• Journal of the Korean Vacuum Society
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• v.7 no.3
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• pp.267-267
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• 1998

The fluorine doped silicon oxide (SiOF) intermetal dielectric (IMD) films have been of interest due to their lower dielectric constant and compatibility with existing process tools. However instability issues related to bond and increasing dielectric constant to water absorption when the SiOF films was exposured to atmospheric ambient. Therefore, the purpose of this research is to study the effect of post oxygen plasma treatment on the resistance of moisture absorption and reliability of SiOF film. Improvement of moisture absorption resistance of SiOF film is due to the forming of thin SiO₂layer at the SiOF film surface. It is thought that the main effect of the improvement of moisture absorption resistance was densification of the top layer and reduction in the number of Si-F bonds that tend to associate with OH bonds. However, the dielectric constant was increased when plasma treatment time is above 5 min. In this study, therefore, it is thought that the proper plasma treatment time is 3 min when plasma treatment condition is 700 W of microwave power, 3 mTorr of process pressure and 300℃ of substrate temperature.

• Journal of the Korean Vacuum Society
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• v.7 no.3
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• pp.221-228
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• 1998

Enhancement of adhesion between polymer films and metal films are obtained by forming the hydrophilic functional groups on the polymer surfaces by ion assisted reaction which uses ion beam in reactive gas environments. In ion assisted reaction, ion dose, blown gas flow rate and ion energy were changed from $5\times 10^{14}$ to $1\times 10^{17}\textrm{ions/cm}^2$, from 0 to 8 sccm, and 0.3 to 1.2 kV, respectively. Wetting angle of water on polymer films modified by $ Ar^+$ ion without blowing oxygen decreases to ~$40^{\circ}$. Contact angle of water on polymer films modified by $ Ar^+$ ion with blowing oxygen decreases to ~$20^{\circ}$, and the surface free energy increases to ~70 dyne/$\textrm{cm}^2$. However, contact angle of water on polytetraflouroethylene (PTFE) modified by ion assisted reaction increases with ion dose. The adhesion strength of metal film deposited on the polymer surface was investigated. In the case of the metal film deposited on the untreated polymers, the metal films are detached from the polymer surface. While, In the case of the metal film deposited on the polymers treated by ion assisted reaction, the metal films are strongly adhere to the polymer surfaces.

• Journal of the Korean Vacuum Society
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• v.21 no.1
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• pp.12-16
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• 2012

Although silver is used for T-OLED (Top emitting organic Light-Emitting Diode) as reflective anode, it is not an ideal material due to its low work function. Thus, we study the effect of annealing and atmospheric pressure plasma treatment on Ag film that increases its work function by forming the thin silver oxide layer on its surface. In this study, we deposited silver on glass substrate using RF sputtering. Then we treated the Ag samples annealing at $300^{\circ}C$ for 30 minutes in atmosphere or treating the atmospheric plasma treatment for 30, 60, 90, 120s, respectively. We measured the change of the mechanical properties and the potential value of surface with each one at a different treatment type and time. We used nano-indenter system and KPFM (Kelvin Probe Force Microscopy). KPFM method can be measured the change of surface potential. The nanoindenter results showed that the plasma treatment samples for 30s, 120s had very low elastic modulus, hardness and Weibull modulus. However, annealed sample and plasma treated samples for 60s and 90s had better mechanical properties. Therefore, plasma treatment increases the uniformity thin film and the surface potential that is very effective for the performace of T-OLED.

• Asian-Australasian Journal of Animal Sciences
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• v.30 no.3
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• pp.432-438
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• 2017

Objective: The objective of this study was to evaluate the effect of combinations of $NaNO_2$ and NaCl concentrations on Listeria monocytogenes (L. monocytogenes) growth in emulsion-type sausage. Methods: Emulsion-type sausages formulated with different combinations of $NaNO_2$ (0 and 10 ppm) and NaCl (1.00%, 1.25%, and 1.50%) were inoculated with a five-strain L. monocytogenes mixture, and stored at $4^{\circ}C$, $10^{\circ}C$, and $15^{\circ}C$, under aerobic or vacuum conditions. L. monocytogenes cell counts were measured at appropriate intervals, and kinetic parameters such as growth rate and lag phase duration (LPD) were calculated using the modified Gompertz model. Results: Growth rates increased (0.004 to 0.079 Log colony-forming unit [CFU]/g/h) as storage temperature increased, but LPD decreased (445.11 to 8.35 h) as storage temperature and NaCl concentration increased. The effect of combinations of NaCl and low-$NaNO_2$ on L. monocytogenes growth was not observed at $4^{\circ}C$ and $10^{\circ}C$, but it was observed at $15^{\circ}C$, regardless of atmospheric conditions. Conclusion: These results indicate that low concentrations of $NaNO_2$ and NaCl in emulsion-type sausage may not be sufficient to prevent L. monocytogenes growth, regardless of whether they are vacuum-packaged and stored at low temperatures. Therefore, additional techniques are necessary for L. monocytogenes control in the product.

• Proceedings of the Korean Vacuum Society Conference
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• 2010.08a
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• pp.297-297
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• 2010

Precise control of the position and density of doping elements at the nanoscale is becoming a central issue for realizing state-of-the-art silicon-based optoelectronic devices. As dimensions are scaled down to take benefits from the quantum confinement effect, however, the presence of interfaces and the nature of materials adjacent to silicon turn out to be important and govern the physical properties. Utilization of visible light is a promising method to overcome the efficiency limit of the crystalline Si solar cells. Si quantum dots (QDs) have been proposed as an emission source of visible light, which is based on the quantum confinement effect. Light emission in the visible wavelength has been reported by controlling the size and density of Si QDs embedded within various types of insulating matrix. For the realization of all-Si QD solar cells with homojunctions, it is prerequisite not only to optimize the impurity doping for both p- and n-type Si QDs, but also to construct p-n homojunctions between them. In this study, XPS and SIMS were used for the development of p-type and n-type Si quantum dot solar cells. The stoichiometry of SiOx layers were controlled by in-situ XPS analysis and the concentration of B and P by SIMS for the activated doping in Si nano structures. Especially, it has been experimentally evidenced that boron atoms in silicon nanostructures confined in SiO2 matrix can segregate into the Si/$SiO_2$ interfaces and the Si bulk forming a distinct bimodal spatial distribution. By performing quantitative analysis and theoretical modelling, it has been found that boron incorporated into the four-fold Si crystal lattice can have electrical activity. Based on these findings, p-type Si quantum dot solar cell with the energy-conversion efficiency of 10.2% was realized from a [B-doped $SiO_{1.2}$(2 nm)/$SiO_2(2\;nm)]^{25}$ superlattice film with a B doping level of $4.0{\times}10^{20}\;atoms/cm^2$.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.20 no.12
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• pp.27-36
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• 2019

The demand for a low dispersion lens with a small refractive index and a high refractive index is increasing, and accordingly, there is an increasing need for a releasable protective film with high heat resistance and abrasion resistance. On the other hand, the optical industry has not yet established a clear standard for the manufacturing process and quality standards for mold-releasing protective films used in aspheric glass lens molding. Optical lens manufacturers treat this technology as proprietary information. In this study, an experiment was conducted regarding the optimization of ion etching, magnetron, and arc current at each source and filter part, and bias voltage in FCVA (filtered cathode vacuum arc)-based Ta-C thin film coatings. This study found that compared to iridium-rhenium alloy thin film sputtering products, the coating conditions were improved by approximately 50%, 20%, and 40% in terms of thickness, hardness, and adhesive strength of the film, respectively. The thin-film coating process proposed in this study is expected to contribute significantly to the development and utilization of glass lenses, which will help enhance the minimum mechanical properties and quality of the mold-release thin film layer required for glass mold surface forming technology.

• Proceedings of the Korean Vacuum Society Conference
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• 2011.02a
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• pp.189-190
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• 2011

Cu가 기존 배선물질인 Al을 대체함에 따라 resistance-capacitance (RC) delay나 electromigration (EM) 등의 문제들이 어느 정도 해결되었다. 그러나 지속적인 배선 폭의 감소로 배선의 저항 증가, EM 현상 강화 그리고 stability 악화 등의 문제가 지속적으로 야기되고 있다. 이를 해결하기 위한 방법으로 Cu alloy seed layer를 이용한 barrier 자가형성 공정에 대한 연구를 진행하였다. 이 공정은 Cu 합금을 seed layer로 사용하여 도금을 한 후 열처리를 통해 SiO2와의 계면에서 barrier를 자가 형성시키는 공정이다. 이 공정은 매우 균일하고 얇은 barrier를 형성할 수 있고 별도의 barrier와 glue layer를 형성하지 않아 seed layer를 위한 공간을 추가로 확보할 수 있는 장점을 가지고 있다. 또한, via bottom에 barrier가 형성되지 않아 배선 전체 저항을 급격히 낮출 수 있다. 합금 물질로는 초기 Al이나 Mg에 대한 연구가 진행되었으나, 낮은 oxide formation energy로 인해 SiO2에 과도한 손상을 주는 문제점이 제기되었다. 최근 Mn을 합금 물질로 사용한 안정적인 barrier 형성 공정이 보고 되고 있다. 하지만, barrier 형성을 하기 위해 300도 이상의 열처리 온도가 필요하고 열처리 시간 또한 긴 단점이 있다. 본 실험에서는 co-sputtering system을 사용하여 Cu-V 합금을 형성하였고, barrier를 자가 형성을 위해 300도에서 500도까지 열처리 온도를 변화시키며 1시간 동안 열처리를 실시하였다. Cu-V 공정 조건 확립을 위해 AFM, XRD, 4-point probe system을 이용하여 표면 거칠기, 결정성과 비저항을 평가하였다. Cu-V 박막 내 V의 함량은 V target의 plasma power density를 변화시켜 조절 하였으며 XPS를 통해 분석하였다. 열처리 후 시편의 단면을 TEM으로 분석하여 Cu-V 박막과 SiO2 사이에 interlayer가 형성된 것을 확인 하였으며 EDS를 이용한 element mapping을 통해 Cu-V 내 V의 거동과 interlayer의 성분을 확인하였다. PVD Cu-V 박막은 기판 온도에 큰 영향을 받았고, 200 도 이상에서는 Cu의 높은 표면에너지에 의한 agglomeration 현상으로 거친 표면을 가지는 박막이 형성되었다. 7.61 at.%의 V함량을 가지는 Cu-V 박막을 300도에서 1시간 열처리 한 결과 4.5 nm의 V based oxide interlayer가 형성된 것을 확인하였다. 열처리에 의해 Cu-V 박막 내 V은 SiO2와의 계면과 박막 표면으로 확산하며 oxide를 형성했으며 Cu-V 박막 내 V 함량은 줄어들었다. 300, 400, 500도에서 열처리 한 결과 동일 조성과 열처리 온도에서 Cu-Mn에 의해 형성된 interlayer의 두께 보다 두껍게 성장 했다. 이는 V의 oxide formation nergyrk Mn 보다 작으므로 SiO2와의 계면에서 산화막 형성이 쉽기 때문으로 판단된다. 또한, V+5 이온 반경이 Mn+2 이온 반경보다 작아 oxide 내부에서 확산이 용이하며 oxide 박막 내에 여기되는 전기장이 더 큰 산화수를 가지는 V의 경우 더 크기 때문으로 판단된다.

• Proceedings of the Korean Vacuum Society Conference
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• 2011.08a
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• pp.119-119
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• 2011

This study examined the synthesis of large area graphene and the change of its characteristics depending on the ratio of CH4/H2 by using the thermal CVD methods and performed the experiments to control the electron-hole conduction and Dirac-point of graphene by using chemical doping methods. Firstly, with regard to the characteristics of the large area graphene depending on the ratio of CH4/H2, hydrophobic characteristics of the graphene changed to hydrophilic characteristics as the ratio of CH4/H2 reduces. The angle of contact also increased to 78$^{\circ}$ from 58$^{\circ}$. According to the results of Raman spectroscopy showing the degree of defect, the ratio of I(D)/I(G) increases to 0.42% from 0.25% and the surface resistance also increased to 950 ${\Omega}$ from 750 ${\Omega}$/sq. As for the graphene synthesis at the high temperature of 1,000$^{\circ}$ by using CH4/H2 in a Cu-Foil, the possibility of graphene formation was determined as a function of the ratio of H2 included in the fixed quantity of CH4 as per specifications of every equipment. It was observed that the excessive amount of H2 prevented graphene from forming, as extra H-atoms and molecules activated the reaction to C-bond of graphene. Secondly, in the experiment for the electron-hole conduction and the Dirac-point of graphene using the chemical doping method, the shift of Dirac-point and the change in the electron-hole conduction were observed for both the N-type (PEI) and the P-type (Diazonium) dopings. The ID-VG results show that, for the N-type (PEI) doped graphene, Dirac-point shifted to the left (-voltage direction) by 90V at an hour and by 130 V at 2 hours respectively, compared to the pristine graphene. Carrier mobility was also reduced by 1,600 cm2/Vs (1 hour) and 1,100 cm2/Vs (2 hours), compared to the maximum hole mobility of the pristine graphene.

• Proceedings of the Korean Vacuum Society Conference
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• 2012.02a
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• pp.271-272
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• 2012

Bulk Metallic Glasses (BMGs or amorphous alloy) exhibit high strength and good corrosion resistance. Applications of thin films and micro parts of BMGs have been used a lot since its inception in the research of BMGs. However, Application and fabrication of BMGs are limited to make structural materials. Thin films of BMGs which is sputtered on the surface of structural materials by sputtering process is used to improve limits about application of BMGs. In order to investigate the difference of properties between designed alloys and thin films, we identified that thin films deposited on the surface that have the characteristic of the amorphous films and the composition of designed alloys. Zr-Cu (Cu=30, 35, 38, 40, 50 at.%) and Zr-Cu-Al (Al=10 at.% fixed, Cu=26, 30, 34, 38 at.%) alloys were fabricated with Zr (99.7% purity), Cu (99.997% purity), and Al (99.99% purity) as melting 5 times by arc melting method before rods 2mm in diameter was manufactured. In order to analyze GFA (Glass Forming Ability), rods were observed by Optical Microscopy and SEM and $T_g$, $T_x$, ($T_x$ is crystallization temperature and $T_g$ is the glass transition temperature) and Tm were measured by DTA and DSC. Powder was manufactured by Gas Atomizer and target was sintered using powder in large supercooled liquid region ($=T_x-T_g$) by SPS(Spark Plasma Sintering). Amorphous foil was prepared by RSP process with 5 gram alloy button. The composition of the foil and sputtered thin film was analyzed by EDS and EPMA. In the result of DSC curve, binary alloys ($Zr_{62}Cu_{38}$, $Zr_{60}Cu_{40}$, $Zr_{50}Cu_{50}$) and ternary alloys ($Zr_{64}Al_{10}Cu_{26}$, $Zr_{56}Al_{10}Cu_{34}$, $Zr_{52}Al_{10}Cu_{38}$) have $T_g$ except for $Zr_{70}Cu_{30}$ and $Zr_{60}Al_{10}Cu_{30}$. The compositions with $T_g$ made into powders. Figure shows XRD data of thin film showed similar hollow peak.

• Proceedings of the Korean Vacuum Society Conference
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• 2011.08a
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• pp.348-348
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• 2011

Carbon nanotube (CNT) field effect transistors and sensors use CNT as a current channel, of which the resistance varies with the gate voltage or upon molecule adsorption. Since the performance of CNT devices depends very much on the CNT/metal contact resistance, the CNT/electrode contact must be stable and the contact resistance must be small. Depending on the geometry of CNT/electrode contact, it can be categorized into the end-contact, embedded-contact (top-contact), and side-contact (bottom-contact). Because of difficulties in the sample preparation, the end-contact CNT device is seldom practiced. The embedded-contact in which CNT is embedded inside the electrode is desirable due to its rigidness and the low contact resistance. Fabrication of this structure is complicated, however, because each CNT has to be located under a high-resolution microscope and then the electrode is patterned by electron beam lithography. The side-contact is done by depositing CNT electrophoretically or by precipitating on the patterned electrode. Although this contact is fragile and the contact resistance is relatively high, the side-contact by far has been widely practiced because of its simple fabrication process. Here we introduce a simple method to embed CNT inside the electrode while taking advantage of the bottom-contact process. The idea is to utilize a eutectic material as an electrode, which melts at low temperature so that CNT is not damaged while annealing to melt the electrode to embed CNT. The lowering of CNT/Au contact resistance upon annealing at mild temperature has been reported, but the electrode in these studies did not melt and CNT laid on the surface of electrode even after annealing. In our experiment, we used a eutectic Au/Al film that melts at 250$^{\circ}C$. After depositing CNT on the electrode made of an Au/Al thin film, we annealed the sample at 250$^{\circ}C$ in air to induce eutectic melting. As a result, Au-Al alloy grains formed, under which the CNT was embedded to produce a rigid and low resistance contact. The embedded CNT contact was as strong as to tolerate the ultrasonic agitation for 90 s and the current-voltage measurement indicated that the contact resistance was lowered by a factor of 4. By performing standard fabrication process on this CNT-deposited substrate to add another pair of electrodes bridged by CNT in perpendicular direction, we could fabricate a CNT cross junction. Finally, we could conclude that the eutectic alloy electrode is valid for CNT sensors by examine the detection of Au ion which is spontaneously reduced to CNT surface. The device sustatined strong washing process and maintained its detection ability.