Lamp Exposure Research Articles

(Invited) Characterization of UV Excitation Accelerated Material Changes on As-Grown SiC Epitaxial Layers and Their Impact on Defect Detection

Silicon Carbide continues to gain acceptance and enjoy widespread adoption in mainstream high voltage applications. Even as both substrate and epitaxial material quality keeps improving, new failure mechanisms can get introduced due to various factors like diameter expansion, process and volume scale up. This forces the industry to evaluate and implement a variety of characterization methods to identify and eliminate any potential root causes for failure modes. Currently every substrate and epitaxial wafer is scanned for defects even in mass production due to the variable presence of various types of killer visual defects and pure crystal defects. Due to the bandgap of SiC, a convenient technique to non-destructively reveal crystal defects in the material is to use excitation light in the Ultraviolet (UV) range. Recently all volume mass production characterization systems have adopted this UV excitation along with detecting crystal defects using either near-ultraviolet (NUV) or infra-red (IR) PL bands [1,2]. Both the widely used KLA CS920 and the Lasertec SICA 88 platforms use UV light excitation using either a laser or a lamp. In our previous reports [3-6] while detecting faint PL signals, we have observed that exposing the wafers to this UV excitation results in material changes and increase in background PL that can be detected via the various PL acquisition channels. This raises concerns on the exact mechanism of the SiC material change. This constantly changing background also causes issues with measurement repeatability and calibration of the tools. In this work, we offer a detailed study of the effects of both UV laser and UV lamp exposure on as-grown SiC epitaxial wafers and explain the changes in the material. Additionally we replicate exactly the changes using various independent processing steps, while also offering various ways to both prevent and remove this effect. Performing repetitive scans on as-grown epitaxial layers by using either an UV laser or UV lamp results in an observable increase in the background PL. This effect is highly repeatable in samples and results in a 25%-35% change in the signal to noise ratio both in the NUV and IR wavelength ranges. This can either adversely affect or enhance the defect signatures depending on which wavelength range is being captured. This causes repeatability issues for the detecting recipes and algorithms due to the signal variation. A few surface treatments done to the affected surfaces have been successful in restoring the surface PL signals to their original values. From this and from performing EDX on pre- and post HF etch samples the formation of a very thin layer of UV-exposure accelerated oxide was observed. This accelerated oxide occurred only in the present of the UV excitation. The cause for the formation of this oxide is proposed to be the highly reactive surface state of the as-grown epitaxial wafers. Passivating the as-grown surface before repetitive scanning completely eliminates the change in background PL. This effect is further replicated on epitaxial wafers by growing thermal oxides of different thicknesses and also depositing PECVD oxide. The effect of the thermal oxides very closely mimics the observed effect, while the deposited oxide does not cause a big change in the PL signals. This shows the oxide – SiC interface is an important factor for this effect, and not just the presence of the oxide. The other effect of UV excitation on the expansion of basal plane dislocations (BPD) into stacking faults (SF) [2] was also studied. SF nucleation was only observed after about 150 scans and even then only in a small fraction of the BPDs. Characterization of the affected surface after repetitive exposures will be presented. High intensity constant exposure low temperature PL spectrum results which are very different in nature to the relative low intensity exposures will also be presented. Both surface treatments to completely recover from the effect and passivation schemes to prevent this effect from UV excitation exposures will be shown. Further characterization of the effect of both thermal and deposited oxides on PL of epitaxial layers will be shown.

Eco-friendly profile of pegylated nano-graphene oxide at different levels of an aquatic trophic chain

Nanographene oxide (nGO) has been recently proposed as a new antitumoral therapeutic agent, drug delivery carrier and gene transfection vehicle, among others. Treatment is carried out by hyperthermia induced by infrared irradiation. After treatment, the nanosystems will be inevitably excreted and released to the environment. To understand the potential impacts of pegylated nGO (nGO-PEG), three key species from different trophic levels were used: the green micro-algae Raphidocelis subcapitata (growth inhibition test), the cladocera Daphnia magna (acute and chronic tests), and the fish Danio rerio (fish embryo test). Besides a regular standard procedure to assess toxicity, and considering the mode of action of nGO-PEG in cancer treatment, a simultaneous infrared lamp exposure was carried out for D. magna and D. rerio. Additionally, and taking advantage of the phenotypic transparency of D. magna, nGO-PEG was fluorescently tagged to evaluate the potential uptake of nGO-PEG. The R. subcapitata growth inhibition test showed effects during the first 48 h, recovering till the end of the test (96 h). No acute or chronic effects were observed for D. magna, under standard or infrared light exposures although confocal microscope images showed nGO-PEG uptake. Very small percentages of mortality and abnormalities were observed in D. rerio exposed with and without the infrared lamp. Although low hazard may be expected for nGO-PEG in aquatic ecosystems, further studies with species with different life traits should be accomplished, in order to derive more accurate conclusions.

Potential cutaneous carcinogenic risk of exposure to UV nail lamp: A review.

The increased use of ultraviolet (UV) nail lamps in recent years has generated safety concerns of this device. A UV nail lamp is a source of artificial UVA radiation, often used to dry, harden, and cure the nails at home and in the salon. UVA radiation is known to be mutagenic and can cause damage to the DNA, resulting in cutaneous malignancy. Currently, there are only a few studies that have evaluated UV nail lamp irradiation and its potential carcinogenic risk. We review the literature on UV nail lamps, its safety, effect on nails and hands, and the potential role in increasing the risk of cutaneous malignancy. Based on available data, the carcinogenic risk is low; nonetheless, the use of a broad spectrum sunscreen with SPF >30 before UV nail lamp exposure is recommended.

Quaternary magnetic BiOCl/g-C3N4/Cu2O/Fe3O4 nano-junction for visible light and solar powered degradation of sulfamethoxazole from aqueous environment

Novel magnetic quaternary BiOCl/g-C3N4/Cu2O/Fe3O4 (BGC-F) nano-heterojunction with excellent photocatalytic activity was prepared by facile co-precipitation method. The visible photodegradation activity of the junction was analyzed for sulfamethoxazole (SME) as target pollutant. BGC-F with a dosage of 0.2 g L−1 exhibits high photocatalytic activity with 99.5% of SME (100 µM) degraded in 60 min under visible (Xe) lamp and 92.1% in 120 min under natural sunlight. The activity of quaternary junction was found to be 7.2, 6.8 and 4.2-fold higher as compared to C3N4/BiOCl/Fe3O4, Cu2O/BiOCl/Fe3O4 and Cu2O/BiOCl/C3N4 junctions respectively. Formation of an effective p-n-p junction (BiOCl-C3N4-Cu2O) leads to shifting of energy bands and rising of an in-built electric field and charge separation. The effect of parameters as pH, catalysts loading amount, NO3− and HCO3− have been studied. The O2− and OH was found to be major reactive species identified by scavenging experiments and the band gap structure analysis The results for mineralization were analyzed in terms of Liquid chromatography-mass spectroscopy (LC-MS), total organic carbon (TOC) removal and chemical oxygen demand (COD). 41.6% of TOC was removed in 3 h experiment under Xe lamp exposure. The drug degradation was also confirmed by testing activity on E. coli and cyto-toxicity on human peripheral blood lymphocytes (PBL). Only 2.1 mm zone of inhibition was observed for E. coli in case of exposure to SME degraded products while for pure SME it was 18.1 mm hinting complete mineralization. In addition 99% cell viability was observed for PBL cells treated with degraded products of SME. Furthermore, BGC-F exhibited good reusability after magnetic separation and regeneration, rendering it a promising multi-functional catalyst with active use of advanced oxidation processes for treating pharmaceutical waste water.

Enhanced photocatalytic activities of low-bandgap TiO2-reduced graphene oxide nanocomposites

In this study, a hydrothermal method was successfully used to prepare a reduced graphene oxide (RG)–titanium dioxide (TiO2) hybrid in 10–20 nm, starting from commercial TiO2 P25 nanoparticles and liquid-exfoliated graphene oxide (GO). Compared to TiO2, an obvious red shift of light absorption (from 3.1 to 2.6 eV) of the as-prepared RG–TiO2 was observed by UV–Vis analysis, and an enhanced photocatalytic degradation of the Rhodamine B (Rh. B) was also observed under Xe lamp exposure test by using the as-prepared RG–TiO2. Multiple characterizations of this RG–TiO2 nanocomposite confirmed that its photocatalytic enhancement could be ascribed to two approaches. Firstly, RG extended the mean free path and photogenerated electrons’ lifetime of TiO2, which minimized electron–hole pairs’ recombination. Secondly, RG expanded the light absorption spectrum of TiO2 from UV range to UV and visible light range. The explication of these improvements was concluded as the energy gap changing and a likelihood of up-conversion photoluminescence mechanism (UCPL). Due to the low-cost, nonpoisonous and excellent photocatalytic properties of RG–TiO2, this material can be applied well in sewage treatment and other related fields.

Tunable cobalt nanoparticle synthesis by intense pulse flash annealing

Magnetically susceptible materials can serve as a basis for the directed assembly of nanoscale network devices which can be used to extract energy from phase change materials. So far, matrix production cost has been a prohibitive factor in the realization of real world applications. Here we report a cost-effective method to synthesize magnetic nanoparticles. Samples were fabricated by sputtering magnetic thin films on carbon nanotube substrates followed by xenon intense pulsed light flash annealing. The results indicate that spatially ordered magnetic spheres can be tuned by various parameters such as initial thin film thickness, xenon lamp exposure excitation energy, local surface geometries, and the presence of an external magnetic field during annealing.

Safety of neonatal phototherapy lamp exposure

A routine review of light exposure within a neonatal intensive care unit is described following the introduction of a new model of neonatal phototherapy lamp. Spectral measurements were undertaken using a Bentham Dmc150 spectroradiometer system. Safety assessments were undertaken based on likely exposure of parents at the cot side, neonates in adjacent cots and the effectiveness of eye protection for neonates with direct phototherapy. An aphakic eye response was used for assessment of neonatal risk and the blue-light response for estimation of adult exposure using current ICNIRP guidelines. Such estimations indicated exposure levels of parents at the cot side and neonates in adjacent cots were within current established safe limits. The level of light blocking provided by the available neonatal eye protection was estimated to be entirely adequate and presented no hazard to the infant when correctly positioned over the neonate. It is likely, however, that an increased safety factor is potentially present for the neonate due to the fact that the neonate’s eyes will typically be shut for over 50% of the time. It is identified, however, that the aphakic response is essentially associated with mature adult retinal cells, and that the maturing cells of the neonate may exhibit additional light sensitivity, especially in the case of premature infants. Changes in neonatal physiology associated with neonatal phototherapy are discussed, which may influence mechanisms of light-induced retinal damage.

Fabrication of multilevel resist patterns by using a liquid crystal mask

Photolithographic processes of multilevel features in microfluidics can be complex and expensive. This paper demonstrates a quick method for manufacturing multilevel patterns, which is based on liquid crystal display masking during a standard lithography process for master mold fabrication for the polydimethysiloxane replica process. An active mask, based on a liquid crystal display, can simplify the process due to the ability to quickly modify designs and reduce the overhead for alignment between mask levels. The possibility of multilevel patterning, with the help of active masking, creates new opportunities for optical lithography processes. We have developed the process for a standard, mercury lamp exposure mask aligner system. The patterning character- istics were evaluated with a step pattern fabricated as an example of three-dimensional patterning for multilevel structuring. The application of a liquid crystal mask for resist contrast measurements was demonstrated. © 2015

Photo-induced degradation and thermal decomposition in ZnSnF6·6H2O:Mn4+ red-emitting phosphor

ZnSnF6·6H2O:Mn4+ red-emitting hexahydrate phosphor is synthesized by the chemical reaction method, and its unique structural and optical properties are investigated using X-ray diffraction measurement, photoluminescence (PL) analysis, PL excitation spectroscopy, and electron spin resonance (ESR) spectroscopy. The Mn4+-activated phosphor exhibits remarkable degradation in the PL intensity under Xe lamp exposure and also by the coherent laser beam irradiation with the following order of degradation: Ar+ (488nm)>He–Cd (325nm)>He–Ne laser (632.8nm). The mechanism of degradation is considered to be due to a change in the valence state of manganese ions from Mn4+ to Mn5+ by the photooxidation and/or disproportionation. The ESR measurement supports decreased Mn4+ spin density in the Xe-lamp exposed, degraded sample. The changes in the structural and PL properties are also observed after thermal annealing above ∼100°C and explained by the thermal-annealing-induced dehydration/decomposition of the host material.

Potency of Silver Nanoparticles (SNPs) as UV protectant for HaNPV

Present investigation was carried out to test the potency of Silver nanoparticles (SNPs) as UV protectants along with tinopal and mango leaf extract at Department of Entomology, Dr. Panjabrao Deshmukh Krishi Vidyapeeth, Akola during 2011 - 2013. Formulated viral suspension was exposed to UV 20 W Philips lamp (Type 05, range 285 - 320 nm) for 15 minutes and to sunlight at noon hours for 30 minutes,1, 1.5 and 2 hours and determined the viability of POBs and larvicidal activity of viral formulations before and after UV lamp and sunlight exposure. Least reduction in POBs i.e 5.2 per cent was observed from HaNPV + Tinopal 1 %, also recording 86.67 per cent larval mortality when exposed to UV lamp, which was at par with HaNPV alone unirradiated. HaNPV alone when irradiated recorded 55.1 per cent reduction in POBs. HaNPV + tinopal 1 % when exposed to sunlight, protected the POBs upto 1.5 hour, recorded 20.5 per cent reduction in POBs and 83.89 per cent larval mortality. When exposed to 2 hours sunlight reduced the insecticidal activity of HaNPV even though tinopal 1% was used as UV protectant with HaNPV. Of the additives, tinopal 1 % was found to be most effective as it protected the POBs from UV degradation and enhanced larval mortality as compared to mango leaf extract 1 % and SNPs.

Optical spectroscopy and degradation behavior of ZnGeF6·6H2O:Mn4+ red-emitting phosphor

We report on a method of synthesizing Mn4+-activated ZnGeF6·6H2O hexahydrate red phosphor by the chemical reaction and its photo-induced degradation behavior. The structural and optical properties of ZnGeF6·6H2O:Mn4+ are investigated using X-ray diffraction measurement, photoluminescence (PL) analysis, PL excitation (PLE) spectroscopy, PL decay measurement, diffuse reflectance measurement, and electron spin resonance (ESR) spectroscopy. The present hexahydrate phosphor exhibits the sharp red emission lines typically observed in various Mn4+-activated phosphors. However, the phosphor shows remarkable PL intensity degradation under Xe lamp exposure for a few minutes or coherent laser beam irradiation at different wavelengths. Its degree is in the order of Ar+ (488nm)>He–Cd (325nm)>He–Ne laser (632.8nm). The photo-induced degradation mechanism is explained by a change in the valence state of manganese ions from Mn4+ to Mn5+ by the photooxidation (Mn4+→Mn5+) or disproportionation reaction (2Mn4+→Mn3++Mn5+). The ESR measurement confirms the decreased Mn4+ spin density in the sample exposed with Xe lamp after Xe lamp exposure for 5min. The photo-induced degradation is concluded to universally occur in AIIBIVF6·6H2O:Mn4+ hexahydrate phosphors.

Luminance Conversion Property of Er and Yb Doped KZnF3Nanocrystal Synthesized by Hydrothermal Method

In order to make full use of exposure energy, one feasible way is to modify the luminance of crystal by rare earth doping technique. KZnF3:Er3+and KZnF3:Er3+/Yb3+nanocrystals of uniform cuboid perovskite type morphology, with average diameter of 130 nm, has been synthesized by hydrothermal method. When Yb3+ions were codoped with Er3+, absorption peak at 970 nm has been heightened and widened, and the photon absorption cross section increased. The common xenon lamp exposure cannot initiate obvious nonlinear phenomenon of the doped Er3+and Yb3+, and exposing at 245 nm only excites the fluorescence around 395 nm. Contrarily, under high power IR exposure at 980 nm, obvious upconversion photoluminescence (PL) has been observed due to the two-photon process. The PL mechanism of the doped Er3+ion in KZnF3:Er3+/Yb3+nanocrystals is confirmed. Furthermore, Yb3+codoped as sensitizer has modified the PL intensity of Er3+from green light range to red range, and the primary channel is changed from4S3/2(Er3+) →4I15/2(Er3+) of only Er3+doped KZnF3nanocrystal to4F9/2(Er3+) →4I15/2(Er3+) of Er3+/Yb3+codoped sample. With exposure energy increasing, such primary transition channel after two-photon excitation is unchanged.

LED‐Induced Polymerization (385, 405, and 455 nm) Using Star‐Shaped Tris(4‐(thiophen‐2‐yl)phenyl)amine Derivatives as Light‐Harvesting Photoinitiators

Two star‐shaped tris(4‐(thiophen‐2‐yl)phenyl)amine derivatives, namely tris(4‐(5‐(3‐pentylthieno[3,2‐b]thiophen‐5‐yl)thiophen‐2‐yl)phenyl)amine and tris(4‐(5‐(3‐pentyl‐2‐(thiophen‐2‐yl)thieno[3,2‐b]thiophen‐5‐yl)thiophen‐2‐yl)phenyl)amine, are developed as photoinitiators for radical and cationic polymerizations under near‐UV and visible light‐emitting diodes (LEDs) (e.g., 385, 405, and 455 nm). When used in combination with an iodonium salt (and optionally N‐vinyl carbazole) or an amine/alkyl halide couples, they lead to excellent photoinitiating abilities for the polymerization of epoxides or (meth)acrylates under air. Compared with commercial photoinitiators, i.e., camphorquinone‐based systems or bis(2,4,6‐trimethylbenzoyl)‐phenylphosphineoxide, the novel photoinitiators exhibit noticeably higher polymerization efficiencies under air (epoxide conversions = 41–57% vs ≈0%, halogen lamp exposure; methacrylate conversions = 50–55% vs 44%, LED at 405 nm exposure; methacrylate conversions = 34–42% vs 0–8%, LED at 455 nm exposure). These systems are also interesting in overcoming oxygen inhibition. The photochemical mechanisms are studied by steady‐state photolysis, electron spin resonance spin trapping, fluorescence, cyclic voltammetry, and laser flash photolysis techniques. image

Developing thioxanthone based visible photoinitiators for radical polymerization

Three new amino-thioxanthone photoinitiators (PIs) with different substituents on nitrogen, including 2-allyl(methyl)amino-9H-thioxanthen-9-one (PI-1), 2-benzyl(methyl)amino-9H-thioxanthen-9-one (PI-2) and 2-butyl(methyl)amino-9H-thioxanthen-9-one (PI-3) were synthesized and characterized. They showed high molar extinction coefficients and very broad absorption range in the visible region. Among them, PI-2 showed the best visible light photoinitiating properties evidenced by the fact that it successfully initiated polymerization of 1,6-hexanedioldiacrylate (HDDA) under xenon light exposure (28 mW cm−2) both in the presence and absence of N,N-dimethylaniline (DMA) for 0.5 h with 92% and 52% conversion, respectively. For TMPTA, the conversion of PI-2 and PI-2/N-methyldiethanolamine (MDEA) systems is 32% and 62% under xenon lamp exposure for 10 min. The photoinitiation mechanisms were analysed through EPR, fluorescence spectra and visible light photolysis experiments.

Unique light-induced degradation in yellow-emitting K2SiF6:Mn2+ phosphor

Photo-induced luminescence intensity degradation in yellow-emitting K2SiF6:Mn2+ phosphor is studied using x-ray diffraction measurement, photoluminescence (PL) analysis, PL excitation (PLE) spectroscopy, PL decay analysis, and electron spin resonance (ESR) measurement. The yellow-emitting K2SiF6:Mn2+ phosphor exhibits remarkable degradation in the PL intensity under Xe lamp exposure. Coherent laser irradiation also induces degradation and its degree is in the order of He–Cd (λ = 325 nm) > Ar+ (488 nm) > He–Ne laser (632.8 nm). The degradation mechanism is proposed to be due to change in the valence state of manganese ions from Mn2+ to Mn3+ by the photooxidation (Mn2+ → Mn3+) or disproportionation reaction (2Mn2+ → Mn+ + Mn3+). The ESR measurement confirms the decreased Mn2+ spin density in the sample exposed with Xe lamp. The PLE spectrum suggests that the excitation of Mn3+ ions occurs through energy transfer upon absorption of exciting radiation by the Mn2+ ions. Thermal annealing of the degraded samples at ≥200 °C causes a blueshift in the PL emission band with an appearance of the Mn4+-related sharp red emission lines.

Copper complexes: the effect of ligands on their photoinitiation efficiencies in radical polymerization reactions under visible light

Twenty-three copper complexes (CuC) containing different ligands were synthesized. Most of them exhibited light absorption in the visible range (adapted to LEDs, laser diodes and halogen lamp exposure). The CuC/iodonium salt (Iod), CuC/Iod/N-vinylcarbazole, CuC/alkyl bromide/methyl diethanolamine photoinitiating systems (PISs) allow good monomer conversion profiles for the free radical polymerization of trimethylolpropane triacrylate. Some of them are better than bisacylphosphine oxide or camphorquinone based systems used as references. Real-Time Fourier Transform Infrared spectroscopy and steady state photolysis were used as analytical methods. The results revealed that the ligands of the copper complexes played an important role towards the photoinitiation ability of these PISs. The use of CuC as photocatalysts to initiate thiol–ene reaction is also discussed.

Reaction and diffusion of chlorine dioxide gas under dark and light conditions at different temperatures

Chlorine dioxide (ClO2) gas is a powerful oxidizing agent in many industrial applications for food processing, drinking water and cleaning treatments. It is considered for use in an increasing number of fresh food applications over a wide range of temperature and pH conditions due to its sanitizing capability. During the disinfectant treatment in a closed chamber or packaging system, ClO2 gas is typically exposed to environmental factors such as light, temperature, and humidity which influence its disinfectant efficiency. Determining ClO2 gas reaction rates and mass transfer properties are extremely important for the design of proper sanitization treatments. The aim of this work was to determine the diffusion coefficient for ClO2 gas in air and reaction rates under dark, UV-A and fluorescent lamp exposure. The effect of temperature on the diffusion of ClO2 was also assessed. A system was designed to measure these properties. The diffusion coefficient was found to be 0.129, 0.145, 0.173cm2s−1 at 5, 23, and 40°C, respectively. Degradation of ClO2 gas under dark, UV-A and fluorescent lamp exposure was found to follow a first-order reaction. Degradation using a 40W UV-A lamp was approximately four orders of magnitude larger than with a 34W fluorescent lamp. A methodology is proposed for quantifying the amount of ClO2 gas needed in a package and/or treatment chamber.

Design of Novel Photoinitiators for Radical and Cationic Photopolymerizations under Near UV and Visible LEDs (385, 395, and 405 nm).

Three novel photoinitiators, namely (2,2′-bithiophen-5-yl)(4-(N,N′-dimethylaminophenyl)ketone, 5,10-dimethoxybenzo[j]fluoranthene and 6,6′-(((1E,1′E)-(2,5-bis(octyloxy)-1,4-phenylene)bis(ethene-2,1-diyl))bis(4,1-phenylene))bis(1,3,5-triazine-2,4-diamine) applicable to different near UV or visible LEDs (385 nm, 395 nm, 405 nm or cold white LED) have been developed. When incorporated into multicomponent photoinitiating systems PISs (in the presence of iodonium salt (and optionally N-vinyl carbazole) or amine/alkyl halide couples), they exhibit quite excellent photoinitiating abilities for the cationic polymerization CP of epoxides or the free radical polymerization FRP of methacrylates under air. Compared to the corresponding camphorquinone-based systems, the newly developed photoinitiating systems display noticeably higher polymerization efficiencies under air (epoxide conversions = 31–55% vs ∼0%, halogen lamp exposure; methacrylate conversion = 56–66% vs 0–8%, LED irradiation). These systems are very interesting to overcome the oxygen inhibition. The photochemical mechanisms have been studied by steady state photolysis, electron spin resonance spin trapping, fluorescence, cyclic voltammetry, and laser flash photolysis techniques.

Simple Cleaning and Conditioning of Silicon Surfaces with UV/Ozone Sources

Within this paper the applicability of three methods to clean and condition the surface of silicon wafers by an ultra-thin oxide layer were tested: two UV/O3 sources (an Hg vapor lamp and a high efficiency excimer module) as well as a wet chemical oxidation in HNO3.It has been demonstrated that organic residues resulting from wafering and masking the surface during alkaline texturing can be removed by UV/O3 (Hg vapor lamp) exposure. Moreover the use of UV/O3 (excimer) and HNO3 oxides result in an improvement of passivation quality and emitter saturation current in combination with Al2O3/SiNx or AlN/SiNx passivation stacks. For n-type silicon wafers with a 70Ω/sq. boron emitter and Al2O3/SiNx passivation very low j0e values of 49 fA/cm2 are achieved by conditioning with UV/O3 or HNO3.Another important application of ultra-thin SiOx layers is as tunnel oxides for the rear side of the TOPCon (Tunnel Oxide Passivated Contact) cell concept [1,2]. High iVOC values exceeding 720mV on planar samples and 710mV on textured samples are obtained with UV/O3 grown tunnel oxides after annealing. The structural properties of the SiOx layers that were analyzed by XPS and compared to the iVOC data, indicate that a minimum oxide layer thickness of approx. 1.4nm and a high amount of oxygen rich sub oxides species (Si2O3, close to the structure of stoichiometric SiO2) are required to obtain a good interface passivation stable up to annealing temperatures of 900°C.

Light-Induced Degradation in Red-Emitting ZnSiF6·6H2O:Mn4+ Hydrate Phosphor

Photo-induced degradation behaviors of the red-emitting ZnSiF6·6H2O:Mn4+ hydrate phosphor are studied using X-ray diffraction measurement, photoluminescence (PL) analysis, PL excitation spectroscopy, PL decay analysis, diffuse reflectance spectroscopy, and electron spin resonance (ESR) measurement. The ZnSiF6·6H2O:Mn4+ hydrate phosphor exhibits remarkable degradation in the PL intensity under Xe lamp exposure for a few minutes. Coherent laser beams also induce degradation and its degree is in the order of Ar+ (488 nm) > He−Cd (325 nm) > He−Ne laser (632.8 nm). The degradation mechanism is found to be due to change in the valence state of manganese ions from Mn4+ to Mn5+ by the photooxidation (Mn4+ → Mn5+) or disproportionation reaction (2Mn4+ → Mn3+ + Mn5+). This is supported by the facts that Mn4+ ion has larger absorbance at 488 nm than at 325 or 632.8 nm and that the Mn5+-related absorption structures appear in the diffuse reflectance spectra at wavelengths below ∼700 nm. The ESR measurement also confirms the decreased Mn4+ spin density in the sample exposed with Xe lamp. A comparative discussion is given on the PL properties of the two different hydrate phosphors, ZnSiF6·6H2O:Mn4+ and K2SnF6·H2O:Mn4+.