刑侦测试标样

This Gunshot Residue Standard is also suitable for use as a calibration and validation sample in the field of analytical Scanning Electron Microscopy (SEM/EDX) investigations.



The SPS-5P-2 is especially designed for the adjustment, calibration and validation of analytical SEM/EDX systems when used for automated analysis of GSR particles. It is especially suitable for quick system validation checks and quality assurance procedures.
Using a special process, Pb/Sb/Ba particles are precipitated onto the surface of an 8mm x 8mm silicon chip which is previously applied with a 10µm polyimide layer. The particles are randomly distributed but at known locations. There are four distinct particle sizes of approximately 0.5µm, 0.8µm, 1.2µm and 2.4µm in diameter. In addition the samples are provided with three 10µm particles in order to facilitate a simple data cross-checking of performed automated particle analysis. The GSR Standard is carbon coated to avoid or minimize charging effects.

It is recommended that the BSE signal is used for imaging the particles as this gives a high contrast differential between the Pb/Sb/Ba particles and the silicon substrate. Beam current should not exceed 2 NA.




Note on the performance and evaluation of the automated particle analysis.

The automated particle analysis has to be performed at least on the 7mm x 7mm center area on the silicon chip. In general a magnification of 200 to 300x will suffice. There is a 100µm x 100µm Pb/Sb/Ba control pad on the chip that can be used to adjust the BSE signal to the required level for analysis. It is recommended to introduce the specimen into the system in such a way that the PB/Sb/Ba pad is displayed in the lower left corner of the BSE image. (see figure, left)

To perform an automated run on the detection of PB/Sb/Ba particles it is necessary to create a particle class containing the elements Pb, Sb and Ba. Because of the production process, the elements carbon and oxygen (from the protective layer) and silicon and fluorine (from the substrate and the production process, resp.) may also appear.

For the evaluation of the automated search it is recommended that the data obtained from the detected Pb/Sb/Ba particles (in particular their X, Y coordinates and their diameter) is displayed as a X, Y plot (e.g. with EXCEL). When using an appropriate display area, a direct comparison can be made of the size and position of the detected particles with the true values by overlaying the achieved results and the attached particle map (e.g. using an overhead film copy).

Because of the special production process it may happen that some of the deposited Pb/Sb/Ba particles are not present and therefore less than the regular 100 particles (see attached particle map) are detected. In addition there may also occur some irregular shaped Pb/Sb/Ba particles (remaining from etch process), but these particles will appear on different locations than the regular Pb/Sb/Ba particles.