There has been excellent progress in the SIMS community in recent years[1,2] to identify the optimum conditions and primary ions for SIMS depth-profiling of polymers. A key step forward was the identification of Type I and Type II behaviour[3], in which polymer damage is dominated by cross-linking and polymer backbone bond-scission respectively. In many cases it is difficult, especially for a non-expert, to judge which of these two types a given polymer matrix is likely to be. For example, PAA, PMAA, PMA and PMMA are of types I, II, I and II respectively, even though their structures are very similar.

We examine this system in detail, largely in the context of XPS where polyatomic and cluster ion sources are set to become much more popular. We develop equations based on a 3D Ising ``resistor removal'' model. Some of the difficult parameters in this model can be estimated from literature values for rates of cross-linking and bond scission of polymers seen in radiation treatment at much higher energies. This model leads to some reasonably simple equations allowing analysts to make objective estimates of (a) which primary ion source is most appropriate for a particular polymer matrix, and (b) an estimate of the sputter-rate, for any arbitrary polymer matrix whose repeat unit is known.

The reliability of the model is tested using measured sputter rates for samples of 20 polymers using polyatomic (coronene) and GCIB (argon cluster) sources. White-light interferomentry combined with a novel kinematic mount for semi-automatic measurement of sputter crater volume have accelerated and improved the accuracy of these measurements.

Finally, based on the new model, we tabulate and plot estimated values for 103 polymers of technological significance.

[1] N. Winograd, Anal Chem 77 (2005) 143A

[2] J. S. Fletcher, X. A. Conlan, E. A. Jones, G. Biddulph, N. P. Lockyer, J. C. Vickerman, Anal Chem 78 (2006) 1827

[3] C. M. Mahoney, Mass Spectrometry Reviews, 29 (2010) 247

Sensors for biological compounds are becoming increasingly important in a wide variety of applications. These devices are typically composed of complex stacks of thin/ultrathin layers of biochemical compounds. The overall behaviour of the sensor is strongly influenced by the elemental and chemical properties of the individual layers, but the interactions at layer interfaces may also have an effect.

There is an increasing requirement for compositional profiling of these devices, combining the chemical selectivity and surface specificity of XPS with some kind of ion beam sputtering. Traditional methods such as argon monomer ion profiling can result in a high degree of chemical modification during the acquisition of depth profiles for organic materials. Over the last few years, there have been numerous studies and investigations into the use of argon cluster beams for depth profiling with the goal of preserving chemical information during analysis of organic materials.

This talk will present data from cluster profiling studies of amino acid based biosensors. The chemical variation between amino acid layers is very subtle, but it will be demonstrated that the combination of rapid acquisition XPS and argon cluster profiling is able to characterise the changes in chemistry throughout the layer stack.

In recent years MCs_x⁺ depth profiling has become increasingly popular for the analysis of thin films using Time-of-Flight SIMS (ToF-SIMS). The MCs_x⁺ mode offers quantitative or semi-quantitative SIMS data and allows for the measurement of electropositive and electronegative elements simultaneously by detecting MCs⁺ and MCs₂⁺, respectively. In addition, the use of heavy cluster ions like Bi₃⁺ or C₆₀⁺ allows for a significant increase of the MCs_x⁺ yields by a factor of up to 1000 with respect to Ga as primary ion projectile and leads to a remarkable improvement of the achievable detection limits [1].

However, one disadvantage of current TOF-SIMS instruments for the quantification in MCs_x⁺ mode is the limited dynamic range, which restricts the possibility of achieving high sensitivity on the MCs_x⁺ clusters and of using the Cs_x⁺ intensity for normalization. The normalization is especially important for the analysis of layer systems where sputter rates or the cesium surface concentration might change from layer to layer. This requires a registration system which is able to detect more than 100 secondary ions of a specific element per primary ion gun pulse with high linearity.

We have developed a new registration system for TOF-SIMS, which increases the useable dynamic range by a factor of 100 i. e. 1E7 counts/sec with an excellent linearity. In addition, the maximum pulsed primary ion current of the bismuth liquid metal ion gun was increased in order to further improve the detection limits for low concentration elements. In this paper we will discuss the characteristics of this new experimental setup and the benefits for the quantitative depth profiling in the MCs⁺ mode.

[1] E. Niehuis, T. Grehl, F. Kollmer, R. Moellers, D. Rading, SIMS Europe, Muenster, 2006

Rutherford Backscattering (RBS) of ~2MeV He ions is well known technique used in surface and thin film analysis. This technique is very sensitive to heavy elements (Au, Pt, Hf, In, Ru) present on surface or in thin film on lower mass substrate (Si, Ti, Cr, Fe, Ge), but have very limited sensitivity for low mass elements on heavy mass substrates. Numbers of examples will be shown for both cases.

Nuclear reaction analysis (NRA) is very good alternative for detection of low mass elements in a heavy elements substrates. This technique uses similar experimental set-up as RBS but is using a different ion beam and it detects different particle. Examples will be shown for Li detection on steel and in LiFePO₄ crystal.

Detection of Hydrogen is not possible using RBS in a typical RBS geometry, and NRA can detect Hydrogen, but it require special high energy ¹⁵N beam (7MeV), but He Forward Scattering (FS) or Elastic Recoil Detection (ERD) can be used for Hydrogen detection and profiling. Examples of ERD will be shown and discussed.

Each of these techniques has its own limitations and advantages. Depth resolution and sensitivity will be discussed in details.