Advances in the Raman Depth Profiling of Polymer Laminates

Abstract

The use of Raman microspectroscopy to depth profile multi-layered polymer laminates is becoming increasingly popular. However, the results are generally degraded by aberrations introduced by the change in refractive index at the air/sample interface. Recent research has suggested that the use of an immersion oil and suitable objective can reduce this effect. This study evaluates this proposal by comparing depth profiling results on a multi-layer poly(styrene)/poly(methylmethacrylate) (PS/PMMA) laminate polymer from both dry metallurgical objectives and immersion objectives (used in combination with an oil of suitable refractive index). The immersion technique enabled successful depth profiling to the full working distance of the objective (100 microm), showing clear and distinct variations in 11 different layers within the laminate; a dry metallurgical objective used for comparison achieved poor resolution of only two layers. This is the first demonstration of depth profiling within a polymer laminate to this depth. The depth profiling results are compared to results obtained by sectioning the PS/PMMA sample after setting it in resin.

The role of beam dispersion in Raman and photo-stimulated luminescence piezo-spectroscopy of yttria-stabilized zirconia in multi-layered coatings

“…It is important to make specific measurements of beam dispersion for the specific YSZ coating being addressed. For other application of Raman spectroscopy, such as the phase detection in materials, the sampling volume is crucial for determining the location and distribution of the detected phases [22] and [23]. 6.…”

“…Higher-resolution measurements can be expected for more opaque materials such as silicon [19] and [20] or when using ultraviolet laser radiation [20]. Even though the depth resolution can be improved by the use of a confocal Raman system combined with oil-immersed objective lenses [21] and [22], the depth resolution in translucent materials can be reduced significantly due to refraction [23] and spherical aberration [24] of the light in the part of the laser beam path within the out-offocus area [25].…”

Transient interfacial tension and dilatational rheology of diffuse polymer-polymer interfaces

“…Notice that the measuring spot has a finite size which will give an apparent diffuse layer, even for a sharp interface. This apparent layer thickness is estimated to be about Ϸ15 m. 30 The size of the measuring spot depends on, among other things, the number of interfaces that have been passed ͑in our case the air-liquid and the liquid-liquid interface͒ and the depth of the spot below an interface. A detailed quantitative analysis of the effects of the varying measuring spot size can be found in Refs.…”

A sparse semi-blind source identification method and its application to Raman spectroscopy for explosives detection

“…where R i denote the ith row of R, and M k the kth row of M. The source assumption implies that 5) which says that every row of R is a nonnegative linear combination of the rows of M. The identification of M's rows is equivalent to identifying a convex cone of a finite collection of vectors. The cone encloses the data rows in matrix R, and is the smallest of such cones.…”

“…These methods are mainly based on Raman spectroscopy, a spectroscopic technique to study the chemical composition of the samples [12,21]. Combined with other spectroscopic techniques such as Ultraviolet and Infrared spectroscopy, Raman spectroscopy has been widely used in materials science, biosciences, geosciences (gemology), forensic sciences, nano-technology, and pharmaceutical chemistry [3,4,5,7,13,15,17,23]. For example, the Swept Wavelength Optical Resonant Raman Detector (SWOrRD) at the Naval Research Laboratory developed in 2009 can generate two dimensional spectral maps of biological agents and chemical substances.…”