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Surface modification of polycarbonate(PC) was performed to improve the wettability by Ar+ ion irradiation with 1 keV energy in oxygen environment. The ion dose ranged from 5 x 1014 to 5 x 1016 ions/cm2 and oxygen flow rate was also varied from 0 to 6 sccm(ml/min.). Contact angle was not much decreased from 78° to 48° for water and from 63° to 32° for formamide by Ar+ ion irradiation without oxygen gas, but largely reduced to 12° for water and to 8° for formamide as Ar+ ion irradiation with 4 seem oxygen gas. Surface energy of modified PC surface which was irradiated with oxygen gas was more increased than that of PC surface irradiated without oxygen gas. It is evident that the increase of surface energy for PC modified with oxygen gas is due to hydrophilic group which result from the chemical reaction between PC surface and oxygen gas. From X-ray photoelectron spectroscopy(XPS) analysis, the newly formed hydrophilic group is identified as hydrophilic C=0 bond, and atomic force microscope(AFM), it is found that the root mean square of surface roughness is changed from 14 Å to 22 ∼ 26 Å for Ar+ ion irradiation only and 26 ∼ 30 Å for Ar+ ion irradiation with 4 seem oxygen gas. Therefore wettability of PC surface is much more affected by newly formed hydrophilic group than surface roughness in keV energy Ar+ ion irradiation.
Changes of crystallinity and surface roughness are discussed in terms of the average energy per deposited atom in the partially ionized beam(PIB) deposition. The average energy per deposited atom can be controlled by adjusting the ionization potential, Vi and acceleration potential, Va. The ion beam consists of a Cu ion beam and residual gas ion beam and residual gases as well as Cu particles that were ionized and accelerated to provide the film with energy required for film-growth. The relative contribution of residual gas ions and Cu ions to total average energy per deposited atom was varied with the ionization potential. At fixed ionization potentials of Vi=400 V and Vi=450 V, the average energy per deposited atom was varied in the range of 0 to 120 eV with acceleration potential Va, of 0 to 4 kV. The relative intensity ratio, 1(111)/I(200), of the Cu films increased from 6 to 37 and the root mean square(Rms) surface roughness decreased with an increase in acceleration potential at Vi=400 V. The relative intensity ratio, I(lll)/I(200), of Cu films increased up to Va=2 kV at Vi=2 kV, above which a decrease occurred, and the surface roughness of Cu films increased as a funtion of acceleration potential. The degree of preferred orientation was closely related with the average energy per deposited atom. The change of Rms roughness might be affected by ion flux, particle energy and preferred orientation.
The electrical properties of gold – polyimide - silicon structures were investigated experimentally by capacitance – voltage (C – V) measurement. Polyimide films were deposited on silicon substrate by using ionized cluster beam deposition (ICBD) of PMDA-ODA followed by in-situ thermal curing in N2 atmosphere. The resulting C – V plots show hysteresis, and it was believed to be due to the injection of carriers. The interface trap density is fairly low because of the clean interface provided by ICB technique.
Tin oxide films were deposited on in-situ heated Si (100)substrates using reactive ionassisted deposition and the effect of average impinging energy of oxygen ions on the crystalline structure and the stoichiometry of deposited films were examined. The transformation from SnO phase to SnO2 phase of the films was dependent on the change of the average impinging energy of oxygen ion (Ea), and the relative arrival ratio of oxygen to tin. Perfect oxidation of SnO2 was performed at Ea = 100, 125 eV/atom at as low as 400 Å substrate temperature. The composition (No/Nsn) of films increased from 1.21 to 1.89, and was closely related to the average impinging energy of oxygen ion. The surface morphology of the films was also investigated by scanning electron microscopy.
Growth behavior and microstructure of oxide scale formed on MoSi2 coating by cyclic oxidation testing in air at 500 °C were investigated using field emission scanning electron microscopy, cross-sectional transmission electron microscopy, glancing angle x-ray diffraction, and x-ray photoelectron spectroscopy. MoSi2 coating was prepared by chemical vapor deposition of Si on a Mo substrate at 1100 °C for 5 h using SiCl4–H2 precursor gas mixtures. After the incubation period of about 454 cycles, accelerated oxidation behavior was observed in MoSi2 coating and the weight gain increased linearly with increasing oxidation cycles. Microstructural analyses revealed that pest oxide scale was formed in three sequential processes. Initially, nanometer-sized crystalline Mo4O11 particles were formed with an amorphous SiO2 matrix at MoSi2 interface region. Inward diffusing oxygen reacted with Mo4O11 to form Mo9O26 nano-sized particles. At final stage of oxidation, MoO3 was formed from Mo9O26 with oxygen and growth of MoO3 took place forming massive precipitates with irregular and wavy shapes. The internal stress caused by the growth of massive MoO3 precipitates and the volatilization of MoO3 was attributed to the formation of many lateral cracks into the matrix leading to pest oxidation of MoSi2 coating.
Ferroelectric properties of SrBi2TaNbO9 (SBTN) thin films were changed by the amount of Bi content in SBTN. We proposed that the addition of excess Bi to the SBTN thin films could be accomplished by heat treating the SBTN/Bi2O3/SBTN heterostructure fabricated by the radio frequency magnetron sputtering method. The Bi composition was controlled by changing the thickness of the inserted Bi2O3 from 50 to 400Å in the SBTN/Bi2O3/SBTN heterostructure. As the thickness of Bi2O3 films was increased from 0 to 100 Å, the grain grew faster and the ferroelectric properties improved. On the other hand, when the thickness, of Bi2O3 films was thicker than 150 Å, the ferroelectric properties deteriorated. In particular, when a 400 Å Bi2O3 layer was inserted between SBTN films, a Bi2Pt phase appeared and the Bi2O3 films remained between SBTN films, resulting in poor ferroelectric properties. A Bi2Pt phase was formed by the reaction between the platinum bottom electrode and Bi2O3 films. On the other hand, the leakage current density of SBTN thin films decreased with the increase of inserted Bi2O3 film thickness. As the thickness of inserted Bi2O3 films was increased from 0 to 50 Å, leakage current density abruptly decreased because Bi content of the SBTN thin films was increased from 8 mol% deficient to stoichiometric composition. As the thickness of inserted Bi2O3 films increased from 100 to 400 Å, leakage current density gradually decreased because the remaining Bi2O3 layer in SBTN thin films increased.
Ar+1 ion irradiation on a polycarbonate (PC) surface was carried out in an oxygen environment in order to investigate the effects of surface chemical reaction, surface morphology, and surface energy on wettability of PC. Doses of Ar+ ion were changed from 5 × 1014 to 5 × 1016 at 1 keV ion beam energy by a broad ion beam source. Contact angle of PC was not reduced much by Ar+ ion irradiation without flowing oxygen gas, but decreased significantly as Ar+ ion was irradiated with flowing 4 sccm (ml/min) oxygen gas and showed a minimum of 12° to water and 5° to formamide. A newly formed polar group was observed on the modified PC surface by Ar+ ion irradiation with flowing oxygen gas, and it increased the PC surface energy. On the basis of x-ray photoelectron spectroscopy analysis, the formed polar group was identified as a hydrophilic bond (carbonyl group). In atomic force microscopy (AFM) study, the root mean square of surface roughness was changed from 14 Å to 22–27 Å by Ar+ ion irradiation without flowing oxygen gas and 26–30 Å by Ar+ ion irradiation with flowing 4 sccm oxygen gas. It was found that wettability of the modified PC surface was not greatly dependent on the surface morphology, but on an amount of hydrophilic group formed on the surface in the ion beam process.
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