Reactive ion etching of silicon oxide and silicon nitride was conducted by the injection of nitrogen trifluoride (NF
3
) and nitrogen oxide trifluoride gas (F
3
NO). The etching process was studied ...using a residual gas analyzer (RGA) and optical emission spectroscopy (OES); this included confirming and comparing the characteristics of the F
3
NO plasma to that of the NF
3
plasma by discharging and measuring the pure NF
3
plasma and F
3
NO plasma. Furthermore, silicon oxide and silicon nitride etching were performed using a process gas (NF
3
, F
3
NO) and an argon mixture. The plasma etching process was similarly diagnosed by RGA and OES, and the etch rate was calculated by measuring the reflection. The etch rate of silicon oxide during F
3
NO/Ar plasma etching is approximately 94% of that for NF
3
/Ar plasma etching and the etch rate of silicon nitride is approximately 76% of that for NF
3
/Ar plasma etching under the same conditions. The RGA and OES measurements confirmed that more O
+
, NO
+
, and O
2
+
ions were generated in the F
3
NO plasma than in the NF
3
plasma. This difference makes it possible to confirm the variation in etch rates between silicon oxide and silicon nitride.
The use of NF3 is significantly increasing every year. However, NF3 is a greenhouse gas with a very high global warming potential. Therefore, the development of a material to replace NF3 is required. ...F3NO is considered a potential replacement to NF3. In this study, the characteristics and cleaning performance of the F3NO plasma to replace the greenhouse gas NF3 were examined. Etching of SiO2 thin films was performed, the DC offset of the plasma of both gases (i.e., NF3 and F3NO) was analyzed, and a residual gas analysis was performed. Based on the analysis results, the characteristics of the F3NO plasma were studied, and the SiO2 etch rates of the NF3 and F3NO plasmas were compared. The results show that the etch rates of the two gases have a difference of 95% on average, and therefore, the cleaning performance of the F3NO plasma was demonstrated, and the potential benefit of replacing NF3 with F3NO was confirmed.
The atmospheric-pressure plasma (APP) process is used in various fields nowadays. One important characteristic of the APP process is the temperature of the wafer heated by the atmospheric-pressure ...plasma. In this study, the effects of the input power and the discharge distance on the heat generated during the atmospheric plasma process were analyzed, and the mechanism was predicted. We used a fluoroptic thermometer and infrared camera to measure the wafer temperature and a VI probe and a current probe to measure the electrical properties. The results showed that, as the input power was increased, the wafer temperature increased, and as the discharge distance was increased, the wafer temperature decreased. Thus, we can confirm that resistance heating was the mechanism that caused the wafer temperature to rise; it is related to the current intensity and the resistance of the current flowing through the wafer.
The efficiency of simultaneous treatment of the cold atmospheric pressure plasma jet (CAP) and hydrogen peroxide (H2O2) was investigated. A CAP with a thin and long plume was generated with Ar gas ...and applied to a common oral bacterium, Enterococcus faecalis (E. faecalis). The bactericidal efficiency was evaluated with the electron microscopy and the colony forming unit (CFU) assay. The underlying mechanisms were studied by measuring extracellular chemical changes in the water solution and by measuring biological responses such as the trans-membrane potential, the intracellular oxidative stress, and the membrane permeability. The combination of CAP with H2O2 could provide dramatic synergistic effects in bacterial disinfection through the enhanced membrane transportation of reactive species and the oxidation of intracellular molecules. Since the byproducts of both H2O2 and CAP are not significantly toxic, the synergistic bactericidal effects of their combination could be a good candidate to clinical applications.
A preliminary derived concentration guideline level (DCGL) was calculated for the soil of the Wolsong nuclear power plant (NPP) (the first commercial pressurized heavy water reactor in South Korea) ...site using the RESRAD-ONSITE computational code. In total, fourteen selected radionuclides were analyzed after considering the preliminary evaluation information of radionuclides observed in the pressure tube specimen in the Wolsong Unit 1 heavy water reactor and previous NPP decommissioning cases. Furthermore, a geological structure model of the Wolsong NPP site was established according to the safety analysis report of the Wolsong NPP. In addition, the distribution coefficients (Kd) of various radionuclides were derived using the JAEA-SDB and the pH information of the groundwater around the Wolsong NPP site. The DCGL for surface soil of the Wolsong NPP site was derived via the application of criteria for the site release to facilitate unrestricted reuse. Moreover, preliminary dose evaluation and relevant analysis were performed according to the Wolsong NPP site resident scenario. The novelty of this study lies in the first calculation of the preliminary DCGL values for the case of the pressurized heavy water reactor (Wolsong NPP) site. It is expected that further reliable DCGL results might be achievable if more precise radionuclide information and site-specific parameters with respect to the Wolsong NPP site are secured and applied in the future.
Methyl 2-hydroxy-4-(5-methoxythiophen-2-yl)benzoate (MHmoTB) and methyl 2-hydroxy-4-(5-cyanothiophen-2-yl)benzoate (MHncTB) have been synthesized and their photophysical properties are investigated ...in various solvents. Introducing methoxy and cyano groups to 5 position of the thiophenyl moiety results in very unique characters in the luminescence properties depending on the substituted group. Compared with the unsubstituted MHTB, the methoxy group as electron donator enhances the quantum yield of the deep blue luminescence more than 9 times in methylene chloride, while do not present an apparent solvatochromic effect on the luminescence spectral feature. In contrast, the cyano group as electron withdrawer enhances the quantum yield slightly. However, the UV excitation (<360 nm) of MHncTB produces not only deep blue emission but also orange emission in dimethylformamide and dimethyl sulfoxide. The new low-energy emission is attributed to an excited-state proton transfer from the solute to the solvent. Quantum mechanical calculations on the structural geometries and the electronic structures have been conducted to reveal ESPT of MHncTB by using the time-dependent density functional theory.
Display omitted
•Methyl 2-hydroxy-4-(5-methoxythiophen-2-yl)benzoate and methyl 2-hydroxy-4-(5-cyanothiophen-2-yl)benzoate were synthesized.•Methoxy group as electron donator enhances quantum yields of the deep blue luminescence more than 9 times.•Cyano group as electron withdrawer enhances the quantum yield slightly.•Quantum mechanical calculations on the structural geometries and the electronic structures were conducted.
This study investigated the effect of temperature on the aspect-ratio etching of SiO2 in CF4/H2/Ar plasma using patterned samples of a 200 nm trench in a low-temperature reactive-ion etching system. ...Lower temperatures resulted in higher etch rates and aspect ratios for SiO2. However, the plasma property was constant with the chuck temperature, indicated by the line intensity ratio from optical emission spectroscopy monitoring of the plasma. The variables obtained from the characterization of the etched profile for the 200 nm trench after etching were analyzed as a function of temperature. A reduction in the necking ratio affected the etch rate and aspect ratio of SiO2. The etching mechanism of the aspect ratio etching of SiO2 was discussed based on the results of the surface composition at necking via energy-dispersive X-ray spectroscopy with temperature. The results suggested that the neutral species reaching the etch front of SiO2 had a low sticking coefficient. The bowing ratio decreased with lowering temperature, indicating the presence of directional ions during etching. Therefore, a lower temperature for the aspect ratio etching of SiO2 could achieve a faster etch rate and a higher aspect ratio of SiO2 via the reduction of necking than higher temperatures.
Capacitively coupled plasma reactive ion etching of silicon by injecting nitrogen trifluoride (NF
3
) gas was conducted, and the etching process was studied with a residual gas analyzer and an ...optical emission spectroscopy. During the etching of silicon by the NF
3
plasma, the currents of F
+
and SiF
+
3
ions were obtained from the residual gas analyzer. At the same time, the line intensity of fluorine was measured using optical emission spectroscopy. The ion currents of F
+
and SiF
+
3
and the line intensity of fluorine were highest for etching at high pressure. With the results of this study, the general characteristics of reactive ion etching of silicon by using NF
3
plasma were confirmed. In addition, by simply changing the flow rate of NF
3
, a high NF
3
flow rate was found to result in a high etch rate because of the reduced residence time.
Colorectal cancer (CRC) is the third most common cancer worldwide and has a high recurrence rate, which is associated with cancer stem cells (CSCs). β-carotene (BC) possesses antioxidant activity and ...several anticancer mechanisms. However, no investigation has examined its effect on colon cancer stemness.
CD133
CD44
HCT116 and CD133
CD44
HT-29 cells were isolated and analyzed their self-renewal capacity by clonogenic and sphere formation assays. Expressions of several CSCs markers and Wnt/β-catenin signaling were examined. In addition, CD133
CD44
HCT116 cells were subcutaneously injected in xenograft mice and analyzed the effect of BC on tumor formation, tumor volume, and CSCs markers in tumors.
BC inhibited self-renewal capacity and CSC markers, including
,
,
,
, Sox2, and β-catenin
. The effects of BC on CSC markers were confirmed in primary cells isolated from human CRC tumors. BC supplementation decreased the number and size of tumors and delayed the tumor-onset time in xenograft mice injected with CD133
CD44
HCT116 cells. The inhibitory effect of BC on CSC markers and the Wnt/β-catenin signaling pathway in tumors was confirmed
as well.
These results suggest that BC may be a potential therapeutic agent for colon cancer by targeting colon CSCs.
Non-thermal atmospheric pressure plasma jet could generate various kinds of radicals on biosolution surfaces as well as inside the biosolutions. The electron temperature and ion density for this ...non-thermal plasma jet have been measured to be about 0.8~1.0 eV and 1 × 10
13
cm
−3
in this experiment, respectively, by atmospheric pressure collisional radiative model and ion collector current. In this context, the hydroxyl OH radical density inside the biosolutions has been also investigated experimentally by ultraviolet absorption spectroscopy when the Ar non-thermal plasma jet has been bombarded onto them. It is found that the emission and absorption profiles for the other reactive oxygen species such as NO (226 nm) and O
2
*
−
(245 nm) are shown to be very small inside the biosolution in comparison with those for the OH radical species. It is found that the densities of OH radical species inside the biosolutions are higher than those on the surface in this experiment. The densities of the OH radical species inside the deionized water, Dulbecco’s modified eagle medium, and phosphate buffered saline are measured to be about 2.1 × 10
16
, 1.1 × 10
16
, and 1.0 × 10
16
cm
−3
, respectively, at 2 mm downstream from the surface under optimized Ar gas flow of 200 sccm. It is also found that the critical hydroxyl OH radical density for the lung cancer H460 cells to experience an apoptosis is observed to be around 0.3 × 10
16
cm
−3
under 1 min plasma exposure in this experiment.
PDF
