Development of a linac-based LEPD experimental station for surface structure analysis and coordination with synchrotron radiation ARPES

TL;DR

This paper presents the development of a linac-based low-energy positron diffraction (LEPD) station for precise surface structure analysis, integrating advanced UHV chambers and compatibility with existing ARPES systems at KEK.

Contribution

It introduces a novel LEPD experimental station with rapid measurement capabilities and integration with other surface analysis tools, enhancing surface structure determination accuracy.

Findings

LEPD station enables quick acquisition of I-V curves

The system maintains surface integrity during measurements

Compatibility with existing ARPES stations at KEK

Abstract

We report on the development of a low-energy positron diffraction (LEPD) experimental station for surface structure analysis using a linac-based slow-positron beam. LEPD, the positron counterpart of low-energy electron diffraction (LEED), offers higher accuracy in surface structure determination. The station enables acquisition of LEPD I-V curves within a few hours, allowing measurements before surface degradation occurs. It consists of two ultra-high vacuum (UHV) chambers: one for sample preparation and the other for LEPD observations. The preparation chamber includes an Ar+ sputtering system, a triple-pocket electron beam evaporator, three gas introduction systems, additional user-configurable ports, and a LEED/Auger electron spectroscopy (AES) system. Sample manipulators enable rapid cooling, precise positioning, and orientation adjustments. In the preparation chamber, the manipulator also supports direct current heating up to 1200 {\deg}C. The sample holder is compatible with the LEPD station at SPF-A4 and the ARPES station at PF BL-13B, both located at the Tsukuba campus of the Institute of Materials Structure Science (IMSS), KEK. Design concepts and experimental demonstrations are presented.