Ion-induced electron emission monitoring of the structure and morphology evolution in HOPG

The temperature dependences of the ion-induced electron emission yield γ of highly-oriented pyrolytic graphite (HOPG) under high-fluence (1018-1019 ions/cm2) 30 keV Ar+ ion irradiation at ion incidence angles from θ = 0o (normal incidence) to 80o have been measured to trace both the structure and morphology changes in the basal oriented samples. The target temperature has been varied during continuous irradiation from T = −180 to 400 oC. The surface analysis has been performed by the RHEED and SEM techniques. The surface microgeometry was studied using laser goniophotometry (LGF). The dependences of γ(T) were found to be strongly non-monotonic and essentially different from the ones for Ar+ and N2+ ion irradiation of the polygranular graphites. A sharp peak at irradiation temperature Tp ≈ 150 oC was found. A strong influence of electron transport anisotropy has been observed, and ion-induced microgeometry is discussed.