An option for the surface science on Cu chalcopyrites: the selenium capping and decapping process

A selenium capping and decapping process for the protection of CuInSe2 surfaces during storage in air was investigated. The quality and cleanness of CuInSe2(0 0 1) surfaces restored in UHV by thermal evaporation of the covering protective Se cap was assessed. For the study, MBE-grown heteroepitaxial CuInSe2/GaAs(0 0 1) films were employed. capping and decapping process was monitored by reflection high-energy electron diffraction. The Se cap layer is amorphous and, after its reevaporation, the initial diffraction pattern of CuInSe2(0 0 1) is restored. The decapping process and the quality of decapped CuInSe2(0 0 1) surfaces were investigated by means of photoelectron spectroscopy using synchrotron radiation with excitation energies of 1050 and 95 eV. For a decapping temperature of 390 °C, an O 1s contamination signal as small as the detection limit was found. Photoelectron spectra taken with the highest surface-sensitivity (hν=95 eV) yield well-resolved valence band emissions confirming the low contamination level and high quality of the decapped surfaces. The investigations show that the Se capping and decapping process is an efficient means for the conservation and restoration of clean and well-defined Cu chalcopyrite surfaces in UHV.