The measurement of viscosity of ultrathin polymer films

Viscosity is a very important property of thin polymer films used in modern microelectronic technology i.e. in nanoimprint lithography.Hence, in this work we present a method for viscosity of ultrathin polymer films determination. The viscosity is evaluated from the response of the oscillating piezoelectric cantilever at the end of which an indentation probe is mounted (Fig. 1a). When a polymer film is indented, the resonant frequency of the oscillations is changed and the parameters of used model (i.e. Maxwell model) can be identified. The frequency of the oscillations is equal to tens of kilohertz therefore the influence of extremely high deformation velocities can be investigated by means of this method. It is also possible to conduct the experiments in elevated temperature (up to 150oC). The oscillations direction can be parallel as well as perpendicular to the film’s surface. The investigated films were made of PMMA. Their thickness ranges from a few nanometers up to 1 micrometer. The results were compared with other methods of the viscosity determination: the investigation of the creep response during nanoindentation, sinus mode nanoindentation and atomic force microscope based technique

Influence of Alkali Ions on Tribological Properties of Silicon Surface

Tribological properties of surfaces (friction, adhesion and wear) provide challenging limitations to the design of reliable machines on the micro- and nanometer scale as the surface to volume area increases and volume, mass and inertia of the mobile parts decrease. This study reports on the reduction in the friction force of silicon surfaces after the alkali metal ion exposure in the form of aqueous solutions. A scanning force microscope equipped with a liquid cell was used to investigate the friction force and the pull-off force of a flat silicon surface immersed in water and in different alkali metal chlorides solutions: LiCl, NaCl and CsCl. The concentration ranged from 0.1 up to 1000 µmol/l. The changes in the free surface energy of the initial surface and of the modified surfaces after drying were determined from contact angle measurements and from the acid–base adhesion theory. In both cases, in the liquid environment and after drying of the exposed silicon substrates in air, the friction force is reduced by approximately 50 %. Our results provide new, fundamental insight into the exchange of surface termination layers in particular for tribology. Also it is suggested to use the procedure as a low-cost alternative to improve the tribological properties of the silicon surface in particular in applications where lubricating fluids are not appropriate, e.g., in nanomachines and devices

Lateral Force Calibration Method Used for Calibration of Atomic Force Microscope, Journal of Telecommunications and Information Technology, 2009, nr 4

Modern heterogeneous micro- and nanostructures usually integrate modules fabricated using various materials and technologies. Moreover, it has to be emphasized that the macro and micro nanoscale material parameters are not the same. For this reason it has become crucial to identify the nanomechanical properties of the materials commonly used in micro- and nanostructure technology. One of such tests is a nanowear test performed using the atomic force microscope (AFM). However, to obtain quantitative measurement results a precision calibration step is necessary. In this paper a novel approach to calibration of lateral force acting on the tip of an AFM cantilever is discussed. Presented method is based on application of known lateral force directly on the tip using a special test structure. Such an approach allows for measurements of nanowear parameters (force, displacement) with the uncertainty better than ±3%. The calibration structure designed specifically for this calibration method is also presented

Impulse talk : ecotribology – development, prospects and challenges

Godkänd; 2013; 20140505 (brap)</p

Impulse talk : ecotribology – development, prospects and challenges

Godkänd; 2013; 20140505 (brap)</p