X-ray Photoelectron Spectroscopy (XPS) is a key and very important surface analysis technique. There are THREE phenomena occurring in this measurement

1- Photoelectrons emission
2- X-ray Fluorescence
3- Auger effect

Let's discuss each one in detail

1- Photoelectrons

An x-rays of known energy are simply bombarded on the sample, and the photoelectrons emitted from the core of the atom. The Kinetic Energy (KE) of the photoelectrons was then detected by the XPS detector. Using the following equation, the Binding Energy (BE) can be calculated

hv = BE+ KE + ϕspec
BE = hv - KE - ϕspec

Where 'hv' is the x-rays energy (known value), KE calculated from the XPS detector, and ϕspec is the work function of the spectrometer (a constant value). Therefore, the BE of the element can be calculated, which is the *fingerprint* of each element that exists in the sample. The BE can reveal many important characteristics about the element. For instance, what element exists, what the atom or element bonded with, the chemical environment, oxidation states, whether the electrons removed or added to the atom.....

2- X-ray Fluorescence (XRF)

There is a vacancy in the core shell as a result of photoelectron. The atom is an excited state and has to relax by simply the falling the higher orbital electrons can to this vacancy. An x-rays produce as a result of the electron falling to the vacancy called X-ray Fluorescence. However, this phenomenon is not considered in XPS, and the peaks do not appear in the spectrum. This is due to the two reasons i) it is a weak phenomena and ii) XPS only detect electrons NOT x-rays.

3- Auger effect

Similarly, when the core vacancy is filled by the higher orbital electrons, an additional electron can emit from the atom called Auger electron. The XPS spectrum shows peaks from these Auger electrons. For instance, the core vacancy is in K-shell, the L-orbital electron filled this core vacancy, and another electron emits from the L-orbital. So, the transition is denoted by KLL, and this notation is used to represent the Auger peak in the XPS spectrum.


XPS - X-rays Photoelectron Spectroscopy || Surface vs. Ultra thin film vs. Thin film
[ Ссылка ]

Why Only Core Electrons Peaks in XPS - X-rays Photoelectron Spectroscopy
[ Ссылка ]

Why p-orbital, d-orbital, f-orbital have TWO Peaks- Doublet in XPS Spectra
[ Ссылка ]

What is Binding Energy (BE) in X-rays Photoelectron Spectroscopy (XPS)?
[ Ссылка ]

Why XPS is a Surface Sensitive Technique?
[ Ссылка ]

Secret Behind "hv = BE+KE+Ø" Equation for X-rays Photoelectron Spectroscopy
[ Ссылка ]

Importance of Survey Spectra in XPS - X rays Photoelectron Spectroscopy
[ Ссылка ]

свернуть