• 한국결정성장학회지
• /
• 제9권1호
• /
• pp.14-19
• /
• 1999

Hexamethyldisilane$(Si_{2}(CH_{3})_{6})$의 single precursor를 사용하여 화학기상증착법으로 $1100^{\circ}C$에서 Si 기판의에 $\beta$-SiC 막을 증착시켰다. 증착과정 중 hexamethyldisilane/$H_{2}$ gas system에 HCI gas를 도입하여 mask 재료에 의해 부분적으로 덮여져 있는 Si 기판에서 SiC 증착의 선택성을 조사하였다. Si 기판과 mask 재료에서 SiC 증착의 선택성을 증진시키기 위해 출발물질과 HCI gas의 공급 방법을 변화시켰다. 결국, HCI gas를 도입함으로서 SiC 증착의 선택성은 증진되었고 펄스 형태로의 gas 공급 방법은 선택성을 향상시키는데 효율적이었다.

• 한국결정성장학회지
• /
• 제8권2호
• /
• pp.233-239
• /
• 1998

화학기상증착법을 이용하여 tetramethylsilane(TMS)과 hexamethyldisilane(HMDS)으로부터 SiC층을 증착시켰다. 반응관 내의 압력은 1torr를 유지시켰으며, $H_2$ 가스를 사용하여 precursor를 반응로내로 수송하였고 $1200^{\circ}C$의 반응온도로 SiC 증착이 이루어졌다. 기판은 tantalum으로 masking한 Si-wafer와 platinum, molybdenum으로 masking한 MgO 단결정을 사용하였다. 금속층(Ta, Pt, Mo)에서의 SiC 증착 양상과 Si, MgO 위에서의 SiC 증착 양상을 비교함으로써 SiC 증착의 선택성을 관찰하였다. 증착층의 주된 상은 X-선 회절분석에 의해 $\beta-SiC$로 확인되었다. 또한 전자현미경 분석을 통해 각 층에서의 증착 양상의 차이를 조사하였다.

• 한국재료학회지
• /
• 제12권5호
• /
• pp.363-368
• /
• 2002

we proposed the use of $Si_2H_ 6/H_2$ chemistry for selective silicon epitaxy growth by low-pressure chemical vapor deposition(LPCVD) in the temperature range $600~710^{\circ}C$ under an ultraclean environment. As a result of ultraclean processing, an incubation period of Si deposition only on $SiO_2$ was found, and low temperature epitaxy selective deposition on Si was achieved without addition of HCI. Total gas flow rate and deposition pressure were 16.6sccm and 3.5mtorr, respectively. In this condition, we selectively obtained high-quality epitaxial Si layers of the 350~1050$\AA$ thickness. In older to extend the selectivity, we kept high pressure $H_2$ environment without $Si_2H_6$ gas for few minutes after first incubation period and then we conformed the existence of second incubation period.

• 한국표면공학회지
• /
• 제49권3호
• /
• pp.238-244
• /
• 2016

Copper electrodeposition on AZ91 Mg alloy was studied in views of preferential deposition on ${\alpha}$- or ${\beta}$- phases and how to achieve uniform deposition over the entire surface on ${\alpha}$- and ${\beta}$-phases in a cyanide solution. The inhomogeneous microstructure of AZ91 Mg alloy, particularly ${\alpha}$- and ${\beta}$-phases, was found to result in non-uniform deposition of zincate layer, preferential deposition of zincate on ${\beta}$-phases, which leads to non-uniform growth of copper layer during the following electrodeposition process. The preferential depositions of zincate can be attributed to higher cathodic polarizations on the ${\beta}$-phases. Pin-hole defects in the copper electrodeposit were observed at the center of large size ${\beta}$-phase particles which is ascribed to gas bubbles formed at the ${\beta}$-phases. The activation of AZ91 Mg alloy in hydrofluoric acid solution was used to obtain uniform growth of zincate layer on both the ${\alpha}$- and ${\beta}$-phases. By choosing an optimum activation time, a uniform zincate layer was obtained on the AZ91 Mg alloy surface and thereby uniform growth of copper was obtained in a cyanide copper electroplating solution.

• 한국신재생에너지학회:학술대회논문집
• /
• 한국신재생에너지학회 2005년도 제17회 워크샵 및 추계학술대회
• /
• pp.561-566
• /
• 2005

Polycrystalline silicon films were deposited using hot wire CVD (HWCVD). The deposition of silicon thin films was approached by the theory of charged clusters (TCC). The TCC states that thin films grow by self-assembly of charged clusters or nanoparticles that have nucleated in the gas phase during the normal thin film process. Negatively charged clusters of a few nanometer in size were captured on a transmission electron microscopy (TEM) grid and observed by TEM. The negatively charged clusters are believed to have been generated by ion-induced nucleation on negative ions, which are produced by negative surface ionization on a tungsten hot wire. The electric current on the substrate carried by the negatively charged clusters during deposition was measured to be approximately $-2{\mu}A/cm^2$. Silicon thin films were deposited at different $SiH_4$ and $H_2$ gas mixtures and filament temperatures. The crystalline volume fraction, grain size and the growth rate of the films were measured by Raman spectroscopy, X-ray diffraction and scanning electron microscopy. The deposit ion behavior of the si1icon thin films was related to properties of the charged clusters, which were in turn controlled by the process conditions. In order to verify the effect of the charged clusters on the growth behavior, three different electric biases of -200 V, 0 V and +25 V were applied to the substrate during the process, The deposition rate at an applied bias of +25 V was greater than that at 0 V and -200 V, which means that the si1icon film deposition was the result of the deposit ion of charged clusters generated in the gas phase. The working pressures had a large effect on the growth rate dependency on the bias appled to the substrate, which indicates that pressure affects the charging ratio of neutral to negatively charged clusters. These results suggest that polycrystalline silicon thin films with high crystalline volume fraction and large grain size can be produced by control1ing the behavior of the charged clusters generated in the gas phase of a normal HWCVD reactor.

• 한국전기전자재료학회논문지
• /
• 제31권3호
• /
• pp.177-181
• /
• 2018

We prepared ZnS thin films via chemical bath deposition (CBD) in an aqueous solution of ammonia ($NH_3$) and hydrazine ($N_2H_4$). The composition ratio of hydrazine used was 0%, 17%, 22%, 29%, or 50%. We investigated the effects of hydrazine and ammonia on the growth, and the structural and optical properties of ZnS in terms of surface uniformity, voids, and grain size. We found that during the growth of ZnS films, hydrazine was very effective for improving the surface morphology and layer uniformity with fast layer formation, while it had no effect on the bandgap energy, $E_g$.

• 수산해양기술연구
• /
• 제30권4호
• /
• pp.350-356
• /
• 1994

We have prepared superconducting Bi-Pb-Sr-Ca.Cu-O thin films by RF magnetron sputtering technique, on heated MgO(100) substrates. Sputtering was carried out in a mixture of argon and oxygen(10%) and the pressure was maintained at 5 mTorr during deposition. The substrate temperature was maintained $400^{\circ}C$ during deposition. The films sputtered were amorphous and insulating. All the films became superconducting by annealing, The films annealed at $880^{\circ}C$ for 30 minutes in air showed high-Tc phase with zero resistivity of 93K. These results indicate that the growth of the high-Tc phase is promoted by the presence of Pb at annealing temperature.

• 한국연소학회:학술대회논문집
• /
• 한국연소학회 1995년도 제2회 KOSCI Workshop
• /
• pp.91-103
• /
• 1995

In recent years, significant advances have been made in the development of methods to predict ash behavior in utility boilers. This paper provides an overview of methods used to assess and predict ash formation and deposition. It has discussed some of the key problems associated with the formation and deposition of ash during the combustion of pulverized coal. Although considerable progress has been made in understanding of the fundamental mechanisms of ash formation, transport, growth, and strength development, there is still much work to be done. There is a need to develop quantitative relationships between the characteristics of the entrained ash and the physical properties of ash deposits that influence deposit growth, strength development, and cleanability. Also data from bench-scale, pilot-scale, and full-scale units are needed in order to determine operating conditions which will minimize deposition problems, maximize efficiency, and reduce emissions.

• 한국전기전자재료학회:학술대회논문집
• /
• 한국전기전자재료학회 2000년도 하계학술대회 논문집
• /
• pp.212-217
• /
• 2000

Bi$_2$Sr$_2$CuO$_{x}$(Bi-2201) thin films have been fabricated by atomic layer-by-layer deposition using ion beam sputtering(IBS) process. During the deposition, 14 wt%-ozone/oxygen mixture gas of typical pressure of 5.0$\times$10$^{-5}$ Torr is supplied with ultraviolet light irradiation for oxidation. XRD and RHEED investigations reveal that a buffer layer with compositions different from Bi-2201 is formed at the early deposition stage of less than 10 units cell and then Bi-2201 oriented along the c-axis is grown.n.

• 한국세라믹학회지
• /
• 제47권6호
• /
• pp.485-490
• /
• 2010

In our previous studies, continuous SiC fiber-reinforced SiC-matrix composites ($SiC_f$/SiC) had been fabricated by two different slurry infiltration methods: vacuum infiltration and electrophoretic deposition (EPD). 12 wt% of $Al_2O_3-Y_2O_3$-MgO with respect to SiC powder was used as additives for liquid-phase assisted sintering. After hot pressing at $1750^{\circ}C$ under 20 MPa for 2 h in Ar atmosphere, a high composite density could be achieved for both cases, whereas the problems such as large grain size and non-uniform distribution of liquid phase were observed, which was resulted in the relatively poor mechanical properties of composites. Therefore, efforts have been made to reduce the grain growth during the sintering, including the optimization for hot pressing condition and utilization of spark plasma sintering using a SiC monolith. Based on the results, spark plasma sintering was found to be effective method in decreasing the amount of sintering additive, time and grain growth, which will be explained in comparison to the results of hot pressing in this paper.