J. J. Yeh

Computer program for photoemission data analysis and display

A computer program for photoemission data analysis which operates using the VAX computer or the Macintosh personal computer is described. It includes functions which give a summary of the data such as centroid and area, performs curve fitting for extracting chemical information from core levels, and it prepares figures for publication, as well as many other functions. A brief description of the program and its capabilities is given.

Strong 5p hole - 5d electron interaction in the electron emission processes for Eu and Yb metals

Abstract We report the observation of intense constant kinetic energy emission structures, in the photoemission spectra of the divalent rare earth elements, Eu and Yb, in the solid state, when excited by photon energies larger than the 5p core ionization thresholds; and we propose a possible explanation of this phenomenon.

Resonance of 4f partial photoionization cross section of Yb and Eu near the 5p threshold

The 4f partial photoionization cross section of the divalent metals Yb and Eu are measured by photoelectron spectroscopy in the 15 to 30 eV range. Both metals show the same resonance effect above the threshold of the first peak of the 5p multiplets in spite of different configurations of valence electrons: the appearance of a replica of the valence band region at fixed kinetic energy arising from a 5p core hole induced Auger‐like decay process. An apparently dissimilar resonance effect is observed above the second peak of the Eu 5p multiplets: no clear feature except a weak enhancement of 4f peak intensity similar to the 4d→4f resonance in oxidized Yb. It is possible that similar process effects exist in all the lanthanides.

Photoelectron Spectroscopy of the Si/Eu Interface Using Synchrotron Radiation

Rare earth metal/semiconductor interfaces have attracted recent interest for properties that are distinct from those observed in other, more extensively studied, metal/semiconductor systems. Rare earth silicide/silicon junctions have the lowest measured Schottky barrier [1] of any metal silicide contact to n-type Si. The thin film reaction kinetics are often controlled by nucleation phenomena [2] instead of atomic diffusion as in many d metals [3]. The contrast in these properties, and others such as the thermodynamics of metal/Si compound formation [4], makes the study of these interfaces important to the general understanding of the formation of Schottky barriers in microscopic terms.

An illustration on the measurement of the net yield of the SSRL beamline I-I monochromator☆

Abstract The measurement of the net yield of a monochromator with the cross section variation of the detecting material filtered out is briefly illustrated. This is achieved by measuring the absorption cross section variation of a thin film that is made of the same material as the flux monitor detecting material at the same time when the monochromator is sweeped. Using this measured absorption cross section, the substrate response can then be divided out and thus give the monochromator yield from the measured total yield. The key point of this measurement is to use same materials at two sites. In principle, the result is independent of the material chosen and this method can be easily applied to various monochromators operated at a wide photon energy range, for example, from infrared to hard X-rays, without the previous knowledge of the photoionization cross section of the detecting material.

The Si(111)-7×7/Eu interface investigated by means of electron spectroscopies

Abstract We present a selection of data from the first spectroscopic investigation on the room temperature growth and annealing of the Si (111)7 × 7 Eu interface. A mixed interface is formed at RT for coverages 5 5p 3 2 core absorption threshold, is recognized as a fingerprint of metallic Eu.