Zygmunt Rymuza

Thin Films Deposition from Hexamethyldisiloxane and Hexamethyldisilazane under Dielectric-Barrier Discharge (DBD) Conditions

Hexamethyldisiloxane (HMDSO) and hexamethyldisilazane (HMDSN) were used as organosilicon reagents for PE-CVD of thin films under filamentary barrier-discharge conditions at atmospheric pressure. Efficient discharges were obtained in the region of moderate frequencies (5 kHz). The following mixtures of organosilicon reagents with carrier gas and oxidants or ammonia were investigated: HMDSO+Ar, HMDSO+N2, HMDSO+O2+Ar, HMDSO+N2O+Ar, and HMDSN+NH3+N2. Under such conditions HMDSO was converted to produce thin films (10–1000 nm) of silicon oxide, generally containing admixtures of residual “organic” content (Si—CHn and Si—H groups). The films deposited from HMDSN+NH3+N2 contained silicon, nitrogen and oxygen.

Energy concept of the coefficient of friction

Abstract Friction is a complex energy process. The traditional ‘laws’ of friction cannot reflect its energetic nature and interdependent phenomena comprising the friction process. The friction force is one of the responses of a tribosystem on the external excitation/initiation of the dissipative flows (degradation of macromechanical energy-entropy production). The mechanical and thermal energy dissipation is accompanied by the production of dissipative new structures playing an active role in the friction process. The energetic concept of a parameter describing friction under dynamic or static conditions is proposed by introducing a new coefficient of friction losses (CFL). Some experimental data of traditional friction coefficient and CFL are presented and discussed. The general background/outlines of friction are given with conclusions and suggestions for further studies.

Static friction and adhesion in polymer-polymer microbearings

Abstract The starting process, i.e., transition from static to kinetic friction in polymer–polymer microbearings, was studied. Load, sliding speed and time of contact before starting were varied during the experiments. AFM studies of rubbing surfaces were performed and the real surfaces were brought into contact in computer simulations to evaluate the adhesive and frictional interactions. Correlation between observed static friction force, adhesive force and calculated friction force characteristics vs. time was found.

Experimental investigation of the contact mechanics of rough fractal surfaces

The nonstationary character of roughness is a widely recognized property of surface morphology and suggests modeling several solid surfaces by fractal geometry. In the field of contact mechanics, this demands novel investigations attempting to clarify the role of multiscale roughness during physical contact. Here we review the results we recently obtained in the characterization of the contact mechanics of fractal surfaces by depth-sensing indentation. One class of experiments was conducted on organic thin films, load-displacement curves being acquired by atomic force microscopy using custom-designed tips. Another class of experiments focused on well-defined crystalline and mechanically polished ceramic substrates probed by a traditional nanoindenter. We observed the first-loading cycle to be considerably affected by surface roughness. Plastic failure was found to dominate incipient contact while contact stiffness increased on decreasing fractal dimension and roughness. Our findings suggest fractal parameters to drive contact mechanics whenever the penetration depth is kept below the interface width.

The role of interfacial energy in the wear of polymeric journal bearings

Abstract Experimental and theoretical relationships between the adhesional energy and the wear rate of a polymer, in the form of a miniature journal bearing for a steel shaft, are presented. Formulae are derived that can be used to predict the wear rate of a polymeric material in such bearings.

Friction and adhesion of carbon nanotube brushes

Abstract Brushes made of carbon nanotubes have been tested by use of atomic force microscopy. Two different cantilevers were used: a silicon cantilever with a spherical tip made of SiO2 and a beryllium bronze cantilever with a tip made of steel. Sliding in the lateral direction was studied to measure the friction coefficient and to examine nanotribological properties. Nanoindentation was used to measure the pull-off force. Finally, a model of adhesion was created and experimental results were compared with it.

Testing miniature, in particular polymer-polymer, journal bearings

Abstract A new system for testing miniature, in particular polymer-polymer, journal bearings, is described. Original methods for measuring friction torque and wear rate in such bearings are discussed. The result of preliminary studies of miniature polymer-polymer journal bearings are given.

Nanomechanical studies of MEMS structures

Abstract The stiffness is a fundamental qualifier of elastically deformable mechanical microcomponents and micromechanisms whose static, modal or dynamic responses need to be evaluated. This paper presents the results of theoretical studies of microcantilevers and microbridges and also a method for experimental stiffness testing using atomic force microscopy. Castiglianos displacement theorem is used herein to derive the stiffness equations. The results of the theoretical and experimental studies are compared and discussed.

Influence of substrate on mechanical properties of TiN/NbN superlattices

Abstract The substrate material and number of periods both significantly impact the hardness and Young’s modulus of TiN/NbN superlattices with a period ‘Λ’ of 4.68 nm. The change of hardness and Young’s modulus as a function of depth as well as distribution of these properties on small areas were measured. The effect of loading rate on the results of nanomechanical measurements was also proved. The structure of the material is very stable and practically no rheological phenomena were observed. The distribution of the hardness and Young’s modulus on the small areas testifies to the high uniformity of the films along the surface.

Development of an experimental technique for testing rheological properties of ultrathin polymer films used in nanoimprint lithography

A new method for the measurement of rheological properties (complex viscosity, viscosity and elasticity) of thin polymeric films is presented. The probe, which is placed on the end of an arm of a mini tuning fork, is caused to oscillate and then is put into poly(methyl methacrylate) films, whose thickness ranges from 30 nm to 1080 nm. All measured properties depend on temperature, thickness of the films, indentation depth and the molecular weight of PMMA. Complex viscosity, viscosity and elasticity are found to be lower at higher temperatures and higher with greater molecular weight. They are also lower for thicker films. The results gained from this experiment may be useful in the development of nanoimprint lithography and many other branches of nanotechnology. Furthermore, the method allows for the measurement of the rheological properties of many different thin films (nanoimprint polymers, oils, lubricants) at different temperatures.