Traceable Characterization of Nanomaterials by X-ray Spectrometry Using Calibrated Instrumentation

Abstract

Traceable characterization methods allow for the accurate correlation of the functionality or toxicity of nanomaterials with their underlaying chemical, structural or physical material properties. These correlations are required for the directed development of nanomaterials to reach target functionalities such as conversion efficiencies or selective sensitivities. The reliable characterization of nanomaterials requires techniques that often need to be adapted to the nano-scaled dimensions of the samples with respect to both the spatial dimensions of the probe and the instrumental or experimental discrimination capability. The traceability of analytical methods revealing information on chemical material properties relies on reference materials or qualified calibration samples, the spatial elemental distributions of which must be very similar to the nanomaterial of interest. At the nanoscale, however, only few well-known reference materials exist. An alternate route to establish the required traceability lays in the physical calibration of the analytical instrument’s response behavior and efficiency in conjunction with a good knowledge of the various interaction probabilities. For the elemental analysis, speciation, and coordination of nanomaterials, such a physical traceability can be achieved with X-ray spectrometry. This requires the radiometric calibration of energy- and wavelength-dispersive X-ray spectrometers, as well as the reliable determination of atomic X-ray fundamental parameters using such instrumentation. In different operational configurations, the information depths, discrimination capability, and sensitivity of X-ray spectrometry can be considerably modified while preserving its traceability, allowing for the characterization of surface contamination as well as interfacial thin layer and nanoparticle chemical compositions. Furthermore, time-resolved and hybrid approaches provide access to analytical information under operando conditions or reveal dimensional information, such as elemental or species depth profiles of nanomaterials. The aim of this review is to demonstrate the absolute quantification capabilities of SI-traceable X-ray spectrometry based upon calibrated instrumentation and knowledge about X-ray interaction probabilities.

Developing Quantitative Nondestructive Characterization of Nanomaterials: A Case Study on Sequential Infiltration Synthesis of Block Copolymers

“…Ex Situ Quantitative GIXRF Characterization. The four sample sets, as-infiltrated polymeric layers and SIS-processed BCP templates after PS removal (Figure 1e), were characterized using synchrotron radiation-based X-ray fluorescence analysis in its RF variant 28,29 (Figure S1a). Using the deconvoluted fluorescence spectra (as in Figure S1b), XRF allowed for the nondestructive analysis of the elemental composition and the absolute quantification, traceable to the SI, of the mass of Al per unit area, the areal density expressed in ng/cm 2.30,31 The XRF quantification measurements are carried out at BESSY II synchrotron facility by using physically calibrated X-ray spectrometry instrumentation so removing the need for a calibration standard 28 and through the fundamental parameters approach based on Sherman's equation, 32 as reported in eq 1.…”

“…The four sample sets, as-infiltrated polymeric layers and SIS-processed BCP templates after PS removal (Figure e), were characterized using synchrotron radiation-based X-ray fluorescence analysis in its RF variant , (Figure S1a). Using the deconvoluted fluorescence spectra (as in Figure S1b), XRF allowed for the nondestructive analysis of the elemental composition and the absolute quantification, traceable to the SI, of the mass of Al per unit area, the areal density expressed in ng/cm 2.…”

“…Ensuring the development of analytical methods for nondestructive and absolute quantification at the nanoscale is also essential to boost the applicability of complex organic–inorganic nanomaterials. RF GIXRF analysis is a well-established technique for the absolute quantification of the mass per unit area of deposited metals and other compounds . The absolute quantification of infiltrated inorganics could be transferred to common mass uptake QCM gravimetric measurements used for in situ control of the SIS process.…”

Small target compatible dimensional and analytical metrology for semiconductor nanostructures using x-ray fluorescence techniques

“…On the one hand side, µXRF is employed to study elemental compositions with lateral resolution in the order of 10 µm. By adopting the reference-free XRF approach, 15 absolute quantification of elemental mass depositions (mass per area or areal mass) can be performed. Employing an X-ray microscope with a more sophisticated focusing unit, even smaller lateral resolution in the order of 100 nm can be achieved allowing also for absolute quantification of amounts of material at such lateral resolution.…”

Nanometrology

“…We are therefore happy that, in this Special Issue, we can present papers from various fields, coming from both academia and metrology institutes. This includes the aspects of traceability for analytical techniques, in particular X-ray-based techniques [ 5 ], electrical SPM [ 6 , 7 ], quantitative data processing [ 8 ], tools for estimation related to data processing [ 9 ] and exploring novel routes for quantitative measurements [ 10 ]. We hope that this will provide a nice example of many different flavors of today’s nanometrology.…”