VARIATIONS IN THE VALUE OF THE CHARACTERISTIC VELOCITY OF THE ZR- SECONDARY-ION EMISSIONS ACROSS THE OXIDE METAL INTERFACE

Calculations, from experiment data, revealed that the Zr- secondary io n yield increased exponentially with increasing emission velocity over the 40 to 250 eV (plus E(b)) emission energy range. The Zr- secondary ion emissions could therefore be characterised by a single characteri stic velocity value over this energy range. This exponential behaviour was also found to vary across the oxide/metal interface. Since this v ariation results from what is commonly referred to as the matrix effec t, the dependence of the matrix effect on emission velocity could also be defined. This was found to decrease in an exponential-like manner with increasing emission velocity. Extrapolating this trend to infinit e velocity indicated complete removal of the matrix effect. This remov al of the matrix effect at infinite velocity is supported by the fact that the known Zr concentration profile could be reproduced from empir ical data (once instrument transmission and sputter yield factors are accounted for) on extrapolation to infinite velocity.