OXYGEN BONDING IN GEO2 GLASS

Interpretation of oxygen bonding from X-ray photoelectron spectroscopy (XPS) spectra of oxide glasses is always ambiguous. In this work, Ge( 100) substrates with native thin GeO2 layers on them were chosen to in vestigate the various oxygen bonds in amorphous GeO2 because the Ge-Ge bond in the substrate provides a reference signal. Four different pea ks used to fit the oxidized Ge 3d photoelectron signal were assigned t o the Ge atoms bonded to four, three, two, and one oxygen atoms. In or der to confirm the assignment, a 2.8 keV Ar+ beam was applied to gradu ally remove the GeO2 film in order to separate the contributions from different types of oxygen bonding and corresponding XPS spectra were t aken to compare with the structural and compositional results obtained from the sample without sputtering. The sputtering results clearly in dicate that Ge atoms bonded to four, three, and two oxygen atoms decre ase in concentration and Ge atoms bonded to one oxygen atom show a sli ght increase with increasing sputter time. The assignment of the peaks to the different types of oxygen bonds inside GeO2 glass networks pro vides an important guide for analyzing the XPS data of GeO2 glass. (C) 1998 Elsevier Science B.V.