Image depth profiling , SIMS

As covered in Section 5.3.2.4.5, sample rotation (also referred to as Zalar rotation) during image depth profiling can minimize the latter. Alternatively, surface topography measurements carried out before and after image depth profiling can account for the latter two. Indeed, the effectiveness of this approach has been demonstrated via ex-situ Atomic Force Microscope (AFM) measurements (van der Heide 1998 Robinson et al. 2012). Based off of the success of this approach, lon-Tof has designed a hybrid APM/TOF-SIMS instrument. 

Static SIMS is labeled a trace analytical technique because of the very small volume of material (top monolayer) on which the analysis is performed. Static SIMS can also be used to perform chemical mapping by measuring characteristic molecules and fiagment ions in imaging mode. Unlike dynamic SIMS, static SIMS is not used to depth profile or to measure elemental impurities at trace levels. 

Today dynamic SIMS is a standard technique for measurement of trace elements in semiconductors, high performance materials, coatings, and minerals. The main advantages of the method are excellent sensitivity (detection limit below 1 pmol mol ) for all elements, the isotopic sensitivity, the inherent possibility of measuring depth profiles, and the capability of fast direct imaging and 3D species distribution. 

SIMS has superb surface sensitivity since most of the secondary ions originate within a few nanometers of the surface and since high detection efficiency enables as little as 10 " of a monolayer to be detected for most elements. Because of its very high surface sensitivity, SIMS can be used to obtain depth profiles with exceptionally high depth resolution (<5 nm). Since the beam of primary ions can be focused to a small spot, SIMS can be used to characterize the surface of a sample with lateral resolution that is on the order of micrometers. Elements with low atomic numbers, such as H and He, can be detected, isotope analysis can be conducted, and images showing the distribution of chemical species across... 

SIMS Up to 10 pm by dynamic SIMS 2-5 nm possible 10-20 nm typical Yes by dynamic SIMS Yes Yes Yes, by imaging SIMS 1 pm imaging 30 pm depth profiling... 

DESI has also been introduced into MS imaging. [39] SIMS is also used for surface imaging and depth profiling. [40]... 

The development of surface analytical techniques such as LA-ICP-MS, GDMS and SIMS focuses on improvements to sensitivity and detection limits in order to obtain precise and accurate analytical data. With respect to surface analytical investigations, an improvement of spatial and depth resolution is required, e.g., by the establishment of a near field effect or the apphcation of fs lasers in LA-ICP-MS. There is a need for the improvement of analytical techniques in the (j,m and nm range, in depth profiling analysis and especially in imaging mass spectrometry techniques to perform surface analyses faster and provide more accurate data on different materials to produce quantitative 3D elemental, isotopic and molecular distribution patterns of increased areas of interest with high spatial and depth resolution over an acceptable analysis time. 

Another widely used application for SIMS is ion imaging, which shows secondary ion intensities as a function of spatial location on the sample surface (Figure 7.46). Further, if imaging is performed in tandem with depth profiling, a three-dimensional compositional map of a sample may also be generated (Figure 7.46). Two modes of imaging via SIMS are possible ... 

Fig. 8.31. Image processing in 3D SIMS generation of a local depth profile and a transaxial layer image (a) and of a coaxial layer image, a spatial diagonal image, and a point analytical information (b) the representation is inspired from Rudenauer [1989]...

Another interesting feature of SIMS is the ability to generate depth profiles of the studied surface, hence limited three-dimensional imaging (22). This is achieved by sputtering monolayers repeatedly off the surface. However, as the sputtering needs very high ion doses, such an analysis is usually limited to atoms or very small fragments. 

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