Analysis of Structural Surface and Coating Properties

Our Services

Current developments in the field of multifunctional optical and technical surfaces pose new challenges for the quantitative characterization of surface structures. Depending on the application, information on roughness is required over wide spatial frequency ranges. In addition, different surface types (from extremely smooth to very rough) require different measurement approaches. Very often, the roughness properties over the entire range relevant to the application cannot be measured using just one method.

We offer:
For a targeted analysis, we offer tailor-made methods for surface characterization to efficiently support your development of innovative surfaces, coatings and materials. We use and combine various measurement methods for this purpose:

• Atomic Force Microscopy (AFM)
• White Light Interferometry (WLI)
• Laser Scanning Microscopy (LSM)
• Focus Variation Microscopy
• Light Microscopy
• Light Scattering Measurement

Parameters
Simple but intuitive roughness parameters can be retrieved from the measured surface profiles. These, however, only contain partial information, for example about the vertical dimension (rms roughness). A more comprehensive description of nanostructures is provided by the power spectral density (PSD) function. The PSD, which is merely the absolute square of the surface profile’s fourier spectrum, contains all information about both the vertical and the lateral structural properties.

In many cases, this distribution is directly relevant for functional properties such as wetting and light scattering. In addition, PSD functions enable thin film growth and polishing processes to be investigated in detail. The results can be fed directly into optimization and modeling procedures.

Furthermore, by using PSD functions, the results of different roughness measurement techniques can be combined and expressed in a uniform and convenient way.

This way, an extremely broad spatial frequency spectrum from LSFR (low-spatial-frequency roughness) to HSFR (high-spatial-frequency roughness) is covered. The ranges and parameters of the individual technologies are shown in the overview diagram (Fig. right).

Surface defects and contamination can have a significant impact on the quality and stability of optical components. As surface requirements tighten and allowable roughness decreases, these issues even become major limiting factors. Reliable detection and analysis of such defects are therefore essential in both quality control and development.

We offer
Depending on the task, we use various methods for defect screening, structural defect analysis and application-oriented analysis using light scattering.

Parameters

• Microscopic defect scan (bright field/dark field) on flat and curved optical surfaces and determination of particle size distribution (d > 2 µm)
• High-resolution structural analysis of individual defects using AFM/ WLI
• Light scattering-based defect mapping of optical components up to large curved surfaces (diameter up to 600 mm)
• Special measurement approaches and analysis methods for the light scattering-based detection of particles and defects down to the sub-micrometer range as well as the non-destructive detection of sub-surface damage (SSD)

In addition to testing and measuring services, we offer the development of customized defect sensors that can be integrated directly into the production environment.

Generally, the development of novel products or materials and the defect analysis requires a simple but precise solution for application-oriented requests. By means of high-resolution field emission scanning electron microscopy (FE-SEM) surfaces and cross sections can be imaged with a resolution in the micro- and nanometer range and a high depth of focus. Samples can be analyzed without a time-consuming preparation and the resulting images exhibit high information content due to the three-dimensional effect of the structures. Also, radiation-sensitive materials (e.g. polymers) can be investigated by the use of low acceleration voltages. By determining the chemical composition using energy-dispersive X-ray spectroscopy (EDX) an extensive characterization of samples, defects, contaminations, etc. is possible.

We offer:

• Examination of the surface topography and microstructure analysis of coatings
• Chemical Analysis by energy dispersive X-ray spectroscopy (EDX)
• Defect analyses on coated and uncoated surfaces
• Element mapping

Parameters
SEM:

• Acceleration voltage: 0.1-30 kV
• Lateral resolution: Up to approx. 3 nm
• Sample geometry: Max. Ø = 250 mm, h = 145 mm

EDX:

• Quantitative element analysis
• Detectable elements: Boron - Polonium
• Detection limits: approx. 0.1-1 %
• Lateral resolution: Up to min. 0.4 µm
• Information depth: approx. 1 µm

We also use additional methods to analyze layer morphology and composition, including:
• Fourier transform infrared spectroscopy (FTIR) for substance identification and chemical-structure analysis
• X-ray reflectometry (XRR) and X-ray diffraction (XRD)
• Light microscopy (reflection/transmittession, bright/dark field, Nomarski microscopy/DIC)