Paruch R, Rzeznik L, Czerwinski B, Garrison B J, Winograd N, Postawa Z
Smoluchowski Institute of Physics, Jagiellonian University, ul. Reymonta 4, 30-059 Kraków, Poland.
J Phys Chem C Nanomater Interfaces. 2009 Apr 9;113(14):5641. doi: 10.1021/jp809769q.
Coarse-grained molecular dynamics computer simulations are applied to investigate fundamental processes induced by an impact of keV C(60) projectile at an organic overlayer composed of long, well-organized linear molecules. The energy transfer pathways, sputtering yields, and the damage induced in the irradiated system, represented by a Langmuir-Blodgett (LB) multilayers composed from molecules of bariated arachidic acid, are investigated as a function of the kinetic energy and impact angle of the projectile and the thickness of the organic system. In particular, the unique challenges of depth profiling through a LB film vs. a more isotropic solid are discussed.The results indicate that the trajectories of projectile fragments and, consequently, the primary energy can be channeled by the geometrical structure of the overlayer. Although, a similar process is known from sputtering of single crystals by atomic projectiles, it has not been anticipated to occur during C(60) bombardment due to the large size of the projectile. An open and ordered molecular structure of LB films is responsible for such behavior. Both the extent of damage and the efficiency of sputtering depend on the kinetic energy, the impact angle, and the layer thickness. The results indicate that the best depth profiling conditions can be achieved with low-energy cluster projectiles irradiating the organic overlayer at large off-normal angles.
采用粗粒度分子动力学计算机模拟，研究了keV C(60)弹丸撞击由长的、排列良好的线性分子组成的有机覆盖层时引发的基本过程。以由钡化花生酸分子组成的朗缪尔-布洛杰特（LB）多层膜为代表，研究了辐照系统中的能量转移途径、溅射产率以及损伤情况，这些都是弹丸动能、撞击角度和有机系统厚度的函数。特别讨论了通过LB膜与更各向同性的固体进行深度剖析的独特挑战。结果表明，弹丸碎片的轨迹以及因此产生的初始能量可以被覆盖层的几何结构引导。虽然，从原子弹丸溅射单晶的过程中已知类似过程，但由于弹丸尺寸较大，预计在C(60)轰击期间不会发生这种情况。LB膜开放且有序的分子结构导致了这种行为。损伤程度和溅射效率都取决于动能、撞击角度和层厚度。结果表明，用低能团簇弹丸以大的离法线角度辐照有机覆盖层可以实现最佳的深度剖析条件。
