FTIR spectrum analysis utility

Show intro / Hide intro

This utility solves the typical task of FTIR spectroscopy: identifying absorbance peaks from a transmittance spectrum of a thin solid film sample taken with an infrared spectrometer. For this purpose, the original transmittance spectrum data set (k, T) is converted to an absorbance spectrum (k, α):

$\alpha(k) = - \frac{1}{2 w \sqrt{2}} \log\left(\frac{T(k)}{1 - r^2}\right).$

The width of the sample film w is a result of direct measurement, i.e. microscopy. The reflectance r is deduced as r = 1 − Tₒ from the mean maximum transmittance level Tₒ disregarding signal oscillations (dashed line in the autodetection mode).

The default demo spectrum was taken from a porous 53-micron thin silicon film previously exposed to electrochemical etching in a fluoric acid solution.

1. Edit and apply a transmittance spectrum (k, T) or an absorption spectrum (k, α) data set. Units: wavenumber, k in cm⁻¹, transmittance, T in %.

For a transmittance spectrum (k, T), take the following steps to convert it to an absorbance spectrum (k, α) first. In case of an absorption spectrum (k, α), skip the following conversion and proceed directly to the peak detection.

Thickness of the film, μm:

Reflectance of the film (autodetect, check the dashed line on the plot above):

2. Convert (k, T) to (k, α).

This app comes with a default built-in reference data set of absorption peaks for silicon films. If it is applicable, proceed directly to the peak identification. Otherwise, enter a different reference data set.

3. Identify absorbance peaks.