MICROSCOPIC ULTRAVIOLET PHOTOELECTRON SPECTROSCOPY USING He-I AND He-II RESONANCE LINES

Abstract

A microscopic ultraviolet photoelectron spectrometer (micro-UPS) is developed using a Schwarzschild objective coated with the two-color multilayer which reflects efficiently both He-I (21.2 eV) and He-II (40.8 eV) resonance lines. The spot size by the use of a pinhole of 300 µm diameter is 5 µm, which was measured using the visible light from a Xe lamp. In the present micro-UPS, a pinhole of 2 mm diameter is used to gain sufficient photon intensity, so that the spot size is 25 µm. The valence band spectra of a NiWO4 microcrystal, which cannot be grown in sufficient size, were measured by the present micro-UPS. The origin of atomic orbitals constituting the valence band of NiWO4 was elucidated.

Microscopic optical and photoelectron measurements of MWO4 (M=Mn, Fe, and Ni)

“…To reduce the thermal noise, the photodiodes were cooled down to -50 1C by cold Cu wires connected to a cryostat of liquid nitrogen. Microscopic UPS measurements were made using also a home-made instrument [4]. The light generated by a rare-gas discharge lamp is transmitted through a pinhole and focused by a Schwarzschild objective on a sample.…”

“…In this study, the electronic structure of NiWO 4 has been investigated experimentally. The other transition-metal tungstates, MWO 4 optical (absorption and reflection) and ultraviolet photoelectron spectroscopy (UPS) measurements, so that the microscopic optical and UPS measurements have been made on these microcrystals. Their crystal structures are of Wolframite type characterized by alternating layers of transitionmetal and tungsten atoms parallel to the (1 0 0) plane [3].…”

Improved thermal stability of Mg/Co multilayer by introducing Zr barrier layer

“…In extreme ultraviolet (EUV) region, high reflective multilayer mirrors (MLMs) are widely used as optical elements for applications such as EUV microscopy [1] , high harmonic femtosecond chemistry [2] , solar astrophysics imaging [3,4] , and synchrotron radiation [5] . In the 25-40 nm wavelength region, Mg-based multilayers, such as Mg/SiC, Mg/Y 2 O 3 and Mg/Co are promising for Mg L 3 absorption edge is located at 25nm [6][7][8][9][10][11] .…”