• Journal of the Institute of Electronics Engineers of Korea SD
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• v.47 no.8
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• pp.1-6
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• 2010

We report on the electrical properties of Ti/Al/Ni/Au (20 nm/ 150 nm/ 30 nm/ 100 nm) Ohmic contacts and the anisotropic conductivity of n-type ${\alpha}$-plane ([11-20]) GaN grown on $\gamma$-plane ([1-102]) sapphire substrates. The Ti/Al/Ni/Au Ohmic contacts and their sheet resistances are characterized by using the transfer length method (TLM) as a function of azimuthal angles. It is found that the specific contact resistance does not depend on the axis orientation and there are significant electrical anisotropy in ${\alpha}$-plane GaN films on $\gamma$-plane sapphire substrates, and the sheet resistance varies with azimuthal angles. The sheet resistance values in the direction parallel to m-axis [1-100] are 25% ~ 75% lower than those parallel to c-axis [0001] directions. Thus, Basal stacking faults (BSFs) are offered as a feasible source of the anisotropic mobility in defected m-axis direction because the band-edge discontinuities owing to the differential band gap structure.

• Korean Journal of Metals and Materials
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• v.47 no.5
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• pp.322-329
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• 2009

60 nm- and 20 nm-thick hydrogenated amorphous silicon (a-Si:H) layers were deposited on 200 nm $SiO_2/Si$ substrates using ICP-CVD (inductively coupled plasma chemical vapor deposition). A 10 nm-Ni layer was then deposited by e-beam evaporation. Finally, 10 nm-Ni/60 nm a-Si:H/200 nm-$SiO_2/Si$ and 10 nm-Ni/20 nm a-Si:H/200 nm-$SiO_2/Si$ structures were prepared. The samples were annealed by rapid thermal annealing for 40 seconds at $200{\sim}500^{\circ}C$ to produce $NiSi_x$. The resulting changes in sheet resistance, microstructure, phase, chemical composition and surface roughness were examined. The nickel silicide on a 60 nm a-Si:H substrate showed a low sheet resistance at T (temperatures) >$450^{\circ}C$. The nickel silicide on the 20 nm a-Si:H substrate showed a low sheet resistance at T > $300^{\circ}C$. HRXRD analysis revealed a phase transformation of the nickel silicide on a 60 nm a-Si:H substrate (${\delta}-Ni_2Si{\rightarrow}{\zeta}-Ni_2Si{\rightarrow}(NiSi+{\zeta}-Ni_2Si)$) at annealing temperatures of $300^{\circ}C{\rightarrow}400^{\circ}C{\rightarrow}500^{\circ}C$. The nickel silicide on the 20 nm a-Si:H substrate had a composition of ${\delta}-Ni_2Si$ with no secondary phases. Through FE-SEM and TEM analysis, the nickel silicide layer on the 60 nm a-Si:H substrate showed a 60 nm-thick silicide layer with a columnar shape, which contained both residual a-Si:H and $Ni_2Si$ layers, regardless of annealing temperatures. The nickel silicide on the 20 nm a-Si:H substrate had a uniform thickness of 40 nm with a columnar shape and no residual silicon. SPM analysis shows that the surface roughness was < 1.8 nm regardless of the a-Si:H-thickness. It was confirmed that the low temperature silicide process using a 20 nm a-Si:H substrate is more suitable for thin film transistor (TFT) active layer applications.

• Journal of the Korean institute of surface engineering
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• v.46 no.3
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• pp.116-119
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• 2013

To improve the corrosion resistance of an electrogalvanized steel sheet, we deposited magnesium film on it using a vacuum evaporation method and annealed the films at $250-330^{\circ}C$. The zinc-magnesium alloy is consequently formed by diffusion of magnesium into the zinc coating. From the anodic polarization test in 3% NaCl solution, the films annealed at $270-310^{\circ}C$ showed better corrosion resistance than others. In X-ray diffraction analysis, $ZnMg_2$ was detected through out the temperature range, whereas $Mg_2Zn_{11}$ and $FeZn_{13}$ were detected only in the film annealed at $310^{\circ}C$. The depth composition profile showed that the compositions of Mg at $270-290^{\circ}C$ are evenly and deeply distributed in the film surface layer. These results demonstrate that $270-290^{\circ}C$ is a proper temperature range to produce a layer of $MgZn_2$ intermetallic compound to act as a homogeneous passive layer.

• Proceedings of the Korean Vacuum Society Conference
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• 2016.02a
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• pp.340-340
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• 2016

We have prepared alumina (Al2O3) doped zinc oxide (AZO) films by DC magnetron sputtering (MS) technique and obtained higher self surface texturing at a high target angle (f). We have characterized the films and applied it as a front electrode of a single junction amorphous silicon solar cell. At a lower f the deposited films show higher values of optical gap (Eg), charge carriers mobility & concentration, crystallite grain size and wider wavelength range of transmission. At higher target angle the sheet resistance, surface roughness, haze factor etc for the films increase. For f=72.5o the haze factor for diffused transmission becomes 6.46% at 540 nm wavelength. At f=72.5o the material shows a reduction in crystallinity and evolution of a hemispherical-type sub-micron surface textures. A Monte Carlo method (MCM) of simulation of the AZO film deposition shows that such an enhanced self-surface texturing of the films at higher f is possible.

• Journal of the Korean Applied Science and Technology
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• v.32 no.2
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• pp.232-239
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• 2015

In this paper, we study the dry transfer technology utilizing PDMS (Polydimethylsiloxane) stamp of a large single-layer graphene grown on Cu-foil as catalytic metal by using Chemical Vapor Deposition (CVD). By changing the surface property of the target substrate through $UV/O_3$ treatment, we can transfer the graphene on the target substrate while minimizing mechanical damages of graphene layer. Multi-layer (1~4 layers) graphene was stacked on $SiO_2/Si$ wafer successfully by repeating thetransfer method/process and then optical transmittance and sheet resistance of graphene layers have been measured as a quality assessment.

• Journal of the Korean Ceramic Society
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• v.52 no.4
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• pp.290-293
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• 2015

The properties of the IZTO thin films on the glass were studied with a variation of the $SiO_2$ buffer layer thickness. $SiO_2$ buffer layers were deposited by plasma-enhanced chemical vapor deposition (PECVD) on the glass, and the In-Zn-Tin-Oxide (IZTO) thin films were deposited on the buffer layer by RF magnetron sputtering. All the IZTO thin films with the $SiO_2$ buffer layer are shown to be amorphous. Optimum $SiO_2$ buffer layer thickness was obtained through analyzing the structural, morphological, electrical, and optical properties of the IZTO thin films. As a result, the IZTO surface roughness is 0.273 nm with a sheet resistance of $25.32{\Omega}/sq$ and the average transmittance is 82.51% in the visible region, at a $SiO_2$ buffer layer thickness of 40 nm. The result indicates that the uniformity of surface and the properties of the IZTO thin film on the glass were improved by employing the $SiO_2$ buffer layer and the IZTO thin film can be applied well to the transparent conductive oxide for display devices.

• Journal of the Korean institute of surface engineering
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• v.38 no.1
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• pp.28-36
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• 2005

In this study, the reflow characteristics of copper thin films which is expected to be used as interconnection materials in the next generation semiconductor devices were investigated. Cu thin films were deposited on the TaN diffusion barrier by metal organic chemical vapor deposition (MOCVD) and annealed at the temperature between 250℃ and 550℃ in various ambient gases. When the Cu thin films were annealed in the hydrogen ambience compared with oxygen ambience, sheet resistance of Cu thin films decreased and the breakdown of TaN diffusion barrier was not occurred and a stable Cu/TaN/Si structure was formed at the annealing temperature of 450℃. In addition, reflow properties of Cu thin films could be enhanced in H₂ ambient. With Cu reflow process, we could fill the trench patterns of 0.16～0.24 11m with aspect ratio of 4.17～6.25 at the annealing temperature of 450℃ in hydrogen ambience. It is expected that Cu reflow process will be applied to fill the deep pattern with ultra fine structure in metallization.

• The Korean Journal of Ceramics
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• v.3 no.2
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• pp.88-91
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• 1997

The diamondlike (DLC) films were deposited by RF plasma CVD system which had cathode consisting of mesh sheet, for the purpose of a protection from wear of OPC surface of the electrophotographic photosensitive body. Material charateristics and tribological properties of the films were also investigated and finally copying performance was evaluated with DLC deposited OPC samples. The surface resistance of the DLC film unaffected by the surface potential of the OPC was about $10^{11}{\Omega}$ and its hardness was about 1200 kg/$\textrm{mm}^2$. In this case the film showed typical material strcture of dimondlike hydrocarbon. The friction coefficient of the film was lowered to 0.2~0.3 at the optimum condition in this investigation and their wear resistant was inproved by DLC-deposition on the OPC surface. DLC-deposited OPC samples with a good copying performance without image flow and draft could be obtained at some depositing conditions.

• Proceedings of the KIEE Conference
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• 1992.07b
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• pp.847-849
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• 1992

Fluorine-doped ($SnO_2$:F) thin films obtained by pyrosol deposition method have been exposed to R.F. excited pure hydrogen plasma under the following conditions; substrate temperature of 200$^{\circ}C$, $H_2$ pressure of 1 Torr, R.F. input power of 50 mW/$\textrm{cm}^{2}$, $H_2$ flow rate of 30cc/min and exposure time of 15-600 seconds. It is found that the sheet resistance of the films remains unchanged or rather slightly reduces for initial exposure time of 30-60 seconds, but increases sharply with further increasing the exposure time. The optical transmittance of $SnO_2$:F films slows a rapid fall with increasing exposure time except for a film obtained with a solution having $CH_3OH/H_2O$ mol ratio of 2.65, its degradations at the exposure time of 30-60 seconds are about 7-15%. In addition, the exposure of the films to hydrogen plasma atmosphere leads to remarkable changes in the microstructure and chemical composition, which should be attributed to the reduction of $SnO_2$ to SnO and to elemental Sn.

• Journal of the Korean Society for Heat Treatment
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• v.28 no.6
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• pp.291-295
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• 2015

IGZO single layer and $IGZO/TiO_2$ bi-layered films were deposited on glass substrate at room temperature with radio frequency magnetron sputtering to investigate the effect of $TiO_2$ buffer layer on the electrical and optical properties of the films. For all deposition, the thickness of IGZO and $TiO_2$ Buffer layer was kept at 100 and 5 nm, respectively. In a comparison of figure of merit, IGZO films with a 5-nm-thick $TiO_2$ buffer layer show the higher figure of merit ($8.40{\times}10^{-5}{\Omega}^{-1}$) than that of the IGZO single layer films ($6.23{\times}10^{-5}{\Omega}^{-1}$) due to the enhanced optical transmittance and the decreased sheet resistance of the films. The observed results mean that a 5 nm thick $TiO_2$ buffer layer in the $IGZO/TiO_2$ films results in better electrical and optical performance than conventional IGZO single layer films.