Vacuum Ultraviolet Excimer Lamp Research Articles

Photochemical removal of acetaldehyde using 172nm vacuum ultraviolet excimer lamp in N2 or air at atmospheric pressure.

The photochemical removal of acetaldehyde was studied in N2 or air (O2 1-20%) at atmospheric pressure using side-on and head-on types of 172nm Xe2 excimer lamps. When CH3CHO was decomposed in N2 using the head-on lamp (HL), CH4, CO, and CO2 were observed as products in FTIR spectra. The initial removal rate of CH3CHO in N2 was ascertained as 0.37min-1. In air (1-20% O2), HCHO, HCOOH, CO, and CO2 were observed as products in FTIR spectra. The removal rate of CH3CHO in air using the side-on lamp (SL) increased from 3.2 to 18.6min-1 with decreasing O2 concentration from 20 to 1%. It also increased from 2.5 to 3.7min-1 with increasing CH3CHO concentration from 150 to 1000ppm at 20% O2. The best energy efficiency of the CH3CHO removal using the SL in a flow system was 2.8g/kWh at 1% O2. Results show that the contribution of O(1D) and O3 is insignificant in the initial decomposition of CH3CHO. It was inferred that CH3CHO is initially decomposed by the O(3P) + CH3CHO reaction at 5-20% O2, whereas the contribution of direct vacuum ultraviolet (VUV) photolysis increases concomitantly with decreasing O2 pressure at < 5% O2. After initial decomposition of CH3CHO, it was oxidized further by reactions of O(3P), OH, and O3 with various intermediates such as HCHO, HCOOH, and CO, leading to CO2 as a final product.

Effects of aging on poly(1‐trimethylsilyl‐1‐propyne) membranes irradiated with vacuum ultraviolet radiation for gas separation

ABSTRACTIn this study, we investigated the effects of physical aging on the surface and gas‐transport properties of highly gas permeable poly(1‐trimethylsilyl‐1‐propyne) membranes irradiated with vacuum ultraviolet (VUV) radiation. VUV excimer lamp irradiation was performed on one side of the membrane for 6 or 60 min. The gas permeabilities for carbon dioxide (CO2) and nitrogen (N2) were determined through a volumetric measurement method at 23 °C. The gas permeabilities for CO2 and N2 increased temporarily at 7 days after 6 and 60 min of VUV irradiation of the membranes. The change in the gas permeability for N2 was more remarkable than that for CO2. These changes were related to the CO or SiOx ratio. The CO ratio was related to the gas permeability of the membranes VUV‐irradiated for 6 min, whereas the SiOx ratio was related to the gas permeability of the membranes VUV‐irradiated for 60 min. These changes affected the gas selectivities of the membranes. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018, 135, 45973.

Improving vacuum-UV (VUV) photolysis of organic compounds in water with a phosphor converted xenon excimer lamp emitting at 193 nm.

A novel vacuum ultraviolet excimer lamp emitting light at 193 nm was used to investigate the degradation of organic micropollutants in ultrapure water and wastewater treatment plant (WWTP) effluent. Overall, light at 193 nm proved to be efficient to degrade the investigated micropollutants (diclofenac, diatrizoic acid, sulfamethoxazole). Experiments with WWTP effluent proved the ability of radiation at 193 nm to degrade micropollutants which are hardly removed with commonly used oxidation technologies like ozonation (diatrizoic acid, ethylenediaminetetraacetic acid, perfluorooctanoic acid, and perfluorooctanesulfonic acid).

Removal of nitric oxide by activated ammonia generated by vacuum ultraviolet radiation

To broaden and lower the narrow temperature window of the selective non-catalytic reduction (SNCR) of nitric oxide (NO), the use of activated ammonia as the reduction agent was examined. A 172nm VUV (vacuum ultraviolet) excimer lamp was employed as the excitation source for molecular ammonia. Activated ammonia generated by VUV radiation in a photochemical reactor was injected into a model flue gas (NO/O2/N2) at room temperature. The effects of reaction temperatures, oxygen concentrations, and NH3/NO molar ratios (MRs) on NO removal were investigated in a lab-scale plug flow reactor. Temperatures ranged from 500°C to 850°C. A temperature window enlargement of 150°C was achieved at the lower boundary of the temperature window. The results are the first clear observations of low temperature SNCR by activated ammonia. Above 600°C, NO removal was affected by injection of activated ammonia, while around 750°C, conventional SNCR by injection of molecular ammonia was effective. An approximate 80% NO removal was attained at 700°C with an MR=2.0 and 8.3% O2. Although the chemical compositions of activated ammonia remained unknown during the present study, the results suggested that effective chemical species for NO removal such as NH2 and H2 were produced from activated ammonia above 600°C. The number of photons emitted per mole of molecular ammonia, Np, was proposed to evaluate the effects of NH3 concentrations and residence times of NH3 gas in the photochemical reactor. The optimum Np range was found to be the point at which maximum NO removal was attained.

Chemical grafting of curcumin at polyethylene terephthalate woven fabric surface using a prior surface activation with ultraviolet excimer lamp

AbstractDurable curcumin‐treated antibacterial polyethylene terephthalate (PET) fabrics (against Staphylococcus aureus) were produced by dyeing with curcumin after surface activation using vacuum ultraviolet excimer lamp at 172 nm. Surface change properties of the exposed fabrics were characterized by surface analysis methods such as wettability, atomic force microscopy, and X‐ray photoelectron spectroscopy. Results show an increase in surface hydrophilicity with a water contact angle of the PET fabric reaching 24° after 10 min excimer irradiation, which could be attributed to an increase in carboxyl group formation as confirmed by X‐ray photoelectron spectroscopy measurements. Varying concentrations of curcumin were immobilized onto untreated and vacuum ultraviolet‐irradiated PET samples using diffusion method at 90°C, and the treated fabrics characterized using K/S (color strength) values at 440 nm. K/S values increased when the PET surface was subjected to a prior excimer irradiation, because of grafting of curcumin at the PET surface. Increased excimer irradiation time increased grafting of curcumin because the inner fabric fiber surfaces were also more thoroughly treated. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011

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.

Debris Characteristics of a Laser-Plasma Colloidal Target Containing Tin Dioxide Nanoparticles

ebris characteristics and theireduction have been investigated for a laser-produced plasma extreme ultraviolet source by using a colloidal jet/droplet target containing tin dioxide nanoparticles. The amount of deposited debris on a silicon witness plate was determined by totalaser energy irradiated onto the target. Double laser pulse irradiation was not effective for deposited debris reduction. Incontrast, in situ low-temperature heating of the witness plate was effective inreducing the amount of deposited debris. Room-temperature photon processing using an incoherent vacuum ultraviolet excimer lamp at 126 nm deoxidized a deposited tin oxide layer

Basic dyeable polyester: a new approach using a VUV excimer lamp

Surface treatment of polyester fabric was carried out using a vacuum ultraviolet (VUV) excimer lamp. The hydrophilicity of the polyester fabric was significantly improved by surface modification, as indicated by the decrease in wetting time and wicking time. This approach can be used to create added value for polyester fabric, which otherwise suffers from low hydrophilicity. Further changes on irradiation were characterised by atomic force microscopy and the crystallinity and tensile strength of the samples were also tested. Basic dyeability of the microdenier polyester fabric was seen to improve greatly on exposure to the excimer lamp, followed by grafting with acrylic acid. The effects were observed to increase with an increase in irradiation time. The best effect was obtained for irradiation time of 10 min. These enhanced properties were accompanied by an insignificant loss in crystallinity and tensile strength of treated fabrics.

Silicon Nitride Film Deposition by Photochemical Vapor Deposition Using an Argon Excimer Lamp

In this paper, we report the deposition of silicon nitride (SiNx) films for the production of semiconductor devices and flat panel displays, by chemical vapor deposition with vacuum ultraviolet excimer lamps (VUV-CVD) using SiH4 and NH3 as raw materials. An Ar2* excimer lamp (λ=126 nm, hν=9.8 eV) with a high photon energy was used to directly excite and dissociate SiH4 through a photochemical reaction. SiNx films were successfully formed at a low temperature of 100 °C with the Ar2* excimer lamp. Although the Si-rich films were obtained using an Ar2* lamp, they showed a quality almost similar to that of films obtained by conventional plasma-CVD at 400 °C.

UV detection for excimer lamps using CVD diamond in various gaseous atmospheres

The recently emerged high-power vacuum ultraviolet excimer lamps operating at 222, 172 and 126 nm will require robust photodetectors to ensure efficient operation for the photo-processing of materials which is often carried out in various ambient atmospheres. Conventional silicon detectors could not meet the stringent requirements, particularly for the 172 and 126 nm lamps. In this paper, we report an initial study on the use of the thin film CVD diamond device for the excimer VUV detection in air, oxygen or nitrogen. The device in the 3 atmospheres exhibits a low similar dark current around 0.3 nA. Working in air leads to significantly prolonged “turn-off” time due to the increased surface conductivity of the device, caused mainly by moisture penetrating into the surface layer. The moisture penetration is enhanced by the increased surface porosity of diamond due to the strongly oxidizing ozone and active oxygen species formed during 172 nm illumination reacting with non-diamond carbon and amorphous materials within the film. However, the UV detection in different environments can still give similar outputs from the same lamp source, probably due to several counteracting effects. Preliminary results on the UV detection for more energetic 126 nm excimer photons using this diamond device have also been reported.

Nitridation in Photon-Assisted Process Using Argon Excimer Lamp

We attempted silicon nitridation that continuously deposits silicon with monosilane (SiH4) and nitrides the silicon with ammonia (NH3) at a low temperature using a vacuum ultraviolet excimer lamp. We used an argon excimer lamp (λ=126 nm, h ν=9.8 eV) so that SiH4 and NH3 can absorb photons and dissociate. Nitrogen exists only near the film surface at a low temperature, and its concentration increases at a high temperature. This photon-assisted process is very feasible for the nitridation of semiconductor devices and flat panel displays in the near future, because it is a low-temperature and low-damage process.

Amorphous Silicon Film Deposition from SiH4 by Chemical Vapor Deposition with Argon Excimer Lamp

We have deposited amorphous silicon thin films from monosilane (SiH4) gas by photochemical vapor deposition using a vacuum ultraviolet excimer lamp (VUV-CVD). We used an argon excimer lamp (λ=126 nm, hν=9.8 eV) whose photons are strongly absorbed by SiH4 gas. The substrate temperatures were changed from 25 to 300°C. When the temperature was lower than 150°C, the films included H–Si–H units and H2 molecules in its structure. When it was higher than 150°C, the main structural unit was Si–H.

Electrical properties of SiO2 films deposited by photon-assisted CVD with vacuum-ultraviolet excimer lamp

R&D is proceeding in various countries on Vacuum-Ultraviolet Chemical Vapor Deposition (VUV-CVD) as the CVD technique for next-generation semiconductor fabrication. Deposition becomes possible at room temperature because the precursor of the film is photodissociated by vacuum-ultraviolet light, which is short-wavelength ultraviolet light. VUV-CVD is a promising damage-free CVD system in processes where charged particles and neutral particles having kinetic energies above the theoretical photon energy do not exist, and process damage such as high heat, impurity injection, and electrical charges of the semiconductor fabrication process are a concern. The authors fabricated silica film by VUV-CVD using an Xe2 excimer lamp and tetraethylorthosilicate [TEOS, Si(OC2H5)4], which has many uses in the fabrication of interlayer insulating film, and octamethylcyclotetrasiloxane [OMCTS, ((CH3)2SiO)4], which has a cyclic Si-O skeleton. The result of evaluating the leakage current characteristics and the relative dielectric constant, which are electrical characteristics of these films, showed that the OMCTS having a cyclic Si-O skeleton is effective as the silica film precursor in VUV-CVD. This paper reports the electrical characteristics of these silica films formed by VUV-CVD. © 2005 Wiley Periodicals, Inc. Electron Comm Jpn Pt 2, 88(3): 36–43, 2005; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ecjb.10196

Formation of Silica Coatings from Perhydropolysilazane Using Vacuum Ultraviolet Excimer Lamp

Silica coatings have been prepared by the spin-coating technique with the 172 nm vacuum ultraviolet (VUV) irradiation using a Xe2∗ excimer lamp. Perhydropolysilazane was used as a precursor. The chemical states, composition and optical transmittance of VUV-irradiated films were investigated by Fourier transform infrared, X-ray photoelectron, UV-visible absorption spectroscopies. The results showed that VUV irradiation was effective to remove hydrogen and nitrogen from the coating film and to incorporate oxygen to the film, so that the film transforms into silica. The effects of VUV treatment on the film were found to be dependent on oxygen concentration in surrounding gas. It was suggested that the effect of oxidation reaction due to active oxygen species and/or ozone is larger than that of the cleavage of a chemical bonding by photon energy.

Observations of Photo-Dissociation Reaction of TEOS Molecules on Silicon Clean Surfaces

Tetraethoxysilane (TEOS : SiO4(C2H5)4) is widely used to fabricate silicon-dioxide insulator thin films in LSI device technologies. We have already reported that TEOS is photo-dissociated to result in oxide layer deposition at room temperature by a vacuum ultraviolet excimer lamp (λ=172 nm). In this paper, we have observed the initial stages of oxide layer deposition on silicon clean surfaces with the scanning tunneling microscope (STM) and time-of-flight (TOF) mass spectrometer. An argon excimer lamp (λ=126 nm) is used for the photo-chemical vapor deposition (CVD). TEOS molecules have been dissociated to be SiO4(C2H5)n(n=1, 2, 3) groups on the clean surfaces. The 126 nm photons dissociate the molecules or radicals to Si-Om(m=1, 3, 4) after 2 min. Finally, the Si-Om adsorbed molecules and Si atoms in the substrate are re-arranged to be a disorder structure by the photons.

Role of O(1D) in the oxidation of Si(100)

Oxidation of silicon with neutral atomic oxygen species generated in a rare gas plasma has recently been shown to produce high-quality thin oxides. It has been speculated that atomic oxygen in the first excited state, O(1D), is a dominant reactive species in the oxidation mechanism. In this study, we investigate the role of O(1D) in silicon oxidation in the absence of other oxidizing species. The O(1D) is generated by laser-induced photodissociation of N2O at 193 nm. We find that, at 400 °C, O(1D) is effective in the initial stages of oxidation, but the oxide growth rate decreases dramatically past 1.5 nm. Oxide films thicker than 2 nm were not achieved regardless of oxidation time or N2O partial pressure (0.5–90 mTorr), indicating O(1D) cannot be a dominant reactive species in thicker rapid oxidation mechanisms. We suggest that quenching of O(1D) to O(3P) (ground state) during diffusion through thicker oxides results in drastically slower oxidation kinetics. In contrast, oxidation with a vacuum ultraviolet excimer lamp operating at 172 nm resulted in rapid oxide growth up to 4 nm. Thus, other species produced in plasmas and excimer lamps, such as molecular and atomic ions, photons, and free and conduction band electrons, likely play a dominant role in the rapid oxidation mechanism of thicker oxides (&amp;gt;2 nm).

Characterization of SiO2 Films Deposited by VUV-CVD Using Organic Siloxane Gases

Recently, much attention has been paid to novel photochemical vapor deposition using vacuum ultraviolet excimer lamps (VUV-CVD), because thin films can be deposited at room temperature. We show some characterization of films and discuss about the reaction mechanism using organic siloxane gases in VUV-CVD. VUV photons dissociate organic gases into radical reactants of Si-O and impurities such as C-H and O-H in the gas phase. The reactants finally condense on the surface into films included SiO2 and impurities. The reaction is different by adding O2. It is caused by the behaviors of ozone and activated oxygen that VUV photons dissociate O2 and are generated. The deposition efficiency is improved both by the low substrate temperature and the higher light-intensity of an excimer lamp. The film deposition at room temperature in VUV-CVD that either thermal or plasma induced damages are completely avoided must become a novel technique in thin films preparations.

Silica film preparation by chemical vapor deposition using vacuum ultraviolet excimer lamps

We have prepared SiO2 thin films on silicon wafers from tetraethoxyorthosilicate (TEOS; Si(OC2H5)4) by photochemical vapor deposition (photo-CVD) with the use of various excimer lamps which emit incoherent light at 308 (XeCl), 222 (KrCl), 172 (Xe2), 146 (Kr2) and 126nm (Ar2). The film deposition is observed at wavelengths shorter than 172nm. With 10mW/cm2 172nm radiation, the growth rate is 8nm/min on the room temperature substrate. The deposition efficiency depends on the wavelength and shows the maximum value for 146nm radiation. Addition of O2 to TEOS induces inhibition of C and H impurity inclusion in the films.

Chemical surface modification on polytetrafluoroethylene films by vacuum ultraviolet excimer lamp irradiation in ammonia gas atmosphere

Irradiation of polytetrafluoroethylene films with vacuum UV light in an ammonia gas atmosphere resulted in a hydrophilic surface, where abstraction of fluorine atoms, and introduction of nitrogen, oxygen, and hydrogen atoms occurred. We used Kr2* and Xe2* excimer lamps at wavelength of 146 and 172 nm, respectively. The reaction mechanism for chemical surface modification is discussed on the basis of x-ray photoelectron spectroscopy, secondary ion mass spectroscopy, and attenuated total reflection Fourier transform infrared spectroscopy analyses.

Principle and Applications of Barrier Discharge Excimer Lamps.

New ultraviolet and vacuum ultraviolet excimer lamps driven by barrier discharge are reviewed. Ar, Kr, Xe, KrCl and XeCl excimer lamps were developed, whose emission wave lengths are 126, 146, 172, 222, and 308nm, respectively. These spectra have full width at half maximum (FWHM) as narrow as 2 to 14 nm. An efficiency of 10% was obtained with a Xe excimer lamp. The principle, structure and application of lamps are described.