I'm working on thin films of GeTe. I wanted to know if I can understand its structure just from Raman spectra, as all its structures have some overlapping peaks in the XRD.
Each crystallographic structure has a "fingerprint" in its Raman spectrum, so You May use Raman Like that. However You will Not get the structural details such as Bond distances etc using Raman alone ...
It depends on what kind of information of structure that you are expected. Micro-raman can give a bit information about the interaction of elements. However, if you conduct a reaction with your materials, you can notice the response of your material towards that reaction (the peaks may change or disappear). For the lower frequencies, some crystallographic structures may be revealed.
Gokul Krishna
I am confused by your comment 'as all its structures have some overlapping peaks in the XRD'. You only have one component (GeTe) from what I understand. How can there be any confusion here - other than, perhaps, amorphous and crystalline content? Or is the substrate interfering? So, what do you mean by 'structure'? Are you looking for the morphology of the layer? I can't understand 'I wanted to know if I know it's structure...' except for the incorrect apostrophe.
A RG search brings up XRD patterns of GeTe. For example:
Article The Tunable Amorphous-Crystalline Transition Temperature by ...
Article Features of the High-Temperature Structural Evolution of GeT...
Important crystal structure information can be viewed here:
https://materialsproject.org/materials/mp-2612
I'm not sure why you're concerned with using Raman here in a 2-element system. What bonds do you expect to see?
Alan F Rawle
By overlapping peaks of XRD what I meant was the Rhombohedral and Cubic structures of GeTe having an overlapping peak at 202 and 200 respectively.
I am getting a peak around 30 and both the rhombohedral and cubic have simulated peaks of 29.7754 and 29.7688.
In few of my samples I do get 101 peaks of Rhombohedral too.
But for others I am rather confused whether the film formed has rhombohedral or cubic structure.
Gokul Krishna
How thick is your 'thin film'? My obvious comment is that you have local heterogeneity with both cubic and rhombohedral structures present. Only in the bulk (annealed?) crystal may you see a single phase.
Gokul Krishna
These are very thin 'thin films' with only a very few atomic layers present. Please display the XRD spectrum (perhaps weak peaks?). I feel that my comment above applies even more strongly now but also add that I'd expect to see significant amorphous content. Have you any TEM micrographs of the structure? I wonder if it has localized domains.
What do you find if you compare your thin film XRD with the XRD pattern of your bulk material XRD (GeTe), which is used to make your thin film. Homogeneity in your film depends on the technique you are using to a large extent. There can be a coexistence of two phases. You need high resolution XRD data with a very slow scan to carefully resolve the issue.
For doing TEM analysis, the cross-sectional samples need to be prepared carefully, and a good knowledge/experience to interpret the SAED patterns
You Can analyze your HRXRD data and use Rietveld refinement and see when you arrive at a close enough goodness of fit (Gof), checking individual for each one of the structures, and the coexistence of both the structures. For this exercise you need to collect very high resolution XRD data with a very slow scan speed.
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