Invited Paper BP-SuA3
Depth Profiling and 3D Analysis of Organic Surfaces

Sunday, October 30, 2011, 3:40 pm, Room 108

Cluster ion impacts have been shown to sputter organic materials, whilst imparting low levels of damage to the freshly exposed surface. When coupled with a surface analytical technique, such as SIMS or XPS, it is possible to generate depth profiles with truly molecular information. Concurrent 2D spectroscopic imagingenables a three dimensional reconstruction of molecular distributions. This offers enormous potential for the label-free and multiplexed imaging of biological materials and medical devices.

The mechanism of cluster ion beam sputtering has been established over the past ten years and the most important factor that permits organic depth profiling is the large sputtering yield of organic material following a cluster ion impact. This is typically of the order of 100 nm³ of material per individual impact. However it has been shown that, for many materials, the sputtering yield changes as the cluster ion dose increases and therefore the interpretation of organic depth profiling data is, in general, not trivial. Additionally, this change in sputtering yield is often associated with sputter-induced roughening with a concurrent degradation of depth resolution. Recently, there has been a growing emphasis on the development of methods by which a wider range of materials can be depth profiled and a constant sputtering yield maintained. The most significant advances have been the use of sample cooling, low ion beam incidence angles and sample rotation. Large argon clusters appear to offer significant improvements over traditional cluster beams, such as C₆₀ in these regards.