New trends in electron spectroscopy for chemical analysis (ESCA)

ESCA is a vital member of the group of techniques that are used for surface analysis. XPS or X-Ray Photoelectron Spectroscopy is another name for ESCA and is used widely on a range of materials. It provides insightful chemical and quantitative state information from the material surface being studied. For an XPS analysis, the average depth of measurement is around 5nm. PHI ESCA instruments are known for providing the ability to gather spectra with a lateral spatial resolution. Depth distribution information is achieved by combining XPS dimensions with sputtering. This characterizes thin film structures. Obtaining spatial distribution information can be done by scanning the micro-focused x-ray beam throughout the sample. XPS provides information about the layers on the surface or thin film structures which is extremely crucial for multiple research and industrial applications like catalysis, nanomaterials, corrosion, adhesion, and surface treatments.

How to Achieve XPS/ESCA?

X-Ray Photoelectron Spectroscopy is usually achieved by exciting a sample surface using mono-energetic rays which cause photoelectron emission from the sample surface. To measure the energy of the emitted photoelectrons, an electron energy analyzer is usually used. This helps in determining the chemical state, elemental identity, binding energy, and quantity of elements accurately. XPS was launched by Kai Siegban along with his research group for detecting limits of elements that are within the 1000 parts per thousand range. For a higher detection limit of parts per million, special conditions are to be used which are basically concentrating at the top surface or over a longer span of time. XPS is used to mainly analyze metal alloys, inorganic compounds, catalysts, ceramics, papers, inks, plant parts, wood, clinical implants, glues, biomaterials, and many other scientific innovations that are brewing across a multitude of industry verticals.

Electronic XPS

Physical e-XPS instruments operate in a manner that is analogous to SEM/EDS instruments. These use a sharply focused electron beam for creating SEM images for point spectra and  sample viewing. With PHI XPS tools, a beam is scanned thoroughly for creating a secondary electron image. The size of the beam can be adjusted for supporting the efficiency in analyzing larger samples along with homogeneous components. This is different from SEM/EDS, which offers a typical in-depth analysis of 1-3 µm, XPS technique is a better option for composition analysis of thin microscale samples as well as ultra-thin layers.

ESCA Lab Services

• This technique for surface analysis is ideal for the evaluation of the passivation of stainless steels, and oxidation for iron and chromium.
• Helps to study the surface chemistry of glasses, polymers along with other insulating materials
• Resolves problems associated with metal interdiffusion, oxidation, and resin-to-metal adhesion.

How Does ESCA Find Results?

The ESCA analysis is eventually broken down into 3 prominent parts. The first is a survey scan which helps in identifying the elemental composition of the surface of the sample. High-resolution multiplex scans measure atomic concentrations of the survey scan-identified elements. The multiplex also helps in measuring the chemical environments of elements via the binding energies. Careful determination of binding energies is established using curve-fitted routines using a NIST database. Measuring the distribution of elements is done via depth profile. Depth resolution depends on sputtering parameters and a sample where a typical sputter takes about 30 Å/min.

In a Nutshell

XPS measures the elemental composition of the surface ranging from 1-10 nm. It also finds out the empirical formula for pure materials and elements that cause contamination on the surface. The electronic or chemical state of each element on the surface can also be found via ESCA as it maintains uniformity of element composition across mapping or line profiling.