• Proceedings of the Korean Vacuum Society Conference
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• 2013.08a
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• pp.155.2-155.2
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• 2013

Strain-relaxed SiGe layer on Si substrate has numerous potential applications for electronic and opto- electronic devices. SiGe layer must have a high degree of strain relaxation and a low dislocation density. Conventionally, strain-relaxed SiGe on Si has been manufactured using compositionally graded buffers, in which very thick SiGe buffers of several micrometers are grown on a Si substrate with Ge composition increasing from the Si substrate to the surface. In this study, a new plasma process, i.e., the combination of PIII&D and HiPIMS, was adopted to implant Ge ions into Si wafer for direct formation of SiGe layer on Si substrate. Due to the high peak power density applied the Ge sputtering target during HiPIMS operation, a large fraction of sputtered Ge atoms is ionized. If the negative high voltage pulse applied to the sample stage in PIII&D system is synchronized with the pulsed Ge plasma, the ion implantation of Ge ions can be successfully accomplished. The PIII&D system for Ge ion implantation on Si (100) substrate was equipped with 3'-magnetron sputtering guns with Ge and Si target, which were operated with a HiPIMS pulsed-DC power supply. The sample stage with Si substrate was pulse-biased using a separate hard-tube pulser. During the implantation operation, HiPIMS pulse and substrate's negative bias pulse were synchronized at the same frequency of 50 Hz. The pulse voltage applied to the Ge sputtering target was -1200 V and the pulse width was 80 usec. While operating the Ge sputtering gun in HiPIMS mode, a pulse bias of -50 kV was applied to the Si substrate. The pulse width was 50 usec with a 30 usec delay time with respect to the HiPIMS pulse. Ge ion implantation process was performed for 30 min. to achieve approximately 20 % of Ge concentration in Si substrate. Right after Ge ion implantation, ~50 nm thick Si capping layer was deposited to prevent oxidation during subsequent RTA process at $1000^{\circ}C$ in N2 environment. The Ge-implanted Si samples were analyzed using Auger electron spectroscopy, High-resolution X-ray diffractometer, Raman spectroscopy, and Transmission electron microscopy to investigate the depth distribution, the degree of strain relaxation, and the crystalline structure, respectively. The analysis results showed that a strain-relaxed SiGe layer of ~100 nm thickness could be effectively formed on Si substrate by direct Ge ion implantation using the newly-developed PIII&D process for non-gaseous elements.

• Proceedings of the IEEK Conference
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• 2000.06e
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• pp.183-186
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• 2000

In this paper we propose a new architecture of a programmable digital automatic gain controller(AGC) for analog interface in mixed mode systems. Compared with conventional analog AGCs which have difficulties in integration due to large capacitors, the proposed AGC is easily integrated. So the production cost can be reduced. In addition, The proposed AGC has a better performance in temperature, and power supply variations, and substrate noise than analog counterparts do. To prevent erroneous operations of the AGC due to noise, a mal-function preventer is newly proposed. In addition, to achieve an optimized AGC time constant, we propose a logic block which controls an up-down counting clock. This is directly related to the changing speed of the AGC gain. Implemented with a 0.25 $\mu\textrm{m}$ 1-poly, 5-metal CMOS parameters, the AGC operates from a single 2.5V power supply with the dynamic range of 36.ldB and occupies active area of 500$\mu\textrm{m}$${\times}$600$\mu\textrm{m}$

• Journal of the Korean Society for Heat Treatment
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• v.23 no.1
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• pp.23-28
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• 2010

The cylindrical magnetron sputtering has not been widely used, although this system is useful for only certain types of applications such as fiber coatings. This paper presents electrode configurations which improved the complicacy of the target assembly by using the positive voltage power supply. It is a modified type which has a target constructed with a large cylindrical part, a conical part and a small cylindrical part. When positive voltage was applied to an anode, a stable glow discharge was established and a high deposition rate was obtained. The substrate bias current was monitored to estimate the effect of ion bombardment. As a result, it was found that the substrate current was large. With cylindrical and conical cathode magnetron sputter deposition on the surface of the substrate to prevent re-sputtering, ion impact because it can increase the effectiveness with excellent ductility and adhesion of Ti film deposition can be obtained. We board at the front end of the ground resistance of $5\;k{\Omega}$ attached to the substrate potential can be controlled easily, and Ti film deposition with excellent adhesion can be obtained. Microstructure and morphology of Ti films deposited on pure Cu wires were investigated by scanning electron microscopy in relation to preparation conditions. High level ion bombardment was found to be effective in obtaining a good adhesion for Cu wire coatings.

• Journal of Environmental Science International
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• v.21 no.12
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• pp.1455-1462
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• 2012

The vertical distributions of nitrifying bacteria in aerobic fixed biofilm were investigated to evaluate the relationship between nitrification performance and microbial community at different HRT. Fluorescent in situ hybridization (FISH) and portable ion selective microelectrode system were adopted to analyze microbial communities and ions profiles according to the biofilm depth. Cilia media packed MLE (Modified Ludzack-Ettinger) like reactor composed of anoxic, aerobic I/II was operated with synthetic wastewater having COD 200 mg/L and $NH_4{^+}$-N mg/L at HRT of 6 hrs and 4 hrs. Total biofilm thickness of aerobic I, II reactor at 4 hrs condition was over two times than that of 6 hrs condition due to the sufficient substrate supply at 4 hrs condition (6 hrs; aerobic I 380 ${\mu}m$ and II 400 ${\mu}m$, 4 hrs; aerobic I 830 ${\mu}m$ and II 1040 ${\mu}m$). As deepen the biofilm detection point, the ratio of ammonia oxidizing bacteria (AOB) was decreased while the ratio of nitrite oxidizing bacteria (NOB) was maintained similar distribution at both HRT condition. The ratio of AOB was higher at 4 hrs than 6 hrs condition and $NH_4{^+}$-N removal efficiency was also higher at 4 hrs with 89.2% than 65.4% of 6 hrs. However, the ratio of NOB was decreased when HRT was reduced from 6 hrs to 4 hrs and $NO_2{^-}$-N accumulation was observed at 4 hrs condition. Therefore, it is considered that insufficient HRT condition could supply sufficient substrate and enrichment of AOB in all depth of fixed biofilm but cause decrease of NOB and nitrite accumulation.

• Journal of Bio-Environment Control
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• v.31 no.4
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• pp.292-299
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• 2022

This study was conducted to analyze physical and chemical properties of horticultural substrates and response of hydroponically grown two cultivars of 'Namcheon' and 'Somirang' perilla by four different substrates: coir (chip:dust = 5:5), perlite, granular rockwool, and commercial mixed substrate (cocopeat:peatmoss:vermiculite:perlite: zeolite = 50:25:10:10:5). There were no significant differences in EC and pH according to substrates. Container capacity was the greatest in granular rockwool, and it showed appropriate levels in mixed substrate and coir. Air space was higher in coir and perlite than the other treatments. Bulky density reached a proper standard in all substrates excepting coir. The leaf length and width of 'Namcheon' indicated the most in mixed substrate, though the value of 'Somirang'was greatest in coir substrate. The leaf weight of both cultivars was highest in mixed substrate, and relatively low in coir and perlite. The total yield of leaves was separated by two groups: higher group, which are mixed substrate and granular rockwool, and lower group, which are coir and perlite. There was a large gap by 28% between these two groups. Therefore, this study suggests that substrates with high water holding capacity such as mixed substrate or granular rockwool are most suitable for the hydroponic cultivation of perilla, which require sufficient moisture supply to the root zone.

• Journal of Sensor Science and Technology
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• v.28 no.2
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• pp.71-75
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• 2019

This paper proposes the extension of the dynamic range in complementary metal oxide semiconductor (CMOS) image sensors (CIS) using switching operation of in-pixel inverter. A CMOS inverter is integrated in each unit pixel of the proposed CIS for switching operations. The n+/p-substrate photodiode junction capacitances are added to each unit pixel. When the output voltage of the photodiode is less than half of the power supply voltage of the CMOS inverter, the output voltage of the CMOS inverter changes from 0 V to the power supply voltage. Hence, the output voltage of the CMOS inverter is adjusted by changing the supply voltage of the CMOS inverter. Thus, the switching point is adjusted according to light intensity when the supply voltage of the CMOS inverter changes. Switching operations are then performed because the CMOS inverter is integrated with in each unit pixel. The proposed CIS is composed of a pixel array, multiplexers, shift registers, and biasing circuits. The size of the proposed pixel is $10{\mu}m{\times}10{\mu}m$. The number of pixels is $150(H){\times}220(V)$. The proposed CIS was fabricated using a $0.18{\mu}m$ 1-poly 6-metal CMOS standard process and its characteristics were experimentally analyzed.

• Journal of Microbiology and Biotechnology
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• v.11 no.6
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• pp.1031-1037
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• 2001

By a sequential action of ${\beta}$-ketothiolase and acetoacetyl-CoA reductase, two molecules of acetyl-CoA re converted into D-3-hydroxybutyryl-CoA, a substrate for PHB synthase to form poly-3-hydroxybutyryl-CoA, a substrate for PHB synthase to form poly-3-hydroxybutyrate (PHB) of rhodobacter sphaeroides. The ${\beta}$-ketothiolase gene, phbA, and acetoacetyl-CoA reductase gene, phbB, were cloned and analyzed for their expression. Enzyme activities of ${\beta}$-ketothiolase and acetoacetyl-CoA reductase showed constitutive levels during aerobic and photoheterotrophic growth of R. sphaeroides. In addition, no difference of each enzyme activity was observed between cells grown aerobically and photoheterotrophically. The constitutive level of the enzyme activities are regulated according to the growth phases along with growth conditions. Thus, phbAB expression is not determinative in regulating the PB content. On the other hand, phbA-deleted cell AZI accumulated only $10\%$ PHB of the wild-type, and an elevated dosage of phbAB in trans in R. sphaeroides resulted in a higher content of PHB, indicating that phbAB codes for the enzymes responsible for providing the main supply of subsyrate for PHB synthase. PHB formation by an alternative pathway that does not does not depend on the phbA-and phbB-coding enzymes is also proposed.

• Journal of the Optical Society of Korea
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• v.16 no.1
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• pp.1-5
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• 2012

This paper describes a 150-Mb/s monolithic optical receiver for plastic optical fiber link using a standard CMOS technology. The receiver integrates a photodiode using an N-well/P-substrate junction, a pre amplifier, a post amplifier, and an output driver. The size, PN-junction type, and the number of metal fingers of the photodiode are optimized to meet the link requirements. The N-well/P-substrate photodiode has a 200-${\mu}m$ by 200-${\mu}m$ optical window, 0.1-A/W responsivity, 7.6-pF junction capacitance and 113-MHz bandwidth. The monolithic receiver can successfully convert 150-Mb/s optical signal into digital data through up to 30-m plastic optical fiber link with -10.4 dBm of optical sensitivity. The receiver occupies 0.56-$mm^2$ area including electrostatic discharge protection diodes and bonding pads. To reduce unnecessary power consumption when the light is not over threshold or not modulating, a simple light detector and a signal detector are introduced. In active mode, the receiver core consumes 5.8-mA DC currents at 150-Mb/s data rate from a single 3.3 V supply, while consumes only $120{\mu}W$ in the sleep mode.

• Journal of Korean Society of Water and Wastewater
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• v.28 no.1
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• pp.55-60
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• 2014

Food waste leachate (FWL) is a serious pollutant waste coming from the food waste recycling facilities in Korea. FWL has a high organic matter content and high COD to nitrogen (COD/N) ratio, which can disturb efficient methane production in the anaerobic digestion of FWL. In the present study a microalga, Clorella vulgaris (C.V), was used as co-substrate for the FWL anaerobic digestion in order to supply nutrients, decrease the COD/N ratio and increase its methane yield. Different co-digestion mixtures (COD/N ratios) were studied by using biochemical methane potential test and modified Gompertz equation for kinetic study. Mixed substrate of FWL and C. vulgaris in the co-digestion clearly showed more the biomethane yield than the sole substrates. The maximum methane production, 827.7 mL-$CH_4$/g-VS added, was obtained for COD/N ratio of 24/1, whereas the highest improvement of methane yield was found for COD/N ratio of 15/1.

• Journal of the Korean institute of surface engineering
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• v.24 no.1
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• pp.1-17
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• 1991

Understanding of the detailed reaction mechanisms during MOVPE and ALE is essential to further improve the properties of the grown crystals and the controllability of the growth parameters. The unified models for the detailed reaction paths are not available at this stage. The study, however, has been advanced to the extent that consensus on some of the reaction paths can be drawn from the scattered data. Metalakyls such as TMGa and TMIn seem to nearly fully decompose in the gas phase through homogeneous reaction at the typical MOVPE growth temperature. Hydrides such as AsH3 and PH3, on the contrary. seem to decompose heterogeneously onthe substrate surfaces as well as homogeneously in the gas phase. However, at lower temperatures, where ALE crystals are typically grown, the growth process is strongly dependent on the surface reactions. It seems that steric hindrance effects which the radicals reaching the substrate exhibit on the surface the growth rate a function of the metalalkyle supply durations. In addition, dydrogens released from hydrides seem to play an essential role in removing carbons leberated from the metalalkyls. High growth temperatures also seem to be effective in desorbing carbons from surface. The understanding of the reaction mechanisms was possible though diverse appraaches utilizing many ex-situ and in-situ diagnostic techniques and genuine experimental designs. It is the purpose of this paper to review and discuss many of these efforts and to draw some possible conclusions from them.