Sputtering of a coarse‐grained benzene and Ag(111) crystals by large Ar clusters – effect of impact angle and cohesive energy

Abstract

Molecular dynamics computer simulations are employed to investigate the role of the substrate cohesive energy on the impact angle dependence of the sputtering yield for Ar 60 and Ar 2953 projectiles bombarding a benzene molecular solid and a Ag(111) atomistic sample. A different dependence of the total sputtering yield on the impact angle is observed for small and large projectiles for benzene, while a similar dependence is observed for Ag (111). It is demonstrated that the increase of the cohesive energy leads to a significant decrease of the total ejection signal for both Ar 60 and Ar 2953 projectiles. The shape of the impact angle dependence, however, is much less sensitive to this parameter. The 'washing out' mechanism and the structural differences of the irradiated samples are proposed to be responsible for the different shapes of the impact angle dependence.

Effect of the Impact Angle on the Kinetic Energy and Angular Distributions of β-Carotene Sputtered by 15 keV Ar2000 Projectiles

“…For the off-normal incidence, maximum of the angular spectra shifts in the specular direction, and the emission becomes azimuthally asymmetric. 14,16,19,22 The effect increases with the projectile size. 14,15,33 For instance, for cluster projectiles composed only of tens of atoms, such as C 60 , the shift is not visible and the angular spectra peak near the surface normal even during bombardment along the 45°incidence angle.…”

“…16 Similar aspects have been studied in MD simulations performed on benzene samples. 14,19,32 For the normal incidence, Lorentz et al report that organic material is ejected at large off-normal angles. However, it should be pointed out that due to limitations of the adopted experimental technique, particle ejection below 40°polar angle could not be detected.…”

“…Therefore, knowledge about these quantities is an important parameter for the successful design of an SNMS experiment. There is a significant database of the angular and the kinetic energy spectra for the atomic projectile bombardment of inorganic samples , Much less is known about directionality and energetics of emission for cluster projectiles, particularly for large gas cluster projectiles bombarding organic solids. − …”

“…It has been reported that the shape of the angular spectra depends on a type of analyzed material and on the properties of the bombarding cluster projectiles. − ,− For cluster ions with sizes typically used in the GCIBs, the size of the projectile and its angle of incidence on the surface have the most significant impact. For large cluster projectiles bombarding inorganic samples, the particles are ejected predominantly at large polar angles. − ,,− This type of sputtering is termed “lateral sputtering”.…”

“…For the off-normal incidence, maximum of the angular spectra shifts in the specular direction, and the emission becomes azimuthally asymmetric. ,,, The effect increases with the projectile size. ,, For instance, for cluster projectiles composed only of tens of atoms, such as C 60 , the shift is not visible and the angular spectra peak near the surface normal even during bombardment along the 45° incidence angle. ,, For large cluster projectiles, the effect is strong for small deviations from the normal incidence, but it becomes less pronounced at larger impact angles. ,, Increase of the incidence angle has two effects on the ejection process. The off-normal bombardment shortens the time necessary to disperse of the blocking cloud .…”