"Photoemission Electron Spectroscopy (PES) is well-known as the standard Electron Spectroscopy for Chemical Ananlysis (ESCA) technique. In brief, PES and XPS serve as an unique probe to impurities and its chemical information on your sample surfaces identifying the defects and contamination of your products."
 P. Songsiriritthigul, B. Kjornrattanawanich, A. Tong-on and H. Nakajima, Nucl. Instr. and Methods in Phys. Res. A 582, 100 (2007), Proceedings of the 14th National Conference on Synchrotron Radiation Instrumentation - SRI 2007. [Science Direct]
 H. Nakajima, A. Tong-on, N. Sumano, K. Sittisard, S. Rattanasuporn, C. Euaruksakul, R. Supruangnet, N. Jearanaikoon, P. Photongkam, N. Chanlek and P. Songsiriritthigul, J. Phys.: Conf. Ser. 425, 132020 (2013), Proceedings of the 11th International Conference on Synchrotron Radiation Instrumentation - SRI2012. [IOP]