Electron-induced extended-fine-structure measurements of thin-film growth and reaction

The application of two electron-beam-induced extended-fine-structure (EFS) techniques [surface extended energy-loss fine structure (SEELFS) and extended appearance-potential fine structure (EAPFS)] to the study of thin films has been demonstrated by measurements on three well-characterized compositional phases of titanium deposited on Si(111). The EFS above the Ti $L_2$,3 edge have been measured for an unannealed (20 °C) pure Ti overlayer, a 250 °C-annealed layer (a Si-rich Ti overlayer), and a 400 °C overlayer (a silicide phase). Data were analyzed by using two routines from extended x-ray-absorption fine structure (EXAFS): the standard optical transform (including Δl=+1 phase shifts) and the ratio method which is independent of phase shifts. The Ti $L_2$,3edge EFS satisfies the dipole pseudo-selection-rule of EAPFS, validating the use of Δl=+1 phase shifts in the EAPFS analysis. The agreement between the measured spectra obtained with SEELFS and EAPFS is very good and is additional confirmation of the use of dipole phase shifts in SEELFS analysis.