Excimer Lamp Research Articles

Effective Photoinactivation of Alpha‐Amylase, Catalase and Urease at 222 nm Emitted by an KrCl‐Excimer Lamp

AbstractThe inactivation of enzymes is of great interest for many industrial applications. The effectiveness of photoinactivation of alpha‐amylase, catalase, and urease with 222 nm radiation was investigated in comparison to that at 254 nm. The enzymes were irradiated with different fluence rates of 222 nm radiation emitted by a KrCl‐excimer lamp and with 254 nm radiation produced by a low‐pressure mercury lamp. The relative activities were calculated before and after irradiation. Degradation caused by UV‐radiation was assessed by SDS‐PAGE analysis. The results clearly demonstrated that inactivation of the proteins is much more effective with the 222 nm excimer lamp compared to the 254 nm mercury lamp. Irradiation with the excimer lamp and a UV‐fluence rate of 1000 J/m2 was sufficient to reduce the relative activities of amylase and urease to 15% and that of catalase to 60%. After irradiation with 4000 J/m2, the enzyme activity was almost completely inhibited. In contrast, after irradiation with the mercury lamp with an UV‐fluence rate of 4000 J/m2, the relative activity was still above 85%. The gel patterns showed no visible degradation after irradiation at 254 nm, but a strong and unspecific degradation was obvious after treatment at 222 nm, presumably caused by cleavage of the peptide bonds.

Two-band emission source based on a three-barrier KrCl-XeBr excilamp

We have created and tested a coaxial excimer lamp (excilamp) with three barriers and two separate compartments representing serially connected gaps. The emission spectrum of the excilamp exhibits two narrow bands of comparable intensity peaking at 222 and 282 nm, representing the emission due to KrCl* and XeBr* molecules, respectively, at an average output radiant power of 1.2 W.

Photochemical Removal of NO by Using 172-nm Excimer Lamp without Using Any Catalysts

Photochemical Removal of NO by Using 172-nm Excimer Lamp without Using Any Catalysts

UV treatment of microorganisms on artificially-contaminated surfaces using excimer and microwave UV lamps

An XeBr excilamp having a peak emission at 283 nm, and microwave UV lamps with peak emissions at 253.7 nm that also generate ozone, have been tested for ability to eradicate high populations of microbial vegetative cells and spores (of bacteria and fungi) artificially added to filter surfaces. The study examined the energy required to completely eradicate large populations on filter surfaces. It was found that both the excilamp and microwave UV lamps were effective at killing large populations on surfaces with killing efficiency dependant on the type of organism, and, whether present in its vegetative or spore forms. The main killing factor is UV radiation following short treatment times. It is considered that for longer irradiation periods that are required to facilitate complete destruction of surface microorganisms, ozone and other oxidising species produced by microwave UV lamps would act to enhance microbial destruction.

Development of Streamers in Dielectric-Barrier-Discharge Excimer Lamp

The development of streamers in a dielectric-barrier-discharge (DBD) excimer lamp has been simulated by using a 2-D fluid model. The DBD is composed of streamer and surface discharges, and the surface discharge significantly affected the shape of the discharge-current waveform. The spatial distributions of electron density, electric field, and excimer density showed the dynamics of the streamer developments, and the behavior of streamers in DBD was clarified in detail.

Direct fabrication of metavanadate phosphor films on organic substrates for white-light-emitting devices

White-light-emitting materials have attracted considerable attention because of their applications, such as large-surface emitting devices. Inorganic phosphor films are expected to be applied to these devices because of good chemical stability; however, a substantial reduction of fabrication temperature is required for future industrial uses such as lighting materials fabricated onto flexible organic substrates. Here we show the optical properties of white-light-emitting metavanadate phosphors, AVO3 (A: K, Rb and Cs), and we report a new direct fabrication process for RbVO3 films onto flexible polyethylene terephthalate (PET) substrates by means of a vacuum ultraviolet irradiation using an excimer lamp. In addition, the (Ca,Sr,Pr)TiO3/a-Al2O3/RbVO3/PET heterostructure prepared by an excimer-laser-assisted metal-organic deposition process has demonstrated the possibility of colour modification for RbVO3 films on PET. Our findings suggest new possibilities for further development of large-surface emitting lighting devices.

VUV Spectroscopic Measurement for Dielectric Barrier Discharge Excited by Piezoelectric Transformer in He–Xe Mixture

A new type of compact excimer lamp has been developed using a piezoelectric transformer (PT) which employs the excitation of dielectric barrier discharge (DBD) in a He-Xe (10.8%) mixture. To investigate the vacuum ultraviolet emission characteristics, a spectroscopic measurement is performed for the He-Xe DBD generated by the PT. The emission peak is observed at 172 nm in a high gas-pressure region, and a sharp peak is observed at 147 nm in a low-pressure region. These are derived from the radiation from the Xe2* excimers and the resonance line of the xenon atoms, respectively.

Eliminating carbon contamination on oxidized Si surfaces using a VUV excimer lamp

In the VUV spectrum we see a significant decrease in reflection due to organic contamination on the surface of mirrors. To study VUV mirrors it is requisite to have calibration standards. Such standards are useless as calibration tools if the surface has organic contamination. For our standard, we use a thermally oxidized silicon wafer with a 27 nm oxide overlayer. We found that silicon wafer samples capped with native oxide acquire 0.1 to 0.2 nm of organic contamination within two hours of being cleaned with stored in closed, but nonvacuum, conditions. After a week there is an additional 0.2 to 0.5 nm deposition after which no further significant deposition is measured up to 90 days. We place the samples in air within one cm of a xenon excimer lamp that radiates 7.2 eV photons which remove half of the remaining contamination every minute. Five minutes exposure is sufficient to clean both fresh and stored samples. Data are determined using spectroscopic ellipsometry (SE) and X-ray photoelectron spectroscopy (XPS). Additionally this paper addresses the need to ensure that these characterization tools are not a source of organic contamination. We determined that the antechamber of our XPS was contaminating samples at a rate of 0.6 nm/30 min as they waited for transfer to the analysis chamber. This contamination was virtually eliminated by attaching an oxygen radical source (ORS) device (Evactron® C De-Contaminator RF Plasma Cleaning System) directly to the antechamber.

Photochemical removal of NO 2 by using 172-nm Xe 2 excimer lamp in N 2 or air at atmospheric pressure

Photochemical removal of NO 2 in N 2 or air (5–20% O 2) mixtures was studied by using 172-nm Xe 2 excimer lamps to develop a new simple photochemical aftertreatment technique of NO 2 in air at atmospheric pressure without using any catalysts. When a high power lamp (300 mW/cm 2) was used, the conversion of NO 2 (200–1000 ppm) to N 2 and O 2 in N 2 was >93% after 1 min irradiation, whereas that to N 2O 5, HNO 3, N 2, and O 2 in air (10% O 2) was 100% after 5 s irradiation in a batch system. In a flow system, about 92% of NO 2 (200 ppm) in N 2 was converted to N 2 and O 2, whereas NO 2 (200–400 ppm) in air (20% O 2) could be completely converted to N 2O 5, HNO 3, N 2, and O 2 at a flow rate of 1 l/min. It was found that NO could also be decomposed to N 2 and O 2 under 172-nm irradiation, though the removal rate is slower than that of NO 2 by a factor of 3.8. A simple model analysis assuming a consecutive reaction NO 2 → NO → N + O indicated that 86% of NO 2 is decomposed directly into N + O 2 and the rest is dissociated into NO + O under 172-nm irradiation. These results led us to conclude that the present technique is a new promising catalyst-free photochemical aftertreatment method of NO 2 in N 2 and air in a flow system.

Influence of Water Vapor on Photochemical Ozone Generation with Efficient 172 nm Xenon Excimer Lamps

The influence of water vapor on photochemical ozone generation has been investigated. Tests of a coaxial ozone generator driven by an efficient, tubular, 172 nm xenon excimer lamp revealed that ozone saturation concentration strongly depends on moisture concentration in the process gas. In order to adequately model the data, catalytic ozone destruction by OH and HO2 radicals formed by reactions with trace amounts of water vapor in the process gas had to be included in the photochemical ozone production rate equation system. Based on the model, optimized ozone photoreactor designs for ambient air, dry air and dry oxygen are described.

Preservation of homochirality of aspartic acid films irradiated with 8.5 eV vacuum ultraviolet light

Enantiomeric excess was reported for amino acids detected from some meteorites. These results imply that these amino acids might escape from racemization processes in space. Here, in an attempt to examine whether non-polarized vacuum ultraviolet (VUV) light was one of racemization factors, we irradiated solid films of homochiral l- or d-aspartic acid ( l- or d-Asp) with a 146 nm excimer lamp in vacuum at 290 K. After irradiation for l-Asp films, l-alanine ( l-Ala) and β-Ala were observed, but d-Asp or d-Ala was not observed. On the contrast, for irradiation to d-Asp films, d-Ala and β-Ala were observed, but l-Asp or l-Ala was not observed. Therefore, we concluded that the chirality was preserved through the photolysis of Asp to Ala. It is of interest to carry out the similar experiments using high-energy particles and/or γ-ray irradiation.

Vacuum ultraviolet irradiation on siliceous coatings on polycarbonate substrates

We studied the effect of vacuum ultraviolet (vuv) irradiation on siliceous coatings of polycarbonate (PC) substrates derived by the sol–gel method, with the aim of improving the abrasion resistance of the substrate surface. Methyltriethoxysilane with colloidal silica was used to prepare the sol solution. The sol solution was spin-coated on PC and this was followed by vuv irradiation with a Xe excimer lamp at 172 nm under N2 atmosphere. The PC substrate with vuv irradiated coating retained its high transmittance in the visible region for about 3 or more times of scraping turns by a steel wool tester on the surface, compared with the non-irradiated or mercury lamp-irradiated coatings, which demonstrated the remarkable improvement of the abrasion resistance by the vuv irradiation. The chemical changes under the vuv irradiation were also investigated by FTIR–ATR spectroscopy, composition analysis conducted with X-ray photoelectron spectroscopy and hardness measurements. It was concluded that the vuv light irradiation resulted in degrading the Si–CH3 bond in sol–gel derived siliceous coatings to yield hardening of the coatings. The transmittance of the coating in vuv region also increased with the Xe lamp irradiation.

Study of the first pulse of Ne-Xe-HCl dielectric barrier discharge for the excimer lamp

A global one-dimensional model of a dielectric barrier discharge which includes the sheath region and the positive column was developed. The model was used to study the electrical properties under operating conditions of the vacuum ultraviolet excimer lamp and to understand the basic processes of plasma kinetics. A 0.5cm interelectrode gap distance is filled with a Ne-Xe-HCl mixture. Time variations of the charged particles and excited species in the positive column were described. Then the one-dimensional model was used in the cathode region to illustrate (i) the spatio-temporal behavior of electronic and ionic densities and the electric field, and (ii) the time variation of the voltage, the current, and secondary currents due to ion and photon (λ=172nm) impact on the cathode. It shows a good resolution inside the sheath at high pressure and it correctly predicts the waveform of the discharge behavior. The obtained results have been discussed and analyzed.

Thermogravimetry Coupled to Single Photon Ionization Quadrupole Mass Spectrometry: A Tool To Investigate the Chemical Signature of Thermal Decomposition of Polymeric Materials

Mass spectrometry (MS) is an established analytical technique to analyze evolved gas in thermogravimetry (TG). In this study, for the first time a novel SPI-MS technique using an electron beam pumped VUV excimer lamp as photon source (lambda = 126 nm) was employed in conjunction with thermogravimetry. The coupling was achieved with an improved heated interface and adjacent transfer capillary between TG and ion source of a quadrupole mass spectrometer. The feasibility of this approach was proven by investigating semivolatile substances such as long-chain alkanes (heptadecane C17H36), polymers, e.g., polystyrene, polycarbonate, and acrylonitrile-butadiene-styrene, polymer mixtures and blends. Mass spectra with almost no fragmentation were obtained, and quantification of selected substances could be achieved. Polymer mixtures could be distinguished by their SPI mass spectra, and the effect of premixing of polymers has been accessed. Its unique attributes render the TA-SPI-MS method a promising new tool for quantitative and qualitative evaluation of complex organic thermal degradation products.

An ultracompact photo-ionization time-of-flight mass spectrometer with a novel vacuum ultraviolet light source for on-line detection of organic trace compounds and as a detector for gas chromatography

A recently developed novel intense rare-gas excimer vacuum ultraviolet (VUV) light source, the electron beam-pumped excimer lamp (EBEL), has been applied to the soft single-photon ionization (SPI) of organic molecules in a compact orthogonal acceleration time-of-flight mass spectrometer (oaTOFMS). The SPI-oaTOFMS system was applied to the on-line monitoring of tobacco smoke. With this setup, it was possible to analyze the composition of individual puffs of cigarette smoke. Furthermore, a gas chromatograph (GC) was coupled to the EBEL SPIoaTOFMS system. Soft photo-ionization represents an additional separation dimension. By combination of the gas chromatographic and the soft-ionization mass spectroscopic separation dimensions, a truly multidimensional comprehensive analytical method could be derived.

Development and Performance of a Fluence Rate Distribution Model for a Cylindrical Excimer Lamp

Ultraviolet disinfection systems employing excimer lamp technology represent a suitable choice in situations where lamp mercury content is restricted, or otherwise undesirable. The XeBr* excimer lamp emits nearly monochromatic radiation at 282 nm, and dose-response experiments with Bacillus subtilis spores have shown that it is germicidally effective. A numerical model was developed to describe the fluence rate (E') distribution emanating from a cylindrical XeBr* excimer lamp, based on liquid water or air as the surrounding medium. The E' distribution model is based on physical phenomena that are known to govern excimer lamps; the model also accounts for refraction, reflection, and absorbance effects of the quartz lamp envelope and the media surrounding the lamp. Measurements of the E' distribution by local actinometry supported the validity of the numerical model. This model can be used as a component (submodel) of a more general model to simulate the behavior of photochemical reactors that employ excimer lamps as their source of electromagnetic radiation.

Preparation and Characterization of Tin-doped Indium (ITO) Film by Photo Reaction of Nano-Particle (PRNP) Using Excimer Laser

ABSTRACTAn ITO film on an SiO2 substrate was prepared from spin-coated nano-particles using a simple thermal process and photo irradiation process. The effects of the excimer lamp and excimer laser on the resistivity of the film were investigated. When the film is 40 nm thick, the combined two-step irradiation by an excimer lamp and laser in N2 is effective for the preparation of the ITO film with a lower resistivity. Using the two-step irradiation and one-step KrF irradiation in N2 at room temperature, the resistivity of the ITO film was 5.94×10−4Ωcm. On the other hand, when using the thermal process, the resistivity of the film sintered at 500 °C in N2 was 4.10×10−3Ωcm. The differences in resistivity are discussed on the basis of the microstructure using SEM, XRD and Hall measurements.

Development of Abrasive-Free Polishing Method for Cu Utilizing Vacuum Ultra-Violet Light

In recent years, with the increase of the demand for higher signal transmission speed of ULSI, it is strongly required to improve the Chemical Mechanical Polishing (CMP) technology for Cu. The conventional Cu-CMP slurries, however, have serious problems relating to detrimental impact on environment, because it includes a lot of organic compounds and abrasives. In this study, a new Cu-CMP method, that is, the polishing method utilizing vacuum ultra-violet (VUV) light irradiation and an electrolyzed water was proposed and developed in order to overcome the above-mentioned problem. In the newly-proposed method, the Xe excimer lamp was adopted as the VUV light source. The lamp has a sharp peek of the wave length at 172 nm, and can generate an ozone gas from decomposition of oxygen. The effects of the VUV light irradiation for Cu-CMP are thought to be as follows 1) an oxidation effect by generated ozone, 2) a photoelectric effect for Cu substrate. Then the polishing experiments for Cu substrate were carried out with in-situ VUV light irradiation. The experimental results revealed that the developed method was effective for obtaining precise smooth surface, namely, the mirror-finished surface under 1 nm Ra was achieved. From the result, it was found that the developed polishing method has an electrochemical effect for polishing, namely, the amount of OH- groups and the density of oxygen or pH of polishing fluid have a strong influence on Cu polishing process.

Improvement of Serviceability Properties of Synthetic Textile Fabrics using 172 nm Ultraviolet Excimer Lamp

The 172 nm ultraviolet (UV) excimer light was exposed to textile fabrics of acetate, nylon 6, poly (ethylene terephthalate), acrylic and polypropylene. No significant changes in the tensile extension parameters and the surface reflectance of the fabrics due to the UV exposure were observed. The water contact angle was measured by the Wilhelmy technique using a single fiber that was taken from the fabric. Remarkable increase in wettability was accomplished by the UV irradiation of 1 minute. The capillary wetting and the moisture absorption of the fabrics, which were determined electrically, were found to increase by the UV exposure. The effect of the UV exposure on detergency was examined using a poly (ethylene terephthalate) plate on which model particulate soil was deposited. The removal was found to increase after the UV treatment. It was concluded that the exposure of UV excimer light to synthetic textile fabrics made it possible to improve their serviceability properties.

Techniques for Measuring Rate Constants for Acid Generation from PAG (Photo Acid Generator) during ArF Exposure

We previously performed in situ FT-IR measurements while subjecting chemically-amplified resists to UV light (248 nm) to observe photodecomposition of the PAG for KrF excimer lasers. Based on these observations, we measured rate constants for acid generation associated with PAG photodecomposition. More recently, we equipped our FT-IR system with a 193-nm excimer lamp (developed by Ushio Inc.) to perform the world's first in situ observations of PAG photodecomposition using 193-nm light. Our report also describes the successful measurement of rate constants for acid generation from the PAG for ArF excimer lasers.