M. Šícha

Barrier-torch discharge plasma source for surface treatment technology at atmospheric pressure

The description and investigation of a new atmospheric plasma source for the treatment and coatings of surfaces are presented in this paper. This new system is a modification of a well-known atmospheric torch discharge stabilized by a flowing channel of the working gas through an RF powered nozzle. The new version of this source prevents the transition to the regime with hot electrodes. This modification is suitable for surface and coatings applications of such substrates sensitive to overheating causing undesirable phase transition or melting. The new source called in our paper as an RF barrier-torch atmospheric discharge employs dielectrically coated nozzles instead of bare metallic ones. In that case, the plasma jet has quite different properties, as it is clear from presented experiments. The new version allowed excitation of the atmospheric plasma channel interacting with the substrate independently on the conductivity of the substrate. Simultaneously it is possible to hold the substrate temperature under atmospheric jet interaction below the limit point of aluminium melting or below an even lower limit of 80°C in a pulse-modulated mode. Extension to the multi-nozzle barrier-torch system was attained with the application of nine quartz nozzles. This multi-plasma jet excitation and its interaction was demonstrated with the substrate made of either quartz or aluminium plate, both possibly with non-flat shape. Emission spectroscopy and RF voltage and current amplitude measurements were employed in order to characterize the RF barrier-torch discharge.

Germanium nitride layers prepared by supersonic r.f. plasma jet

Abstract Rutherford backscattering spectroscopy (RBS) and X-ray photoelectron spectroscopy (XPS) have been used to characterize GexNy films grown on Si substrates. The films were deposited in a plasma chemical reactor by a radio frequency (r.f.)-generated supersonic plasma jet. The Ge nozzle of the r.f. electrode was reactively sputtered in the plasma jet generated in the nitrogen and the germanium nitride films were created in the reactor. The RBS method showed that the ratio Ge:N in the layer was close to the expected stoichiometric ratio 3:4 (for example, 0.73, which is within experimental error) when traces of oxygen were suppressed. The chemical bonding state of GeN, as found by XPS analysis, showed that, close to the thin film surface, the Ge:N ratio was also near 3:4. The impurities present, although in small amount, were preferentially bonded into the film.

Investigation of RF and DC plasma jet system during deposition of highly oriented ZnO thin films

Abstract RF and DC plasma jet sputtering systems were investigated as sources for deposition of ZnO thin films. Deposited zone films have a strong orientation of hexagonal crystallites with the ‘ c ’ axis perpendicular to the substrate surface. Temperature of the substrate did not exceed 150 °C during the deposition. Langmuir probe measurement performed at the substrate revealed two groups of electrons with different temperatures in the DC plasma jet. A single group of electrons was found in the RF plasma jet system. Electron concentration in the RF jet was found to be about n eRF ≈5×10 9 –10 10 cm −3 with temperature T eRF ≈2.5–3.5 eV. In the DC plasma jet, concentration of cold electrons was usually n ec ≈10 9 cm −3 with temperature T ec ≈0.5 eV and concentration of hot electrons was n eh ≈10 8 cm −3 with temperature T eh ≈2–3.5 eV. Photographs also confirmed that the plasma density is higher in the position of the substrate in the RF jet than in the DC jet. Other obtained macroscopic parameters as plasma potential and floating potential relative to the grounded reactor are presented.

The high pressure torch discharge plasma source

We present a plasma source which works on the principle of the arc torch discharge. The powered electrode of the arc torch discharge was made from a thin pipe that simultaneously acts as the nozzle through which the working gas flows to the discharge region. The flow of the working gas stabilizes the arc torch discharge and a well defined plasma channel is created. The advantage of this system is that it is able to work at high pressure of working gas up to atmospheric pressure inside the plasma-chemical reactor and also in free space.

Low-pressure RF multi-plasma-jet system for deposition of alloy and composite thin films

A plasma-chemical reactor with a multi-plasma-jet RF hollow-cathode system has been developed for the deposition of alloy and composite thin films. Two primary plasma-jet channels and one secondary plasma channel were created in the volume of the reactor. High-density plasma flowing in these plasma-jet channels is generated inside the nozzles. These work simultaneously as RF hollow cathodes. An RF hollow cathode discharge is generated in these nozzles and is subsequently blown out of the reactor, creating flowing plasma jets. These jets were used for the deposition of SiGe and ZrCN thin films as an example of the deposition of alloy and composite thin films with this system. Co-sputtering or reactive co-sputtering of the nozzle material using high-density RF hollow-cathode plasma was applied for the deposition process. Control of the composition of the thin films was accomplished by setting the relative distance between the nozzle outlets without changing the plasma density inside the RF hollow cathodes. The composition of films was investigated with an electron microprobe system equipped with an X-ray microanalyser. This apparatus allowed quantitative analysis of the films. The stoichiometric homogeneity of the films was studied with this technique. Optical emission spectroscopy was used to investigate the secondary plasma-jet channel.

Studium der Stationären und Laufenden Schichtung in der Entladung in Neon Mit Hilfe eines Lokalen Hochfrequenzfeldes

ZusammenfassungEs wurde ein Verfahren zur Erregung von stationären Schichten, der Schichtungswelle und der laufenden Schichten in der Gleichstromentladung ausgearbeitet, das auf der Einwirkung eines Hochfrequenzfeldes auf einen kurzen Abschnitt der positiven Säule beruht. Dieses Verfahren wurde zum Studium aller drei angeführten Schichtungsarten in Neon benützt, insbesondere jedoch zum Studium des Zusammenhanges zwischen den laufenden und den stationären Schichten.Bei stationären Schichten wurden zweifache Strukturen festgestellt und es wurde deren Abhängigkeit vom Entladungsstrom und von der Größe des erregenden Hochfrequenzfeldes verfolgt.Bei der Schichtungswelle wurde die Stelle deren Entstehung ermittelt und es wurde nachgewiesen, daß das Hochfrequenzfeld diese Welle lokal an der Stelle dessen Einwirkung auf die positive Säule hervorruft.Bei den laufenden Schichten wurde deren Resonanzfrequenz in Abhängigkeit vom Entladungsstrom und die Abhängigkeit der Wellenlänge der Schichten von der Frequenz untersucht.Es wurde festgestellt, daß der extrapolierte Wert der Wellenlänge für die Nullfrequenz erheblich niedriger ist als die Länge der stationären Schichten. Weiter wurde eine Übereinstimmung der Frequenz der laufenden Schichten in der Schichtungswelle mit der Resonanzfrequenz der künstlich hervorgerufenen laufenden Schichten festgestellt.AbstractБыл разработан метод возбуждения стацион арных слоев, волны расслоения и по движных слоев в разряде при по стоянном токе, основа нный на воздействии высокоч астотного поля на короткий отрезок п оложительного столб а. Этот метод применялся для иссле дования всех трех упомянутых типов расслоения в не оне, особенно для исследо вания взаимосвязи между подвижными и ст ационарными слоями.У стационарных слоев была найдена двойная структура и была исследована её з ависимость от тока разрядом и от в еличины возбуждающе го высокочастотного по ля.У волны расслоения ис следовалось место ее возникновения и было доказано, что высокоч астотное поле возбуждает эту в олну локально в месте своего воздействия на полож ительный столбец.У подвижных слоев исс ледовалась их резона нсная частота в зависимост и от тока разрядом и зависимость длины в олны от частоты.Было установлено, что экстраполированное значение длины волны для нулев ой частоты получается намного м еньше чем длина волны стационарных слоев. Д алее, было установлен о согласие между часто той подвижных слоев в волне расслоения и резонан сной частотой искусс твенно возбуждаемых подвиж ных слоев.

CNx coatings deposited by pulsed RF supersonic plasma jet: hardness, nitrogenation and optical properties

Abstract A low pressure pulsed RF supersonic plasma jet system (RPJ) has been used for deposition of CN x thin films. The aim of the CN x thin films deposition was an application for tribological coatings. Chemical composition, mechanical and optical properties of deposited CN x films have been measured. The obtained parameters were found to be similar to those of CN x films prepared by DC magnetron sputtering. The deposition rate for the CN x films prepared in RPJ reactor was of approximately 2 μm/h. During the deposition process, the substrate temperature did not exceed 250°C, as required for certain kinds of machine tribological coatings. A strong correlation between DC bias magnitude, nitrogen concentration and mechanical properties was found. The value of the substrate bias V DC =−100 V was found to be optimal for deposition of hard CN x films with maximum microhardness H =22 GPa. The films with the highest microhardness had the lowest atomic concentration of nitrogen. Analogous correlation has been found in ‘Diamond Relat. Mater. 7 (1998) 417’, although the deposition method and conditions were quite different. The chemically active plasma has been investigated in the RF supersonic plasma jet channel during the deposition process by means of ‘in situ’ emission spectroscopy. The mechanism of CN x formation has been studied as well.

The connection between low-gradient form of the positive column in oxygen and moving striations

The method of sliding photomultipliers was used to study the connection between two forms of the positive column in oxygen — the so-called low-gradientT-form and the highgradientH-form — and the presence of moving striations in the positive column. It was shown that in theT-form of a positive column striations are always present which move from the cathode to anode with a velocity of several thousand metres/sec. The highgradient form of theH-positive column, on the other hand, is not striated. The non-single-valuedness of the value of the longitudinal electric field in a discharge in oxygen is thus explained by the presence or absence of phenomena of a time variable character.AbstractМетодом подвижных φо тоумножителей иссле дована связь двух φор м положительного столба в кислороде — т ак называемых „низко градиентной“ „Т”-φор мы и „высокоградиент ной“ „ H ”-φормы — с присутстви ем движущихся слоев в положительном столбе. Доказано, что в „Т“-φорме положитель ного столба всегда пр исутствуют слои, которые движутс я от катода к аноду со с коростью нескольких тысяч метров/сек. Высокоградиентная φ орма „Н” положительн ого столба, наоборот, н е расслоена. Неоднозн ачность значения продольног о электрического пол я в разряде в кислород е, следовательно, объяс няется присутствием или отсутствием явле ний, изменяющихся во времени.

Влияние сильного выс окочастотного поля на расслоение положи тельного столба постоянного тлеющег о разряда@@@The influence of a strong high-frequency field on the stratification of the positive column of a D-C glow discharge

AbstractВ статъе эксперимент алъно исследуется за тухание движущихся с лоев в постоянном тлеющем разряде под в лиянием силъного выс окочастомного поля. Р езулътаты измерений находятся в согласии с представлениями о в озникновении и механ изме распространени я движущихся слоев. Кро ме процесса затухани я, в работе описываетс я стационарное рассл оение положителъного смол ба постоянного разря да под влиянием налож ения въсокочацтотно го разряда.AbstractAn experimental study is made of the damping of moving striations in a d-c glow discharge by a strong high-frequency field. The results of measurement are in agreement with existing conceptions on the production and mechanism of propagation of moving striations. Apart from the process of damping the paper also describes the standing stratification of the positive column of a d-c discharge as a result of a superposed high-frequency discharge.An experimental study is made of the damping of moving striations in a d- c glow discharge by a strong high-frequency field. The results of measurement are in agreement wtth existing conceptions on the production and mechanism of propagation of moving striations. Apart from the process of damping the paper also describes the standing stratification of the positive column of a d-c discharge as a result of a superposed high-frequency discharge. (auth)

Probe diagnostics of the RF barrier-torch discharge at atmospheric pressure

Abstract Accurate control of plasma microparameters at the position of the substrate is crucial factor in applications of the barrier-torch plasma source for technological purposes. We present measurements of the electron temperature T e in the RF barrier-torch discharge by means of the planar RF-compensated Langmuir probe. The probe was mounted at the substrate position. The error caused by collisions of charged particles with neutrals in the space-charge sheath around the probe (collision probe working regime) at atmospheric pressure is discussed. In order to minimize this error the single probe technique was used to acquire the probe data, which were then recalculated to get the double probe characteristic. From this the electron temperature T e has been obtained in usual manner. The T e was measured at the position of the substrate in the single- and multi-torch barrier atmospheric plasma-jet systems. Using He as a working gas T e was found to be in the interval T e =2.7–6 eV depending on the applied RF power and system configuration. The neutral gas temperature has been measured by optical diagnostics and found to be 400–800 K. The plasma of the RF barrier-torch discharge is therefore strongly non-isothermal even at such high operation pressure.