Convenient calibration of FTIR peak 'size' for thin organic/polymer films

Thin films of organic/polymer material can be fabricated as self‐assembled monolayers and by dip‐coating, spin‐coating, etc. for use in microelectronics, particularly in applications in the BioChip area, molecular electronics, microfluidics and cell‐phone fuel cells. In any analysis the inevitable question is ‘How much’ (not how tall, but how many atoms per square centimeter). A unique feature of organic/polymer films is the molecular vibrations of the organic groups; these can be measured with Fourier transform infrared spectroscopy (FTIR) and we will use this method for quantitation. Using weight gain measurements, we provide the methodology for determining the amount of material in a thin film using transmission FTIR. We provide the calibration factors for CH2, C=O, and N–H bonds using Nylon‐6 as an example. Films as thin as 200 Å are used in this study and we estimate that, under certain conditions, films as thin as a few tens of angstroms could be measured. The calibration factors that we provide can be used directly for films where these functional groups are in similar chemical environments. Where the chemical environments are significantly different, we have suggested a method for determining the appropriate calibration factors. Copyright © 2001 John Wiley & Sons, Ltd.