Quantitative x-ray spectrometry using the environmental scanning electron microscope

It is desirable to know the elemental composition of features viewed in the environmental scanning electron microscope (ESEM) using energy dispersive x-ray spectrometry (EDS). This analysis is complicated by the spread of the electron beam by chamber gas molecules and the necessity for charge neutralization. The research reported herein assesses the feasibility of doing x-ray analysis in the ESEM.; The results reported in this dissertation demonstrate that x-ray analysis in the ESEM is capable of achieving the less than ±5% relative error expected of traditional EDS in a scanning electron microscope. The relative standard deviation is less than 5%. Estimates of accuracy and precision are based on studies of NIST 482, a series of gold-copper alloys. In order to achieve these results it is necessary to have a path to ground near or on the surface of the specimen. The current through the ground path is maintained at zero by adjusting the voltage to the Gaseous Secondary Electron Detector™ and by adjusting the chamber gas pressure. It is postulated that this procedure serves to neutralize electrical charges that accumulate on the specimen surface due to electron irradiation.; Two electron beam scatter correction methods were evaluated using NIST SRM 2066 glass microspheres imbedded in lead. The Doehne/Bilde-Soerenson correction method directly corrects x-ray intensity by extrapolating the x-ray count versus gas pressure line to zero pressure. The Gauvin method determines the fraction of the I electron beam spread by the chamber gas at various pressures and plots this against x-ray intensity. This line is extrapolated to the no-beam scatter condition. Both methods yield elemental compositions within the nominal uncertainty limits for microspheres between 20 and 40 μm in diameter.; Solid phase synthesis polymers containing chlorine, sulfur, and bromine were evaluated as a practical system of interest. The nominal Cl, S, and Br compositions of the polymers ranged from 2 to 10% by weight. The x-ray analysis results for Cl and S were in good agreement with the nominal compositions and with results from elemental analysis followed by ion chromatography.