In searching for surface testing for your conductive or semi-conductive product or device, you, no doubt, have come across the terms: AES Analysis, Auger Analysis, and Auger Microscopy. Each of these terms refers to Auger Electron spectroscopy, one of the most popular surface analysis techniques.
Read on to learn why AES is a popular tool among manufacturers, how it works, and how to analyze results.
What is AES Analysis?
AES provides nondestructive and semi-quantitative analysis determination of surfaces, thin films, and interfaces.
This ultra-high vacuum technique has high surface sensitivity (<100 Å) and a remarkably low detection limit (~0.1 atomic percent).
It can detect elements from lithium to uranium and beyond. And if you need to distinguish between elements that are close together on the periodic table, AES is an excellent tool for the analysis.
How Does Auger Microscopy Work?
A finely focused, high-energy electron beam is used to excite the atoms on the surface of a sample. When the beam strikes a solid atom, a core-level electron emerges and produces a singly ionized excited atom. The resulting vacancy in the core level is filled with an outer level electron. Another electron is emitted from the atom, removing the excess energy.
The emitted electrons are called Auger electrons. The kinetic energy of these electrons is evident in the top 3-5 nm of the sample and produce information about the surface composition of a material.
How Do You Analyze a Sample with Auger Electron Spectroscopy?
Our scanning AES testing process consists of four parts:
- The survey scan — Provides qualitative identification of excited electrons.
- The multiplex scan — Measures the atomic concentration of the elements identified in the survey scans. For most elements, detection limits are about 0.1 atom percent.
- The mapping process — Provides photographic imaging depicting variations in the elemental composition of the surface.
- The depth profile — Characterizes elemental composition as a function of depth in the sample.
How to Analyze AES Results
In an AES scan, the x-axis represents electron energy, and the y-axis shows atomic number Z and the elements. The elements at the farthest left of the spectrum are KLL electrons, followed by LMM, and then MNN.
Each Auger peak represents a different element. While the basic structure and shape of an Auger peak are similar across elements, the location of the peak on the x and y axes is different for each element.
These Auger peaks are used to determine the number of emitted electrons for each detected element. The number of electrons is indicative of the elements present at or near the surface of the material. Note, however, AES is unique in that chemical bonds cause the energy of Auger electrons to change and the peaks to move on the axes. Analyzing this shift provides a means to assess the chemical bonds.
Surface mapping allows analysis of different parts of a sample, providing insights into the lateral distribution of elements on the surface with a spatial resolution of about 0.3 microns. The depth profile offers a more detailed analysis of elemental distribution throughout surface layers.
What Are the Applications of Auger Analysis?
If you are looking for in-depth surface analysis, AES offers many advantages. AES is
nondestructive and works for small conductive and semi-conductive areas, particles, and inclusions — and in products such as small diameter wires and bonding pads. Here are the top applications:
Material composition and surface contamination can significantly impact product safety and performance. AES is ideal for quality control products such as small diameter wires and bonding pads because it can determine atomic concentrations of elements, map the lateral distribution of elements, and measure the distribution of elements as a function of depth.
Medical Device Passivation
AES can be used to test the surface of a device to determine the depth of passivation layers and to detect impurities that could affect product performance. For example, one of our clients used AES to assess the integrity of medical device passivation layers on nitinol stents.
Will Auger Electron Spectroscopy Work for You?
Depending on your needs, AES may or may not be ideal for you. But regardless, Innovatech is sure to have a materials analysis option that will work for you. Our skilled analysts would love to help you determine what testing is ideal for your next project. To learn more, contact us.