Effect of cosputtering and sample rotation on improving C60(+) depth profiling of materials.

In the past decade, buckminsterfullerene (C(60))-based ion beams have been utilized in surface analysis instruments to expand their application to profiling organic materials. Although it had excellent performance for many organic and biological materials, its drawbacks, including carbon deposition, carbon penetration, continuous decay of the sputtering rate, and a rough sputtered surface, hindered its application. Cosputtering with C(60)(+) and auxiliary Ar(+) simultaneously and sample rotation during sputtering were proposed as methods to reduce the above-mentioned phenomena. However, the improvement from these methods has not been compared or studied under identical conditions; thus, the pros and cons of these methods are not yet known experimentally. In this work, a series of specimens including bulk materials and thin films were used to explore the differences between cosputtering and sample rotation on the analytical results. The results show that both of these methods can alleviate the problems associated with C(60)(+) sputtering, but each method showed better improvement in different situations. The cosputtering technique better suppressed carbon deposition, and could be used to generally improve results, especially with continuous spectra acquisition during sputtering (e.g., dynamic secondary ion mass spectrometry (SIMS) depth profiling). In contrast, for the scheme of sputter-then-acquire (e.g., alternative X-ray photoelectron spectrometry or dual-beam static SIMS depth profiling), a better result was achieved by sample rotation because it resulted in a flatter sputtered surface. Therefore, depending on the analytical scheme, a different method should be used to optimize the experimental conditions.