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ISO/TR 19693:2018—Surface chemical analysis—Characterization of functional glass substrates for biosensing applications gives an overview of methods, strategies, and guidance to identify possible sources of problems related to substrates, device production steps (cleaning, activation, and chemical modification), and shelf life (storage conditions and aging). It is particularly relevant for surface chemical analysts characterizing glass‐based biosensors, and developers or quality managers in the biosensing device production community. Based on quantitative and qualitative surface chemical analysis, strategies for identifying the cause of poor Performance during device manufacturing can be developed and implemented. A review of measurement capabilities of surface analytical methods is given to assist readers from the biosensing community.
The certified reference material BAM-L200, a nanoscale stripe pattern for length calibration and specification of lateral resolution, is described. BAM-L200 is prepared from a cross-sectioned epitaxially grown layer stack of AlxGa1-xAs and InxGa1 xAs on a GaAs substrate. The surface of BAM-L200 provides a flat pattern with stripe widths ranging down to 1 nm. Calibration distances, grating periods and stripe widths have been certified by TEM with traceability to the length unit. The combination of gratings, isolated narrow stripes and sharp edges of wide stripes offers a plenty of options for the determination of lateral resolution, sharpness and calibration of length scale at selected settings of imaging surface analytical instruments. The feasibility of the reference material for an analysis of the lateral resolution is demonstrated in detail by evaluation of ToF-SIMS, AES and EDX images. Other applications developed in the community are summarized, too. BAM-L200 fully supports the implementation of the revised International Standard ISO 18516 (in preparation) which is based on knowledge outlined in the Technical Report ISO/TR 19319:2013.
Micropatterns and nanopatterns of gold embedded in silver and titanium embedded in gold have been prepared by combining either photolithography or electron-beam lithography with a glue-free template-stripping procedure. The obtained patterned surfaces have been topographically characterized using atomic force microscopy and scanning electron microscopy, showing a very low root-mean-square roughness (<0.5 nm), high coplanarity between the two metals (maximum height difference ≈ 2 nm), and topographical continuity at the bimetallic interface. Spectroscopic characterization using X-ray photoelectron spectroscopy (XPS), time-of-flight secondary-ion mass spectrometry (ToF-SIMS), and Auger electron spectroscopy (AES) has shown a sharp chemical contrast between the two metals at the interface for titanium patterns embedded in gold, whereas diffusion of silver into gold was observed for gold patterns embedded in silver. Surface flatness combined with a high chemical contrast makes the obtained surfaces suitable for applications involving functionalization with molecules by orthogonal adsorption chemistries or for instrumental calibration. The latter possibility has been tested by determining the image sharpness and the analyzed area on circular patterns of different sizes for each of the spectroscopic techniques applied for characterization.This is the first study in which the analyzed area has been determined using XPS and AES on a flat surface, and the first example of a method for determining the analyzed area using ToF-SIMS.
CCQM key comparison K-129 for the quantitative analysis of Cu(In,Ga)Se2 (CIGS) films has been performed by the Surface Analysis Working Group (SAWG) of the Consultative Committee for Amount of Substance (CCQM). The objective of this key comparison is to compare the equivalency of the National Metrology Institutes (NMIs) and Designated Institutes (DIs) for the measurement of mole fractions of Cu, In, Ga and Se in a thin CIGS film. The measurand of this key comparison is the average mole fractions of Cu, In, Ga and Se of a test CIGS alloy film in the unit of mole fraction (mol/mol). Mole fraction with the metrological unit of mol/mol can be practically converted to atomic fraction with the unit of at%.
In this key comparison, a CIGS film with certified mole fractions was supplied as a reference specimen to determine the relative sensitivity factors (RSFs) of Cu, In, Ga and Se. The mole fractions of the reference specimen were certified by isotope dilution - inductively coupled plasma/mass spectrometry (ID-ICP/MS) and are traceable to the SI. A total number counting (TNC) method was recommended as a method to determine the signal intensities of the constituent elements acquired in the depth profiles by Secondary Ion Mass Spectrometry (SIMS), X-ray Photoelectron Spectroscopy (XPS) and Auger Electron Spectroscopy (AES). Seven NMIs and one DI participated in this key comparison. The mole fractions of the CIGS films were measured by depth profiling based-SIMS, AES and XPS. The mole fractions were also measured by non-destructive X-Ray Fluorescence (XRF) Analysis and Electron Probe Micro Analysis (EPMA) with Energy Dispersive X-ray Spectrometry (EDX).
In this key comparison, the average degrees of equivalence uncertainties for Cu, In, Ga and Se are 0.0093 mol/mol, 0.0123 mol/mol, 0.0047 mol/mol and 0.0228 mol/mol, respectively. These values are much smaller than that of Fe in a Fe-Ni alloy film in CCQM K-67 (0.0330 mol/mol). This means that the quantification of multi-element alloy films is possible by depth profiling analysis using the TNC method.
Interfaces provide the structural basis for function as, for example, encountered in nature in the membrane-embedded photosystem or in technology in solar cells. Synthetic functional multilayers of molecules cooperating in a coupled manner can be fabricated on surfaces through layer-by-layer self-assembly. Ordered arrays of stimulus-responsive rotaxanes undergoing well-controlled axle shuttling are excellent candidates for coupled mechanical motion. Such stimulus-responsive surfaces may help integrate synthetic molecular machines in larger systems exhibiting even macroscopic effects or generating mechanical work from chemical energy through cooperative action. The present work demonstrates the successful deposition of ordered mono- and multilayers of chemically switchable rotaxanes on gold surfaces. Rotaxane mono- and multilayers are shown to reversibly switch in a coupled manner between two ordered states as revealed by linear dichroism effects in angle-resolved NEXAFS spectra. Such a concerted switching process is observed only when the surfaces are well packed, while less densely packed surfaces lacking lateral order do not exhibit such effects.
Argon cluster sputtering of an organic multilayer reference material consisting of two organic components, 4,4'-bis[N-(1-naphthyl-1-)-N-phenyl- amino]-biphenyl (NPB) and aluminium tris-(8-hydroxyquinolate) (Alq3), materials commonly used in organic light-emitting diodes industry, was carried out using time-of-flight SIMS in dual beam mode. The sample used in this study consists of a ~400-nm-thick NPB matrix with 3-nm marker layers of Alq3 at depth of ~50, 100, 200 and 300 nm. Argon cluster sputtering provides a constant sputter yield throughout the depth profiles, and the sputter yield volumes and depth resolution are presented for Ar-cluster sizes of 630, 820, 1000, 1250 and 1660 atoms at a kinetic energy of 2.5 keV. The effect of cluster size in this material and over this range is shown to be negligible.
Lateral resolution of secondary ion mass spectrometry - results of an inter-laboratory comparison
(2007)
Recently, BAM organised an inter-laboratory comparison focussed on lateral resolution and accuracy of sub-micron length measurements by secondary ion mass spectrometry (SIMS). Results were submitted by 16 laboratories from 10 countries. The task was to analyse a cross-sectioned semiconductor multilayer stack. The resulting strip pattern in the surface of the sample shows narrow strips, step transitions and gratings of different periods. Imaging analysis of this pattern enables the determination of relevant parameters related to the lateral resolution: (i) The width (FWHM) of the primary ion beam, (ii) the distance between 16% and 84% intensity points in a profile across the image of a step transition and (iii) the modulation of intensity in the images of gratings with different periods. The parameter's data reported by the participants vary in a wide range. A strong variation in the data of primary ion beam width was observed for results measured with the same type of instrument. The distance between two narrow strips was measured with high accuracy. Twelve of sixteen of the submitted values are within the limits of uncertainty of the reference value 964 ± 35 nm. This result shows that the calibration of the length scale of the SIMS instruments is already rather precise in most of the participating laboratories.
Pulsed plasma deposited styrene and ethylene films were studied by Time of Flight Static Secondary Ion Mass Spectrometry (ToF-SSIMS) before and after exposure to ambient air. The influence of the external plasma parameters on the secondary ion mass spectra of plasma deposited films was investigated. Approaches for the interpretation of SSIMS spectra of organic materials were reviewed and applied to the evaluation of SSIMS data of plasma deposited films. From these data, information on the chemical character of the plasma deposited films was derived.
When the plasma polymers are exposed to air oxygen incorporation occurs. The oxygen uptake is high at the beginning and then it levels of.
A relation that higher the regularity of the film lower is the oxygen uptake was found. Harder plasma conditions, which could be obtained by applying higher plasma power or lower monomer flow rate, result in higher oxygen uptake and vice versa.
Organic thin films with defined chemical structures and physical properties are required for various applications. Plasma polymerization is of technological interest, since the deposition of plasma polymers is possible on any material of any shape in the desired thickness. We report on the TOF-SIMS (TOF: time-of-flight) and XPS investigations of pulse plasma poly(acetylene) and alkali metal doped pulse plasma poly(acetylene) films. The combination of TOF-SIMS and XPS supplies detailed information on the surface chemistry of these films. Application of both methods provides the possibility for cross-checking certain results. Moreover the different sensitivities of the methods can be utilized. According to the TOF-SIMS and XPS data it can be concluded that the interaction of alkali metals with plasma poly(acetylene) results in electrovalent bonds of the type Me?+C?- between carbon and metal. Furthermore carbonoxygenmetal interactions were observed. These interactions are of the type C=O?-cdots, three dots, centeredMe?+ and/or CO?-Me?+.