Direct detection and quantification of molecular surface contaminants by infrared and Raman spectroscopy

Abstract

Detection and identification of surface molecular contamination is important for improving process and product yields in a wide range of industrial applications. In particular, molecular compounds can easily deposit on the surface of hardware, optical components, semiconductor devices, medical devices, etc. with the risk of impairing their functionality. In this work, qualitative and quantitative metrological methodologies for surface molecular contamination detection based on Fourier transform infrared spectroscopy and micro-Raman spectroscopy are presented. The specificity of detection of two ubiquitous industrial contaminants i.e. poly(methylphenylsiloxane) and paraffin oil by infrared and Raman fingerprints is first demonstrated. Moreover, in order to obtain homogeneously contaminated surfaces that can be used as standard materials for Raman calibration, films of different thicknesses of contaminants were prepared on calcium fluoride windows, within a contamination range of 70-900 ng cm-2, by a spin coating method. The amount of contaminants spread on the surface was quantified by applying a pre-set FT-IR calibration curve in accordance with the European Cooperation for Space Standardization procedure (ECSS-Q-ST-70-05C) and it was subsequently used to calibrate the Raman equipment which demonstrated a sensitivity up to 10-8 g cm-2. A real case study of industrial contaminated surfaces i.e. a glass lens for a laser cutting machine is also presented to assess the applicability of both techniques in molecular contamination monitoring. In the discussed case Raman analysis turned out to be particularly useful for punctual investigation of the surface, especially when the sample is not transparent to the infrared radiatio

Modelling clay materials used in artworks: an infrared spectroscopic investigation

“…Additional bands at 717, 1378 and 1463 cm −1 are observed as shoulders on the overlapping CaCO 3 bands in this spectrum. The presence of these bands, along with the sharp aliphatic C-H stretching bands, confirm the presence of paraffin [10,11,13,14].…”

“…The identification of kaolinite and CaCO 3 in this material is supported by SEM-EDS analysis, with more Si than Ca detected for this sample ( Table 2). The spectrum of the Boonma sample also provides evidence of the use of paraffin oil, including sharp aliphatic C-H stretching bands in the 3000-2800 cm −1 region [10,11,13,14]. However, the relative intensities of the paraffin bands compared to the mineral components are lower than those observed in the earlier oil-based modelling clay spectra.…”

“…A small band at 766 cm −1 and a contribution to the broad O-H stretching region indicates goethite is present [21,22]. SEM-EDS analysis of the Hinder sample indicates the presence of goethite, [10,11,13,14] 849, 872 CaCO 3 C-O bending [6][7][8][9] 1030 Oxidation products C-O stretching [17,23] 1190 Oxidation products C-C stretching [17,23] 1367, 1378 Paraffin C-H bending [10,11,13,14] 1414 CaCO 3 C-O stretching [6][7][8][9] 1463, 1470 Paraffin C-H bending [10,11,13,14] 1720, 1730 Oxidation products C=O stretching [16][17][18] 1790 CaCO 3 C=O stretching [6][7][8][9] 2520 CaCO 3 overtone/combination band [7,8] 2847, 2874, 2916, 2950 Paraffin C-H stretching [10,11,13,14] with the presence of a small quantity of Fe detected ( Table 2). The detection of sulphur also supports the presence of gypsum.…”

“…The bands in the C-H stretching region below 3000 cm −1 indicate an aliphatic hydrocarbon is present. The lack of evidence of aromatic and carbonyl groups indicates that the hydrocarbon constituent is of petrochemical origin, most likely paraffin oil (also known as mineral oil) and/or paraffin wax [10][11][12][13][14]. As the infrared spectrum of paraffin oil and wax are very similar, it is difficult to determine the relative contribution to the overall composition of this modelling clay.…”

In Situ Real-Time Quantitative and Qualitative Monitoring of Molecular Contamination

“…To complement this measurement, various chemical analyses can thus be carried out, such as in situ mass spectrometry, gas chromatography coupled to mass spectrometry, Fourier transform infrared spectroscopy, etc. [8][9][10][11][12]. Unfortunately, all of these techniques have severe limitations.…”