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Industrial quality control (QC) nowadays requires the visualization of surface modifications from the macro-scopic to the microscopic or even nanoscopic scale. This is a prerequisite to the evaluation of functionality and reliability, the detection of defects and their separation of artefacts. The diversity of applications ranges from low-E glazings and solar panels, micro- and optoelectronics, micro- and smart devices to sensor-on-chip and lab-on-chip systems [1]. Optical microcopy (light, confocal laser scanning, white light interference) as established QC-tool is operated at normal incidence, i.e. p- and s-polarization are undistinguishable. Either light-intensity in terms of grey scale and colour or intensity-correlated effects of phase shifts are used. In case of ellipsometry, operated at oblique incidence, p- and s-polarization matter, and amplitude ratios and phase shifts upon reflection are measured. Hence, information content must be much higher.
The visualization of surface modifications may be very challenging for coating/substrate systems of either al-most identical optical constants, e.g. transparent films on substrates of the same material, or minor film thick-ness, substance quantity and affected area, e.g. ultra-thin or island films. Ellipsometry gives access to the con-trast of intensity (I), amplitude ratio (Ψ), and phase shift (Δ) with nanometer-scaled vertical and micrometer-scaled lateral sensitivity, one is able to identify tiny changes within an unmodified surface. As both mapping ellipsometry (ME) and imaging ellipsometry (IE) are operated in the optical far-field, surface inspection is also possible on the macroscopic scale. Near the Brewster-angle of the bare, undamaged, clean, and fresh substrate, the contrast to add-on and sub-off features is superior.
Fig. 1 shows three examples of ellipsometric imaging, i.e. a thin SnO:Ni film on SiO2/Si (Fig. 1a), a dried stain of an anti-body solution on cyclo-olefin-polymer (COP) shown in Fig. 1b, and a polyimide film residue on SiO2/Si (Fig. 1c). For all of these examples, ellipsometry provides much better contrast between substrate and surface modification than optical microscopy, sometimes primarily caused by the oblique incidence (Figs. 1a and 1c), in other cases related to the phase sensitivity of ellipsometry (Fig. 1b). Other examples are laser surface modifications and the corrosion of glass. In these cases, optical microscopy and IE yield to similar results, how-ever only ellipsometry gives access to modelling.
Further investigated coating/substrate systems are 100Cr6 steel, native oxide on silicon, borosilicate glass, and the polymer polycarbonate with deposited films of graphene and ta-C:H, printed and dried pattern of liquids such as water, cleaning agents, and dissolved silicone. Besides imaging ellipsometry, referenced spectral ellipsometry (RSE) has been applied, combining the advantages of both optical microscopy (fast measurement) and ellipsometry (high sensitivity to tiny modifications).
Gas sensors are an important tool in various areas for example in industrial process control as well as Gas sensors are an important tool in various areas for example in industrial process control as well as safety applications or in research. A useful gas detector should be selective, precise, stable and cost-effective. In the present research a surface based gas detection technique is investigated using the SPR effect with ellipsometric readout. This technique is called surface plasmon resonance enhanced ellipsometry (SPREE).
The sensor consists of a gold layer (40 nm) top-coated with a doped metal-oxide (M:SnOₓ,
5 nm). The coating is added by magnetron sputtering with doped targets with different doping concentrations. It could be shown that, without the top-coating, these type of sensors can detect various gases, e.g. CO, H2, O2, O3, He, N2, with sensitivities down to the ppm range (in air).
The goal of the present study is to characterize the additional coating materials in dependence of the coating conditions. With the help of the doped-metal oxide, the sensitivity increases dramatically by a factor of 100. Additionally, a selectivity for specific gases is observed which depends on the doping conditions of the coating. Changing the properties of the plasma coating process and the doping metal gives access to a variety of different layers and enables us to find the best conditions.
Interlaboratory comparison: optical property classification of carbon-based films by ellipsometry
(2017)
The paper addresses the “INTERLABORATORY COMPARISON: OPTICAL PROPERTY CLASSIFICATION OF CARBON-BASED FILMS BY ELLIPSOMETRY” and the following points are discussed in more detail: Established classification for mechanical properties, Complementary classification for optical properties, Ellipsometry for determination of optical constants n-k plane as material fingerprint, Samples, participants & set-ups (samples: Japan, participants: Japan, Germany, France, set-ups: Japan, Germany, USA) and Results of interlaboratory comparison: thickness, n & k.
The talk addresses the STANDARDIZATION OF ELLIPSOMETRY and the following points are discussed in more detail: historical background of ellipsometry, history of International Conferences on Ellipsometry, Workshops Ellipsometry in Germany and Europe, information on German/European Working Group Ellipsometry, technical/industrial importance of ellipsometry, applications on non-ideal material systems and standardization activities on ellipsometry.
Transparent conductive oxide (TCO) films are a vital part of a large part of modern technology. The production of TCO materials has sparked much development in plasma coating technology. Quality control measurements of these layers are therefore important in many fields of optics and electronics such as high efficiency thin film photovoltaics. In this presentation, we report on optical measurements of ZnSnOx layers generated by DC/RF magnetron plasma co-sputtering. By changing the respective power on two different targets, the overall power, the gas composition and post-treatment, the properties of this type of layers can be varied in a number of parameters. The optical, electrical, and chemical properties of TCO layers are the technically most important properties together with the layer thickness. The dielectric function of layers is accessible by means of spectroscopic ellipsometry, which also yields the very important value for the layer thickness at the same time. It would be a significant step forward in quality control to use this non-destructive method also as a fast test for electrical properties. Therefore, we report on the optical properties connected to the production parameters, and also on our preliminary results connecting the optical dielectric function (in the visible and near infrared) to the electrical conductivity of the layers. We discuss the effect of deposition parameters on the optical properties of the layers and present an approach for correlating optical and electrical properties. Further, we discuss the question of accuracy of optical properties gained from model-fit-based optical methods and the use of different parameterised models for the dielectric function to achieve this.
Porous materials play an important role in several fields of technology, especially for energy applications like photovoltaics, electrolysis or batteries. The activity of thin porous films is affected by properties like porosity, film thickness, chemical composition of the material as well as the homogenous dispersion of the active species within the porous matrix. The complex morphology of such porous films constitutes a challenge even for modern analytical techniques and requires new approaches employing the combination/complementation of data of different analytical methods. In this contribution we characterize thin mesoporous iridium-titanium mixed oxide film properties by complementary analysis of SEM/EDS, ToF-SIMS, NanoSIMS, AES and spectroscopic ellipsometry.
Mesoporous iridium oxide - titanium oxide (IrOx-TiOx) films can be prepared by a well-established Synthesis route via soft-templating. IrOx-TiOx films are very sensitive to the conditions of synthesis. Analysis by SEM and NanoSIMS imaging suggests IrOx-TiOx films with and without a homogenous dispersion of IrOx within the TiOx film matrix under different synthesis conditions.
Auger electron spectroscopy (AES) analysis in the depth-profile mode as well as cross-section line-scan AES measurements of an inhomogeneous IrOx-TiOx film indicate the presence of an IrOx-rich Phase dispersion both at the surface of IrOx-TiOx film as well as within the film.
The contribution will assess in detail the sensitivity of the synthesis conditions and the characterization of the thin metal oxide films. Moreover, the correlation between and comparison to other measurement techniques will be discussed.
Porous materials play an important role in several fields of technology, especially for energy applications like photovoltaics, electrolysis or batteries. The activity of porous films is affected by properties like porosity, film thickness, chemical composition of the material as well as the crystallinity of the framework. The complex morphology of such porous films constitutes a challenge even for modern analytical techniques and requires new approaches employing the combination/complementation of data of different analytical methods. In this contribution we characterize thin mesoporous iridium-titanium mixed oxide film properties by Electron Probe Microanalysis (EPMA) with energy dispersive X-ray spectroscopy (EDS) at an SEM.
Ellipsometry has been an extremely successful and fast expanding method in the past decades along with other related techniques using polarisation sensitive measurements. Opening new fields of application for a successful measurement technique brings some requirements and issues that have to be solved. From a metrological point of view, ellipsometry has the problem that uncertainties are difficult to determine for model-based analysis techniques in general. In this presentation, we will explore how the usefulness of polarimetric methods like ellipsometry can be increased.
Ellipsometry as a method could profit from several current developments which will be discussed in this presentation:
• Standardisation initiatives on national and international level developing standards for best practice when using ellipsometry. A series of at least six standards is currently developed on national German and international level covering different levels of sample complexity.
• Projects on traceability of ellipsometry and structured surface spectrometry as well as new dielectric function database initiatives.
• Metadata handling and data ontology providing a better framework for exchange and collaborative use of research data.
We will also explore the quantification of measurement uncertainty using examples from projects in which BAM is involved. Examples will be presented of multilayer and non-ideal materials as well as the determination of layer properties for technical applications such as thin layer catalysts and complex polymers. The definition of reference materials will be discussed.
Ellipsometry is a highly valuable technology for bridging different measurement methods. As a fast, highly sensitive, and non-destructive optical technique with low environmental requirements, it is ideal for transporting measurement accuracy and for up-scaling measurements in the production environment. It can be used for highly precise determination of properties, material identity and correctness confirmation, as well as defect detection.
Comparable, traceable, and accurate electrical measurements, especially at small scales are one of the biggest challenges in the development of the electrical and electronic devices of the future.
In this project, we develop structured thin layer systems of the transparent conductive material indium tin oxide (ITO) to prove the concept of using these systems as standards for conductivity and permittivity. The layers are produced in a reactive magnetron sputtering process from raw ITO targets with additional oxidation achieved by oxygen injection. We present results of a study correlating the coating process conditions with the properties of the final layer material. We found that especially the temperature development during coating is of key importance and determines the layer properties to a large extent. We will discuss questions of homogeneity and reproducibility of the coating processes used. The finished layers undergo lithographic structuring and etching to produce patterns to serve as reference structures for scanning probe electrical measurements. TCOs have a large variety of applications. In this work we also study the usability of ITO for other purposes and investigate the stability of this material under application conditions.
Interactions between a polymer and a substrate interface play a vital role in understanding the improvement in thin film material properties as well as serving as a model for nanocomposites. For any non-repulsive polymer-substrate interactions, polymer segments form an irreversibly adsorbed layer and show a slowdown in the glassy dynamics and thus an increase in the thermal glass transition temperature compared to the bulk-like values. The growth kinetics of the adsorbed layer obey a two-step mechanism: formation of immobilized layer with flat segmental conformations and a loosely bound layer with stretched chains pinned to the surface. Here the adsorbed layer was studied for: poly (bisphenol-A carbonate) (PBAC) and polysulfone (PSU), two bulky polymers containing a functional group (phenyl ring) in the backbone and compared to poly (2-vinyl pyridine) (P2VP), where the backbone is a vinyl-derivative and the functional group (pyridine) is in the side chain. The growth kinetics for PBAC and PSU were found to deviate from the well-known mechanism, observed for polymers such as P2VP. Atomic force microscopy and ellipsometry were used for this investigation and was additionally supported by broadband dielectric spectroscopy.