Accuracy of Spatial Measurements at Elevated Temperatures in an Environmental Scanning Electron Microscope

Abstract

One of the unique abilities of the environmental scanning electron microscope is that it permits realtime dynamic observations of materials under controlled temperature/atmosphere conditions [1]. The need for accurate and precise measurements of dimensional changes at elevated temperatures arise in many material areas including determining the longitudinal and transverse coefficient of thermal expansion of fibers, sintering studies, hydration and dehydration of absorbent polymers, and strain measurement of materials under an applied load. The purpose of this research is to evaluate the capabilities of an ElectroScan 2020 environmental scanning electron microscope (ESEM™) in performing precise in situ spatial measurements at elevated temperatures. Identification and proposed solution and/or compensation of imaging difficulties such as specimen drift, sample stability, and thermal strain of a reference grid are addressed.In general, the accuracy of spatial measurements in a scanning electron microscope (SEM) depends on several factors including calibration of the scanned area, the effects of lens hysteresis and reproducibility in the working distance and column alignment.