Invited Paper AS-MoA1
ASSD 30th Anniversary Lecture: XPS: Three Challenges and an Opportunity

Monday, October 19, 2015, 2:20 pm, Room 212D

The 3 challenges refer to ambitions that have been on the books for many years.:

1, to obtain XPS data from individual sub-micro particles using a laboratory instrument. Cazaux (1975) scanned an electron beam across the reverse of an Al foil holding the particles. A similar arrangement was adopted by Jenkins and Castle (1994), Their object was to examine the interface region of microtomed thin sections of adhesive joints. Useful parameters were determined but this, reverse-side excitation of x-rays is not easily adapted for use in a laboratory instrument. Recently Castle et al(2013) have returned to the subject using an Auger spectrometer. The particles are scattered on Al or Mg foil from which X-rays are produced by the impact of an electron beam close to the particle. Examples will be given

2, the need to make the Auger Parameter (AP) more intuitive. The AP, Wagner (1974), depends on the relaxation energy of the chemical structure. It is so easily determined but yields a number that is so readily forgettable! Mg has a value of 2488eV whilst Ca is 644eV. West and Castle(1982) showed how a universal scale for the AP might be produced. The zero point is that for a non-polarisable lattice. Since the refractive index (RI) also depends on lattice polarizability the zero-point can be found using the value of RI = 1 on a suitable plot and thus elements placed on a common scale. More recently (2002), Castle et al used the method to compare AP’S for V and O for a series of compounds It is concluded that a universal scale would greatly benefit those in applied surface chemical analysis .

3,is codifying the procedures that would enable manufacturers to give a first estimate of near-surface structure from the survey scan: helping to plan the detail scans which follow the survey. Castle and Baker (1999) gave an indication of how this might be approached and a very detailed set of rules was published by Castle (2007) An ISO standard for recognition of a C1s peak as contamination is being developed by ISO TC201. With this, manufacturers should have the confidence that any automated data processing will have the backing of users.

The opportunity would bring to fruition the vision of those members of ASSD when they launched Surface Science Spectra as a Journal and a database in 1993. As a Journal it is still unique in our field and is much valued for its provision of reference spectra for materials of current interest. The opportunity is to provide a searchable data base of peak energies for all elements in the diverse set of 1000 materials included in the 22 volumes now available.