광화학증착법에 의한 직접패턴 PZT 박막의 제조 및 특성

박형호,박형호,김태송,Park, Hyeong-Ho,Park, Hyung-Ho,Kim, Tae-Song,Hill, Ross-H. 한국재료학회 2008 한국재료학회지 Vol.18 No.2

The ferroelectric properties of UV irradiated and non-irradiated PZT films prepared via photochemical metal-organic deposition using photosensitive precursors were characterized. Fourier transform infrared spectroscopy showed that complete removal of organic groups was possible through UV exposure of the spin-coated PZT precursor films at room temperature. The measured remnant polarization values of UV-irradiated and non-irradiated PZT films after annealing at $650^{\circ}C$ were 29 and $23\;{\mu}C/cm^2$, respectively. The UV irradiation was found to be effective for the enhancement of the <111> growth orientation and ferroelectric property of PZT film and in the direct patterning in the fabrication of micro-patterned systems without dry etching.

$CHF_3/C_2F_6$ 반응성이온 건식식각에 의한 실리콘 표면의 변형에 관한 연구

박형호,권광호,곽병화,이수민,권오준,김보우,성영권,Park, Hyeong-Ho,Gwon, Gwang-Ho,Gwak, Byeong-Hwa,Lee, Su-Min,Gwon, O-Jun,Kim, Bo-U,Seong, Yeong-Gwon 한국재료학회 1991 한국재료학회지 Vol.1 No.4

실리콘 산화막을 $CHF_{3/}C_2F_6$ 혼합가스를 사용하여 반응성이온 건식식각을 행할 때 실리콘 표면에 형성되는 잔류막과 손상층을 X-선 광전자 분광기(XPS)와 이차이온 질량 분석기(SIMS)를 사용, 연구하였다. 실리콘, 탄소, 산소 및 불소의 angle-resolved XPS분석기술을 이용한 비파괴적 화학결합상태의 깊이분포 분석을 통하여 잔류막의 표면부에 O-F 결합이 존재하며 잔류막은 주로 탄소와 불소의 결합체인 C-F 플리머로 구성되어져 있고 Si-O, Si-C 및 Si-F 결합 등이 존재함을 알았다. 손상층은 실리콘 표면에서 약 60nm 깊이까지 탄소와 불소의 침투에 의해 형성되어져 있음을 알았다. The effects of $SiO_2$ reactive ion etching (RIE) in $CHF_{3/}C_2F_6$ on the surface properties of the underlying Si substrate were studied by X-ray photoelectron spectroscopy(XPS) and secondary ion mass spectrometry(SIMS) techniques. Angle-resolved XPS analysis was carried out as non-destructive depth profile one for investigating the chemical bonding states of silicion, carbon, oxygen and fluorine. The residue layer consists of C-F polymer. O-F bond was found on the top of the polymer layer and Si-O, Si-C and Si-F bonds were detected between Si substrate and polymer film. A 60nm thick damaged layer of silicon surface mainly contains carbon and fluorine.

화합물 반도체 에피기술 동향

박형호,Park, Hyeong-Ho 한국전기전자재료학회 2015 전기전자재료 Vol.28 No.10

하전 입자의 비구형 응집 성장에 대한 수치적 연구

박형호,김상수,장혁상,Park, Hyeong-Ho,Kim, Sang-Su,Jang, Hyeok-Sang 대한기계학회 2002 大韓機械學會論文集B Vol.26 No.2

A numerical technique for simulating the aggregation of charged particles was presented with a Brownian dynamic simulation in the free molecular regime. The Langevin equation was used for tracking each particle making up an aggregate. A periodic boundary condition was used for calculation of the aggregation process in each cell with 500 primary particles of 16 nm in diameter. We considered the thermal force and the electrostatic force for the calculation of the particle motion. The electrostatic force on a particle in the simulation cell was considered as a sum of electrostatic forces from other particles in the original cell and its replicate cells. We assumed that the electric charges accumulated on an aggregate were located on its center of mass, and aggregates were only charged with pre-charged primary particles. The morphological shape of aggregates was described in terms of the fractal dimension. In the simulation, the fractal dimension for the uncharged aggregate was D$\_$f/ = 1.761. The fractal dimension changed slightly for the various amounts of bipolar charge. However, in case of unipolar charge, the fractal dimension decreased from 1.641 to 1.537 with the increase of the average number of charges on the particles from 0.2 to 0.3 in initial states. In the bipolar charge state, the average sizes of aggregates were larger than that of the uncharged state in the early and middle stages of aggregation process, but were almost the same as the case of the uncharged state in the final stage. On the other hand, in the unipolar charge state, the average size of aggregates and the dispersion of particle volume decreased with the increasing of the charge quantities.

용융탄산염 연료전지에서 양극측 분리판의 부식기구 해석

박형호,이민호,이규택,Park, Hyeong-Ho,Lee, Min-Ho,Lee, Kyu-Taek 한국재료학회 1998 한국재료학회지 Vol.8 No.6

본 연구에서는 용융탄산염 연료전지용 분리판으로서 오스테나이트계 스테인레스강 중, 310S를 사용하여 용융염 전해질 및 양극측 분위기에서 부식거동, 부식생성물의 형성과정 및 기구에 관한 고찰을 실시하였다. 분리판의 부식 진행과정은 부식반응 이후 안정 부식생성물이 형성되기까지 빠른 부식이 진행되는 부식생성물 형성단계와 안정 부식생성물 형성 후 보호파괴가 일어나기 까지의 부식 억제단계, 그리고 보호파괴 이후 부식이 다시 증가되는 부식 진행단계의 3단계 과정을 경유하며 진행하였다. 분리판 내 원소들의 농도분포는 부식생성물 형성영역에서는 Fe가, 부식 방어영역에서는 Cr이, 그리고 Ni은 Cr 고갈영역과 기지 안쪽에서 높게 형성되었다. 또한 양극측에서 분리판은 전해질의 이온화에 의한 부식이 주된 부식기구였으며, 최종 부식생성물은 $LiFeO_2$와 $LiCrO_2$였다. This study was carried out for investigating the corrosion behaviors, corrosion mechanisms, and behaviors of elements on a separator for a molten carbonate fuel cell under both the electrolyte and anode side environment. A 310S austenitic stainless steel was used as the separator material. Corrosion proceeded via three steps; the formation step of corrosion product in which rapid corrosion takes place until stable corrosion product is formed after the beginning of corrosion, the protection step against corrosion until breakaway occurs after the formation step of stable corrosion product and the advancing step of corrosion after the breakaway. From the standpoint of the behavior of the elements in the specimen, Fe and Cr, Ni were enriched in the region of corrosion product, in the region of corrosion protection, and at the Cr-deplete zone, respectively. With respect to corrosion mechanism, ionization of electrolyte at the anode side was the main corrosion mechanism, and the final corrosion products were $LiFeO_2$ and $LiCrO_2$ at the anode side.

Photo-induced hybrid nanopatterning of metal oxide via direct imprint lithography

박형호(Hyeong-Ho Park),최대근(Dae-Geun Choi),Xin Zhang,김기돈(Ki-don Kim),최준혁(Jun-Hyuk Choi),이지혜(Jihye Lee),박형호(Hyung-Ho Park),Ross Henry Hill,이응숙(Eung-Sug Lee),정준호(Jun-Ho Jeong) 한국생산제조학회 2011 한국생산제조시스템학회 학술발표대회 논문집 Vol.2011 No.4

A novel ultraviolet (UV)-assisted imprinting procedure that employs photosensitive zirconyl 2-ethylhexanoate is presented for the fabrication of both amorphous and crystalline zirconium dioxide (ZrO₂) nanostructures. Upon annealing at 400 C for 1 h, the lateral shrinkage and thickness shrinkage of ZrO₂ nanostructures were 69.8 and 66.7%, respectively, indicating an isotropic volume loss. During UV irradiation and annealing treatment, the refractive index of UV-irradiated ZrO₂ film is gradually increased by improvement in the packing density and crystallinity of the film. With increasing UV exposure time and annealing temperature, the optical band gap (Eg) of the UV-irradiated ZrO₂ film is red-shifted from 5.745 to 5.265 eV, due to the removal of organic groups and the resultant densification of the film during the photochemical reaction and the heat-induced increase in the crystallinity of the film. These results suggest that the refractive index and optical Eg of ZrO₂ nanostructures could be controlled by tuning the conditions of UV exposure time and annealing treatment. Nanopatterns of ZrO₂, fabricated by direct UV-assisted nanoimprint lithography, are potential candidates for protective coatings for optical mirrors and filters, e.g. high-reflectivity mirrors and broadband interference filters, as well as active electro-optical devices where ordered surface nanostructures are necessary.

습식세정에 따른 GaAs표면 결합상태의 연구

강민구,박형호,서경수,이종람,강동규,Gang, Min-Gu,Park, Hyeong-Ho,Seo, Gyeong-Su,Lee, Jong-Ram,Gang, Dong-Gyu 한국재료학회 1996 한국재료학회지 Vol.6 No.4

본 연구에서는 GaAs 소자제작 및 epi-layer 성장 공정에 있어 이용되어지는 HCI, H3PO4, 탈이온수(de-ionized water:DIW)를 통한 습식제정후 공기중 노출에 따른 오염을 최소화하여 표면상태 변화를 진성적(intrinsic)으로 관찰하고자 모든 세정처리를 아르곤 가스(argon gas)로 분위기가 유지되는 glove box에서 수행하였으며, 표면조성 및 결합상태 변화에 대한 관찰은 X-선 광전자 분광기(X-ray photoelectron spectroscopy)를 통해 이루어졌다. 고진공하에서 GaAs를 벽개하여 관찰함으로써 Ga이 대기중 산소이온과 우선적으로 결합함을 알 수 있었고, 이런 GaAs 표면의 반응성에 대한 고찰을 바탕으로 습식세정에 따른 화학반응 기구가 제시 되어졌다. HCI 및 H3PO4/DIW/HCI처리후 CI-이온의 Ga 이온과의 반응에 의한 Ga-CI결합의 형성과 As 산화물의 높은 용해도에 따른 As 산화물의 완전한 제거 및 식각전 초기(bare)GaAsvyaus에 존재하는 원소(elemental)As 상태의 식각후 잔류가 관찰되어졌다. 또 HCI, H3PO4/DIW/HCI 처리하고 DIW로 세척후 표면상태 변화를 관찰한 결과, DIW처리에 의해 elemental As 상태가 증가함을 알 수 있었다.

온도에 따른 탄탈 분말 제조와 특성

윤재식,박형호,배인성,이상백,김병일,Yun, Jae-Sik,Park, Hyeong-Ho,Bae, In-Seong,Lee, Sang-Baek,Kim, Byeong-Il 한국재료학회 2001 한국재료학회지 Vol.11 No.12

Pure tantalum powder has been produced by sodium as a reluctant, $K_2TaF_7$as a feed material and KCl/KF as a diluent in an inconel stainless steel bomb by the metallothermic reduction. The influence of experimental variable, such as temperature of reduction on the yield and characteristics of the Ta powder has been studied. As the temperature of the reduction was varied from$ 800{\circ}C~980{\circ}C$, the yield of tantalum powder increased from 41% to 56%. However no appreciable improvement was observed above$920{\circ}C$. The fraction of fine Ta Powder decreased appreciably with the increase of temperature, and particle size was$2~3{\mu}m$at reduction temperature of$920{\circ}C$.Therefore a reduction temperature of$920{\circ}C$was optimally fixed for subsequent runs.

습식식각된 구리 표면의 결합상태에 대한 정량적 분석 연구

강민구,박형호,Gang, Min-Gu,Park, Hyeong-Ho 한국재료학회 1996 한국재료학회지 Vol.6 No.2

열증착기(thermal evaporator)로 증착시킨 Cu를 상온에서 3.5M CuCl2+0.5M HCI+0.5MKCI 용액을 사용하여 습식각하고 2일간 대기중 노출시킨 후 X-선 광전자 분광기를 이용하여 표면의 결합상태를 관찰하였다. 그 결과 습식식각된 Cu 표면에서는 C, O, Ci 및 Cu가 존재함을 알 수 있었다. 표면원소에 대한 오제이 전자 스펙트라(Auger electron spectra)와 광전자 스펙트라(photoelectron spectra)의 정량적인 비교를 통하여 표면의 모든 결합상태를 확인할 수 있었고 그 상대적인 양까지도 얻어낼 수 있었다. 식각된 Cu의 표면에는 Cu-Cu, 2Cu-O, Cu-Ci, Cu-2(OH), 및 Cu-2Cl의 결합상태가 존재함을 알 수 있었고, CuLMMAuger line spectrum의 관찰을 통하여 계산된 각 결합의 정량적인 비교를 검증할 수 있었다. 따라서 chemical shift가 거의 관찰되지 않아 결합상태 분리가 불가능한 식각된 구리표면의 정량적 결합상태는 각 결합상태의 상대적 비교를 통하여 얻어질 수 있음을 알 수 있었다.

Na환원법에 의한 희석제량에 따른 탄탈 분말 제조와 특성

윤재식,박형호,배인성,김병일,정성만,Yoon, Jae-Sik,Park, Hyeong-Ho,Bae, In-Sung,Kim, Byung-Il,Jung, Sung-Man 한국재료학회 2002 한국재료학회지 Vol.12 No.9

High-pure tantalum powder was fabricated through Na reduction process and has been produced by using $K_2$TaF$_{7}$, and KCI, KF for raw material and diluent, respectively. A raw material and diluent were charged at the hestalloy bomb by the weight rate of 1:2, 1:1, 1:0.5 and 1:0.25 each other, investigated properties of morphology, chemical composition and yield and particle size after reduced. Ta metal has been achieved by reduction of $K_2$$TaF_{7}$ 500g with 1% sodium in excess of stoichiometric amount in the charge at a reduction temperature of $850^{\circ}C$ for 3hours. According to amount of the diluent, a formation of the powder doesn't have an effect. The diluent prevented the temperature rising caused from the heat of reaction and it maintained the speed of reducing reaction. But in the mixture ratio of raw material and diluent in the 1 : 2 and 1 : 0.25, an oxide and partially not reacted K were detected. As the amount of diluent increased, the size of tantalum powder decreased. According as raw material and the mixture ratio of diluent change from 1:0.25 to 1:2, the size is decreased from 5$\mu\textrm{m}$ to 1$\mu\textrm{m}$, and a particle size distribution which is below 325 mesh in fined powder increases from 71% to 83%. In the case of average size of Tantalum powder which is the mixture ratio (1:0.5), we would get the Ta powder with grain size about 3$\mu\textrm{m}$, which come close to the average size (2~4$\mu\textrm{m}$) of tantalum powder which is used commonly in the present is Ta powder about 3$\mu\textrm{m}$.