be parallel to its counterpart in the HOLZ, analogous to

excess and defect lines in Kikuchi patterns. It is the

HOLZ lines in the ZOLZ that are used for most HOLZ line

measurements.

 An example of what one expects to see in a

transmitted disc containing HOLZ lines is shown in Figure

4.1. The lines in the disc (labelled a in the figure) are

the HOLZ lines. The lines outside the discs but seen as

continuations of the HOLZ lines (labelled b in the figure)

are the Kikuchi lines. The Kikuchi lines extend across

the transmitted disc, thus overlapping the HOLZ lines in

the disc.

 The clarity and contrast of the HOLZ line patterns

and the accuracy of the HOLZ line positions are dependent

on at least five factors. First, there are limitations to

the thickness of the diffracting crystal (Jones et al.,

1977). This thickness should usually be on the order of

100-200 nm. If the crystal is much thicker, excessive

diffuse scattering in the ZOLZ will attenuate the HOLZ

lines entirely; if much thinner, no HOLZ lines will be

present at all.

 Second, the energy loss as the beam is transmitted

through the sample added to the inherent energy spread of

electron sources (i.e., W filament, LaB6, or FEG) can

affect the accuracy of the line position. This energy

loss will affect the thickness of the HOLZ line, reducing

the accuracy to which it can be measured. Foil