An impedance analyzer is described which used direct sampling of the stimulating and response signals into a laboratory data acquisition system. The analyzer uses subsampling in order to extend the range to frequencie...
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An impedance analyzer is described which used direct sampling of the stimulating and response signals into a laboratory data acquisition system. The analyzer uses subsampling in order to extend the range to frequencies higher than the sampling frequency. An algorithm which computes the optimum sampling rate is described. The analyzer can be used in the frequency range from above 10(5) Hz to below 10(-2) Hz. In the range from 50 kHz to 0.01 Hz the relative amplitude error was found to be less than 0.01% and the phase error to be less than 0.1 degree.
In recent years spectroscopic ellipsometry has been successfully applied to non-destructively characterize multi-layer materials and to monitor surface processes as a function of time. The extraction of the relevant p...
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In recent years spectroscopic ellipsometry has been successfully applied to non-destructively characterize multi-layer materials and to monitor surface processes as a function of time. The extraction of the relevant parameters of these samples from the spectroscopic data requires extensive computer analysis. For this purpose the sample is described by means of a stratified-layer theory in combination with an effective medium approximation. The computer program presently discussed performs this analysis of spectroscopic-ellipsometric data for any arbitrary model and any arbitrary number of data points. It applies a least-squares fitting procedure based on a modified Levenberg-Marquardt routine. A special feature of the program is the implementation of linked lists to obtain a very efficient data structure that allows a high flexibility of the program.
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