• 한국진공학회:학술대회논문집
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• 한국진공학회 2016년도 제50회 동계 정기학술대회 초록집
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• pp.77-77
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• 2016

Thin films synthesized by plasma processes have been widely applied in a variety of industrial sectors. The structure control of thin film is one of prime factor in most of these applications. It is well known that the structure of this film is closely associated with plasma parameters and species of plasma which are electrons, ions, radical and neutrals in plasma processes. However the precise control of structure by plasma process is still limited due to inherent complexity, reproducibility and control problems in practical implementation of plasma processing. Therefore the study on the fundamental physical properties that govern the plasmas becomes more crucial for molecular scale control of film structure and corresponding properties for new generation nano scale film materials development and application. The thin films are formed through nucleation and growth stages during thin film depostion. Such stages involve adsorption, surface diffusion, chemical binding and other atomic processes at surfaces. This requires identification, determination and quantification of the surface activity of the species in the plasma. Specifically, the ions and neutrals have kinetic energies ranging from ~ thermal up to tens of eV, which are generated by electron impact of the polyatomic precursor, gas phase reaction, and interactions with the substrate and reactor walls. The present work highlights these aspects for the controlled and low-temperature plasma enhanced chemical vapour disposition (PECVD) of Si-based films like crystalline Si (c-Si), Si-quantum dot, and sputtered crystalline C by the design and control of radicals, plasmas and the deposition energy. Additionally, there is growing demand on the low-temperature deposition process with low hydrogen content by PECVD. The deposition temperature can be reduced significantly by utilizing alternative plasma concepts to lower the reaction activation energy. Evolution in this area continues and has recently produced solutions by increasing the plasma excitation frequency from radio frequency to ultra high frequency (UHF) and in the range of microwave. In this sense, the necessity of dedicated experimental studies, diagnostics and computer modelling of process plasmas to quantify the effect of the unique chemistry and structure of the growing film by radical and plasma control is realized. Different low-temperature PECVD processes using RF, UHF, and RF/UHF hybrid plasmas along with magnetron sputtering plasmas are investigated using numerous diagnostics and film analysis tools. The broad outlook of this work also outlines some of the 'Grand Scientific Challenges' to which significant contributions from plasma nanoscience-related research can be foreseen.

• Bulletin of the Korean Chemical Society
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• 제23권8호
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• pp.1139-1143
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• 2002

Analysis of lysophosphatidic acids (LPAs) is of clinical importance as they can serve a potential marker for ovarian and other gynecological cancers and obesity. It is critically important to develop a highly sensitive and specific method for the early detection of gynecological cancers to improve the overall outcome of this disease. We have established a novel quantification method of LPAs in human plasma by negative ionization tandem mass spectrometry (MS-MS) using multiple reaction monitoring (MRM) mode without the conventional TLC step. Protein-bound lipids, LPAs in plasma were extracted with methanol : chloroform (2:1) containing LPA C14:0 as an internal standard under acidic condition. Following back extraction with chloroform and water, the centrifuged lower phase was evaporated and reconstituted in methanol. The reconstituted solution was directly injected into electrospray source of MS/MS. For MRM mode, Q1 ions selected were m/z 409, 433, 435, 437 and 457 which corresponds to molecular mass [M-H]- of C16:0, C18:2, C18:1, C18:0 and C20:4 LPA, respectively. Q2 ions selected for MRM were m/z 79, phosphoryl product. Using MS/MS with MRM mode, all the species of LPAs were completely separated from plasma matrix without severe interferences. This method allowed simultaneous detection and quantification of different species of LPAs in a plasma over a linear dynamic range of 0.01-25 ㎛olL-1 . The detection limit of the method was 0.3 pmol/mL, with a correlation coefficient of 0.9983 in most LPAs analyzed. When applied to the plasmas of normal and gynecological cancer patients, this new method differentiated two different groups by way of total LPA level.

• 한국진공학회지
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• 제7권4호
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• pp.320-327
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• 1998

원격 플라즈마 화학기상증착법(Remote Plasma Enhanced-Ultrahigh Vacuum Chemical Vapor Deposition)에 의해 활성화된 질소 원자를 사용하여 사파이어 기판의 표면 을 저온에서 질화처리한 후 표면의 화학적 조성을 조사하였다. 질화처리에 의해 주로 표면 에 형성된 물질은 AIN임을 X-선 광전자 분광방법(X-ray photoelectron spectroscopy:XPS) 을 사용하여 확인하였다. 또한 플라즈마의 RF 출력, 반응 온도 및 시간에 따라서 기판의 Al 과 반응한 질소의 상대적인 양과, 표면 형태를 XPS와 AFM(atomic force microscopy)을 사 용하여 조사하였다. 플라즈마에 의해서 질소는 RF출력에 따라 증가한 후 일정하게 됨을 관 찰하였다. 그러나 질화 처리 온도와 시간의 증가에 따른 AIN의 상대적인 양은 비교적 무관 함을 관찰하였다. 또한 Ar스퍼터링을 통한 XPS의 depth profile을 관찰한 결과 질화층은 깊 이에 따라 3개의 다른 층으로 이루어져 있음을 확인하였다.

• 한국결정성장학회지
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• 제25권6호
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• pp.272-279
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• 2015

$Y_2O_3:Eu^{3+}$는 우수한 적색 발광 특성을 가지고 있는 형광체로 최근 고화질 디스플레이에 대한 수요가 증가함에 따라 관련 연구가 활발히 진행되고 있다. 본 연구에서는 RF 열플라즈마 합성법과 고상법을 이용하여 $Y_2O_3:Eu^{3+}$ 적색 형광체를 합성하였으며, 합성 방법에 따른 $Y_2O_3:Eu^{3+}$ 적색 형광체의 결정 구조, 미세 구조, 발광 특성의 차이를 XRD, TEM, PL 분석을 통해 비교하였다. 고상법으로 합성된 $Y_2O_3:Eu^{3+}$ 적색 형광체의 입자는 약 $10{\sim}20{\mu}m$ 크기를 가지는 반면, RF 열플라즈마 합성법을 통해 합성된 적색 형광체는 반응부는 약 100 nm, 필터부는 약 30 nm의 크기를 갖는 나노 형광체로 확인되었다. 합성된 모든 분말들은 PL 측정결과 611 nm($^5D_0{\rightarrow}^7F_2$)에서 발광하는 것을 확인하였으며, 결정 크기와 입도가 증가할수록 PL intensity가 증가하였다. 또한, 추가 열처리 공정이 필요 없는 one-step 공정의 RF 열플라즈마 공정을 통해 합성된 $Y_2O_3:Eu^{3+}$ 적색 나노 형광체는 고상법으로 합성된 적색 형광체와 비슷한 발광 특성을 보이는 것을 확인할 수 있었다.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2011년도 제40회 동계학술대회 초록집
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• pp.17-18
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• 2011

Plasma in liquid phase has attracted great attention in the last few years by the wide domain of applications in material processing, decomposition of organic and inorganic chemical compounds and sterilization of water. The plasma in liquid is characterized by three main regions which interact each - other during the plasma operation: the liquid phase, which supply the plasma gas phase with various chemical compounds and ions, the plasma in the gas phase at atmospheric pressure and the interface between these two regions. The most complex region, but extremely interesting from the fundamental, chemical and physical processes which occur here, is the boundary between the liquid phase and the plasma gas phase. In our laboratory, plasma in liquid which behaves as a glow discharge type, is generated by using a bipolar pulsed power supply, with variable pulse width, in the range of 0.5~10 ${\mu}s$ and 10 to 30 kHz repetition rate. Plasma in water and other different solutions was characterized by electrical and optical measurements. Strong emissions of OH and H radicals dominate the optical spectra. Generally water with 500 ${\mu}S/cm$ conductivity has a breakdown voltage around 2 kV, depending on the pulse width and the repetition rate of the power supply. The characteristics of the plasma initiated in ultrapure water between pairs of different materials used for electrodes (W and Ta) were investigated by the time-resolved optical emission and the broad-band absorption spectroscopy. The deexcitation processes of the reactive species formed in the water plasma depend on the electrode material, but have been independent on the polarity of the applied voltage pulses. Recently, Coherent anti-Stokes Raman Spectroscopy method was employed to investigate the chemistry in the liquid phase and at the interface between the gas and the liquid phases of the solution plasma system. The use of the solution plasma allows rapid fabrication of the metal nanoparticles without being necessary the addition of different reducing agents, because plasma in the liquid phase provides a reaction field with a highly excited energy radicals. We successfully synthesized gold nanoparticles using a glow discharge in aqueous solution. Nanoparticles with an average size of less than 10 nm were obtained using chlorauric acid solutions as the metal source. Carbon/Pt hybrid nanostructures have been obtained by treating carbon balls, synthesized in a CVD chamber, with hexachloro- platinum acid in a solution plasma system. The solution plasma was successfully used to remove the template remained after the mesoporous silica synthesis. Surface functionalization of the carbon structures and the silica surface with different chemical groups and nanoparticles, was also performed by processing these materials in the liquid plasma.

• Bulletin of the Korean Chemical Society
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• 제25권10호
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• pp.1508-1512
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• 2004

A gas chromatography/mass spectrometric (GC/MS) method has been developed for the determination of trace mono-n-butyltin (MBT), di-n-butyltin (DBT), and tri-n-butyltin (TBT) compounds in sediments. Samples were extracted by 10% acetic acid in methanol containing 0.03% tropolone and were then derivatized for GC/MS analysis. Ethylation by sodium tetraethylborate and phenylation by sodium tetraphenylborate were evaluated as a derivatization reaction of the organotins in sample extract. n-Hexane was added into reaction media in the beginning of the reaction for the continuous extraction of derivatized organotins. Ethylation requires less than 2 hours to get proper derivatization yields for MBT, DBT, and TBT altogether and produces relatively low amounts of side reaction products. Compared to ethylation, phenylation requires much longer time but provides relatively lower yield and produces considerable amounts of side reaction products. Therefore, the ethylation reaction was applied for the analysis of organotin compounds in sediment. An isotope dilution mass spectrometric (IDMS) method based on GC/MS has been applied to the accurate determination of DBT compounds in the sediments. The IDMS results from the analyses of sediment samples showed a reasonable repeatability and a good agreement with the values obtained by IDMS based on liquid chromatography/induced coupled plasma/mass spectrometry.

• 한국세라믹학회지
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• 제40권12호
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• pp.1150-1153
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• 2003

Carbon nanofilaments were formed on silicon substrate using microwave plasma-enhanced chemical vapor deposition method. The structures of carbon nanofilaments were identified as carbon nanotubes or carbon nanofibers. The formation of bamboo-like carbon nanotubes was initiated by the application of the bias voltage during the plasma reaction. The growth kinetics of bamboo-like carbon nanotubes increased with increasing the bias voltage. The growth direction of bamboo-like carbon nanotubes was vertical to the substrate.

• 한국진공학회지
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• 제7권s1호
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• pp.190-196
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• 1998

Amorphous ternary $Si_xC_yN-z$ thin films were obtained by plasma enhanced chemical vapor deposition(PECVD) using $N_2, SiH_4 \;and \;C_2H_4$ as the reaction sources. The chemical state were characterized by x-ray photoelectron spectroscopy (XPS) and Fourier transform infrared spectroscopy(FTIR). The optical properties of the thin films were investigated by UV-visible spectrophotometer and ellipsometer, and the optical band gaps of thin films were determined from corresponding transmittance spectra following Tauc equation.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2015년도 제49회 하계 정기학술대회 초록집
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• pp.64-64
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• 2015

Control of plasma processing methodologies can only occur by obtaining a thorough understanding of the physical and chemical properties of plasmas. However, all plasma processes are currently used in the industry with an incomplete understanding of the coupled chemical and physical properties of the plasma involved. Thus, they are often 'non-predictive' and hence it is not possible to alter the manufacturing process without the risk of considerable product loss. Only a more comprehensive understanding of such processes will allow models of such plasmas to be constructed that in turn can be used to design the next generation of plasma reactors. Developing such models and gaining a detailed understanding of the physical and chemical mechanisms within plasma systems is intricately linked to our knowledge of the key interactions within the plasma and thus the status of the database for characterizing electron, ion and photon interactions with those atomic and molecular species within the plasma and knowledge of both the cross-sections and reaction rates for such collisions, both in the gaseous phase and on the surfaces of the plasma reactor. The compilation of databases required for understanding most plasmas remains inadequate. The spectroscopic database required for monitoring both technological and fusion plasmas and thence deriving fundamental quantities such as chemical composition, neutral, electron and ion temperatures is incomplete with several gaps in our knowledge of many molecular spectra, particularly for radicals and excited (vibrational and electronic) species. However, the compilation of fundamental atomic and molecular data required for such plasma databases is rarely a coherent, planned research program, instead it is a parasitic process. The plasma community is a rapacious user of atomic and molecular data but is increasingly faced with a deficit of data necessary to both interpret observations and build models that can be used to develop the next-generation plasma tools that will continue the scientific and technological progress of the late 20th and early 21st century. It is therefore necessary to both compile and curate the A&M data we do have and thence identify missing data needed by the plasma community (and other user communities). Such data may then be acquired using a mixture of benchmarking experiments and theoretical formalisms. However, equally important is the need for the scientific/technological community to recognize the need to support the value of such databases and the underlying fundamental A&M that populates them. This must be conveyed to funders who are currently attracted to more apparent high-profile projects.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2002년도 춘계학술대회 논문집 센서 박막재료 반도체재료 기술교육
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• pp.7-11
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• 2002

In this study, Au thin films were etched with a $Cl_2/Ar$ gas combination in an in an inductively coupled plasma. The etch properties were measured for different gas mixing ratios of $Cl_2/(Cl_2+Ar)$ while the other process conditions were fixed at rf power (700 W), dc bias voltage (150 V), and chamber pressure (15 mTorr). The highest etch rate of the Au thin film was 3500 $\AA/min$ and the selectivity of Au to $SiO_2$ was 4.38 at a $Cl_2/(Cl_2+Ar)$ gas mixing ratio of 0.2. The surface reaction of the etched Au thin films was investigated using x-ray photoelectron spectroscopy (XPS) analysis. There is Au-Cl bonding by chemical reaction between Cl and Au. During the etching of Au thin films in $Cl_2/Ar$ plasma, Au-Cl bond is formed, and these products can be removed by the physical bombardment of Ar ions. In addition, Optical emission spectroscopy (OES) were investigated to analyze radical density of Cl and Ar in plasma. The profile of etched Au investigated with scanning electron microscopy (SEM).