Jürgen Schreiber

Laser-Speckle-Photometry – A Method for Non-Contact Evaluation of Material Damage, Hardness and Porosity

Abstract The Laser Speckle Photometry is a newly developed non-contact non-destructive testing method which is based on the detection and analysis of thermal or mechanical activated characteristically speckle dynamics. The determination of the material damaged state is based on the understanding of structural changes on different scaling levels given by the physical mesomechanics. The hierarchical behavior of the mesomechanical structures (meso-structures) leads to the hypothesis of the fractal nature of the deformation structure. The fractal dimension DF is a suitable parameter to characterize the fatigued material state. In the case of the laser speckle photometry method the modified auto-correlation function from the pixel intensity changes of the speckles images was used for the computation of Parameter DF. The hardness or porosity of materials is defined by micro-structural variation and is combined with several thermal properties of the material. Therefore the speckle thermal diffusivity parameter K was determined using thermal conduction equation from the pixel intensity of speckle images changes during thermal activation. Afterwards correlation between the norm K and hardness and porosity, respectively was found. Results of this research will be presented in the present contribution.

Detection of cancer cells in prostate tissue with time-resolved fluorescence spectroscopy

Goals: Improving cancer diagnosis is one of the important challenges at this time. The precise differentiation between benign and malignant tissue is in the oncology and oncologic surgery of the utmost significance. A new diagnostic system, that facilitates the decision which tissue has to be removed, would be appreciated. In previous studies many attempts were made to use tissue fluorescence for cancer recognition. However, no clear correlation was found between tissue type and fluorescence parameters like time and wavelength dependent fluorescence intensity I(t, λ). The present study is focused on cooperative behaviour of cells in benign or malignant prostates tissue reflecting differences in their metabolism. Material and Methods: 50 prostate specimens were obtained directly after radical prostatectomy and from each specimen 6 punch biopsies were taken. Time-resolved fluorescence spectra were recorded for 4 different measurement points for each biopsy. The pathologist evaluated each measurement point separately. An algorithm was developed to determine a relevant parameter of the time dependent fluorescence data (fractal dimension DF ). The results of the finding and the DF -value were correlated for each point and then analysed with statistical methods. Results: A total of 1200 measurements points were analysed. The optimal algorithm and conditions for discrimination between malignant and non-malignant tissue areas were found. The correct classification could be stated in 93.4% of analysed points. The ROC-curve (AUC = 0.94) confirms the chosen statistical method as well as it informs about the specificity (0.94) and sensitivity (0.90). Conclusion: The new method seems to offer a very helpful diagnostic tool for pathologists as well as for surgery.

Chemically activated nanodiamonds for aluminum alloy corrosion protection and monitoring

In the present study, a smart coating for light metal alloys was developed and investigated. Chemically activated nanodiamonds (CANDiT) were electrophoretically deposited onto anodized aluminum alloy AA2024 substrates in order to increase corrosion resistance, enhance bonding properties and establish a means of corrosion monitoring based on the fluorescence behavior of the particles. In order to create stable aqueous CANDiT dispersions suitable for electrophoretic deposition, mechanical milling had to be implemented under specific chemical conditions. The influence of the CANDiT volume fraction and pH of the dispersion on the electrochemical properties of the coated samples was investigated. Linear voltammetry measurements reveal that the chemical characteristics of the CANDiT dispersion have a distinct influence on the quality of the coating. The fluorescence spectra as well as fluorescence excitation spectra of the samples show that corrosion can be easily detected by optical means. Furthermore, an optimization on the basis of smart - algorithms for the data processing of a surface analysis by the laser-speckle-method is presented.

Functionalized Nanodiamonds as Nanoagents in Materials and Life Sciences

Abstract Ultradisperse nanodiamonds can be implemented as nanoagents in materials and life sciences by chemical or biological activation. In this paper we show the potential of nanodiamonds for specific applications in the fields of corrosion resistance and cell biology. We demonstrate that nanodiamonds can be used to refine surfaces in order to improve corrosion resistance, to increase adhesion properties, or to establish an on-line surface analysis technique, e.g. for corrosion monitoring, based on their optical properties. We further applied ultradisperse nanodiamonds in cell biology. Our data show that nanodiamonds can be taken up by living cells via transfection in the presence of dendrimers. Upon functionalization with antibodies, nanodiamonds can be targeted to specific intracellular structures.

Smoothing of substrate roughness by carbon-based layers prepared by pulsed laser deposition (PLD)

In order to obtain high reflectance of EUV and X-ray multilayer mirrors, highly polished substrate surfaces with rms roughness σrms = 0,1-0.2 nm are necessary. However, the simultaneous achievement of low micro-roughness and precise surface figure is very challenging and often not accomplished. Therefore deposition techniques capable to deposit layers with smoothing properties are very desirable. One potential method that enables the formation of such layers is the pulsed laser deposition (PLD). This technique generates particles with high kinetic energies of up to several 100 eV. We investigated the deposition of carbon based smoothing layers by PLD on numerous substrates with roughness between σrms = 0.15 and 0.75 nm using different laser power densities and film thicknesses. Besides pure carbon layers we also used metal/carbon (metal = Ni, W, Pt) multilayers with respect to their capabilities to smooth surface roughness. As a general trend it turns out that a better smoothing can be obtained with higher laser power densities, whereby diamond-like carbon films are created. Furthermore, the intrinsic stress of the smoothing layers has been investigated. Due to the high kinetic energy of the impinging particles during the film growth, the layers show compressive stress. The degree of the stress depends on the concrete metal that is combined with carbon in the multilayer stack. Up to now the lowest compressive stress is obtained with Ni/C multilayers.

The influence of structural instabilities and non-linear electron-phonon coupling on the isotope effect

Abstract In the framework of a two-component Φ 4 -lattice model structural phase transitions are considered. It was found that both long-range ordered phases and glassy-like states can be described in this model. On the basis of the standard Eliashberg theory the phonon-driven superconducting transition of electrons in a single band is investigated. To do this, the electron-phonon coupling is taken linear and quadratic in the fluctuations of the lattice order parameters. The dependence of the superconducting transition temperature and the isotope effect on the defect concentration is discussed for various parameter sets. Different qualitative features are obtained. Tje La 2− x Sr x CuO 4 is taken as a reference system.

International Scientific Laboratory for Laser-Optical Diagnostics in Service for Nondestructive Materials Testing

Abstract The latest achievements developed by the ISL-LOD in the area of elaborating and application of novel optical methods for nondestructive testing and material characterization are discussed. A special attention is given to the application of quasi-nondiffracting Bessel light beams for: i) conical beam-based profilometry for characterization of cylindrical machinery parts; ii) Stokes polarimetry based on super-Gaussian and Bessel beams; iii) Bessel beam-based interferom-etry; iv); quasi-nondiffracting speckle-photometry for remote sensing. Also the description is given of a new thermo-optical method for measurement of thermal diffusion coefficient and hardness of metal and alloys. Finally, a novel method for surface state evaluation based on three dimensional scatterometry technique is described.

Materials characterization of micro-devices

During the design of ever smaller sized micro-systems, the question appears how much the properties of the materials used differ from those of bulk material and even to laterally extended thin films. The aim of this paper is to analyze mechanical behavior of micro-structured metallic systems like Cu- and Al- interconnections in microelectronic devices or metallic components in micro-opto-electro-mechanical systems (MOEMS). Using atomic force microscopy (AFM) several features like roughness, grain size and dimension accuracy of the materials could be measured for the initial state and in-situ during thermo-mechanical load. For that purpose, meander like line structures produced in CMOS technology as well as special structures fabricated by laterally resolved ion beam sputtering by a focused ion beam equipment (FIB) were used for bending tests. Additionally the elastic and plastic deformation of the lines can be assessed nondestructively by the change of the line resistance measured with high precision. The analysis of the experimental results reveals abnormal plastic-elastic mechanical properties of metallic systems of micro- and sub-micrometer dimension. Practical consequences are discussed concerning the reliability of metallic interconnects, the quality of micro-mirror materials as well as a new approach of micro-material tailoring by surface treatment.

On nonlinear electron-lattice interaction and anharmonicity in HTSC

A model of electron-phonon coupling quadratic in the lattice displacements is applied to the Cu-0 and Bi-O based superconductors. Tc, the isotope effect and the renormalization of phonon frequencies are discussed.