surface recombination, nitrogen was doped in the $Al_2O_3$ thin film and the improvement of passivation was studied.