Optimum Acceleration Voltage for SEM Observation of Carbon Fiber

Abstract

Important factors to obtain a sharp secondary electron image for light element materials has been examined firstly. It has been found that in scanning electron microscopy there is an optimum acceleration voltage for the sample in observation to obtain the most sharp secondary electron image. The effective resolving power is defined in the present paper as that for the optimum acceleration voltage. Element carbon is a typical light element. SEM observation is an important method for studies of structures of carbon fibers. To get good cross sections of carbon fibers a method of cutting of the carbon fibers has been developed. With the same magnification photographs of secondary electron images for the same cross section of the carbon fiber have been taken with changing ac-celeration voltage between 1 and 40 kV. Similar photographs have been obtained for a fracture surface of a cast iron and a silicon microcircuit for comparison. The optimum acceleration voltage for a carbon fiber has been determined to be 2 kV. The effective resolving power for the carbon fiber has been estimated to be 0.05 jim with the optimum acceleration voltage of 2 kV. It has also been investigated the effect of metallic coating on the carbon fiber specimen.