Quencher Concentration Research Articles

Contactless measurements of photocarrier transport properties in perovskite single crystals

The remarkable properties of metal halide perovskites arising from their impressive charge carrier diffusion lengths have led to rapid advances in solution-processed optoelectronics. Unfortunately, diffusion lengths reported in perovskite single crystals have ranged widely – from 3 μm to 3 mm – for ostensibly similar materials. Here we report a contactless method to measure the carrier mobility and further extract the diffusion length: our approach avoids both the effects of contact resistance and those of high electric field. We vary the density of quenchers – epitaxially included within perovskite single crystals – and report the dependence of excited state lifetime in the perovskite on inter-quencher spacing. Our results are repeatable and self-consistent (i.e. they agree on diffusion length for many different quencher concentrations) to within ± 6%. Using this method, we obtain a diffusion length in metal-halide perovskites of 2.6 μm ± 0.1 μm.

Turn-off fluorescence studies of novel thiophene substituted 1,3,4-oxadiazoles for aniline sensing

In the present work, fluorescence quenching of three novel thiophene substituted 1,3,4-oxadiazole derivatives namely; 2-(4-(thiophen-3-yl)phenyl)-5-(5-(thiophen-3-yl)thiophen-2-yl)1,3,4oxadiazole [TTO], 2-(4-(benzo[b]thiophen-2-yl)phenyl)-5-(5-(benzo[b]thiophen-2-yl)thiophen-2-yl)1,3,4oxadiazole [TBO] and 2-(4-(thiophen-2-yl)phenyl)-5-(5-(thiophen-2-yl)thiophen-2-yl)-1,3,4-oxadiazole [TMO] by aniline were carried out at room temperature in five different solvents like ethyl acetate, DMSO, methanol, ethanol and propan-2-ol through steady-state and time-resolved methods to understand the internal mechanisms and to characterize novel fluorophores as favorable aniline sensing media. Further, parameters like Stern-Volmer constants (ksv and ksv'), quenching rate parameters (kq & kq'), the probability of quenching per encounter (P & P') and activation energy of quenching (Ea & Ea') were determined from both the methods. Time-resolved measurements of fluorescence demonstrate that, quenching is dominated by collisional interactions between the 1,3,4-oxadiazole derivatives and the aniline with a minor static component. The magnitudes of the probability of encounter as well as activation energy of quenching also suggest that, quenching reaction is not solely controlled by material diffusion. Further, a linear variation in the fluorescence intensity of the dyes with quencher concentration and the large quenching constants reveals that TTO, TBO and TMO fluorophores may be used as aniline sensors for future detection of aniline via fluorescence quenching.

Monitoring the confinement of methylene blue in pyrene labeled poly(acrylic acid)

This work was devoted to investigate the aggregation of methylene blue (MB) with pyrene labeled poly(acrylic acid) (PAA25Py3) by using the measurements of UV–vis absorption, steady-state and time-resolved fluorescence. For comparison, the effect of unlabeled poly(acrylic acid) (PAA25) on the self-association of MB was also evaluated. The spectral positions of the absorption and emission bands of MB as well as the pyrene monomer and excimer emissions were used to assess the local changes of polymer/MB microenvironment. The binding mechanism and thermodynamic analysis for the interaction between MB and pyrene labeled poly(acrylic acid) were evaluated by fluorescence quenching measurements. Moreover, the strategy of switching of pyrene excimer/monomer emission was used to manage the self-aggregation of the pH-responsive fluorescent polymer with phenothiazinium dye. The UV–vis absorption and fluorescence results showed that low amounts of polymers provoked the self-association of MB. At high concentrations of polymer, the MB monomer is stabilized. The labeling of polymer with pyrene induced a dramatic changing of optical properties suggesting that a peculiar process occurred between PAA25Py3 and MB. At low quencher concentrations, both steady-state and time-resolved fluorescence data indicated a static quenching process. The thermodynamic parameters (∆H, ∆S and ∆G) and the efficiency of pyrene excimer formation revealed that the association of MB with the fluorescent polymer occurred spontaneously due to non-covalent hetero π-π stacking, hydrophobic and electrostatic interactions. The study highlights the key contribution of the π-π stacking interactions in the capturing of methylene blue in pyrene labeled poly(acrylic acid). The outcome may be useful in biomedical applications or in wastewater treatment.

Fluorescence modulation of CdTe nanowire by azobenzene photochromic switches

Photoinduced electron transfer (ET) and Forster Resonance Energy Transfer (FRET) between azobenzene derivatives (Quencher) and CdTe nanowires have been investigated. Needle-like cadmium telluride (CdTe) 1D nanowires were successfully prepared. The surface modification was done by the capping agent 3-marcaptopropanoic acid (MPA) and NH3. The azobenzene derivatives (E)-5-((4-chlorophenyl) diazenyl)-2-hydroxybenzaldehyde Q(I) and (E)-4-((3-formyl-4-hydroxyphenyl) diazenyl) benzene sulfonic acid Q(II) have been prepared and glued to MPA capped CdTe nanowires. After UV treatment, the azo compounds Q(I) and Q(II) experience a reversible trans–cis isomerization. The photoinduced trans to cis change supports the transfer of electrons from the conduction band (CB) of the CdTe nanowires to the lowest unoccupied molecular orbital (LUMO) of cis isomer of the azo compounds and the overlapping absorbance spectra of acceptor (QI & QII) with the emission spectrum of donor (CdTe nanowires) also suggests quenching of PL due to Forster energy transfer (FRET). Using steady state (SSPL) and time resolved fluorescence (TRPL) measurements, we have noticed that with the increase in Quencher (I) & (II) concentrations, the fluorescence is quenched with a subsequent decrease in decay life time. Hence fluorescence can be modulated at different quencher concentrations.

Effect of viscosity and dielectric constant variation on fractional fluorescence quenching analysis of coumarin dye in binary solvent mixtures.

Photo physical properties of fluorescent organic compounds give an immense improved knowledge on characteristics of excited state that is beneficial to devise innovate molecules and understand their performance in particular applications. Coumarin derivatives have been extensively investigated in this regard. This article narrates steady state fluorescence quenching measurements of a coumarin derivative namely 3-hydroxy-3-[2-oxo-2-(3-oxo-3H-benzo[f]chromen-2-yl)-ethyl]-1,3-dihydro-indol-2-one (3HBCD) in a binary mixture of acetonitrile and 1,4-dioxane. Aniline is used as quencher. Fluorescence intensity is large in acetonitrile and decreases as the percentage of 1,4-dioxane in the solvent mixture increases. With modest quencher concentration a deviation towards the x axis is noticed in the Stern-Volmer (S-V) plots. This downward curvature is interpreted as due to the presence of 3HBCD in different conformers in the lowest energy level. Ground state intramolecular hydrogen bonding formation is observed due to the conformational changes in the solute. Figured estimations of various quenching parameters recommend that, while dynamic quenching prompts linearity in S-V plot at lower quencher concentration, increasing quenching efficiency with increasing medium viscosity suggests that reaction is not entirely controlled by material diffusion. Stern-Volmer constant increases with decreasing medium dielectric constant.

Resist image quality control via acid diffusion constant and/or photodecomposable quencher concentration in the fabrication of 11 nm half-pitch line-and-space patterns using extreme-ultraviolet lithography

Extreme-ultraviolet (EUV) lithography will be applied to the high-volume production of semiconductor devices with 16 nm half-pitch resolution and is expected to be extended to that of devices with 11 nm half-pitch resolution. With the reduction in the feature sizes, the control of acid diffusion becomes a significant concern. In this study, the dependence of resist image quality on TPEBDacid and photodecomposable quencher concentration was investigated by the Monte Carlo method on the basis of the sensitization and reaction mechanisms of chemically amplified EUV resists. Here, TPEB and Dacid are the postexposure baking (PEB) time and the acid diffusion constant, respectively. The resist image quality of 11 nm line-and-space patterns is discussed in terms of line edge roughness (LER) and stochastic defect generation. For the minimization of LER, it is necessary to design and control not only the photodecomposable quencher concentration but also TPEBDacid. In this case, Dacid should be adjusted to be 0.3–1.5 nm2 s−1 for a PEB time of 60 s with optimization of the balance among LER and stochastic pinching and bridging. Even if it is difficult to decrease Dacid to the range of 0.3–1.5 nm2 s−1, the image quality can still be controlled via only the photodecomposable quencher concentration, although LER and stochastic pinching and bridging are slightly increased. In this case, accurate control of the photodecomposable quencher concentration and the reduction in the initial standard deviation of the number of protected units are required.

Fast Decomposition of Three-Component Spectra of Fluorescence Quenching by White and Grey Methods of Data Modeling

‘White’ and ‘grey’ methods of data modeling have been employed to resolve the heterogeneous fluorescence from a fluorophore mixture of 9-cyanoanthracene (CNA), 10-chloro-9-cyanoanthracene (ClCNA) and 9,10-dicyanoanthracene (DCNA) into component individual fluorescence spectra. The three-component spectra of fluorescence quenching in methanol were recorded for increasing amounts of lithium bromide used as a quencher. The associated intensity decay profiles of differentially quenched fluorescence of single components were modeled on the basis of a linear Stern-Volmer plot. These profiles are necessary to initiate the fitting procedure in both ‘white’ and ‘grey’ modeling of the original data matrices. ‘White’ methods of data modeling, called also ‘hard’ methods, are based on chemical/physical laws expressed in terms of some well-known or generally accepted mathematical equations. The parameters of these models are not known and they are estimated by least squares curve fitting. ‘Grey’ approaches to data modeling, also known as hard-soft modeling techniques, make use of both hard-model and soft-model parts. In practice, the difference between ‘white’ and ‘grey’ methods lies in the way in which the ‘crude’ fluorescence intensity decays of the mixture components are estimated. In the former case they are given in a functional form while in the latter as digitized curves which, in general, can only be obtained by using dedicated techniques of factor analysis. In the paper, the initial values of the Stern-Volmer constants of pure components were evaluated by both ‘point-by-point’ and ‘matrix’ versions of the method making use of the concept of wavelength dependent intensity fractions as well as by the rank annihilation factor analysis applied to the data matrices of the difference fluorescence spectra constructed in two ways: from the spectra recorded for a few excitation lines at the same concentration of a fluorescence quencher or classically from a series of the spectra measured for one selected excitation line but for increasing concentration of the quencher. The results of multiple curve resolution obtained by all types of the applied methods have been scrutinized and compared. In addition, the effect of inadequacy of sample preparation and increasing instrumental noise on the shape of the resolved spectral profiles has been studied on several datasets mimicking the measured data matrices.Graphical ᅟ

Syntheses and photophysical properties of diaminotetraphenylporphyrins and their corresponding polyimides

Two free base porphyrins, 5,10-bis(4-aminophenyl)-15,20-diphenylporphyrin (cis-DATPP), 5,15-bis(4-aminophenyl)-10,20-diphenylporphyrin (trans-DATPP), and their zinc metalated analogues (cis-ZnDATPP and trans-ZnDATPP) were synthesized. A series of their corresponding polyimides were obtained by the condensed polymerization of the respective monomeric isomer DATPP with a 1:1 ratio of 2,2′-bis(trifluoromethyl)-4,4′-diaminobiphenyl (PFMB) and 4,4′-hexafluoroisopropylidenediphthalic anhydride (6FDA). The inclusion of PFMB and 6FDA into the polymeric backbone causes the polymers to be moderately to highly soluble in organic polar solvents. The molar content of the respective DATPP monomer varied between 5 and 30%. All compounds were structurally characterized by 1H NMR and ATR-IR spectroscopy and the porphyrin content in the polyimides was determined by UV–Visible absorption spectroscopy. Photophysical properties consisted of measuring both the UV–Visible (ground state) absorption and fluorescence (excited state) spectra, fluorescence quantum yields (Φf), and fluorescence lifetimes (τf) in dichloromethane and N,N-dimethylacetamide. Fluorescence quenching was also measured and observed by the Stern-Volmer relationship, using 9,10-anthraquinone (AQ) as the quencher molecule. Both the bimolecular rate constant of fluorescence quenching (kq) and the Stern-Volmer constant (KQ) were calculated from this relationship. Furthermore, deviations from linearity depicted in the Stern-Volmer plots for TPP and ZnTPP at higher concentrations of AQ were also measured as a means of examining and explaining the simultaneous occurrence of dynamic (collisional) quenching and static quenching in the mechanisms of fluorescence quenching. It was found in this work that the significantly larger values in the static quenching constant (KS) than in the dynamic quenching constant (KD) are indicative that static quenching and ground state complex formation between the fluorophore and quencher is the dominant mechanism of fluorescence quenching of these systems at higher quencher concentrations.

Steady-state and time-resolved fluorescence studies on interactions of carbon “quantum” dots with nitrotoluenes

Carbon “quantum” dots or carbon dots, generally defined as small carbon nanoparticles with various surface passivation schemes, have emerged to represent a rapidly advancing and expanding research field. A wide variety of technological applications of carbon dots have been pursued, including especially their uses as fluorescence probes or sensors. In the work reported here, carbon dots obtained from the surface chemical functionalization of small carbon nanoparticles with 2,2′-(ethylenedioxy)bis(ethylamine) (EDA) were selected as structurally compact and defined fluorescence probes, and their interactions with nitrotoluene compounds were studied on the basis of fluorescence quenching in steady-state and time-resolved measurements. The fluorescence quenching of the carbon dots by the nitrotoluenes, which are commonly used as signature compounds for nitroaromatic explosives, was found to be extremely efficient in ambient solution, though still at the very upper-limit of diffusion-control. There were some static quenching contributions at high nitrotoluene quencher concentrations, especially for the compound that is more electron deficient, which could be rationalized in terms of some near-neighbor charge transfer interactions. Mechanistic implications of the results and the potential for carbon dots to serve as highly sensitive fluorescence probes in the detection of nitroaromatic explosives are discussed.

Fluorescence and circular dichroism studies on the accessibility of tryptophan residues and unfolding of a jacalin-related α-d-galactose-specific lectin from mulberry (Morus indica)

MLGL (Mulberry Latex Galactose-specific Lectin) is an α-d-galactose binding lectin isolated from the latex of mulberry (Morus indica) tree and contains two tryptophan residues in each of its subunits. The fluorescence emission maximum of native MLGL seen at 326nm shifts to 350nm upon incubation with 6M guanidinium thiocyanate (Gdn.SCN), suggesting that the tryptophans are located inside the hydrophobic core of the protein and become fully exposed upon denaturation. Fluorescence quenching studies revealed that the neutral acrylamide exhibits the highest quenching, with ~33% of total fluorescence in the native protein being quenched at a quencher concentration of 0.5M, whereas iodide (~24%) and cesium (~4%) ions showed significantly lower quenching. With the denatured protein, acrylamide quenching involves both dynamic and static processes as evident from an upward curving Stern-Volmer plot. Time-resolved fluorescence studies showed two lifetime components of 3.7ns and 1.3ns for the native protein, while three lifetime components were observed for the denatured protein. MLGL showed high resistance to urea (up to 8M) and guanidine hydrochloride (up to 6M), whereas treatment with 6M Gdn.SCN completely denatured the protein, via a broad sigmoidal transition with a transition midpoint at ~3.75M. Circular dichroism studies and hemagglutination assays showed that the secondary and tertiary structures as well as lectin activity of MLGL were unaffected up to 70°C. Additionally, pH dependent studies showed that the secondary structure of MLGL is unaltered in the pH range 6.2 to 8.5, but a decrease in lectin activity is observed (~50%) at pH6.2.

Theoretical study on effects of photodecomposable quenchers in line-and-space pattern fabrication with 7 nm quarter-pitch using chemically amplified electron beam resist process

The line width roughness (LWR) is a significant issue in the development of chemically amplified resists. The increase in sensitizer concentration is inevitable for the suppression of LWR in the sub-10 nm fabrication. In this study, we investigated the effects of photodecomposable quenchers from the viewpoint of the excluded volume effect, assuming line-and-space patterns with 7 nm quarter-pitch (7 nm space width and 28 nm pitch). The pattern formation of chemically amplified electron beam resists with photodecomposable quenchers was calculated and compared with those with conventional quenchers. It was found that the sum of the concentrations of acid generators and quenchers (photodecomposable or conventional quenchers) can be reduced without decreasing the chemical gradient (an indicator of LWR) by using the photodecomposable quenchers. The photodecomposable quenchers are considered essential in the high-resolution fabrication.

Bimolecular Photoinduced Electron Transfer in Static Quenching Regime: Illustration of Marcus Inversion in Micelle.

Ultrafast bimolecular photoinduced electron transfer (PET) between six coumarin dyes and four viologen molecules in the stern layer of sodium dodecyl sulfate micelle have been studied using femtosecond broadband transient absorption spectroscopy and femtosecond fluorescence up-conversion spectroscopy over a broad reaction exergonicity (ΔG0). Emanating the formation of radical cation intermediates of viologen molecules using the transient absorption and the fast decay component of coumarins using the fluorescence up-conversion studies the forward bimolecular electron transfer rate (ket) have been measured with high accuracy. The relationship of ket with ΔG0 found to follow a Marcus type bell-shaped dependence with an inversion at -1.10 eV. In this report, we have studied PET reaction using ultrafast spectroscopy at the quencher concentration where static quenching regime prevails. Moreover, the incompetency of Stern-Volmer experiments in studying ultrafast PET has been revealed. In contrary to previous claims, here we found that the ket is lower for lower lifetime coumarins, indicating that static, nonstationary and stationary regime of quenching have the minimal role to play to in the bimolecular electron transfer process. By far, this report is believed to be the most efficient and immaculate way of approaching Marcus inverted region problem in the case of bimolecular PET and settles the long-lasting debate of whether the same can be observed in micellar systems.

Relationship between sensitizer concentration and resist performance of chemically amplified extreme ultraviolet resists in sub-10 nm half-pitch resolution region

The development of lithography processes with sub-10 nm resolution is challenging. Stochastic phenomena such as line width roughness (LWR) are significant problems. In this study, the feasibility of sub-10 nm fabrication using chemically amplified extreme ultraviolet resists with photodecomposable quenchers was investigated from the viewpoint of the suppression of LWR. The relationship between sensitizer concentration (the sum of acid generator and photodecomposable quencher concentrations) and resist performance was clarified, using the simulation based on the sensitization and reaction mechanisms of chemically amplified resists. For the total sensitizer concentration of 0.5 nm−3 and the effective reaction radius for the deprotection of 0.1 nm, the reachable half-pitch while maintaining 10% critical dimension (CD) LWR was 11 nm. The reachable half-pitch was 7 nm for 20% CD LWR. The increase in the effective reaction radius is required to realize the sub-10 nm fabrication with 10% CD LWR.

A Spectroscopic Approach with Theoretical Studies to Study the Interaction of 9-aminoacridine with Certain Phenols

Abstract The influence of phenols upon the fluorescence quenching of 9-aminoacridine (9-AA) was examined in acetonitrile solution by employing steady state and time-resolved fluorescence measurements. On increasing the concentration of quencher molecules the absorption spectra of 9-AA change with significant bathochromic shift. The fluorescence intensity of 9-AA change in presence of quencher molecules were measured at various temperatures as a function of the quencher concentrations. The observed bimolecular quenching rate constant (kq) depends on the nature and electronic effect of substituent present in the quencher molecules. The bimolecular quenching rate constant (kq) decreases on increasing the oxidation potential of quencher molecules. To examine the quenching behavior, kq values were correlated with the free energy change (ΔG). To get forthcoming in the quenching process, fluorescence quenching experiments were carried out in different solvents of varying polarities. The observed result suggest the involvement of charge-transfer quenching mechanism. Lifetime measurements support static quenching. Further, the radical scavenging potential is calculated from density functional theory (DFT) calculations to address the quenching behavior of the quencher molecules. DFT result reveals that electronic features are important in tuning the quenching ability of the quencher molecules and found to agree with the obtained experiment result.

Evaluation of Surface Ligands on Semiconductor Nanoparticle Surfaces Using Electron Transfer to Redox Species

A simple method for evaluating the conditions of ligands used to stabilize photoluminescent cadmium chalcogenide nanoparticles is reported. Photoluminescence quenching in the presence of electron acceptors was observed for nanoparticles modified with alkylamines and alkanethiols having different chain lengths, which are commonly used as capping ligands for semiconductor nanoparticles. The magnitude of quenching significantly varied with the ligand type and with time after nanoparticle purification; the plots of quenching magnitude against quencher concentration showed unexpected curvatures. For the origin of this curvature to be revealed, a model of the quenching process was established based on the Tachiya model. In this model, the layer of ligands has several voids through which the quenchers are bound to the cores of nanoparticles. An equation was developed by considering the statistical distribution of the number of quenchers attached to a nanoparticle. The analyses of photoluminescence quenching reve...

Photoacoustic imaging of the excited state lifetime of fluorophores

Photoacoustic (PA) imaging using pump–probe excitation has been shown to allow the detection and visualization of fluorescent contrast agents. The technique relies upon inducing stimulated emission using pump and probe pulses at excitation wavelengths that correspond to the absorption and fluorescence spectra. By changing the time delay between the pulses, the excited state lifetime of the fluorophore is modulated to vary the amount of thermalized energy, and hence PA signal amplitude, to provide fluorophore-specific PA contrast. In this study, this approach was extended to the detection of differences in the excited state lifetime of fluorophores. PA waveforms were measured in solutions of a near-infrared fluorophore using simultaneous and time-delayed pump–probe excitation. The lifetime of the fluorophore solutions was varied by using different solvents and quencher concentrations. By calculating difference signals and by plotting their amplitude as a function of pump–probe time delay, a correlation with the excited state lifetime of the fluorophore was observed. The results agreed with the output of a forward model of the PA signal generation in fluorophores. The application of this method to tomographic PA imaging of differences in the excited state lifetime was demonstrated in tissue phantom experiments.

Amplification in Light Energy Conversion at Q-CdTe Sensitized TiO2 Photonic Crystal, Photoelectrochemical Stability in Se2– Electrolyte, and Size-Dependent Type II Q-CdTe/CdSe Formation

This study investigates the ability of Se2– redox electrolyte to separate the photoholes and stabilize Q-CdTe quantum dot solar cell with a liquid junction. We examined the photophysical and photoelectrochemical behaviors of Q-CdTe in two sizes, green-emitting dots of 2.3–2.7 nm diameter and red-emitting dots of 4 nm diameter, in the presence of alkaline Se2– electrolyte prepared under inert atmosphere. Photoelectrochemical, absorbance, emission and emission quenching measurements revealed the presence of size dependence in Se2– surface binding to Q-CdTe, growth of type II Q-CdTe/CdSe, and stability in the photoelectrochemical cell. Emission quenching measurements show that Se2– scavenges the Q-CdTe photohole, with mechanisms that depended on size and quencher concentration. Binding of Se2– to green-emitting Q-CdTe occurred with a greater binding constant compared to the red-emitting dots, resulting in formation of type II Q-CdTe/CdSe at the smaller core indicated in red-shifted absorbance and emission sp...

Chromo/Fluorogenic Detection of Co(2+), Hg(2+) and Cu(2+) by the Simple Schiff Base Sensor.

Herein, we reported the ditriazole Schiff base derivative 1 and evaluated its photophysical properties on induction of varieties of metal ions including Na(+), Ag(+), Ni(2+), Mn(2+), Pd(2+), Co(2+), Hg(2+), Cu(2+), Pb(2+), Cd(2+), Zn(2+), Sn(2+), Fe(2+), Fe(3+), Cr(3+) and Al(3+), in order to figure out its potential as ion sensor. The ligand 1 exhibited the strong colorimetric change in the reaction solution as well as absorption spectral shifting with the concomitant appearance of well-defined isosbestic points only upon Co(2+), Hg(2+) and Cu(2+) addition corroborates its applicability as multichannel ion detector. The different extent of spectral shifting as well as unique chromogenic change in the probe solution upon Co(2+), Hg(2+) and Cu(2+) introduction can be used as the discrimination tool for these metal ions. The ligand-metal binding stoichiometry was assessed by their optical response which was further supported by the FT-IR, NMR and mass spectrometric analysis. The association constant and the detection limits of the ligand toward Co(2+), Hg(2+) and Cu(2+) ions were calculated to be 1.52×10(-8), 3.26×10(-9), 1.16×10(-8) and 3.87×10(-10), 5.47×10(-11), 8.91×10(-11)M, respectively, employing the Benesi-Hilderbrand equation and 3 σ slope(-1) methods. Furthermore, the successive addition of Co(2+), Hg(2+) and Cu(2+) induce the constant decline in the fluorescence emission signal intensity of the probe. The quenching efficiency of the probe upon metallic induction was fitted to the Stern-Volmer equation which yielded the upward curvature in case of all the three metals ions (Co(2+), Hg(2+) and Cu(2+)) when (Io/I-1) was plotted against the quencher concentration indicating the occurrence of both the dynamic and static quenching process in the system with the average Stern-Volmer quenching constant values of 9.25×10(-7), 1.14×10(-7), 1.829×10(-7), respectively.

Optimum concentration ratio of photodecomposable quencher to acid generator in chemically amplified extreme ultraviolet resists

In chemically amplified resists used for ionizing radiations such as an extreme ultraviolet radiation, thermalized electrons and protons play important roles in pattern formation. Photodecomposable quenchers are important for 11 nm half-pitch fabrication because they capture both thermalized electrons and protons. However, their effects are complicated for the same reason. In this study, the optimum concentration ratio of photodecomposable quenchers to acid generators in terms of the trade-off relationships between resolution, line width roughness (LWR), and sensitivity was theoretically investigated, assuming line-and-space patterns of 11 nm half-pitch. To suppress LWR to less than 20% critical dimension (CD), the recommended total sensitizer concentration (the sum of acid generator and photodecomposable quencher concentrations) was in the range of 0.20–0.22 nm−3. The expected sensitivities were 30–40 mJ cm−2 when the resist performance of the latest chemically amplified resists was assumed. The optimum ratio of photodecomposable quencher concentration to the total sensitizer concentration was 0.55.

Vibrational relaxation of 13CO2(ν2) by atomic oxygen

The rate coefficient for the vibrational relaxation of isotopically-pure 13CO2 by ground state oxygen atoms was measured between 239 and 358K. O3 was photolyzed in a slow-flowing mixture of 13CO2, O3, and Xe to simultaneously create O atoms and stimulate a temperature-jump, shifting population into the first vibrationally-excited state of 13CO2. The population redistribution was monitored via transient diode laser absorption spectroscopy and the rate coefficient was extracted from the dependence of this redistribution on quencher concentration. The results are in good agreement with previous measurements of the 12CO2–O system, but with decreased uncertainty due to experimental improvements.