Quantitative Depth Profile Analysis of Micrometer-Thick Multilayered Thin Coatings Using Step-Scan FT-IR Photoacoustic Spectroscopy

Abstract

This paper demonstrates the results of the comparison of step-scan FT-IR photoacoustic spectroscopy with other established spectroscopic and microscopic techniques in the quantitative depth profile determination of micrometer- and submicrometer-thick multilayered thin coatings. The power of the phase rotation and phase spectrum analytical methods to clearly distinguish the infrared signature of submicrometer-thick coatings is demonstrated. The thickness determined by the step-scan FT-IR photoacoustic method is in very reasonable agreement with optical microtomy/microscopy measurements performed at-line during the coating process. The former technique described in detailed here offers substantial benefits in terms of measurement time and operator dependency, while not sacrificing the accuracy of the measurement. The problem of saturation and its effect on "real-life" samples is also discussed.

Soil Chemical Insights Provided through Vibrational Spectroscopy

“…Sample preparation of soil samples is perhaps the most important factor for effectively applying this technique. For example, for IRMS analysis in transmission mode, thin sections of <10 μm thickness are required to avoid total light adsorption (Gregoriou and Rodman, 2002). This can be achieved by embedding the soil (typically air-or freeze-dried) in an epoxy resin and then microtoming with a diamond or glass knife.…”

Depth profiling of SBS/PET layered materials using step-scan phase modulation Fourier transform infrared photoacoustic spectroscopy and two-dimensional correlation analysis

“…The phase angle of the two peaks at an intensity of zero are respectively 109.0° and 172.5°, and the difference between them reflects the thickness of the SBS layer. Phase analysis has been applied in depth profiling due to its accurate results [5,15,[20][21][22][23]. Because PA signals from the deeper layers always have larger phase lags than that from the shallower layer, spectral information from different depths was resolved with the phase.…”

“…However, since the sampling depth varies with wave number, it is not used in quantitative depth profiling of inhomogeneous or layered samples. Based on the fact that the diffusion time of thermal waves to the surface changes with depth and thus a phase lag exists, step-scan phase modulation is used to acquire a constant frequency and a uniform sampling depth [6,[13][14][15][16]. This method explores the spectral information of different depths and has been utilized in the investigation of inhomogeneous polymer samples, layered compositional materials, molecular sieve membranes, and the human stratum corneum [13][14][15][16][17][18][19][20][21][22][23].…”

Application of infrared photoacoustic spectroscopy in catalysis

“…Some of them contain general content of the use and application of FT-IR/PAS [22][23][24][25][26][27][28][29][30][31], others are more specific and are devoted to real-time PA parallel detection of products from catalyst libraries [32], step-scan and depth profiling analysis [33][34][35][36][37][38][39][40], the effect of particle size on FT-IR/PAS spectra [41][42][43][44], the temperature effect on PA signal [45], sample emission effects [46], and synchrotron IR/PAS [47]. During a PA measurement the sample is enclosed in a small, tightly closed sample compartment called PA cell [48][49][50][51][52][53][54].…”