• Journal of Microbiology and Biotechnology
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• 제27권2호
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• pp.342-349
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• 2017

Polylactic acid (PLA) has been highlighted as an alternative renewable polymer for the replacement of petroleum-based plastic materials, and is considered to be biodegradable. On the other hand, the biodegradation of PLA by terminal degraders, such as microorganisms, requires a lengthy period in the natural environment, and its mechanism is not completely understood. PLA biodegradation studies have been conducted using mainly undefined mixed cultures, but only a few bacterial strains have been isolated and examined. For further characterization of PLA biodegradation, in this study, the PLA-degrading bacteria from digester sludge were isolated and identified using a polymer film-based screening method. The enrichment of sludge on PLA granules was conducted with the serial transference of a subculture into fresh media for 40 days, and the attached biofilm was inoculated on a PLA film on an agar plate. 3D optical microscopy showed that the isolates physically degraded the PLA film due to bacterial degradation. 16S rRNA gene sequencing identified the microbial colonies to be Pseudomonas sp. MYK1 and Bacillus sp. MYK2. The two isolates exhibited significantly higher specific gas production rates from PLA biodegradation compared with that of the initial sludge inoculum.

• 한국표면공학회지
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• 제17권2호
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• pp.29-40
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• 1984

The structure of rapidly solidified Al-Si-based alloys and its relationship to subsequent anodic film growth in near neutral and acid solutions have been investigated. Solidification of the alloys proceeds via pre-dendritic nuclei, associated with rugosity of the casting surface, from which cellular-type growth, comprised of aluminium-rich material surrounded by silicon-containing material, emanates. Observation of ultramicrotomed sections of the alloys and their anodic films reveals the local oxidation of the silicon-rich phase and its incorporation into the anodic alumina film, formed in near neutral solutions. Such incorporation occurs but resultant isolation of the silicon-rich phase is not possible for anodizing in phosphoric acid, and a three-dimensional network of the oxidized silicon-containing phase, with continuing development of porous anodic alumina, is observed.

• Transactions on Electrical and Electronic Materials
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• 제16권4호
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• pp.173-178
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• 2015

In lieu of the excellent radio frequency (RF) performance of microelectromechanical system ( MEMS) switches, these micro switches need higher actuation voltage for their operation. This requirement is secondary to concerns over the swtiches’ reliability. This paper reports high reliability operation of RF MEMS switches with low voltage requirements. The proposed switch is optimised to perform in the Q-band, which results in actuation voltage of just 16.4 V. The mechanical stress gradient in the thin micro membrane is computed by simulating von Mises stress in a multi-physics environment that results in 90.4 MPa stress. The computed spring constant for the membrane is 3.02 N/m. The switch results in excellent RF performance with simulated isolation of above 38 dB, insertion loss of less than 0.35 dB and return loss of above 30 dB in the Q-band.

• 한국전기전자재료학회논문지
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• 제16권9호
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• pp.771-774
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• 2003

In this paper, the programming characteristics of the multi-bit devices based on SONOS structure are investigated. Our devices have been fabricated by 0.35 $\mu\textrm{m}$ complementary metal-oxide-semiconductor (CMOS) process with LOCOS isolation. In order to achieve the multi-bit operation per cell, charges must be locally frapped in the nitride layer above the channel near the source-drain junction. Programming method is selected by Channel Hot Electron (CUE) injection which is available for localized trap in nitride film. To demonstrate CHE injection, substrate current (Isub) and one-shot programming curve are investigated. The multi-bit operation which stores two-bit per cell is investigated. Also, Hot Hole(HH) injection for fast erasing is used. The fabricated SONOS devices have ultra-thinner gate dielectrics and then have lower programming voltage, simpler process and better scalability compared to any other multi-bit storage Flash memory. Our programming characteristics are shown to be the most promising for the multi-bit flash memory.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2011년도 제40회 동계학술대회 초록집
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• pp.68-68
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• 2011

As feature size is smaller, new technology are needed in semiconductor factory such as gap-fill technology for sub 100nm, development of ALD equipment for Cu barrier/seed, oxide trench etcher technology for 25 nm and beyond, development of high throughput Cu CMP equipment for 30nm and development of poly etcher for 25 nm and so on. We are focus on gap-fill technology for sub-30nm. There are many problems, which are leaning, over-hang, void, micro-pore, delaminate, thickness limitation, squeeze-in, squeeze-out and thinning phenomenon in sub-30 nm gap fill. New gap-fill processes, which are viscous oxide-SOD (spin on dielectric), O3-TEOS, NF3 Based HDP and Flowable oxide have been attempting to overcome these problems. Some groups investigated SOD process. Because gap-fill performance of SOD is best and process parameter is simple. Nevertheless these advantages, SOD processes have some problems. First, material cost is high. Second, density of SOD is too low. Therefore annealing and curing process certainly necessary to get hard density film. On the other hand, film density by Flowable oxide process is higher than film density by SOD process. Therefore, we are focus on Flowable oxide. In this work, dielectric film were deposited by PECVD with TSA(Trisilylamine - N(SiH3)3) and NH3. To get flow-ability, the effect of plasma treatment was investigated as function of O2 plasma power. QMS (quadruple mass spectrometry) and FTIR was used to analysis mechanism. Gap-filling performance and flow ability was confirmed by various patterns.

• 전자통신동향분석
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• 제5권1호
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• pp.55-70
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• 1990

SIMOX SOI is known to be one of the most useful technologies for fabrications of new generation ULSI devices. This paper describes the current status of SIMOX SOI technology for ULSI applications. The SIMOX wafer is vertically composed of buried oxide layer and silicon epitaxial layer on top of the silicon substrate. The buried oxide layer is used for the vertical isolation of devices The oxide layer is formed by high energy ion implantation of high dose oxygen into the silicon wafer, followed by high temperature annealing. SIMOX-based CMOS fabrication is transparent to the conventional IC processing steps without well formation. Furthermore, thin film CMOX/SIMOX can overcome the technological limitations which encountered in submicron bulk-based CMOS devices, i.e., soft-error rate, subthreshold slope, threshold voltage roll-off, and hot electron degradation can be improved. SIMOX-based bipolar devices are expected to have high density which comparable to the CMOX circuits. Radiation hardness properties of SIMOX SOI extend its application fields to space and military devices, since military ICs should be operational in radiation-hardened and harsh environments. The cost of SIMOX wafer preparation is high at present, but it is expected to reduce as volume increases. Recent studies about SIMOX SOI technology have demonstrated that the performance of the SIMOX-based submicron devices is superior to the circuits using the bulk silicon.

• 한국포장학회지
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• 제16권1호
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• pp.19-25
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• 2010

It is becoming increasingly important to utilize alternative raw materials for plastic industries other than petrochemical-based plastics. Cellulose derivatives were the bases of the original synthetic plastics. Cellulose and its derivatives, especially the widely used cellulose acetate (CA), constitute one of the main classes of raw materials for production on artificial fibers, films, plastics etc. CA is one of the well known polymers produced from naturally available plant substance. Many researches have focused on the isolation of cellulose from the plant cells to use them as cellulose derivatives and composite materials. Chemical and mechanical treatments provide changes on the molecular structures influencing the fundamental properties of these naturally abundant polymer. The aim of this review article is to review biodegradation, synthesis, formation, and utilization of cellulose esters, especially di-acetate, used in packaging related researches.

• Journal of electromagnetic engineering and science
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• 제8권3호
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• pp.129-133
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• 2008

An integrated passive device(IPD) technology by semi-insulating(SI)-GaAs-based fabrication has been developed to meet the ever increasing needs of size and cost reduction in wireless applications. This technology includes reliable NiCr thin film resistor, thick plated Cu/Au metal process to reduce resistive loss, high breakdown voltage metal-insulator-metal(MIM) capacitor due to a thinner dielectric thickness, lowest parasitic effect by multi air-bridged metal layers, air-bridges for inductor underpass and capacitor pick-up, and low chip cost by only 6 process layers. This paper presents the Wilkinson power divider with excellent performance for digital cellular system(DCS). The insertion loss of this power divider is - 0.43 dB and the port isolation greater than - 22 dB over the entire band. Return loss in input and output ports are - 23.4 dB and - 25.4 dB, respectively. The Wilkinson power divider based on SI-GaAs substrates is designed within die size of $1.42\;mm^2$.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2003년도 하계학술대회 논문집 Vol.4 No.1
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• pp.80-83
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• 2003

In this paper, the programming characteristics of the multi-bit devices based on SONOS structure are investigated. Our devices have been fabricated by $0.35\;{\mu}m$ complementary metal-oxide-semiconductor (CMOS) process with LOCOS isolation. In order to achieve the two-bits per cell operation, charges must be locally trapped in the nitride layer above the channel near the junction. Channel hot electron (CHE) injection for programming can operate in multi-bit using localized trap in nitride film. CHE injection in our devices is achieved with the single power supply of 5 V. To demonstrate CHE injection, substrate current (Isub) and one-shot programming curve were investigated. The multi-bit operation which stores two-bit per cell is investigated with a reverse read scheme. Also, hot hole injection for fast erasing is used. Due to the ultra-thin gate dielectrics, our results show many advantages which are simpler process, better scalability and lower programming voltage compared to any other two-bit storage flash memory. This fabricated structure and programming characteristics are shown to be the most promising for the multi-bit flash memory.

• 대한의용생체공학회:의공학회지
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• 제44권6호
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• pp.465-475
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• 2023

In this study, we demonstrated a silica nanofibrous membrane based on the electrospinning process and evaluated its DNA isolation and purification performance in PCR pretreatment. Generally, silica membranes made of non-woven fabric are used for PCR pretreatment, but this study aimed to improve the efficiency of the pretreatment process by developing a nanofiber-type silica membrane with high specific surface area and porosity. In order to manufacture a nanofiber-shaped silica film while maintaining the original physical properties of silica, nanofiber membranes produced by adding various concentrations of PEO (5 wt%, 8 wt%, and 10 wt%) to silica prepared by the sol-gel method were compared. In terms of nanofiber membrane production, the higher the PEO concentration, the more effective it was in producing nanofiber membranes. The produced silica nanofiber membrane was inserted to a pretreatment device used in commercial PCR equipment, and the pretreatment performance was compared and verified using Salmonella bacteria. When Salmonella was used, samples containing 5 wt% PEO showed superior PCR efficiency compared to samples containing 8 wt% and 10 wt% PEO. These results show that adding 5 wt% of PEO can effectively improve DNA purification and separation by producing a nanofiber-shaped silica film while maintaining the physical properties of silica. We expect that this study will contribute to the development of effective PCR pretreatment technology essential for various molecular biology applications.