Determination of the fluorine content in a-Si:H:F by infrared spectroscopy, electron probe microanalysis, x-ray photoelectron spectroscopy, and secondary ion mass spectrometry

We have measured the fluorine content in a-Si:H:F with 0%–10% F by electron probe microanalysis (EPMA), x-ray photoelectron spectroscopy (XPS), secondary ion mass spectrometry (SIMS), and infrared (IR) spectroscopy. The techniques differ in accuracy and availability of calibration standards. EPMA is the most reliable of these measurements, with a calibration to internal standards that is accurate to ±1 at. % F. XPS measures only the top 30 Å which, after Ar+ sputtering, has 2.0±0.3 times less fluorine than the bulk. We compared SIMS to EPMA and XPS and found that the ratio of the F/Si SIMS intensities is linear in F content. The sum of the integrated IR absorbances of the Si-F stretches is proportional to the F content with 11±1 cm−1/at. % F. After correcting for the systematic variation in Si density with F content, this gives an average absorption cross section of 16±1 cm2/mM. The correlation between IR absorbance and F content is contrasted with previous reports and we find that this cross section may be applied to a-Si:H:F and a-SiGe:H:F deposited by photochemical vapor deposition or glow discharge. As IR spectroscopy is a readily available technique, this will facilitate the reporting of F content and thus allow comparisons between different studies of fluorinated materials.