Accuracy and Repeatability of Linear Measurements using the Field Emission Scanning Electron Microscope (FE-SEM) Built-in Measurement Tool for Nanomaterials and Nano-enabled Products

The FE-SEM is an analytical tool used primarily for imaging the surface of a sample.  Some FE-SEM systems such as the one housed in ADMATEL has a built-in measurement tool that enables the user to get dimensional information on particular features of interest.  ADMATEL’s FE-SEM is capable of acquiring the following measurements: linear, diameter, rectangular length & width and angle.  This study focused on diameter measurement only.  Accuracy and repeatability of measurements are important especially, for dimensions/sizes of nanomaterials/nano powders  that are in the nano-scale.  The range of uncertainty must be minimized to ensure that readings are always near the true value.  This is a critical parameter on quality control for  products and processes that have pass/fail criteria which are dependent on certain physical dimensions.  Measurements were obtained from standard polystyrene nanospheres with known nominal diameter.  All sample preparation methods and trials were carried out in a class 100k cleanroom with a controlled ambient temperature of 20-25degC and RH of 50-60%.  An average diameter value of 61.59nm was obtained from a total of 500 readings spread among 5 analysts.  A measurement uncertainty of ±3nm was reported.  Calculated mean and measurement uncertainty were close to the true value of the standard sample, thus confirming the accuracy and repeatability of measurements using the FE-SEM’s built-in measurement tool.