I would like to record the infrared spectrum (MIR, 4000-400 cm-1) of hybrid metal oxide films (e.g. TiO2), deposited by spin coating, with thickness around 100-200 nm.
Is ATR-IR (attenuated total reflectance) a suitable choice, or is another technique needed for thin films? What kind of substrate should I use?
Thank you in advance!
Hi Claudio,
You can use FTIR with ATR mode but the range you will get is from 4000 to 650 cm-1.So if you mind a peaks in the range of 650 to 400 cm-1 you must do FTIR with no ATR mode. However the sample preparation is the same, as you have a thin film you should first spin coat your sample on the KRS-5 disc substrate and later you can try both FTIR and ATR mode.
For KRS-5 disc you may ask the person in charge for FTIR instrument in your department.
Precaution: KRS-5 disc is highly toxic.
Hi Hossein, thank you for your answer.
4000-650 cm-1 would be fine, I will try ATR. Can I use a different substrate, such as silicon, if KRS-5 is not available?
I have suggested KRS-5 disk because it possess excellent transmission in infra red region. However, if is not available you can use potassium bromide (KBr) disk or aluminium oxide (Al2O3) disk.
Refractive index of KRS-5 is 2.4 i.e. - even lower than that of amorphous TiO2 (n appr. = 2.5) THUS, by using KRS-5 you will be unable to realize the total reflectance. In other words - if you would like to obtain an ATR spectrum of TiO2 you should use as substrate Si (n=3) or Ge (n=4). But I am sure that the best result you will obtain by using a common IR-technique - a transmission mode - because your film is very thin !!!
For FTIR transmission mode: you should use substrate with low index of refraction.
For FTIR-ATR mode: if is not affect your method, you don't need to use any substrate and you can drop cast your sample directly on ATR crystal which is made by high refractive index material.
Thank you for your advice!
I will try first in transmission mode, then in ATR mode if the results are not satisfying.
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