Pavel Sťahel

Deposition of hard thin films from HMDSO in atmospheric pressure dielectric barrier discharge

An atmospheric pressure dielectric barrier discharge burning in nitrogen with a small admixture of hexamethyldisiloxane (HMDSO) was used for the deposition of thin organosilicon films. The thin films were deposited on glass, silicon and polycarbonate substrates, and the substrate temperature during the deposition process was increased up to values within the range 25 - 150 C in order to obtain hard SiOx-like thin films.

Deposition of Yarrowia lipolytica on plasma prepared teflonlike thin films

Abstract The adhesion of Yarrowia lipolytic a to teflonlike thin films deposited by plasma on polycarbonate substrates was investigated through a series of tests in order to develop a substrate for strong and selective adhesion of Yarrowia lipolytica cells. Teflonlike thin films were prepared using atmospheric pressure surface barrier discharge with mixtures of octafluorocyclobutane (C4F8) and nitrogen as plasma gas. A variety of plasma gas feedrates and different deposition times were studied. The films were characterised by Fourier transform infrared and contact angle measurements using the sessile drop technique. Total surface energy and its components were calculated using the acid base theory. Attachment of the yeast cells was assessed by optical and scanning electron microscopy. The optimal deposition conditions for cell adhesion were determined using standard adhesion tests.

Metastability of Phosphorus or Boron doped a-Si:H films

The effects of light-soaking on either phosphorus- or boron-doped a-Si:H films were studied as functions of the doping level and the temperature. In the case of boron-doped films, the most important effect is the improvement of the conductivity during light-soaking, which is related to the activation of boron. On the contrary, phosphorus-doped films present a remarkable stability, although lightly phosphorus-doped ones show a decrease of their conductivity by five orders of magnitude when light-soaking is performed below 40 °C. This effect is attributed to the formation of P-H complexes which are stable at low temperature only. Our results suggest that in both types of doped a-Si:H films the creation of metastable defects is a second order effect with respect to the activation or passivation of dopants, which results from their interaction with hydrogen.

Plasma Surface Treatment of Textile Fibres for Improvement of Car Tires

A new low-temperature plasma surface modification of advanced polyester tire cord at atmospheric pressure was tested. Plasma surface treatment was performed in the barrier discharge plasmas (BDPs, atmospheric pressure glow discharge (APG) and plasma of gliding are (Glid Arc). The surface properties were characterized by the electron spin resonance spectroscopy (ESR), measurements of the contact angle of various polar and non-polar liquids with polyester cords, H-test, peel test and partially by zeta potential measurements. Further tests have been performed at an industrial testingimpregnation line where the common technology was applied on both plasma treated and untreated fibres. The standard H-test and peel-tests were used to characterize the adhesion of the fibre to usual testingrubbers.

Defect states in the intrinsic layer of amorphous silicon solar cells studied by the constant-photocurrent method

Abstract The constant-photocurrent method (CPM), which has been widely used for the study of the defect density in the gap of hydrogenated amorphous silicon (a-Si: H) films, is applied to study the defect density in the intrinsic layer of a-Si: H-based solar cells. The analysis of the CPM-derived absorption spectrum in p-i-n devices indicates that reliable measurements can be performed under short-circuit or reverse-bias conditions. In these conditions the CPM measurement is limited by the transport of holes and therefore is a good indicator of the quality of the intrinsic layer. Moreover, we show that CPM is sensitive to that part of the i layer in which the Fermi level is around midgap. Comparison of CPM spectra in films and cells is used to determine the conditions under which the measurements in the solar cell are relative to the properties of the intrinsic layer or sensitive to interface effects. Deconvolution of the CPM spectrum according to a standard model of the defect density distribution in a-S...

Diffuse Coplanar Surface Barrier Discharge in Artificial Air:Statistical Behaviour of Microdischarges

Abstract Diffuse Coplanar Surface Barrier Discharge (DCSBD) is a novel type of atmospheric-pressure plasma source developed for high-speed large-area surface plasma treatments. The statistical behavior of microdischarges of DCSBD generated in artificial air atmosphere was studied using time-correlated optical and electrical measurements. Changes in behavior of microdischarges are shown for various electrode gap widths and input voltage amplitudes. They are discussed in the light of correlation of the number of microdischarges and the number of unique microdischarges’ paths per discharge event. The ‘memory effect’ was observed in the behavior of microdischarges and it manifests itself in a significant number of microdischarges reusing the path of microdischarges from previous half-period. Surprisingly this phenomenon was observed even for microdischarges of the same half-period of the discharge, where mechanisms other than charge deposition have to be involved. The phenomenon of discharge paths reuse is most pronounced for wide electrode Graphical Abstract

Deposition of teflon like coatings in surface barrier discharge

The plasma deposition at atmospheric pressure becomes a promising technology due to its economical and ecological advantages.The objective of the present work is to develop technique for deposition of thin films with desired surface energy, permeability and wear resistance on pulp board surface by means of discharge at atmospheric pressure.The deposition of thin films was carried out by surface discharge at atmospheric pressure. The films were deposited from the different mixtures of C4F8 with nitrogen. The properties of the thin film substrate systems were investigated by means of the contact angle measurement and industrial permeability tests. The mechanical properties were studied by means of the depth sensing indentation test. In the case of the mechanical tests glass plates were used as the substrate.

Activation of polyethylene and polypropylene in atmospheric pressure glow discharge

The atmospheric pressure glow discharge was used for activation of polymer materials. The discharge was generated between two plane metal electrodes covered by a glass dielectric barrier. The discharge was ignited in pure nitrogen or in mixtures of nitrogen with hydrogen or nitrogen with ammonia. Studied polymers were polyethylene and polypropylene. The surface energy of both activated and non-activated polymers was determined by means of contact angle measurements. The influence of treatment time on the surface free energy of polymers was studied.

Properties of atmospheric pressure plasma oxidized layers on silicon wafers

Abstract In this research a new process of plasma oxidation of crystalline silicon at room temperature is studied. The plasma oxidation was carried out using Diffuse Coplanar Surface Barrier Discharge (DCSBD) operating in ambient air and oxygen at atmospheric pressure. The influence of exposition time, plasma parameters and crystallographic orientation of silicon on oxidized layers and their dielectric properties were investigated. Thickness, structure and morphology of these layers were studied by ellipsometry, infrared absorption spectroscopy and scanning electron microscopy. During the treatment time, from 1 to 30 minutes, oxidized layers were obtained with thickness from 1 to 10 nm. Their roughness depends on the crystallographic orientation of silicon surface and exposure time. Electrical parameters of the prepared layers indicate the presence of an intermediate layer between silicon substrate and the oxidized layer. Graphical Abstract

INFLUENCE OF SUBSTRATE THICKNESS ON DIFFUSE COPLANAR SURFACE BARRIER DISCHARGE PROPERTIES

In presented work the influence of dielectric barrier thickness on the parameters of Diffuse Coplanar Surface Barrier Discharge was investigated. The discharge was operated at atmospheric pressure laboratory air. The electrical parameters of the system were studied both experimentally and using numerical simulations. The discharge pattern was studied as well using intensified CCD camera.