Results are presented which show that it is necessary to sputter-clean titanium crystals in the study of the variation of secondary emission with the angle of incidence of the primary beam. The nature and cause of the errors introduced when titanium is not sputter-cleaned are described. The asymmetrical structure observed in the angular dependence studies is attributed to misalignment of the crystals and some experimental results are given as evidence. The energy dependence of the magnitude of the structure in the angular dependence curves for tungsten is examined and found to be basically the same as for titanium and germanium. It is also demonstrated that sputter-cleaning is not necessary for angular dependence studies in the case of tungsten.
展开▼
