The effect of incident angle on the C60+ bombardment of molecular solids

The effect of incident angle on the quality of SIMS molecular depth pro. ling using C-60(+) was investigated. Cholesterol films of similar to 300 nm thickness on Si were employed as a model and were eroded using 40 keV C-60(+) at an incident angle of 40 degrees and 73 degrees with respect to the surface normal. The erosion process was characterized by determining at each angle the relative amount of chemical damage, the total sputtering yield of cholesterol molecules, and the interface width between the film and the Si substrate. The results show that there is less molecule damage at an angle of incidence of 73 degrees and that the total sputtering yield is largest at an angle of incidence of 40 degrees. The measurements suggest reduced damage is not necessarily dependent upon enhanced yields and that depositing the incident energy nearer the surface by using glancing angles is most important. The interface width parameter supports this idea by indicating that at the 73 degrees incident angle, C-60(+) produces a smaller altered layer depth. Overall, the results show that 73 degrees incidence is the better angle for molecular depth pro. ling using 40 keV C-60(+). (C) 2008 Elsevier B. V. All rights reserved.