This specimen serves to measure in multiple ways, including medium resolutions, astigmatism, and image shift in scanning electron microscopes while using a single specimen. The tin balls differentiate in size ranging from 10nm to 100nm. The notably high atomic number of tin gives the spheres high contrast when compared to the carbon substrate, thus facilitating backscattered electron performance testing. The magnification reduction ability of the specimen allows for initial focusing at low accelerating voltages.
The smallest features on the specimen are the spaces between the spheres and can be used for measurement of instrument resolution. Note that the smallest spheres and gaps between them can be found in the shadow of the largest spheres. Please also note that if operating at low accelerating voltages, the smallest gaps may not be resolved and areas with larger spheres should be chosen.
To ensure that the chosen areas are facing the SED detector, some adjustment of the specimen may be required. The smallest gap between the two spheres that can be is a measure of the resolution of the SEM at the accelerating voltage and working distance being used in your application. Take caution when adjusting the specimen towards the detector, as horizontal measurements are the only ones valid. In order to achieve optimal results and magnification, we suggest calibrating the magnification first, according to your application.
During the manufacturing process, the spheres are produced nearly perfect, free from any interference with electron beams. Astigmatism will be evident if the spheres appear distorted. Due to their round nature, it is easy to detect any kind of distortion or abnormality in the spheres. Apply corrections as appropriate to your application.
Specimens can also serve to check the state of the electron column. This is performed by monitoring the amount of correction needed to remove the present astigmatism. If, however, the astigmatism cannot be corrected, the tin on carbon specimen can serve to confirm whether the astigmatism is innate in the column or caused by the specimen itself.
If the electron column has been disturbed or apertures exchanged, readjustment may be required. The largest tin spheres on the specimen can be used at low magnification in order to observe image shifts with changes in accelerating voltage or spot size. When the adjustment(s) is made, magnification can then be increased. Furthermore, smaller spheres can be selected for more precise alignment.