Constant Energy Mode Research Articles

Excimer laser model based on a temporal convolutional neural network.

Excimer lasers play a key role in deep ultraviolet lithography. To further study the voltage and energy features of the excimer laser and control it to work in a constant energy mode, a temporal convolutional neural network was designed to fabricate an excimer laser voltage-energy model. The proposed model uses the currently measured energy data to predict the subsequent output energy data. For the voltage-energy data that cannot be obtained, we simulated the initial energy data corresponding to the part of the voltage value based on the relationship between energy and voltage as the initial input of the model. The energy data of any voltage for the excimer laser at each moment were obtained. Finally, a continuous excimer laser voltage-energy model was established. The difference between the means of the measured and generated energy data is less than 0.5 mJ.

Green spectrofluorimetric methods for tramadol assay with ibuprofen or chlorzoxazone: comparison of greenness profiles.

At this time, green analytical chemistry is gaining more interest and concern. The present work details three green spectrofluorimetric methods for tramadol (TRM) determination using ibuprofen (IBU) (mixture 1) and chlorzoxazone (CLZ) (mixture 2). In first method, two excitation wavelengths (λex ), 220 and 280 nm, were used to record the emission spectra for IBU and TRM, respectively (mixture 1) followed by a first derivative treatment. For mixture 2, one λex (280 nm) was optimum for both drugs followed by a first derivative technique for TRM and a second derivative for CLZ determinations. The second method measured the first derivative values for synchronous spectra using constant-wavelength mode at 280 nm for TRM and 260 nm for IBU, and at 270 nm for TRM and 292 nm for CLZ. The third method used constant-energy mode to record synchronous spectra. First derivative values were computed at 282 nm for TRM and 260 nm for IBU in mixture 1 and at 272 nm for TRM and 292 nm for CLZ in mixture 2. ICH validation guidelines were assessed in full and assay of the two TRM binary mixtures in their drug products was successful. Green profile evaluation for the developed methods compared with the reported chromatographic methods was performed using the 'analytical eco-scale' and the 'green analytical procedure index'. These two assessment tools corroborated that the proposed methods achieved the most green parameters, therefore recommending their use as a green option for analyzing the studied drugs in bulk and dosage forms for routine quality control.

B-bar virtual element method for nearly incompressible and compressible materials

We present a B-bar formulation of the virtual element method (VEM) for the analysis of both nearly incompressible and compressible materials. The material stiffness is decomposed into dilatational and deviatoric parts, and only the deviatoric part of the material stiffness is utilized for stabilization of the element stiffness matrix. A feature of the formulation is that locking behavior for nearly incompressible materials is successfully removed by the spectral decomposition of the material stiffness. The eigenvalue analysis demonstrates that the method eliminates higher energy modes associated with locking behavior for nearly incompressible materials, while capturing constant strain energy modes for both compressible and nearly incompressible materials. The convergence and accuracy of the B-bar VEM are discussed using 2D and 3D examples with various element shapes (convex and non-convex).

Artificial neural networks for processing fluorescence spectroscopy data in skin cancer diagnostics

Over the years various optical spectroscopic techniques have been widely used as diagnostic tools in the discrimination of many types of malignant diseases. Recently, synchronous fluorescent spectroscopy (SFS) coupled with chemometrics has been applied in cancer diagnostics. The SFS method involves simultaneous scanning of both emission and excitation wavelengths while keeping the interval of wavelengths (constant-wavelength mode) or frequencies (constant-energy mode) between them constant. This method is fast, relatively inexpensive, sensitive and non-invasive. Total synchronous fluorescence spectra of normal skin, nevus and melanoma samples were used as input for training of artificial neural networks. Two different types of artificial neural networks were trained, the self-organizing map and the feed-forward neural network. Histopathology results of investigated skin samples were used as the gold standard for network output. Based on the obtained classification success rate of neural networks, we concluded that both networks provided high sensitivity with classification errors between 2 and 4%.

Focus on lasers and optics

Focus on lasers and optics

Dissociative ionization of methane by chirped pulses of intense laser light.

Measurements have been made of optical field-induced ionization and fragmentation of methane molecules at laser intensities in the 10(16) W cm(-2) range using near transform limited pulses of 100 fs duration as well as with chirped pulses whose temporal profiles extend up to 1500 fs. Data is taken both in constant-intensity and constant-energy modes. The temporal profile of the chirped laser pulse is found to affect the morphology of the fragmentation pattern that is measured. Besides, the sign of the chirp also affects the yield of fragments like C2+, H+, and H2+ that originate from methane dications that are formed by optical field-induced double ionization.

Seedless Electrodeposition of Cu on Unmodified Tungsten

The electrodeposition of Cu onto barrier surfaces is of considerable importance in the development of Cu interconnect processes for deep submicrometer devices. Current processing usually involves electrodeposition from a sulfate bath onto a Cu seed layer, which is first deposited by plasma vapor deposition ~PVD! or metallorganic chemical vapor deposition ~MOCVD!. Conformal, uniform seed layer deposition becomes increasing problematic as device dimensions continue to shrink; 1 electrodeposition in the absence of a seed layer is desirable. Surface science studies carried out in ultrahigh vacuum ~UHV!, however, indicate that the ability of Cu adlayers to wet ~grow conformally on! a Ta or W barrier surface is severely degraded by the presence of even monolayer coverages of oxygen. 2-4 The electrodeposition of Cu onto reactive metal surfaces in aqueous environments therefore presents obvious difficulties. Under acidic conditions ~pH ;1 or lower!, and cathodic potentials, W metal is predicted 5 to be thermodynamically stable relative to its oxides. Exploratory studies of Cu electrodeposition on W in the absence of a Cu seed layer were therefore carried out under these conditions. Experimental Studies were carried out in a flat three-electrode cell fitted with a Luggin capillary and a platinum-rhodium counter electrode. All potentials reported here are referenced to Ag/AgCl. The cell was configured so that the area of the electrode accessible by the electrolyte was 1c m 2 . The solutions used for these studies consisted of 0.05 M CuSO4 in H2SO4 at pH 1.0. Solutions were purged with N2 for .1.5 h prior to each experiment. Polycrystalline W foils ~.99.95% pure! were used as working electrodes. Foils were rinsed in acetone, ethanol, and distilled water prior to use. Electrochemical measurements were carried out using a commercially available potentiostat ~EG&G 263A! and software. Scanning electron microscopy ~SEM! data were acquired using a JEOL 300S model with an energy dispersive analysis by X-ray ~EDAX! attachment for elemental analysis. X-ray photoelectron spectroscopy ~XPS! data were acquired with a hemispherical analyzer operated in constant pass energy mode ~50 eV! and unmonochromatized Mg Ka radiation.

Thermal Evolution of Anodized Nb by XPS

XPS spectra acquired on anodized niobium during a thermal treatment from 300 to 1223 K are reported. The anodization process consists of growing a layer of oxide of known thickness on the metal surface; the sample is kept in a solution of ammonia inside an electrochemical cell and a d.d.p. is applied to the electrodes. We acquired XPS spectra by using a PHI 5600 ESCA multitechnique spectrometer with an Al Kα monochromatized source. The spherical capacitor analyzer operated in the constant energy mode at a pass energy of 5.85 eV. Measurements at two emission angles, 0° and 70°, and at temperatures between 300 and 1223 K are reported. This XPS study puts in evidence the existence of a transition on the Nb surface from Nb pentoxide to Nb pure metal during the heating phase.

A multi-detector system for a triple-axis spectrometer

Until now there have been only a few attempts to use many scattering angles simultaneously in triple-axis spectrometry with neutrons. We present a novel Multi-Analyzer Detector (MAD) unit for a Triple-Axis Spectrometer (TAS) set up at the Forschungsreaktor München (FRM). The layout is based on the principle of monochromatic defocusing. Up to 61 analyzers are mounted around the sample in the constant final energy mode. This arrangement supplies the flexibility of a TAS with a multi-channel analyzer capacity similar to a Time-of-Flight Spectrometer. The gain in measurement time can be more than an order of magnitude.

Quasi-particle spectra and Fermi surface mapping

Abstract The low-lying electronic excitations of conventional metals can be described as quasi-particles with characteristic spectral properties which can in principle be probed by angle-resolved photoelectron spectroscopy (ARPES). Data taken on a suitable Fermi liquid (FL) material are discussed in terms of quasi-particle energy renormalization and lifetime width narrowing towards the Fermi level. In contrast, the unusual behavior observed in the spectra of a quasi-one-dimensional metal indicates a possible breakdown of the quasi-particle picture. I further discuss the mapping of Fermi surfaces using ARPES in the constant energy mode and suggest a method for precise Fermi vector determination based on FL properties.

Angle-resolved photoelectron spectroscopy on the Fermi liquid reference compound TiTe 2

The layered compound TiTe 2 can, for several reasons, be viewed as an ideal candidate for electron spectroscopic studies of Fermi liquid behavior. High-resolution angle-resolved photoemission (ARPES) spectra near the Fermi energy reflect the expected energy renormalization and lifetime narrowing of the quasiparticle excitations. These results support a many-body interpretation of ARPES on low-energy excitations in terms of the spectral function A( k, ω) . We further present ARPES data measured in the constant energy mode and suggest a new method for obtaining precise information on the Fermi surface, which utilizes the discontinuity in the momentum distribution function of a Fermi liquid.

Calculations of a CHA transmission function for quantitative analysis in the constant pass energy mode. I. Point sources for AES

AbstractThe analyser transmission function T of a concentric hemispherical analyser (CHA) with an input lens system has been studied, and the behaviour of T under suitable operation conditions for a point source has been determined by means of numerical calculations. One of the significant factors controlling T was found to be the aberrations of the input lens, which have a strong dependence on the retardation ration γ and the angular magnification Mα of the lens. The Mα also determines the entering angles of electrons to the CHA, and thus this should be kept sufficiently small as far as the aberrations in the CHA are concerned. The calculated results showed, however, that for each γ there exists an optimum Mα, which corresponds to a compromise point between the aberrations of the input lens and those of the CHA. If Mα is kept constant, T varies according to the increase or decrease in the lens aberrations as functions of γ. Lineshapes calculated for a monochromatic point source were also shown. These were found to be asymmetrical and have tailings on the low‐energy side due to the aberrations of the CHA.

Triplet states of ammonia excited by low-energy electrons

A low-energy crossed-beam electron spectrometer is used to investigate excitation of ammonia. Spectra obtained at low residual energies and large scattering angles in both constant residual energy mode and energy loss mode show excitation of two triplet states of ammonia, labelled a and b. A triplet b state is observed for the first time in the present work, while for the a state several lower, previously unobserved vibrational levels are detected. The threshold electron spectrum obtained by detecting zero residual energy electrons reveals a strong influence of threshold resonance in the excitation of he lowest Rydberg a state. Also a very large threshold peak in the excitation of the v=1 level of the symmetric stretch mode (v1) of the ground electronic state suggests a resonant process at very low energies.

Electron spectrometer transmission functions for quantitative AES AND XPS

Experimental data of the transmission functions for quantitative AES and XPS of the electron spectrometers PHI Perkin Elmer 660 and 590 SAM Systems, VG Scientific Microlab MKII in the main modes of signal registration are given. The method of T( E) calibration is based on utilization of a reference copper background electron spectrum. The influences of energy resolution, constant retarding ratio and constant analyzer energy modes, multiplier voltage etc. on the T( E) behaviour are considered. The transformations of copper background electron spectrum shape against the primary electron beam energy, the angle of incidence of the electron beam and the angle of emission are given. Recommendations for the T( E) calibration for quantitative XPS analysis are made.

Molecular effects in carbon K-shell Auger-electron production by 0.6–2.0 MeV protons and extraction of an atomic cross section

Carbon K-shell Auger-electron production cross sections are reported for 0.6–2.0 MeV protons incident on CH 4 (methane), C 2H 2 (acetylene), C 2H 4 (ethylene), C 2H 6 (ethane), nC 4H 10 (normal butane), i-C 4H 10 (isobutane), C 6H 6 (b monoxide), and CO 2 (carbon dioxide). A constant-energy mode 45° parallel-plate electrostatic analyzer was used for detection of Auger electrons. The carbon KLL Auger-electron cross sections for all molecules were found to be lower than that found for CH 4 by 9–23%. All carbon KLL Auger-electron data could be brought into agreement when corrected for the chemical shift of the carbon K-shell binding energy in molecules and for intramolecular scattering. KLL Auger-electron production cross sections are compared to first Born and ECPSSR theories and show good agreement with both after the chemical shift of the carbon K-shell binding energy in molecules and the effects of intramolecular scattering are considered.

Compact analyzer and goniometer for angle-resolved electron spectroscopy

We discuss the design and construction of a modified electrostatic plane mirror electron energy analyzer mounted on a novel dual axis goniometer. The system is compact, bakable, and well suited for ultrahigh vacuum angle-resolved photoelectron spectroscopy. The device is relatively inexpensive and simple to construct, yet provides ample performance and versatility. In particular, preaccelerating electron optics have been developed which allow operation of the analyzer in the constant pass energy mode with uniform sensitivity over an increased energy range. A differentially driven goniometer allows the polar and azimuthal directions of detection to be varied independently and read directly. Test results are presented and angular and energy resolutions of 3° and 3% are reported.

An electron-optical system for the efficient operation of a constant energy mode π/4 electrostatic parallel plate electron analyzer

Two Einzel lenses are used in conjunction with an intermediately located deceleration grid arrangement to efficiently manipulate the shape and energy of an electron beam prior to the analyzer entrance slit. This system decelerates all electrons to be analyzed to a selectable transmission energy that is held constant for a given spectrum. The Einzel lens parameters are varied dynamically with the deceleration grid potential so that the desired electron energy band is focused and passed to the entrance slit. The cylindrical symmetry of the first lens enhances the intensity. The efficiency of detection is further aided by the planar symmetry of the second lens. The design of this variable band, selectable band width electron filter is discussed. Operational parameters and sample spectra are presented.

Miniature plane mirror analyzer suitable for angle-resolved photoelectron spectroscopy

A plane-parallel-plate electron energy analyzer is described based on the second-order-focusing 30° injection geometry. The small size of the analyzer permits it to be attached to a commercial rotary feedthrough and to be used in angle-resolved photoemission studies. The analyzer is operated in a constant pass energy mode, and the electron energy spectrum is obtained by sweeping the voltage on a preretardation/acceleration stage. A resolution function ΔE/E equal to ∼6% leads to a resolution of lower than 0.2 eV at sufficiently low pass energies. The performance is illustrated with results obtained using synchrotron radiation in a system having two identical analyzers.

A 304 Å photoelectron spectrometer for band structure studies

A high resolution electrostatic spectrometer and associated Helium resonance radiation lamp has been constructed which is particularly suitable for the determination of the energy-angular distribution of photoelectrons from solid surfaces. The relative intensity of 304/581 Å radiation from the lamp has been estimated by an indirect method to be 25 per cent under optimum conditions. The transmission efficiency of the system when operating in the constant energy mode of analysis has been determined and the operation of the spectrometer illustrated with reference to a study of photoemission from the conduction band of gold.