Nitric oxide assisted C₆₀secondary ion mass spectrometry for molecular depth profiling of polyelectrolyte multilayers

Abstract

NO-dosing provides a tool for extending the applicability, in SIMS depth profiling, of the widely spread fullerene ion sources. In view of the acceptable erosion rates on inorganics, obtainable with C60, the method could be of relevance also in connection with the 3D-imaging of hybrid polymer/inorganic systems.

A wavelet‐PCA method saves high mass resolution information in data treatment of SIMS molecular depth profiles

“…The inspection of the loadings plot shows that the outer region is mostly characterized by the presence of the typical fragments of PSS molecules (negative loadings), while the positive loadings region (corresponding to the inner part of the organic film) mostly contains C x N clusters, and a few C x H y O z peaks. The presence of C x N is reasonably diagnostic of ion beam‐induced damage accumulation along the sample depth, causing NO uptake, not surprising for a system in which some components (namely, PSS) are known to undergo extensive damage under C 60 bombardment in the absence of NO dosing . Notably, the damage‐related peaks are present in a depth region where the intensity of peaks diagnostic of the undamaged polymer is rather low (Fig.…”

“…Polyelectrolyte‐based multilayers deposited on silicon substrates represent the model sample selected for this research study. A detailed characterization of this kind of samples, including the evaluation of beam‐induced sample damage, is reported elsewhere . The particular sample chosen for testing is characterized by three different regions along depth, each composed of a common polycation (PDDA) and with a different polyanion (PSS, PAA, and PSS in the first, second, and third regions, respectively).…”

“…PSS–PDDA, PAA–PDDA, and PSS–PDDA. The thickness of each region was obtained by measuring, by means of atomic force microscopy, the depth of incisions made on the sample by means of a sharp blade . The thickness values of the three regions of the test sample used here are 110, 600, and 270 nm, from the inner to the outer one, respectively.…”

“…Polyelectrolyte multilayers were prepared using the spin-assembly technique [36,37] as described elsewhere. [35] Polystyrene sulfonate (PSS) (MW = 70 000), poly acrylic acid (PAA) (MW = 1 000 000), and polydiallyldimethylammonium chloride (PDDA) (MW = 200 000-350 000) were purchased from Sigma-Aldrich. Solutions of each polymer were prepared in Millipore water (1 mg/ml) adding sodium chloride (0.15 M).…”

“…A detailed characterization of this kind of samples, including the evaluation of beam-induced sample damage, is reported elsewhere. [35] The particular sample chosen for testing is characterized by three different regions along depth, each composed of a common polycation (PDDA) and with a different polyanion (PSS, PAA, and PSS in the first, second, and third regions, respectively). As it generally happens in structured polymer systems, the spectra are characterized by a large number of peaks, many of them common to all the regions.…”