New Apxps Endstation at Nsrrc: Status and Scientific Opportunity
Yaw-Wen Yang1,2*, Chia-Hsin Wang1, Sun-Tang Chang1, Sheng-Yuan Chen1
1Scientific Research Division, National Synchrotron Radiation Research Center, Hsinchu, Taiwan
2Department of Chemistry, National Tsing Hua University, Hsinchu, Taiwan
* Presenter:Yaw-Wen Yang,
Traditional X-ray Photoemission Spectroscopy (XPS) needs to be performed in an environment better than high-vacuum to eliminate electron-gaseous molecule scattering problem. Surface science studies require an even stringent UHV environment to keep the samples in clean conditions; as a result, the knowledge gained from this type of studies is noted for a weakness stemmed from so-called pressure gap and materials gap. To bridge the gaps, Ambient Pressure XPS (APXPS) technique was conceived and developed during the past one and a half decade. Now, the technique has reached a mature stage such that soft X-ray photoemission spectroscopy can be carried out at a pressure of ~130 mbar, enabling an in-situ and in-operando investigation of gas-solid, liquid-solid, and liquid-gas heterogeneous reactions. This unconventional technique allows researchers to extract the crucial information heretofore unavailable in many important research areas including catalysis, energy storage, environmental and atmospheric sciences.

The design and construction of a new APXPS endstation at a soft X-ray beamline was begun two years ago at NSRRC. The machine was delivered in June this year and, after a short commissioning period, the machine was quickly made available for user operation beginning in September. This new endstation has an analysis chamber for carrying out photoelectron spectroscopy, and a preparation chamber hooked up to the top section of the analysis chamber. The preparation chamber is essentially a UHV surface science machine. The mu-metal analysis chamber is equipped with a SPECS PHOIBOS 150 NAP electron energy analyzer for APXPS measurements. The sample is mounted on a 5-axes manipulator with the sample coordinates controlled from the software, and the sample temperature can be varied and stabilized from 120 to 1070 K by means of a PID-controlled, high-power laser heating device and LN2 cooling. A mass spectrometer mounted in the pre-lens section of the analyzer is used to detect the gases, though of lesser sensitivity, evolved from the reactions carried out in the analysis chamber. In this presentation, I will use the data drawn from users’ and ours to illustrate the present measurement capability, and near-future development plan to argument machine capability will also be discussed.

Keywords: Ambient Pressure X-ray Photoemission Spectroscopy, Synchrotron Radiation, Energy Materials