I am depositing SiOx film from HMDSO / Oxygen mixture. I am observing shift in the Si - O - Si peak at 1056 cm-1 towards a lower or higher wave number side while varying experimental parameters. What is really indicated by this peak shift?
If peak shift is towards higher wave number side, mass of that molecule is reduced. Because frequency of vibration is inversely proportional to mass of vibrating molecule. so lighter the molecule, more the vibration frequency and higher the wave numbers.
There are many effects which determine the measured position of a vibrational band.
For very thin films, local surface chemistry at both surfaces, as well as internal ordering and strains induced by the growth process are important. Tensile bond strain generally decreases the observed wavenumber, for example, and a film deposited at high temperature can build up a large amount of strain as it cools. Some materials also exhibit strong coupling between the electronic and vibrational bands, which can vary dramatically for thin films.
Finally, the way the spectrum is measured is important as optical artifacts can affect the measured peak position and lineshape significantly. There are good articles on this for grazing incidence (RAIRS) and normal incidence "transflection" measurements by the groups of Rohit Bhargava and Peter Gardner as well as our group.
Here are two publications that may help. Firstly, as you change your deposition parameter you may influence the SiOx structure which can change the peak position that you are monitoring.
See the last paragraph in this publication:
http://www.gelest.com/goods/pdf/Library/11Infra.pdf
Table 1 in this publication maybe of help:
http://joam.inoe.ro/arhiva/pdf7_1/Lisovskyy.pdf
Hi, the deconvolution of the main Asymetric Stretching Si-O-Si band into Gaussian profiles provides information about the stoichiometry x in the SiOx material. See this article dealing with PECVD :
https://www.researchgate.net/publication/255820751_A_thorough_FT-IR_spectroscopy_study_on_micrometric_silicon_oxide_films_deposited_by_atmospheric_pressure_microwave_plasma_torch
by Landreau, X., Lanfant, B., Merle, T., Dublanche-Tixier, C., Tristant, P.
doi : 10.1140/epjd/e2012-20647-x
Interprétations of the results are mainly based on this reference :
Lehmann, A., Schumann, L. and Hübner, K. (1984), Optical Phonons in Amorphous Silicon Oxides. II. Calculation of Phonon Spectra and Interpretation of the IR Transmission of SiOx. Phys. Status Solidi B, 121: 505–511. doi: 10.1002/pssb.2221210209
Article A thorough FT-IR spectroscopy study on micrometric silicon o...
I have a question. Iron oxide nanoparticles are coated with citric acid and The asymmetric and symmetric –COO- stretching frequencies of CA shifted
to higher wavenumber. Can I conclude that indicates outer sphere Fe-carboxylate complex formation?
If peak shift is towards higher wave number side, mass of that molecule is reduced. Because frequency of vibration is inversely proportional to mass of vibrating molecule. so lighter the molecule, more the vibration frequency and higher the wave numbers.
I agree with Purvi Kiklani. But it will be proper to discuss conclusively under what experimental parameter changes, the shift is towards lower or higher wave number side.
The internal stresses around the defects and in particular the charged defects (stoichiometric defects or trapped electrons) can reach the elastic limit because around a defect and in a cluster of a few million atoms the localized energy is considerable. Do you know a publication on the study of the effect of charges on the IR spectrum. It exists under electric field and under mechanical stress.
This publication can help you understand the importance of the question you ask:
AIP Advances 8, 095228 (2018); https://doi.org/10.1063/1.5047673
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