Auger Electron Spectroscopy in Thin Film Applications

In this interview, Randy Dellwo, founder of RBD Instruments, talks to AZoM about their range of products including the microCMA Compact Auger Analyzer.

Please tell us about RBD Instruments and the work you do?

RBD Instruments started out 30 years ago providing service and parts for older surface analysis X-ray photoelectron and Auger electron spectrometers.  In the last 10 years, RBD has developed new products related to water vapor desorption, ion sputtering, current measurement, and spectroscopy.

What is Auger Electron Spectroscopy?

Auger Electron Spectroscopy (AES) is one of the most surface-sensitive elemental analysis techniques. A finely focused electron beam is used to excite the sample surface, which causes electrons with element-specific kinetic energies to be emitted. The Auger electron spectrometer measures the kinetic energies of these electrons and the results can be quantified. AES is very useful for elemental analysis of metals and semiconductors but does not work well with insulating samples.

The microCMA Compact Auger Analyzer is an affordable, surface-sensitive analytical tool that can fit on your existing vacuum chamber. How does this product compare to other tools out there? Was there a gap in the market?

When Auger electron spectrometers first became commercially available in the 1960s, they were very simple instruments that provided basic elemental composition of the surface of the samples. Incremental improvements over the years have resulted in today’s state-of-the-art high-resolution scanning Auger systems that can provide elemental images of fine features at extremely high magnifications. However, today’s state-of-the-art scanning Auger systems can also cost well over $1,000,000.00. There was a gap in the market for researchers who wanted an affordable way to obtain non-scanning elemental information on their samples in situ. Many vacuum chambers have an extra unused port and by designing the microCMA to fit on a 2.75" / 70 mm flange, this gap can now be filled.

Please tell us about the features and benefits of the microCMA. Why did you make it so small? Will this mean that the signal is smaller?

The microCMA is a turnkey Auger electron spectrometer system that can provide data about the top few monolayers of samples in situ. Automated electron gun operation and quantitative data manipulation help to make sample analysis simple. We designed the microCMA in a small form factor so that it can fit on existing chambers, but also for researchers who are designing new chambers for specific experiments. Because the microCMA is much smaller than a conventional CMA (cylindrical mirror analyzer), the vacuum chamber and related vacuum pumps can also be much smaller. Smaller chambers and pumps translate into faster pump-down times and lower cost of ownership. Because the design is based on a second-order focusing of 42.3 degrees, the microCMA has signal-to-noise that is comparable to the much larger CMAs mounted on 10" flanges. The same 42.3-degree electrons are collected by the microCMA, just at a closer distance to the sample.

Which applications will benefit from the microCMA and its size? How?

One of the applications that we have seen benefit from the microCMA is in situ analysis on MBE (molecular beam epitaxy) systems. MBE systems grow thin films of materials in UHV and researchers often need to know the elemental composition of their samples to see if they are actually growing what they intended, or to simply look at how much oxygen is on the surface in between layer depositions. ALD (atomic layer deposition) systems also grow thin layers and can benefit from in situ analysis. Being able to analyze samples in situ prevents samples from being contaminated in the air when they are transferred to another analytical tool.

Do you need an off-axis electron gun?

The microCMA includes a built-in co-axial 3 kV electron gun that greatly simplifies the alignment of the sample to the CMA. The electron gun was one of the biggest challenges with designing the microCMA because the small geometry only allows for an area of about the size of the tip of your little finger for the electron gun to sit in. With such a small size, arcing, outgassing, and thermal stability are all critical. The software has routines that automatically outgas and warm up the filament, which result in a simple-to-use and stable electron gun.

What impact will the microCMA have on Thin Film applications?

The microCMA is already impacting thin-film development by providing a relatively inexpensive way to add an in situ surface analysis technique to an existing vacuum chamber. The more tools that researchers have, the more quickly new materials can be explored and developed.

Tell us how the microCMA will work in semiconductors and metals.

The microCMA works quite well for elemental analysis of semiconductors and metals. The electron beam that is used to excite the sample produces a small amount of heat, and this heat can cause damage to the sample surfaces. Semiconductors and metals are able to absorb this heat with minimal sample damage. Insulating samples such as ceramics and glass are generally not suitable for AES analysis because the samples are not conductive and the electron beam will cause charging that shifts the peaks. Samples such as polymers are also not suitable for AES because the electron beam will damage the samples even at very low currents. Therefore, thin films composed of metals and semiconductors are ideal candidates for AES analysis.

What is in store for the future of the microCMA? Are there any new or upcoming applications that will benefit from the microCMA?

Upcoming improvements in the microCMA will be focused on the CMapp software program. New features will make it even easier to operate the microCMA and manipulate the data.

Where can our readers go to find out more?

Please visit us at RBD Instruments microCMA https://www.rbdinstruments.com/products/microcma.html

About Randy Dellwo

Randy Dellwo began his career in the surface analysis industry in the 1970s during the transition from chart recorder instruments to the first computerized systems while at Physical Electronics, a pioneering company in Auger electron spectroscopy. As a founder of RBD Instruments, for the last 30 years he has guided the ongoing support for older PHI systems and components and also the development of new products related to surface analysis and materials science.