Raw Spectrum – O (1s) Signal
Example: Raw spectrum of O (1s) signal from a silicon wafer – no background
O (1s) Signal with Iterated Shirley Background
Iterated Shirley Background was added. The start and finish endpoints are located at 524 eV and 540 eV. The next spectrum is a Vertical Expansion to show the endpoints.
Vertically Expanded View of O (1s) Signal with Shirley Background
The O (1s) spectrum was vertically expanded to verify that the Shirley Background endpoints were added to flat regions of the spectrum.
Shirley Background compared to Linear Background
Raw spectrum of Ni (2p3) from pure Nickel metal
Overlay of Shirley Background and Linear Background – having identical endpoints – for Ni (2p3) of pure Nickel metal
Overlay of 3 different Shirley Backgrounds – for Ti (2p) spectrum of fresh exposed bulk of a single crystal of TiO2
Which is the best choice? It some sense, it depends on what sort of information you want.
Best choice depends on whether or not you are “peak-fitting” or measuring “atom% values”.
Two slightly different Shirley Backgrounds on a C (1s) spectrum. (Ignore the linear backgrounds)
The 2 Shirley backgrounds have different endpoints at the High BE end. This small difference produces a small 0.1/25.57 variance in the atom%, a small effect in this example.
From J. Vegh, Surface Science 563, (20040 183-190
From Practical Surface Analysis: Appendix 3, written by Peter Sherwood.
From S. Tougaard paper, JVST A39,
From M Aronniemi, J. Sainio and J Lahtinen, Surf Sci, v578, p108-123 (2005)