Influence of alternating low voltage component on field photoemission current forma semiconductor tip

In this work we considered the influence of low alternating voltage of up to 100 V on the field photoemission process from a semiconductor tip under high voltage of 0.7-5.0 kV and photon excitation of 1.3 eV energy. Considered cathodes were made of high-resistivity silicon with p-type conductivity

Influence of alternating low voltage component on field photoemission current forma semiconductor tip

In this work we considered the influence of low alternating voltage of up to 100 V on the field photoemission process from a semiconductor tip under high voltage of 0.7-5.0 kV and photon excitation of 1.3 eV energy. Considered cathodes were made of high-resistivity silicon with p-type conductivity

Quantitative measurements of magnetic stray field dynamics of Permalloy particles in a photoemission electron microscopy

By example of a Permalloy particle (40 × 40 μm(2) size, 30 nm thickness) we demonstrate a procedure to quantitatively investigate the dynamics of magnetic stray fields during ultrafast magnetization reversal. The measurements have been performed in a time-resolving photoemission electron microscope using the X-ray magnetic circular dichroism. In the particle under investigation, we have observed a flux-closure-dominated magnetic ground structure, minimizing the magnetic stray field outside the sample. A fast magnetic field pulse introduced changes in the micromagnetic structure accompanied with an incomplete flux closure. As a result, stray fields arise along the edges of domains, which cause a change of contrast and an image deformation of the particles geometry (curvature of its edge). The magnetic stray fields are calculated from a deformation of the X-ray magnetic circular dichroism (XMCD) images taken after the magnetic field pulse in a 1 ns interval. These measurements reveal a decrease of magnetic stray fields with time. An estimate of the lower limit of the domain wall velocity yields about 2 × 10(3) m s(-1)

Wavelength dependence of polarisation of photoelectrons ejected by unpolarised VUV radiation from argon and krypton atoms

Heinzmann U, Schönhense G, Kessler J. Wavelength dependence of polarisation of photoelectrons ejected by unpolarised VUV radiation from argon and krypton atoms. Journal of Physics B: Atomic, Molecular and Optical Physics. 1980;13(5):L153-L156

Energy dependence of the electron spin polarisation parameters for Hg 5d photoionisation with circularly polarised light

Schäfers F, Heckenkamp C, Schönhense G, Heinzmann U. Energy dependence of the electron spin polarisation parameters for Hg 5d photoionisation with circularly polarised light. Journal of Physics B: Atomic, Molecular and Optical Physics. 1988;21(5):769-774.Circularly polarised VUV radiation from the storage ring BESSY was used to measure all three spin polarisation parameters of photoelectrons from the Hg 5d shell in the photon energy range from threshold to approximately 35 eV. The experimental results are compared with theoretical calculations in the relativistic and non-relativistic random-phase-approximation scheme (RRPA and RPAE respectively) and Dirac-Slater (DS) calculations. A discussion of the influence of relativistic and potential barrier effects on the experimental data is given

Chemical microanalysis by selected-area ESCA using an electron energy filter in a photoemission microscope

Schmidt O, Ziethen C, Fecher GH, et al. Chemical microanalysis by selected-area ESCA using an electron energy filter in a photoemission microscope. In: Journal of Electron Spectroscopy and Related Phenomena. JOURNAL OF ELECTRON SPECTROSCOPY AND RELATED PHENOMENA. Vol 88. ELSEVIER SCIENCE BV; 1998: 1009-1014.We present a new and simple device for microspectroscopy being independent of the mode of electron-excitation. Micro-Xray photoelectron spectroscopy, electron-induced Anger-spectroscopy, as well as local energy-loss spectroscopy were used to investigate metal-adsorption on silicon. This new approach employs a non-imaging electron energy analyser attached to a new-generation photoemission electron microscope with integral microarea selector. Photoelectron microspectroscopy was performed using the direct beam of an undulator (U2 at BESSY) being monochromatised and focused by means of multilayer optics at hv = 95 eV. Similarly, local Auger-electron and EELS spectra have been taken using a simple electron gun for the excitation. The chemical compositions of inhomogenities in thin layers of indium on silicon and the local state of oxidation of a structured Pt-Co multilayer have been determined. (C) 1998 Elsevier Science B.V

Spin-polarised photoelectrons produced from CH3Br molecules by unpolarised and circularly polarised VUV radiation

Heinzmann U, Osterheld B, Schäfers F, Schönhense G. Spin-polarised photoelectrons produced from CH3Br molecules by unpolarised and circularly polarised VUV radiation. Journal of Physics B: Atomic, Molecular and Optical Physics. 1981;14(3):L79-L84.It has been experimentally verified for CH3Br that spin-polarised photoelectrons can be ejected from unoriented molecules if the radiation is circularly polarised or even unpolarised. The polarisation values and the experimental data of the asymmetry parameter beta are discussed by use of Cherenkov's formulae (1981)

Time-of-flight photoelectron emission microscopy TOF-PEEM: first results

Spiecker H, Schmidt O, Ziethen C, et al. Time-of-flight photoelectron emission microscopy TOF-PEEM: first results. NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION A-ACCELERATORS SPECTROMETERS DETECTORS AND ASSOCIATED EQUIPMENT. 1998;406(3):499-506.The time structure of the synchrotron radiation at BESSY (Berlin) is used to operate a photoemission electron microscope in a time-of-flight (TOF) mode. The electrons which are emitted from the sample surface with different energies are dispersed in a drift tube subsequent to the imaging optics. The screen of the microscope was replaced by a fast scintillator (tau = 1.4 ns) and the light is detected by an ultra fast gated intensified CCD camera (800 ps gate 1 MHz repetition rate). The resolving power in the energy domain is demonstrated and possible implications on the spatial resolution (chromatic correction) are discussed. Additionally, an improved contrast at very low emission energies is shown. The capability of the setup as an efficient microspectroscopic tool is illustrated. (C) 1998 Elsevier Science B.V. All rights reserved