Raman Spectroscopy vs. Inelastic Electron Tunneling

[Yosty22]

I am a first year graduate student in physics and am becoming familiarized with Raman spectroscopy to study structure of materials based off of their vibrational states.

In some personal study outside of this, I came across the idea of inelastic electron tunneling spectroscopy (IETS) and was wondering if anyone knew of when/why one is used over the other. I did some research and it seems Raman is a much more widely used technique, but IETS seems to offer more information with little extra work. Since it doesn't work by shining laser light on a material and measuring a response (but rather inelastic tunneling, obviously by the name), IETS can give information on optically forbidden transitions unlike Raman.

This is more a question out of curiosity more so than something super technical, but does anyone have experience working with IETS? I'm interested to hear any comparisons between IETS and Raman. Could anyone contrive a situation where IETS may be more practical or "useful" than Raman?

Thanks in advanced!

 

[eljose79]

Dear first year graduate student,

Thank you for your post and for your interest in Raman spectroscopy and inelastic electron tunneling spectroscopy (IETS). As a scientist who has experience working with both techniques, I can offer some insights and comparisons between the two.

Raman spectroscopy and IETS are both powerful techniques for studying the vibrational states of materials. However, they work on different principles and have different strengths and limitations. Raman spectroscopy relies on the interaction of light with the material, while IETS relies on the interaction of electrons with the material.

Raman spectroscopy is a non-destructive technique, as it involves shining a laser on the material and measuring the scattered light. This makes it a good choice for studying delicate or sensitive materials. It is also capable of providing information on the crystal structure and symmetry of the material, which can be useful in identifying unknown materials. However, Raman spectroscopy has limitations in its ability to detect optically forbidden transitions, as you mentioned. In addition, it may not be as sensitive as IETS in detecting small changes in the vibrational states of a material.

On the other hand, IETS is a more sensitive technique as it involves measuring the changes in electron tunneling current between a metal tip and the material under study. This can provide information on the vibrational states of a material with high resolution. It is also capable of detecting optically forbidden transitions, making it a useful tool for studying materials with complex vibrational spectra. However, IETS is a destructive technique, as it involves applying a voltage to the material which can cause damage. It also requires specialized equipment and expertise, which may limit its accessibility for some researchers.

In terms of practicality and usefulness, it really depends on the specific research question and the properties of the material being studied. If the goal is to obtain information on the crystal structure and symmetry, Raman spectroscopy may be the better choice. However, if the focus is on studying small changes in the vibrational states of a material, IETS may be more suitable. In some cases, both techniques can be used together to complement each other's strengths.

I hope this helps answer your question and gives you a better understanding of the differences between Raman spectroscopy and IETS. Ultimately, the choice of which technique to use will depend on the specific needs of your research. Good luck with your studies!