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Ansari, Shafeeque G.,Seo, Hyung-Kee,Kim, Gil-Sung,Shahjahan, Md.,Shin, Hyung-Shik 한국화학공학회 2004 Korean Journal of Chemical Engineering Vol.21 No.1
We studied the use of carbon nanotubes as a seeding layer for the nucleation of diamond on Si (100) substrate by using a hot filament chemical vapor deposition (HFCVD) system. Prior to deposition, substrates were seeded with multi-wall carbon nanotube (MWCNT) powder which was prepared separately. MWCNTs were used as nucleation precursors. The diamond grains grew essentially over the nanotubes with a higher growth density in comparison with the un-seeded substrates. The scanning electron microscopy (SEM) image of surface morphology shows crystallites of cauliflower shaped grains. The micro Raman spectroscopic results show a sharp peak at 1,332㎝^(-1) corresponding to diamond phase, X-ray photoelectron spectroscopic study show the presence of carbon (C_(1x)) phase.
신형식,김길성,Shafeeque G. Ansari,Hyung-Kee Seo,Mushtaq Ahmad Dar,Md. Shahjahan 한국화학공학회 2004 Korean Journal of Chemical Engineering Vol.21 No.1
We studied the use of carbon nanotubes as a seeding layer for the nucleation of diamond on Si (10) sub-strate by using a hot filament chemical vapor deposition (HFCVD) system. Prior to deposition, substrates were seededwith multi-wal carbon nanotube (MWCNT) powder which was prepared separately. MWCNTs were used as nucle-ation precursors. The diamond grains grew esentialy over the nanotubes with a higher growth density in comparisonwith the un-seeded substrates. The scaning electron microscopy (SEM) image of surface morphology shows crystal-lites of cauliflower shaped grains. The micro Raman spectroscopic results show a sharp peak at 1,332 cm-1 corespond-ing to diamond phase. X-ray photoelectron spectroscopic study show the presence of carbon (C1s) phase.
( Bo Ryoun Kim ),( Shafeeque G. Ansari ),( Young Soon Kim ),( Gil Sung Kim ),( Sang Chul Hwang ),( Hee Gyoun Lee ),( Hyung Shik Shin ) 한국화학공학회 2003 Korean Journal of Chemical Engineering Vol.20 No.4
We have investigated the effect of the deposition temperature on the growth of Y₁Ba₂Cu₃O_(7-x) (YBCO) thin film using liquid solution sources on MgO (100) single crystalline substrate and have characterized the superconducting properties. The YBCO films were prepared by aerosol assisted chemical vapor deposition (AACVD). Single solution source of Y, Ba, and Cu β-diketonates dissolved in tetrahydrofuran (THF) was used as precursor. This precursor was passed through an ultrasonic aerosol generator and transported into a hot-wall CVD reactor using Ar as reactant gas (400 sccm). The substrate was placed normal to the gas stream and the substrate temperature was varied from 760 to 860℃. Deposition was carried out in oxygen atmosphere maintaining total pressure of 3.2 Torr inside the chamber. Deposition time was also varied from 10 to 30 min. The grown YBCO thin films were highly oriented to (001) orientation perpendicular to the substrate. The film deposited at 815℃ had a sharp transition to superconducting state about 87 K. The activation energy estimated from the Arrhenius plot is ~19.14 kJ/mol at the deposition temperature of 815℃.
The Synthesis of Maghemite and Hematite Nanospheres
Dar Mushtaq Ahmad,Ansari Shafeeque G.,Wahab Rizwan,Kim Young-Soon,Shin Hyung-Shik 한국분말야금학회 2006 한국분말야금학회 학술대회논문집 Vol.2006 No.1
Maghemite and hematite nanospheres were synthesized by using the Sol-gel technique. The structural properties of these nanosphere powders were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), field emission scanning electron microscopy (FESEM), and pore size distribution. Hematite phase shows crystalline structures. The mean particle size that resulted from BET and XRD analyses were 4.9 nm and 2 nm. It can be seen from transmission electron microscopy that the size of the particles are very small which is in good agreement with the FESEM and the X-ray diffraction. The BET and pore size method were employed for specific surface area determination.
Kim, Bo-Ryoun,Ansari, Shafeeque G.,Kim, Young-Soon,Kim, Gil-Sung,Hwang, Sang-Chul,Lee, Hee-Gyoun,Shin, Hyung-Shik 한국화학공학회 2003 Korean Journal of Chemical Engineering Vol.20 No.4
We have investigated the effect of the deposition temperature on the growth of Y₁Ba₂Cu₃O_(7-x) (YBCO) thin film using liquid solution sources on MgO (100) single crystalline substrate and have characterized the superconducting properties. The YBCO films were prepared by aerosol assisted chemical vapor deposition (AACVD). Single solution source of Y, Ba, and Cu β-diketonates dissolved in tetrahydrofuran (THF) was used as precursor. This precursor was passed through an ultrasonic aerosol generator and transported into a hot-wall CVD reactor using Ar as reactant gas (400 sccm). The substrate was placed normal to the gas stream and the substrate temperature was varied from 760 to 860℃. Deposition was carried out in oxygen atmosphere maintaining total pressure of 3.2 Torr inside the chamber. Deposition time was also varied from 10 to 30 min. The grown YBCO thin films were highly oriented to (001) orientation perpendicular to the substrate. The film deposited at 815℃ had a sharp transition to superconducting state about 87 K. The activation energy estimated from the Arrhenius plot is ~19.14 kJ/mol at the deposition temperature of 815℃.
Chiem, Chu Van,Seo, Hyung-Kee,Ansari, Shafeeque G.,Kim, Gil-Sung,Seo, Jae Myung,Shin, Hyung-Shik 한국화학공학회 2003 Korean Journal of Chemical Engineering Vol.20 No.6
In this paper, the growth of Lonsdaleite diamond using hot-filament chemical vapor deposition (HFCVD) on flashed and reconstructed Si (100) is reported. Surface morphology studies using scanning electron microscopy (SEMI show that the film is composed of decahedron and icosahedron diamond particles. The X-ray -tion (XRD) pattern has a strongest peak at 47° and a peak at 41°. which is indicative of Lonsdaleite name of the grown diamond film. The Raman spectrum of the film shows a broadened diamond peak at wave number of 1,329 ㎝^(-1), which has shifted towards the peak position corresponding to Lonsdaleite nahxe of the diamond (1,326 ㎝^(-1)).
신형식,김영순,강길선,Mushtaq Ahmad Dar,Shafeeque G. Ansari,Hyung-il Kim,Chu Van Chiem 한국화학공학회 2005 Korean Journal of Chemical Engineering Vol.22 No.5
Diamond films on the p-type Si(111) and p- type(100) substrates were prepared by microwave plasma chemical vapor deposition (MWCVD) and hot-filament chemical vapor deposition (HFCVD) by using a mixture of methane CH4 and hydrogen H2 as gas feed. The structure and composition of the films have been investigated by Xray Diffraction, Raman Spectroscopy and Scanning Electron Microscopy methods. A high quality diamond crystalline structure of the obtained films by using HFCVD method was confirmed by clear XRD-pattern. SEM images show that the prepared films are polycrystalline diamond films consisting of diamond single crystallites (111)-orientation perpendicular to the substrate. Diamond films grown on silicon substrates by using HFCVD show good quality diamond and fewer non-diamond components.