Alkali-germanium surface compound formation on a Ge(100)-(2x1) surface

Alkali-germanium surface compound formation and decomposition has been studied by means of temperature-programmed desorption (TPD), AES and EELS measurements using alkali metal and germanium codeposition on a Ge(100)-(2 x 1) surface at room temperature. At a sodium coverage (theta(Na)) of one monolayer on a Ge(100) surface, the codeposition of Ge does not change the multipeak structure in the Na TPD spectra as compared to Na adsorption on bare Ge(100). A clear peak appears in the Na TPD spectra at around 490 K after Ge codeposition when theta(Na) > 1 ML. Well pronounced EELS peaks situated at 5.5, 13 and 30 eV develop in the EELS spectra after Ge codeposition on sodium-covered Ge(100) surface, and are attributed to a Na-Ge compound. Two cycles consisting of K deposition followed by Ge deposition were carried out. Decomposition of a thus prepared K-Ge surface compound shows the same peak at 550 K in the K TPD spectra as in the Na-Ge case. (C) 1998 Elsevier Science B.V. All rights reserved.