Premysl Fitl

Evaluation of the adhesion strength using digital microscope and international standards

The most frequently used method for scratch test in the international standards is progressive loading scratch test mode. Although the mentioned standards to measure practical adhesion of nano and micro thin films require optical microscope with magnifications between 100× and 500×, not only the optical microscopes, but even the international standards are not usually and largely used to study new biocompatible thin films. The authors designed a method and a custom-written program for the measurement and evaluation of scratches using digital microscope and digital microscope image analysis, which is based on the requirements of international standards for the determination of critical normal forces and capabilities of existing scratch testers. The proposed procedure and software were tested on the samples of TiN, Au, Pt and Pd biocompatible nano-thin layers. Delamination or loss of adhesion was observed in all cases, and two types of critical normal forces were determined. It was found that the calculated critical normal forces are largely similar in the three operations of the measurement of a sample. Thus, evaluation using critical scratch loads measured by three test operations seems to be sufficient. The new software and procedures allow us to evaluate the practical adhesions of a wide range of substrate and thin film materials, and gave us credible results.

Noise in quartz crystal microbalance

There are several mechanisms that are related to fluctuation phenomena in QCM. The aim of our research is oriented to study the sensitivity and influence of different kind of noises on sensor resolution. Our experiments are provided on sensor with sorption layer of polypyrrole which is suitable for detection of water vapor. Based on these experiments, we suppose that 1/f noise caused by quartz internal friction and adoption-desorption (generation-recombination) noise from analyzed gas create the main components of measured noise spectral density. The value of the adoption-desorption noise depends on the physical and chemical parameters of analyzed gas and it is proportional to gas density. Adsorption-desorption kinetics is described by Kolmogorov equation and compared with Wolkenstein and Langmuir equations.

Modification of detection process on ZnO sensors by ultraviolet radiation

The contribution deals with influence of radiation in the near UV region (λ = 396 nm) on detection properties of conductive type gas sensors. The ZnO active layers of the sensors were deposited on Alumina substrates by Pulsed Laser Deposition method. Resulting thickness of active layers was ∼ 450 nm. The dc-sensitivity was evaluated from resistance change under exposition of hydrogen and acetone and toluene vapours in synthetic air. The sensitivity to acetone was doubled using the UV radiation at 250°C.