Linear Background

Linear Background

Example of Linear Background. One linear background is based on a single data point at both ends of the linear background. The other linear background is based on an average of 7 adjacent data points in the spectrum at both ends of the linear background. This is called “Endpoint Averaging” or “Background Average”. Endpoint averaging is useful because it provides more accurate background and more accurate atom% values.  Be careful not to use too many endpoints.

Another example of using a Linear Background to generate atom% values. In this case we are working with an expanded region of a Survey spectrum, which typically has less data-points/eV, for example:  1 pt/eV, or 1 pt/0.7 eV.   High res chemical state spectra use more data-points/eV, for example: 10 pt/eV or 20 pt/eV.

Full survey spectrum shown below.  Limited range for C (1s) shown above.

Linear Background versus Shirley Background using the exact same endpoints.  In this case there is almost no difference in peak area, but the next spectrum (below) shows that there can be significant differences in peak area, which directly affect atom% values.

In this Linear versus Shirley peak area integration there is a significant difference in peak areas.  This difference is mainly due to the difference in peak-shapes.  The C (1s) above is symmetrical and simple. The Fe (2p3) signal below has a satellite peak that produces a lot of asymmetry that affects the peak area.