Angle-resolved Electron Spectrometer Research Articles

Design of the Angle-Resolving Electron Spectrometer Aboard the PRESET Mission

Design of the Angle-Resolving Electron Spectrometer Aboard the PRESET Mission

Scanning photoelectron microscope for nanoscale three-dimensional spatial-resolved electron spectroscopy for chemical analysis

In order to achieve nondestructive observation of the three-dimensional spatially resolved electronic structure of solids, we have developed a scanning photoelectron microscope system with the capability of depth profiling in electron spectroscopy for chemical analysis (ESCA). We call this system 3D nano-ESCA. For focusing the x-ray, a Fresnel zone plate with a diameter of 200 μm and an outermost zone width of 35 nm is used. In order to obtain the angular dependence of the photoelectron spectra for the depth-profile analysis without rotating the sample, we adopted a modified VG Scienta R3000 analyzer with an acceptance angle of 60° as a high-resolution angle-resolved electron spectrometer. The system has been installed at the University-of-Tokyo Materials Science Outstation beamline, BL07LSU, at SPring-8. From the results of the line-scan profiles of the poly-Si/high-k gate patterns, we achieved a total spatial resolution better than 70 nm. The capability of our system for pinpoint depth-profile analysis and high-resolution chemical state analysis is demonstrated.

A new energy and angle resolving electron spectrometer – First results

A new energy and angle resolved analyzer for photoelectron spectroscopy is described. This analyzer is based on combining an advanced focusing electron lens system with time-of-flight measurements. A position sensitive detector gives time and position for the electron events. From this information the kinetic energy and start direction are obtained through a transformation procedure, giving both a large luminosity and a very high energy resolution. The instrument analyses the angles of emission of the electrons in a cone with 30° opening angle and simulations show that extremely high energy and angular resolution can be achieved simultaneously. We report the first results from this instrument, obtained at the PM-3 beam line at BESSY (Berlin, Germany). This analyzer opens up new possibilities for angular resolved electron spectroscopy, band-mapping and other applications.

TEARES: toroidal energy- and angle-resolving electron spectrometer—results, recent modifications and instrument performance

The toroidal energy- and angle-resolving electron spectrometer (TEARES) is a state-of-the-art instrument, which enables both the energy and angle of ejection of an electron to be measured simultaneously. First synchrotron results from TEARES are presented in this progress report. Relative cross-sections and asymmetry parameters for the Argon 3s3p 64p P 1 ° 1 ‘window’ resonance region have been measured; the results are in good agreement with the previously published data of Codling et al. In addition, significant modifications have been made to the spectrometer, which have greatly enhanced its performance. The reasons for these changes and their resulting effects on the data are presented.

TEARES: a toroidal energy- and angle-resolved electron spectrometer

The toroidal energy- and angle-resolved electron spectrometer (TEARES) is a state-of-the-art high-resolution electron detector, which measures both the energy and ejection angle of electrons simultaneously over a range of angles. A double-focussing cylindrical slit entrance lens transports and focusses electrons that are ejected near the plane perpendicular to the main axis of the spectrometer and which originate from an interaction volume of approximately 1 mm 3 to the entrance of the toroidal analyser. In addition, the lens adjusts the kinetic energy of the electrons to be analysed to match the pass energy of the analyser with a relatively constant unit magnification. The toroidal deflector analyser is comprised of an inner and an outer toroidal sector, which disperses and focuses the electrons according to their energy in the radial dimension, it is defined by a spherical radius of 125 mm, a cylindrical radius of 120 mm and a sector angle of 142°. These dimensions have been chosen to ensure optimum focussing properties. A 1 mm high entrance slit provides an analyser resolution (ΔE/PE) of 0.0081 (=1/125). A single-focussing conical slit exit lens transports, demagnifies, focuses and accelerates the electrons from the exit of the analyser onto an imaging detector. Electrons travel through the spectrometer with their initial angular direction preserved. The whole of the spectrometer has no blind spots and incorporates a working distance defined by a 38–40 mm radius. The TEARES system is designed to operate over a kinetic energy range of <0.5≤KE≤1000 eV and a pass energy range of ∼0.5≤PE≤25 eV with a useful angular range of ∼230°.

The development of a fast imaging electron detector based on the CODACON concept

A fast imaging electron detector is being developed as part of the Toroidal Energy- and Angle-Resolved Electron Spectrometer (TEARES), a high-resolution electron spectrometer for use on synchrotron sources. The analysed solid angle of TEARES is about 100 times greater than that of a conventional hemispherical analyser of similar radius and entrance slit sizes. A ‘typical’ solid sample at a third-generation synchrotron source would yield count rates in excess of 1 GHz, >10 3 times the capability of available imaging electron detectors. We describe a prototype detector based on low-resistance microchannel plates and an adaptation of the cartesian two-dimensional CODACON encoder that aims to achieve a relatively modest 2 MHz counting rate with 32 by 128 simultaneous energy and angle channels. The encoder pattern has been optimised for the output electron distribution of TEARES and directly generates a binary address for each event using simple electronics and the minimum number of signal channels.

A high performance angle-resolving electron spectrometer

We report on our new versatile photoelectron spectrometer Angular Spectrometer for Photoelectrons with High Energy REsolution (ASPHERE) which is part of beamline W3.2 (photon energies from 5 to 40 eV) but also compatible with beamline BW3 (40–1500 eV) at the Hamburger Synchrotronstrahlungslabor (HASYLAB). ASPHERE is a 180° spherical analyzer ( r 0=100 mm) with a four-element input lens and is mounted on a two-axes goniometer with computer-controlled stepper motors which enables sequential angle-scanned measurements. The input lens is equipped with an iris aperture so that the angular resolution can be continuously adjusted from 0.2° to 5°. The fringe field of the condenser has been corrected for by tilting the angle of the input lens against the base plane of the hemispheres resulting in an overall energy resolution of 10 meV. To improve the speed of data acquisition three standard channeltron detectors are installed in the image plane of the analyzer which will be replaced by a multidetection system in the near future.

Angle-resolving electron-electron coincidence setup

We introduce a novel angle-resolving electron-spectrometer system for coincidence studies of gas-phase targets using the timing structure of synchrotron radiation. The experimental setup, mainly consisting of a cylindrical mirror analyzer with a position sensitive detector and an electron time-of-flight spectrometer is particularly useful in cases where low-kinetic-energy electrons are measured in coincidence with high-kinetic-energy electrons. The experimental method and corresponding electronics are discussed. As an example, we present argon LMM Auger electron spectra taken in coincidence with KL2,3L2,3 and KL1L2,3 Auger electrons after resonant 1s→4p photoexcitation.

Surface Science

Omicron Associates has launched the AR 65 MCD angle-resolved electron spectrometer. The magnetic circular dichroism analyser could be used for both synchrotron and laboratory applications. The spectrometer is a 180° hemispherical instrument with a radius of 65 mm. The analyser has a typical angular acceptance of ±° over the complete retard ratio range and has an analysis area with a diameter of 1 mm. A compact design allows a 14° approach angle to be used. The AR 65 MCD is available as a base component mounted on a single-axis rotary stage, a two-axis goniometer stage with an angular resolution of 0.1°, or as part of a complete surface analysis system.

Design of a high-resolution angle-resolving photoelectron spectrometer system

The design and construction details, along with performances, of an angle-resolving electron spectrometer specifically designed for use on the Synchrotron Radiation Research Center in Taiwan are described. The spectrometer is a 160° spherical deflecting-type analyzer with a mean radius of 36.5 mm, including input and output lenses in order to enhance the energy resolution and the count rates. Two real apertures defining an acceptance angle and a probe area are located in the field free region ahead of the input lens, and the entrance and exit apertures of the spherical deflecting sector are set to be virtual. In the design, constant angular resolution, constant energy resolution, and constant transmission are achieved by the spectrometer. The performance of the spectrometer has been tested and is in good agreement with the theoretical calculations.

A new method for the investigation of the angular distribution of photoelectrons from laser-aligned core-excited atoms

A new method for photoionization experiments with the combined use of laser and synchrotron radiation is introduced. It consists in determination of the intensity modulation of the photoelectron signal caused by rotation of the direction of polarization of the laser radiation. Compared with the usual determination of the angular distribution of photoelectrons by rotation of the spectrometer, this method offers the advantage of being insensitive to smaller mis-alignments of apparatus and independent of the numerical value of the atomic alignment and absolute count rates produced by the laser pumping. The method is applied to the investigation of core-excited Ca 3p 5 3d4s4p resonances with two different detector configurations (angle resolved electron spectrometer and cylindrical mirror 180° analyzer). The results are discussed in connection with theoretical predictions and are used for the determination of the asymmetry coefficient β.

Development of High Resolution Angle Resolved Electron Spectrometer (HR-ARES) for Measurements of Angular Distribution of Elastically or Inelastically Scattered Electrons.

A high resolution angle-resolved electron spectrometer (HR-ARES) system with extremely high vacuum and extremely low residual magnetic field has been developed. This system can be used for the precise measurements of angular distribution of elastically or inelastically scattered electrons (photoelectrons, Auger electrons) excited by the incidence probes of X-ray (Mg Kα) and electron beams. Since the main chamber was made of 5 mm-thick mu-metal alloy which has high magnetic-shieldng ability, the residual magnetic field in the inner space was found to be decreased to less than 4 mG. This extremely low magnetic field enables the precise angle-resolved measurements of ultralow energy electrons of about 1 eV. Using our sophisticated UHV techniques, the HR-ARES system with many equipments for surface analysis and treatment has attained the extremely high vacuum of less than 10-9 Pa.

高分解能角度分解分光装置用大型ミューメタルチャンバーの真空排気特性

高分解能角度分解分光装置用大型ミューメタルチャンバーの真空排気特性

Differential cross sections of atomic Au for electron scattering (30-200 eV)

Differential cross sections for elastic scattering and for excitation of the 2P1/2 and 2P3/2 states of atomic gold have been measured with an angle resolving electron spectrometer. The primary energy extended from 30 to 200 eV and the scattering angle from 5 to 140'. The energy and angle resolutions were about 80 meV and 1' FWHM respectively. The measured relative cross sections are in good agreement with theory. Absolute values were derived by normalisation against Ar and Cu cross sections. They were found to be about three to ten times larger than those predicted by different theories.

Experimental and theoretical study of configuration interaction states of CO+2

Configuration interaction states of CO+2 have been observed as satellites in a high resolution photoelectron spectrum of CO2 using an angle resolved electron spectrometer and far UV synchrotron radiation in the 30–55 eV photon energy range. Ten satellites have been identified in the 22–40 eV binding energy region and classified as the result of outer and inner valence ionization processes on the basis of their asymmetry parameter ( β) values. Theoretical calculations of configuration interaction states of CO+2 using an ab-initio SCF-CI method show that three-hole-two-particle excited configurations are necessary to explain the line positions and intensities. The calculated satellite spectrum, corrected for transition moments at 45 and 1254 eV, shows an excellent agreement with experiment and allows assignments of both outer and inner valence satellite lines, with Πg, Πu, Σ+g, and Σ+u symmetries.

Design criteria for an angle resolved electron spectrometer of novel toroidal geometry

A charged particle analyser based on the use of polar trajectories in a toroidal sector is described in which a large number of particle emission angles are detected simultaneously. An analysis of the trajectories of particles in this class of analyser is presented and we develop transfer matrices which enable the imaging properties of such devices to be determined analytically. Expressions for the axial and radial magnification and for the energy resolving power are also derived. The analysis and the derived properties are compared with a numerical simulation and with all available published data.

A toroidal angle-resolving electron spectrometer for surface studies

An electron spectrometer with toroidal geometry has been developed which enables angularly resolved spectra to be obtained simultaneously at a large number of angles. This reduces data acquisition times by a factor of 100 and makes accessible many experiments on surfaces and interfaces which involve reactive materials or which require long experiment times. Photoelectron spectra of gases are presented which demonstrate the analyzer's energy and angular resolution showing it to be more than adequate for surface studies.

A toroidal angle-resolving electron spectrometer for surface studies

A toroidal angle-resolving electron spectrometer for surface studies

High resolution angle-resolved photoelectron spectrometer system

The design and construction details for a new high resolution, angle-resolved electron spectrometer system specifically designed for use on the National Bureau of Standards' synchrotron radiation facility (SURF-II) are described. The system features two 10.2 cm mean-radius hemispherical electron energy analyzers in a cryogenically-pumped, magnetically-shielded chamber and may be used to measure vibrationally resolved photoelectron branching ratios and angular distributions from small molecules.

5216. Angle-resolved electron spectrometer with multidetection: G V Hansson et al,Rev Sci Instrum,52 (4), 1981, 517–522

5216. Angle-resolved electron spectrometer with multidetection: G V Hansson et al,Rev Sci Instrum,52 (4), 1981, 517–522