共查询到20条相似文献,搜索用时 31 毫秒
1.
Vivek M. Prabhu Sharadha Sambasivan Linda K. Sundberg 《Applied Surface Science》2006,253(2):1010-1014
Near-edge X-ray absorption fine structure (NEXAFS) spectroscopy was used to quantify the surface composition and depth profiling of photoacid generators in thin film photoresist materials by varying the entrance-grid bias of a partial electron yield detector. By considering model compositional profiles, NEXAFS distinguishes the surface molar excess within the top 6 nm from the bulk. A surface enriched system, triphenylsulfonium perfluorooctanesulfonate, is contrasted with a perfluorobutanesulfonate photoacid generator, which displays an appreciable surface profile within a 6 nm segregation length scale. These results, while applied to 193-nm photoresist materials, highlight a general approach to quantify NEXAFS partial electron yield data. 相似文献
2.
Jürgen Ihlemann 《Applied Physics A: Materials Science & Processing》2008,93(1):65-68
Precise patterning by laser ablation requires sufficient absorption. For weak absorbers like fused silica indirect methods
using external absorbers have been developed. A novel approach using a solid SiO absorber coating is described. Irradiation
by an ArF excimer laser (wavelength 193 nm) is leading to ablation of the coating and, at sufficiently high fluence, of the
fused silica substrate. The remaining coating in the unexposed areas is removed afterwards by large area irradiation. The
fluence threshold for substrate ablation using a 28 nm thick absorber layer is about 1.1 J/cm2. Single pulse ablation rates of up to 800 nm and a surface roughness of R
a<5 nm are obtained. High resolution grating patterns with 400 nm period and a modulation depth of 80 nm are possible. The
process can be described as controlled plasma mediated ablation. 相似文献
3.
Quenching of fluorescence from Na(32
P) and K(42
P) atoms by various collision partners was studied at 973 and 1273K. Excited alkali atoms were produced photolytically by excimer
laser light at 193nm. For each collision pair, the appropriate relative velocity was computed and used to evaluate the quenching
cross-section from the measured rate constants. Cross sections for CO2, O2 and N2 are large (10–60Å2) while for Ar, the values are <1 Å2. The results are compared with those of previous investigations as a function of relative velocity. Finally, implications
for combustion diagnostics are briefly discussed.
Received: 29 March 1996 相似文献
4.
Suruchi Anand Prabhat Verma S C Abbi K P Jain M J Tafreshi K Balakrishnan R Dhansekaran 《Pramana》1996,47(2):133-143
The single crystal ZnSe:I sample was grown by the chemical vapor transport (CVT) method using iodine as the transporting agent.
The iodine incorporates itself effectively as a donor in the lattice. The sample shows a 〈111〉 optical quality surface and
has an absorption edge at 2.55 eV due to a deep impurity band nearly 0.15eV below the conduction band. The photoluminescence
emission spectra of this crystal have been measured for its temperature dependence as well as for excitation energy dependence.
The photoluminescence is in accordance with a donor-acceptor complex formation involving iodine activated donors and self-activated
acceptors. The configuration coordinate model has been used to explain the temperature dependent changes in the peak position
and the bandwidth of the emission band. The decrease in luminescence efficiency with increasing temperature is explained by
using a simple model for thermal quenching. The activation energy at low temperature range (T<200K) is different from that at high temperature range (200K<T<300K). 相似文献
5.
M. A. Majeed?Khan M. Wasi?Khan Mansour Alhoshan M. S. AlSalhi A. S. Aldwayyan 《Applied Physics A: Materials Science & Processing》2010,100(1):45-51
Pure and Co-doped ZnO nanostructured samples have been synthesized by a chemical route. We have studied the structural and
optical properties of the samples by using X-ray diffraction (XRD), field-emission scanning electron microscopy (FESEM), field-emission
transmission electron microscope (FETEM), energy-dispersive X-ray (EDX) analysis and UV–VIS spectroscopy. The XRD patterns
show that all the samples are hexagonal wurtzite structures. Changes in crystallite size due to mechanical activation were
also determined from X-ray measurements. These results were correlated with changes in particle size followed by SEM and TEM.
The average crystallite sizes obtained from XRD were between 20 to 25 nm. The TEM images showed the average particle size
of undoped ZnO nanostructure was about 20 nm whereas the smallest average grain size at 3% Co was about 15 nm. Optical parameters
such as absorption coefficient (α), energy band gap (E
g
), the refractive index (n), and dielectric constants (σ) have been determined using different methods. 相似文献
6.
E. Birckner U.-W. Grummt H. Rost A. Hartmann S. Pfeiffer H. Tillmann H.-H. Hörhold 《Journal of fluorescence》1998,8(1):73-80
The absorption and fluorescence of substituted distyrylbenzene (DSB) derivatives and segmented poly(phenylene vinylene) (PPV)
derivatives are characterized by long-wavelength absorption maxima and absorption coefficients of λa = 380–450 nm, ε = 20,000–60,000 M−1 cm1 and fluorescence maxima, quantum yields, and decay times of λr = 440–530 nm, Φf = 0.2–0.9, and Τ = 0.8–2.5 ns, respectively. Alkoxy substituents at the central phenylene ring of DSB groups increase the
bathochromic shift in the spectra in comparison to DSB, without a significant decrease in the high DSB fluorescence quantum
yield. Both phenyl and cyano substitutions at the vinylene bridge lead to a further bathochromic shift of the fluorescence
and a decrease in the quantum yield to ca. 0.4. The DSB derivatives and the related segmented PPV derivatives show nearly
the same absorption spectra, fluorescence spectra, and radiative rate constantsk
f= Φf/Τ, indicating the efficacy of the segmentation of the polymer chain. The radiative rate constants determined by the Φf and Τ values and by the Strickler/Berg formula are in reasonable agreement. This supports the possibility of interpreting
the properties of the polymers in terms of their DSB units. The decrease in the emission anisotropy can be ascribed to multistep
energy transfer processes between different oriented segments. 相似文献
7.
J. Yon R. Lemaire E. Therssen P. Desgroux A. Coppalle K. F. Ren 《Applied physics. B, Lasers and optics》2011,104(2):253-271
The refractive index of soot is an essential parameter for its optical diagnostics. It is necessary for quantitative interpretation
of LII (Laser Induced Incandescence) signals, light scattering or extinction measurements as well as for emissivity calculations.
The most cited values have been determined by intrusive methods or without taking into account the soot size distribution
and its specific morphology. In the present study, soot generated by the combustion of diesel and diesel/rapeseed methyl ester
(RME) mixture (70% diesel and 30% RME) are extensively characterized by taking into account the morphology, the aggregate
size distribution, the mass fraction and the spectral dispersion of light. The refractive index m for wavelengths λ between 300 and 1000 nm is determined for diesel and diester fuels by both in-situ and ex-situ methods. The ex-situ method
is based on the interpretation of extinction spectra by taking into account soot sizes and fractal morphology with the RDG-FA
(Rayleigh–Debye–Gans for Fractal Aggregate) theory. The in-situ approach is based on the comparison of the LII signals obtained
with two different excitation wavelengths. The absorption function E(m) and the scattering function F(m) are examined. This study reveals similar optical properties of soot particles generated by both studied fuels even at ambient
and flame temperatures. The function E(m) is shown to reach a maximum for λ=250 nm and to tend toward a plateau-like behavior close to E(m)=0.3 for higher wavelength (600<λ (nm)<1000). The function F(m) is found to be quite constant for 400<λ (nm)<1000 and equal to 0.31. 相似文献
8.
Xu Fei Ying Wan Haiming Zhang Zhanchen Cui Daming Zhang 《Applied Physics A: Materials Science & Processing》2009,96(2):467-472
A linear fluorinated bis-phenol-A novolac resin (LFAR) for optical waveguide was synthesized based on 4,4′-(hexafluoro-isopropylidene)diphenol,
epoxy chloropropane and formaldehyde. Negative fluorinated photoresist (FP) was made by composing the LFAR, diphenyl iodonium
salt and solvent. The film, which was made by spin-coating FP, had good UV light lithograph sensitivity, large hardness and
high glass transition temperature (T
g
>170°C, after crosslinking). Low-loss optical waveguides with very smooth top surface were fabricated from the resulting FP
by direct UV exposure and chemical development. For waveguides without upper cladding, the propagation loss of the channel
waveguides was measured to be 0.21 dB/cm at 1550 nm. 相似文献
9.
First measurements of effective absorption coefficient and penetration depth are given here from the ablation of poly-methylmethacrylate
(PMMA) and poly-tetrafluoroethylene (PTFE) samples at 125 nm (≈10 eV). The coherent VUV source used which provides smooth,
efficient and clean etched areas, is briefly described. Experimental curves of etch depth as a function of the number of laser
shots and etch rate as a function of energy density are obtained and compared with previous works performed at 157 nm (F2 laser) and 193 nm (ArF laser). Experimental results are described with a Beer–Lambert absorption law and discussed.
Received: 2 March 1999 / Accepted: 8 March 1999 / Published online: 11 August 1999 相似文献
10.
Mizue Mizoshiri Hiroaki Nishiyama Junji Nishii Yoshinori Hirata 《Applied Physics A: Materials Science & Processing》2010,98(1):171-177
We report the fabrication of three-dimensional (3-D) SiO2 surfaces using femtosecond-laser lithography-assisted micromachining, which is a combined process of nonlinear lithography
and plasma etching. Using pattern transfer of photoresist structures written by femtosecond laser-induced nonlinear absorption,
SiO2-based Fresnel lens arrays with 3-D surfaces were obtained for this study. Using the open-aperture z-scan method, the femtosecond laser two-photon absorption coefficient of the KMPR resist was estimated as 17–23 cm/TW, assuming
that single-photon absorption was negligible. By adding O2 to the etching gas (CHF3) during pattern transfer, the surface roughness of the transferred structures was reduced to RMS 16.90 nm, which corresponds
to one quarter of that without adding O2. When 632.8-nm-wavelength light was coupled to the lenses with 3-D surfaces, the focal length was measured as 2790 μm, which
agreed well with the theoretical value. 相似文献
11.
A K Sood K Sankaran Y Hariharan S Vijayalakshmi V Sankara Sastry S Kalavathi J Janaki 《Pramana》1988,31(5):389-397
We report infrared absorption of Y1Ba2Cu3O7−δ
as a function of oxygen stoichiometry (0<δ<1) and copper substitution by iron in the spectral range of 450–700 cm−1. The strong bands associated with Cu-O vibrations undergo significant changes in their frequencies and intensities asδ is varied across the orthorhombic to tetragonal phase. These changes coupled with those arising as a result of doping with
iron has helped in identifying the nature of the vibrational modes. 相似文献
12.
Huang-Lu Chen Jin-Cherng Hsu Yung-Hsin Lin Chi-Ren Liu 《Applied Surface Science》2009,256(4):1232-1235
A novel and effective process to fabricate high quality fluoride thin films was presented. Aluminum fluoride films deposited by a conventional thermal evaporation with an ion-assisted deposition (IAD) using SF6 as a working gas at around room temperature were investigated. In this study, the optimal voltage and current, 50 V and 0.25 A, were found according to the optical properties of the films: high refractive index (1.489 at 193 nm), low optical absorption and extinction coefficient (<10−4 at 193 nm) in the UV range. The physical properties of the film are high packing density and amorphous without columnar structure. It was proved that using SF6 working gas in IAD process is a good choice and significantly improves the quality of AlF3 films. 相似文献
13.
A. N. Obraztsov I. Yu. Pavlovskii H. Okushi H. Watanabe 《Physics of the Solid State》1997,39(10):1594-1598
Photoacoustic spectroscopy is used to study optical absorption in diamond powders and polycrystalline films. The photoacoustic
spectra of diamond powders with crystallite sizes in the range from ∼100 μm to 4 nm and diamond films grown by chemical vapor deposition (CVD) had a number of general characteristic features corresponding
to the fundamental absorption edge for light with photon energies exceeding the width of the diamond band gap (∼5.4 eV) and
to absorption in the visible and infrared by crystal-structure defects and the presence of non-diamond carbon. For samples
of thin (∼10 μm) diamond films on silicon, the photoacoustic spectra revealed peculiarities associated with absorption in the silicon substrate
of light transmitted by the diamond film. The shape of the spectral dependence of the amplitude of the photoacoustic signal
in the ultraviolet indicates considerable scattering of light specularly reflected from the randomly distributed faces of
the diamond crystallites both in the polycrystalline films and in the powders. The dependence of the shape of the photoacoustic
spectra on the light modulation frequency allows one to estimate the thermal conductivity of the diamond films, which turns
out to be significantly lower than the thermal conductivity of single-crystal diamond.
Fiz. Tverd. Tela (St. Petersburg) 39, 1787–1791 (October 1997) 相似文献
14.
The evolution of submicrodefects on loaded Cu and Pd surfaces annealed after polishing is investigated by tunneling profilometry.
The shallowest defects formed in a sample under tension appear in the form of prismatic indentations with a vertex angle ≈70°.
On Cu surfaces they have a depth of 15±3 nm and dimensions in the plane of the surface 50×50 nm. On Pd surfaces the defects
have a depth of ≈5 nm and dimensions in the plane of the surface 10×20 nm. The defects grow with time, attaining depths ≈1
μm and areal dimensions of a few micrometers before fracture. This process evolves in a stop-go pattern: The defect depth remains
approximately constant for a certain time, then changes suddenly, stabilizes again, changes once more, and so on. Defects
of depth <100 nm are distributed uniformly over the surface of the sample, while defects of depth ⩾200 nm are clustered at
the boundaries of blocks.
Fiz. Tverd. Tela (St. Petersburg) 39, 1560–1563 (September 1997) 相似文献
15.
Philipp Wagener Stephan Barcikowski 《Applied Physics A: Materials Science & Processing》2010,101(2):435-439
We present a novel approach for laser fragmentation of melamine cyanurate microcrystals suspended in liquid into colloidal
nanoparticles. Laser fragmentation is done by irradiating a liquid jet of melamine cyanurate suspended in water with intense
picosecond pulses. The free liquid jet is generated by a nozzle with small diameter and provides a thin liquid filament (d
fil<1 mm) perpendicular to the focused laser beam. This geometry allows tight focusing resulting in high intensities without
the danger of damaging an optical element like windows necessary in conventional flow cells or cuvettes. It reduces losses
of excitation light by avoiding scattering or absorption in front of the focus. We stabilized the nanoparticles electrosterically
in-situ with neutral and polyelectrolytic polymers preventing agglomeration and precipitation. The threshold for sufficient
stabilization of laser-fragmented nanoparticles (d
hydrodyn≈200 nm) is reached at a mass fraction of 0.25 wt% dextrin as a neutral polymer and 0.01 wt% polyacrylic acid as a polyelectrolytic
polymer. Hydrodynamic size and zeta-potential of the nanoparticles can be controlled by mass fraction of the stabilization
agent. 相似文献
16.
17.
P.N. Dyachenko S.V. Karpeev E.V. Fesik V.S. Pavelyev G.D. Malchikov 《Optics Communications》2011,284(3):885-888
We report on the fabrication of metallodielectric photonic crystals by means of interference lithography and subsequent coating by gold nanoparticles. The grating is realized in a SU-8 photoresist using a He-Cd laser of wavelength 442 nm. The use of the wavelength found within the photoresist low absorption band enables fabricating structures that are uniform in depth. Parameters of the photoresist exposure and development for obtaining a porous structure corresponding to an orthorhombic lattice are determined. Coating of photonic crystals by gold nanoparticles is realized by reduction of chloroauric acid by a number of reductants in a water solution. This research shows that the combination of interference lithography and chemical coating by metal is attractive for the fabrication of metallodielectric three-dimensionally periodic microstructures. 相似文献
18.
V. K. Dolganov V. M. Zhilin K. P. Meletov 《Journal of Experimental and Theoretical Physics》1999,88(5):1005-1009
Surface molecular ordering in ultrathin molecular films is investigated. The optical transmission spectra of molecular films
ranging in thickness from 2 to 13 smectic layers (6.7–43 nm) in the region of the electronic absorption bands in the smectic
A phase of cyanobiphenyl CB9 are measured. The thickness and temperature dependences of the permittivity are determined. It
is found that the orientational ordering of the molecules depends on the film thickness. The penetration depth of the surface
molecular orientational order does not exceed two smectic layers (<7 nm).
Zh. éksp. Teor. Fiz. 115, 1833–1842 (May 1999) 相似文献
19.
We have demonstrated proof-of-principle of an incoherent ArF∗ emission source with a quasi-point emission geometry using a laser-produced plasma in an Ar/F2/He/Ne mixed gas. The VUV emission characteristics, such as the emission size, were dependent on those of the plasma-initiating
laser. The average emission power was 10 μW at a repetition rate of 10 Hz at 193 nm. The average power conversion efficiency
of the 193-nm emission from the plasma-initiating Nd:YAG laser was 6.3×10−6. The average emission power at 193 nm was proportional to that of the plasma-initiating laser, indicating the scaling of
the emission source. 相似文献
20.
Etienne Shaffer Amr S. Helmy Dominique Drouin Jan J. Dubowski 《Applied Physics A: Materials Science & Processing》2008,93(4):869-874
We have investigated ArF (λ=193 nm) excimer laser-induced crystallization of amorphous CdSe semiconductor thin films. The crystallization has been monitored
by a related photoluminescence emission in the free-exciton and defect-band transition regions. For different irradiation
conditions, we have observed formation of nanorods, up to 2 μm long, as well as the formation of arrays of CdSe nanobeads
with a narrow size distribution and characteristic dimensions corresponding to λ/2 and λ/8. The successful crystallization has also been confirmed by confocal Raman spectroscopy. 相似文献