UV-O3 Treatment Research Articles

Substrate-dependent resistance decrease of graphene by ultraviolet-ozone charge doping

Graphene's resistance can decrease as much as 80% via UVO treatment depending on a substrates' band gap and photogenerated charge carriers.

Ultraviolet/ozone treated polystyrene microcarriers for animal cell culture

BACKGROUND Microcarrier based cell culture offers many advantages when compared with conventional cell cultures, and this technology has been widely used in the production of many important biological materials. In this work, microcarriers were produced using materials and methods that are relatively simple and low-cost. RESULTS Polystyrene (PS) microspheres were prepared by using an emulsion solvent–evaporation method and the effects of process conditions on the size of microspheres were investigated. The mean size of microspheres decreased with increasing agitation speed, concentration of polyvinyl alcohol (PVA) and polymer to solvent ratios but increased with increasing oil to water phase ratios. To enhance its cell attachment abilities, surfaces of PS microspheres were loaded with oxygen functional groups by using an ultraviolet/ozone (UVO3) system. Analysis by Fourier transform infrared (FTIR), energy dispersive X-ray spectroscopy (EDX), toluidine blue O (TBO) assay and relative contact angle measurements showed increased surface oxygen concentration after UVO3 treatment. Results from spinner flask culture revealed that UVO3 treated PS microspheres support the growth of Vero cells to high cell density. CONCLUSION UVO3 treatment successfully rendered the hydrophobic surface of PS microspheres hydrophilic. This newly developed microcarrier could serve as a low-cost alternative to commercial microcarriers available in the market today. © 2015 Society of Chemical Industry

Passivation of Metal Oxide Surfaces for High-Performance Organic and Hybrid Optoelectronic Devices

The exciton quenching properties of solution-processed nickel oxide (NiOx) and vanadium oxide (VOx) are studied by measuring the photoluminescence (PL) of a thin emitting layer (EML) deposited on top of the metal oxides. Strong exciton quenching is evidenced at the metal oxide/EML interface, which is proved to be detrimental to the performance of optoelectronic devices. With a thin polyvinylpyrrolidone (PVP) passivation polymer adsorbed on top of metal oxides, the PL quenching is found to be effectively suppressed. A short UV–O3 treatment on top of the PVP-passivated metal oxides turns out to be a key procedure to trigger the chemical binding between the PVP passivation polymer and the metal oxide surface species, which turns out to be necessary for efficient hole injection and extraction for organic light emitting diodes (OLEDs) and solar cell devices, respectively. With the PVP passivation layer followed by UV–O3 treatment, the OLEDs incorporating NiOx as a hole transport layer (HTL) shows a record curr...

Effect of UV/ozone treatment on polystyrene dielectric and its application on organic field-effect transistors

The influence of UV/ozone treatment on the property of polystyrene (PS) dielectric surface was investigated, and pentacene organic field-effect transistors (OFETs) based on the treated dielectric was fabricated. The dielectric and pentacene active layers were characterized by atomic force microscopy, X-ray photoelectron spectroscopy, and scanning electron microscopy. The results showed that, at short UVO exposure time (<10 s), the chemical composition of PS dielectric surface remained the same. While at long UVO exposure time (>60 s), new chemical groups, including alcohol/ether, carbonyl, and carboxyl/ester groups, were formed. By adjusting the UVO exposure time to 5 s, the hole mobility of the OFETs increased to 0.52 cm2/Vs, and the threshold voltage was positively shifted to -12 V. While the time of UVO treatment exceeded 30 s, the mobility started to shrink, and the off-current was enlarged. These results indicate that, as a simple surface treatment method, UVO treatment could quantitatively modulate the property of PS dielectric surface by controlling the exposure time, and thus, pioneered a new way to modulate the characteristics of organic electronic devices.

Fluoropolymer-assisted graphene electrode for organic light-emitting diodes

Organic light-emitting diodes (OLEDs) were fabricated on a graphene electrode, with synthesized graphene being transferred and simultaneously doped with supporting polymers. Poly[methyl methacrylate] (PMMA) and fluoropolymer (CYTOP) layers were used as the supporting polymers. The sheet resistance of CYTOP-assisted graphene (CYTOP-G) with 4 layers of graphene is 200Ω/sq., which is lower than that of PMMA-assisted graphene (PMMA-G, 330Ω/sq.) The transmittance value of PMMA-G and CYTOP-G with 4 graphene layers is higher than 85%. CYTOP-G is shown to exhibit a higher tolerance to UV–O3 treatment and thermal annealing than PMMA-G. Work function of CYTOP-G is 4.7eV, which is higher than that of PMMA-G (4.3eV). X-ray photoemission and Raman spectroscopy data indicate that CYTOP-G has numerous C-F bonds on the surface exhibiting p-type semiconductor properties, owing to the high electronegativity of fluorine. The turn-on voltage of an OLED based on CYTOP-G with 4 graphene layers is 4.2V, which is lower than that of indium tin oxide (ITO)-based one (4.5eV). Furthermore, the luminance ratio of graphene-based OLEDs to ITO-based OLEDs was calculated to be 104% for CYTOP-G, and 97% for PMMA-G. According to the ultraviolet photoemission spectra, the hole injection barrier in CYTOP-G is lower by about 0.5eV than the hole injection barrier in PMMA-G. These results are very encouraging to the prospect of replacing ITO electrodes with graphene ones in OLED applications.

High-performance NiO/Ag/NiO transparent electrodes for flexible organic photovoltaic cells.

Transparent electrodes with a dielectric-metal-dielectric (DMD) structure can be implemented in a simple manufacturing process and have good optical and electrical properties. In this study, nickel oxide (NiO) is introduced into the DMD structure as a more appropriate dielectric material that has a high conduction band for electron blocking and a low valence band for efficient hole transport. The indium-free NiO/Ag/NiO (NAN) transparent electrode exhibits an adjustable high transmittance of ∼82% combined with a low sheet resistance of ∼7.6 Ω·s·q(-1) and a work function of 5.3 eV after UVO treatment. The NAN electrode shows excellent surface morphology and good thermal, humidity, and environmental stabilities. Only a small change in sheet resistance can be found after NAN electrode is preserved in air for 1 year. The power conversion efficiencies of organic photovoltaic cells with NAN electrodes deposited on glass and polyethylene terephthalate (PET) substrates are 6.07 and 5.55%, respectively, which are competitive with those of indium tin oxide (ITO)-based devices. Good photoelectric properties, the low-cost material, and the room-temperature deposition process imply that NAN electrode is a striking candidate for low-cost and flexible transparent electrode for efficient flexible optoelectronic devices.

Effect of ultraviolet/ozone treatment on the surface and bulk properties of poly(dimethyl siloxane) and poly(vinylmethyl siloxane) networks

We present a comparative study aiming at comprehending the effect of ultraviolet/ozone treatment on the modification of poly(dimethyl siloxane) (PDMS) and poly(vinylmethyl siloxane) (PVMS) silicone elastomers networks (SENs). Both PDMS and PVMS SENs undergo dramatic changes in their properties when exposed to UVO. The surface chemical composition of both PDMS and PVMS at long UVO treatment times changes substantially and features a high density of hydrophilic groups. There are two major differences in behavior in the two classes of materials. First, relative to PDMS, the PVMS-based SENs get modified throughout the entire bulk. Second, the physico-chemical changes detected in PVMS take place on much shorter time scale relative to PDMS. These results are in accord with our earlier reports that indicated that when exposed to UVO, the topmost ≈5 nm of PDMS gets converted into a silica-like material, which then acts as a barrier for diffusion of atomic oxygen. In this case, the bulk of PDMS maintains its elasticity. In contrast, both the surface and bulk of PVMS films undergo substantial changes in properties when exposed to UVO. First, the surface modification of PVMS SENs takes place after only a few seconds of the UVO treatment. In addition, we register substantial modification of bulk properties, including the complete densification accompanied with increased bulk modulus. Likely, the susceptibility of the vinyl bonds to radical reactions is responsible for this effect.

Influence of microwave plasma pre-treatments of TiO2 electrodes on dye-sensitised solar cell efficiencies

The use of ozone and other pre-treatments of TiO2 photo-electrodes has become an important process step used to increase the efficiency of dye-sensitised solar cells (DSSCs). These pre-treatments are applied to reduce surface contamination and defects in order to improve current density, open circuit voltage and the overall efficiency of DSSCs. This study evaluates the scope of using low pressure microwave (MW) plasma pre-treatments of nanocrystalline TiO2 electrode layers as an alternative pre-treatment method to be applied prior to the dye adsorption step and evaluates the DSSC fabricated using such electrodes. Compared to control cells, (which had not been plasma treated), the power conversion efficiencies of the MW oxygen plasma treated cells exhibited significant improvement, for example up to 23% higher values.When comparing the 30sMW plasma pre-treatment with a 20min, UV-O3 treatment of TiO2 photo-electrodes, the former showed an increase of maximum power density by 23.5% compared to the 14.4% exhibited by the latter. Even though MW plasma treatment is carried out under low pressure (750Pa) compared to the atmospheric pressure UV-O3 treatments, the MW plasma treatment has the additional advantage of a shorter treatment time requiring only 30s instead of the 20min needed for the UV-O3 treatment. The observed improvement in cell efficiencies were shown to have a strong correlation with a decrease in the concentration of oxygen vacancy related Ti3+ defects in TiO2. The cell efficiency decreased with an increase in Ti3+ defects as Ti3+ defects serve as charge recombination centres for back electron transfer pathways. A decrease in Ti3+ concentration also increases the level of dye adsorption as the sensitizers are anchored via Ti4+, again paving the way for improved light harvest and an enhancement in the cell output. These results indicate that the MW plasma treatment represents an alternative rapid method for the pre-treatment of TiO2 photo-electrodes prior to dye adsorption in DSSC manufacturing.

Efficient polymer solar cells with a solution-processed and thermal annealing-free RuO2anode buffer layer

A new method is developed to prepare RuO2 films through UVO treatment of solution-processed ruthenium(III) acetylacetonate (Ru(acac)3) without thermal annealing. By introducing RuO2 as an anode buffer layer, highly efficient polymer solar cells (PSCs) have been achieved. The resultant RuO2 layer exhibits high light transmittance in the visible range. Remarkable improvements in the short-circuit current density (Jsc) of the PSCs can be achieved upon the introduction of the RuO2 buffer layer. The PSCs with the RuO2 anode buffer layer demonstrate improved photovoltaic performance in comparison with the devices using poly(3,4-ethylenedioxythiophene):poly(4-styrenesulfonate) (PEDOT:PSS) as the anode buffer layer. The power conversion efficiency (PCE) of the PSCs based on P3HT:PCBM and P3HT:ICBA reaches as high as 4.19% and 7.07%, respectively. An even higher PCE of 7.45% is realized by adopting a new conjugated polymer, PBDTBDD, as the donor. The results demonstrate that RuO2 has great potential as a hole collection material for highly efficient PSCs.

Corrosion behaviour of SUS304 stainless steel after UV–O3 treatment in sealed air environment

Ultraviolet ozone (UV–O3) treatment was carried out on SUS304 stainless steel in a sealed chamber and polarisation curves on the steel were measured. The surface composition and the surface structure of the specimen following UV–O3 treatment and polarisation were discussed. As a result, the corrosion resistance of SUS304 stainless steel could be enhanced by UV–O3 treatment in a sealed chamber for short treatment times. However, longer illumination times of more than 14·4 or 21·6 ks did not additionally enhance the corrosion resistance. In addition, cyclic illumination with replenishment of air in the sealed chamber was helpful for improving corrosion resistance. The composition of the film on the steel surface changed after UV–O3 treatment, namely, chromium and carbon decreased considerably, oxygen increased slightly and iron increased considerably. This demonstrated that increased iron oxide and decreased chromium oxide affected the corrosion resistance of the steel.

Fabrication and Wettability Patterning of Nano-structured Silicon Surface by using Self-organized Polymer Structures

We demonstrate here a creation of superhydrophobic and superhydrophilic patterned surface by using reactive ion etching (RIE) of silicon with a self-organized porous polymer structures and UV-O3 treatments through the photo-mask. Honeycomb-patterned films of polystyrene and amphiphilic polymer were prepared by casting of their chloroform solution. After UV-O3 treatment, honeycomb-patterned films were fixed on silicon substrates up side down with Poly (vinyl alcohol) solution. After peeling of the bottom layer of the honeycomb-patterned films, porous polymer masks were formed on the silicon substrate. After RIE, the silicon nanospike-array structure was obtained. Water contact angles on the silicon nanospike-array structures were c. a. 165 degree. From the results of X-ray photoelectron spectrum of the silicon nanospike-structures, fluorine was detected. The result suggests that superhydrophobicity was originated by absorbed fluorocarbons on the surface of the silicon nanospike-array structures and their surface structures. After UV-O3 treatment with photo-masks, fluorine was partially removed at irradiation area, and the area shows superhydrophilicity. These results suggest that we can easily design superhydrophobic and superhydrophilic patterned surfaces by UV-O3 treatment through photo-masks.

Reformation of CVD-SiO2 Films by UV Irradiation in Highly Concentrated Ozone

The post UV-O3 treatment of as-deposited CVD-SiO2 film using Tetraethoxysilane gas was carried out to improve the dielectric properties of the film at lower temperature than 450°C. Application of highly-concentrated (>90 vol.%) ozone under irradiation of UV light (210nm<λ<450 nm) resulted in the improvement of the film properties including the dielectric constant, etching endurance against buffered HF, and insulating properties (leakage current through the film) for the process temperature as low as 100°C. Because these improvements were reduced at absence of either UV light or highly concentrated ozone, the diffusion of electronically excited oxygen atom generation by photodissociation of ozone into the film is considered to play a key role to the improvement of the film properties.

Enhanced efficiency of dye-sensitized solar cells by UV–O3 treatment of TiO2 layer

Solar conversion efficiency of dye-sensitized solar cells was improved by UV–O3 treatment of TiO2 before and/or after sintering. The enhancement was resulted from the removal of the residual organics originated from the TiO2 precursor pastes, increased adsorption of dyes to the TiO2, surface, and longer diffusion length and shorter electron transit time of electrons through the TiO2 mesoscopic structure. The power conversion efficiency of the cells reaches to 7.2% with the open circuit voltage of 0.71 V, the short circuit current density of 15.2 mA/cm2 and the fill factor of 0.67 under illumination with AM 1.5 (100 mW/cm2) simulated sunlight.

SUS304 鋼表面でのミクロな大気汚染物の付着および紫外線・オゾン処理によるそれらの除去

Micro-contaminants on SUS304 stainless steel were observed and confirmed by atomic force microscope, and micro-contaminant removal was carried out by ultraviolet-ozone (UV-O3) treatment. With an increase in the holding time in air, particle- and film-like micro-contaminants appeared and their amount increased on the specimen surface. Then, the amount of particle-like contaminants decreased and finally almost all the surface was covered by film-like contaminants. The amount of micro-contaminants on the specimen surface decreased with an increase in UV-O3 treatment time, with extensive removal of the organic substance in the contaminants but leaving part of the contained water in the contaminants. The micro-contaminants slowly re-adhered on the treated surface when the surface was re-exposed to air, with a long period of more than 172 ks for the recovery to the state before the UV-O3 treatment. The surface for macro-droplets after the UV-O3 treatment became hydrophilic, while no large change of the wettability for micro-droplets on the same surface can be observed.

Enhanced Nucleation Behavior of Atomic-Layer-Deposited Ru Film on Low-k Dielectrics Afforded by UV-O[sub 3] Treatment

The effect of UV-O 3 treatment on the nucleation behavior of ruthenium (Ru) film on low-k dielectrics was investigated. A continuous Ru film was not formed on the as-deposited or N 2 -annealed low-k layer, but after the UV-O3 treatment, full coverage with a continuous Ru layer was obtained. The microstructure and Ru/Row-k interface were studied using transmission electron microscopy, specular X-ray reflectivity, and Auger electron spectroscopy. The enhanced nucleation behavior of Ru may be due to the increased chemisorption probability of the Ru precursor on the low-k film surface, which comes from a modified oxygen-based dense layer (SiO x ).

The Enhanced Nucleation Behavior of Atomic-Layer-Deposited Ru Film on Low-K Dielectrics by UV-O3 Treatment

not Available.

EVALUATION OF UV/O3 AND UV/H2O2 PROCESSES FOR NONBIODEGRADABLE COMPOUNDS: IMPLICATIONS FOR INTEGRATION WITH BIOLOGICAL PROCESSES FOR EFFLUENT TREATMENT

Poorly biodegradable compounds reduce the efficiency of biological effluent treatment processes. These are often encountered in pharmaceutical and speciality chemical industries. Advanced oxidation technologies (AOT) are appropriate for the conversion of such compounds into biodegradable entities. Tetrahydrofuran, 1,4-dioxane, and pyridine are heterocyclic compounds that are known to be recalcitrant and nonbiodegradable. AOT were investigated for the destruction of these model compounds. Two forms of AOT, UV-O3 and UV-H2O2, were studied. UV-H2O2 treatment resulted in higher biodegradability for tetrahydrofuran; UV-O3 treatment resulted in higher biodegradability for 1,4-dioxane. For pyridine, neither treatment improved biodegradability. For efficient integration of AOT with biological processes for effluent treatment, it is necessary to evaluate the AOT with multiple objectives, such as level of destruction of target compound, level of reduction in COD, and enhancement of biodegradability. Due to the presence of multiple pollutants in real effluents and in AOT, kinetics of oxidation elucidated with single compounds is unlikely to be useful.

Polymer dielectric treatment using ultraviolet-ozone: A photoelectron spectroscopy and ellipsometric porosimetry study

Ultraviolet-ozone (UV-O3) treatment of polyarylene, a semiconductor dielectric polymer, has been characterized using contact angle measurements, x-ray photoelectron spectroscopy, spectroscopic ellipsometry (SE), and ellipsometric porosimetry. Significant modification of the film surface composition is already observed after a short exposure time (30s). Longer treatment time leads to further increase in oxygen concentration and formation of an oxidized surface layer and densification of the film as evidenced by solvent adsorption data. Results obtained from SE indicate few changes in optical parameters, thickness, and refractive index (RI) of the film, up to 5min of UV-O3 treatment. Increasing the exposure time further leads to a substantial change in film thickness and an increase in RI. The same trend was observed for porous polyarylene but to a stronger extent. A dense layer at the porous polymer surface is only formed after 20min of treatment. Under these conditions, the optical properties of the material are strongly modified, with a substantial thickness shrinkage and increase in RI.

Changes in structures and electrical conduction mechanisms of chemical vapor deposited Ta2O5 thin films by annealing under O3 atmosphere with ultraviolet light radiation

The electrical conduction mechanisms of approximately 8-nm-thick Ta2O5 films grown by metalorganic chemical vapor deposition were investigated by measuring the current density–voltage characteristics at various temperatures. The Ta2O5 films were grown in two steps with or without intermittent annealing at 450 °C under an O3 atmosphere with ultraviolet light radiation (UV-O3 treatment). High-resolution transmission electron microscopy of the films after post-deposition annealing at 750 °C under an O2 atmosphere showed that the intermittent UV-O3 treatment improved the crystallization of the film during post-annealing. Auger electron spectroscopy of the variously treated samples showed that the improvement in crystallization was due to the increase in the oxygen concentration of the Ta2O5 films by the UV-O3 treatment. The Ta2O5 film without the UV-O3 treatment mostly exhibited a Poole–Frenkel conduction behavior with the electron trap level of 0.62 eV from the conduction band edge. The whole layer UV-O3 treated Ta2O5 films also showed a Poole–Frenkel conduction behavior with an almost identical electron trap level and a reduced density. The partially UV-O3 treated Ta2O5 films exhibited a direct tunneling behavior in a relatively low voltage region by the tunneling through the thin (∼3.8 nm) UV-O3 treated surface layer. However, these films showed a Poole–Frenkel conduction behavior in the high-voltage region. In general, the UV-O3 treatment was an efficient method to reduce the leakage current of the high-dielectric Ta2O5 films.

Deformation Processes during Indentation of Mesoporous Silica Thin Films

ABSTRACTNanoindentation was used to probe the mechanical response of mesoporous silica films as a function of processing treatment. A contrasted behaviour appears between low temperature processed films which retain the templating agent and are thus little compressible, and high temperature processed films, which are more condensed and also exhibit high porosity. We suggest that the behaviour of the former is dominated by shear flow, at least above a given threshold, while the latter are characterized by a yield strength in compression as is commonly found in porous materials. The response to indentation allows fast qualitative comparison of mechanical responses: in the present work, we show that a fast UV-O3 treatment results in mechanical properties which are undistinguishable from a much more cumbersome high temperature heat treatment.