WO2014094695A1

WO2014094695A1 - Method of generating plasma at atmospheric pressure in a slot jet and device for performance the method

Info

Publication number: WO2014094695A1
Application number: PCT/CZ2013/000167
Authority: WO
Inventors: Jan ZAHRADNIK; Milos Klima; Michal MAKOVEC; Maja GASIC
Original assignee: Masarikova Univerzita
Priority date: 2012-12-19
Filing date: 2013-12-16
Publication date: 2014-06-26
Also published as: WO2014094695A4; CZ2012935A3

Abstract

The invention relates to a method of generating plasma at atmospheric pressure in a slot jet, in which a stream of working gas flowing through the slot jet is acted upon by an electromagnetic field. In the slot jet a high-frequency electromagnetic field created and formed by at least one high-voltage electrode (7) dielectrically separated from the cavity of the slot (3) and by at least one grounded electrode (8) acts upon the flowing atomic working gas, by which means high-pressure high-frequency plasma is created at a high or low electric potential, by which as a feedback loop the original high-frequency electromagnetic field changes and the high-pressure high-frequency plasma is statistically distributed along the entire length of the slot (3) and is blown out of the entire length of the slot (3) by the stream of the atomic working gas. The invention also relates to a device for generating plasma at atmospheric pressure comprising at least one hollow body (1) provided with at least one inlet (2) of working gas and further provided with at least one slot (3) which forms the outlet orifice of the plasma, at least one electrode being aligned with the hollow body (1). The slot (3) is formed by a gap between a pair of dielectric plates (9), whereby aligned with the slot (3) is at least one high- voltage high-frequency electrode (7), separated from the cavity of the slot (3) by the dialectric plate (9), and at least one grounded electrode (8).

Description

Method of generating plasma at atmospheric pressure in a slot jet and device for performance the method

Technical field The invention relates to a method of generating plasma at atmospheric pressure in a slot jet, in which a stream of working gas flowing through the slot jet is acted upon by an electromagnetic field.

The invention relates to a device for generating plasma at atmospheric pressure comprising at least one hollow body provided with at least one inlet of working gas and is further provided with at least one slot which forms the outlet orifice of the plasma, whereby at least one electrode is aligned with the hollow body.

Background art CZ 286 310 (analogically US 6 525 481 and EP 1 077 021) discloses a method of creating a physically and chemically active environment by means of a plasma jet of a cylindrical configuration with a circular outlet orifice of plasma, the plasma jet being based on the principle of a hollow metal cathode of cylindrical geometry or a dielectric capillary enlaced by a hollow cathode. CZ 286 310 also describes various arrangements for utilization of a cylindrical plasma jet, including a combination of more such cylindrical plasma jets in multijet systems. Within these multijet systems, however, individual streams of the generated plasma are separated from each other relatively rigorously and are independent of each other, though there is known occurrence of collisions of two and more plasma streams from individual cylindrical plasma jets.

From the patent application EP 07466017 there are known various arrangements for utilization of plasma jets of cylindrical geometry with a dielectric capillary, i.e. the arrangement according to CZ 286 310 for simultaneous treatment of a large substrate surface, when multijet systems comprising jets arranged in a linear or matrix system are created according to CZ 286 310. The arrangement of individual plasma jets, used especially for strengthening reaction processes, is also known from CZ 286 310.

Typical working conditions of a capillary plasma jet according to CZ 286 310 having an inner diameter of 2.5 mm are as follows: - power - 100 - 150 W at a frequency of 13.56 MHz and a voltage of 2 -

3 kV

- argon gas flow - 1 - 5 l/min

- precursors - can be delivered directly into the plasma inside the jet and/or into part of the plasma outside the jet - deposition velocity - usually ranging from hundreds of nm/s to 1 - 2 pm/s.

Typical working conditions of a multijet system comprising 20 jets according to CZ 286 310 arranged in two rows behind each other, each row having a width of 10 cm and comprising 10 jets CZ 286 310 with an inner ^' capillary diameter of 2.5 mm, are as follows:

- power - 200 - 650 W at a frequency of 13.56 MHz and a voltage of 2 - 4 kV

- argon gas flow - 50 l/min

- precursors - can only be delivered directly into the plasma inside the jet - deposition velocity - usually hundreds of nm/s.

In some applications for the treatment of large surface areas it has been found out that these known arrangements have disadvantages, including a relatively high incoherence of the plasma discharge on the areas of transition between individual jets and also the fact that demanding technology is necessary for operating and maintaining the whole system of otherwise more or less autonomous plasma jets additionally arranged in a holder into a linear or matrix multijet system.

Unlike the above method of generating high-pressure discharge, products of the series "ULS" and "ULD" made by the company AcXys Technologies, for example, are based on the principle of bipolar discharge inside a jet (see Fig.O), the discharge being blown out of the inner space of the jet by a very large flow of nitrogen. After that, outside the jet, there is only a afterglow discharge, which comprises mostly only radicals and excited molecules which subsequently act upon the surface of the treated materials. Some devices (local) are intended for application of thin layers and in those cases a precursor is only added into the stream of afterglow plasma outside the jet. For the products of "ULS" series the deposition conditions of SiO₂ layers are as follows:

- consumption of N₂ - 70 - 150 l/min per one jet 7 mm long

- VN linear source - 3kV, 100 kHz, 1000W

- precursor consumption (hexamethyldisilane - HMDSO) 0.2 - 0.5 ml/min

- deposition velocity 20 nm/s

- substrate is preheated to 50 - 550 °C.

In the case of "ULD"series it is possible to generate a discharge (plasma) in slots having a length of 6 to 50 cm. The required flow of the working gas N2 depends on the length of the slot, where, for example, for a slot of 60 mm the flow rate of the working gas nitrogen is 120 l/min, for a slot of 120 mm the flow rate of working gas N₂ is 250 l/min, for a slot of 250 mm the flow rate of working gas N₂ is 250 l/min, for a slot of 380 mm the flow of working gas N₂ 380 l/min a for a slot of 500 mm the flow rate of working gas N₂ is 500 l/min. Generally, nitrogen or compressed air is used as the working gas.

The disadvantage of this method of generating plasma is the necessity to use large flows of working gas, so that the discharge could be blown out of the jet, since actively generated discharge is only formed inside the jet. Another - drawback is the fact that air or nitrogen are used as as working gas. These are molecular gases and therefore generating a discharge is generally more difficult than in the case of atomic gases, such as argon. Moreover, the discharge generated with the aid of molecular gases has typically a different behaviour as well as different properties in comparison with the discharge generated with the aid of atomic gases, for example a discharge generated by means of air or nitrogen is a lot warmer, less electrically conductive and also less non- isothermal than a discharge generated by means of argon. Another example of a jet plasma device is the system Atomflo™ 400L of the company Surfx Technologies LLC, USA, which is a system for generating linear plasma having a frequency of 13.56 MHz, whereby the length of the slot is 12.5 mm, 25 mm or 50 mm. The device is suitable for the treatment of flat surfaces, the working medium being a mixture of helium and oxygen. The power of the source is 60 - 150 W, the length of the slot being 25 mm, or, as the case may be, the power of the source is 120 - 200 W, the length of the slot being 50 mm. The flow of helium is 15 l/min, the length of the slot being 25 mm, or 30 l/min for a slot 50 mm long. The flow of oxygen is 0 - 1.5 l/min. The details of the principle of generating a discharge are not known to us, nevertheless the disadvantages of this solution include the necessity to use expensive helium as well as only a limited length of the slot caused especially by the requirement of maintaining sufficient homogeneity of the plasma along the entire length of the slot.

Other types of slot plasma jets (e.g. product of the company SOFTAL

Corona & Plasma GmbH, DE - Linear Plasma) are based on a corona discharge principle using a high voltage in the order of at least 10 kV, a frequency of up to 100 kHz and a very low flow density. These types of devices display a low reactability and efficiency of the generated discharge, caused by a low density of the absorption performance per unit volume of the generated plasma, but the slot may have a length in the order of tens of centimeters to a few metres.

As far as we know on the basis of the current data, all these plasma slot jets for generating plasma use a HV electrode, which is located inside the cavity of the slot. Thus primarily only plasma having a high electric potential is generated, but the potential is subsequently lost upon the contact with the large surface of the grounded electrode, on which the discharge closes. The plasma is outside the jet only decaying (i.e. it is not actively generated by an electromagnetic field, an electric current does not pass through it, it contains only a small concentration of charged particles, but it contains radicals and metastable particles formed in the plasma, the radicals and metastable particles carrying the reaction energy from the plasma to the treated material surface), whereby the plasma being blown out of the slot is secured only at very large flows of the working gas.

The aim of the invention is to eliminate or at least reduce the disadvantages of the background art, especially with regard to a possibility of the treatment of large surface areas by means of a single device with a high efficiency and plasma homogeneity which would also provide a possibility of effective coating of the surface area.

Principle of invention The goal of the invention is achieved by a method of generating plasma at atmospheric pressure in a slot jet, whose principle consists in that in the slot jet a high-frequency electromagnetic field, which is created and formed by at least one high-voltage electrode dielectrically separated from the slot and by at least one grounded electrode, acts upon a flowing atomic working gas, by which means high-pressure high-frequency plasma is generated at a high or low electric potential, by which means the original high-frequency electromagnetic field changes as a feedback loop, the high-pressure plasma is statistically distributed along the entire length of the slot and is blown out of the slot by a stream of atomic working gas. The principle of the device for generating plasma at atmospheric pressure in a slot jet consists in that the slot is formed by a gap between a pair of dielectric plates, whereby at least one high-voltage high-frequency electrode, separated from the slot by a dielectric plate, and at least one grounded electrode are aligned with the slot. The invention enables to generate highly reactive and homogeneous plasma at atmospheric pressure without difficulty, the length of the plasma ranging from tens of cm to 1 m or more, and therefore it lends itself relatively easily to industrial applications for surface treatment of large surface areas of various materials, which is connected to a high variability of the invention which is made possible by the variability of arrangements of electrodes as well as the geometry of the discharge space itself. In addition, the invention enables to utilize without difficulty applications of aerosol dosing of suitable precursors for creating appropriate functional surface coatings, using the same geometry of the slot jet arrangement or of the slot jet system arrangement. Furthermore, the invention enables to achieve a velocity of creating compact homogeneous coatings in the order of hundreds of nm/s to a few μιη/s, which is an unrivalled velocity in relation to the existing plasma technologies using non-isothermal, „cool" plasma, which are in comparison to the possibilities according to the

- present invention by two orders lower (deposition velocities of low-pressure plasma range in the order of tenths of nm/s, in the case of atmospheric types of discharge it is usually a maximum of a few nm/s). The properties of coatings created using this invention are comparable to or even better than the coatings created by using low-pressure plasma, especially with respect to homogeneity, compactness and fineness of the nanostructure of the surface finish, that is to say the resulting products are high-quality, thin layers. Description of drawings

The background art and the invention are schematically represented in the drawing, where Fig.O shows an arrangement of the device of AcXys Technologies, series "ULS" and "ULD" according to background art, Fig. 1

- shows a front view of the device for generating high-pressure plasma according to the invention, Fig. 2 represents a cross section of the plane A-A from Fig. 1 ,

Fig. 2a shows a photo of a microchannel discharge according to the invention, Fig. 2b shows a photo of a afterglow discharge according to the invention, Fig. 2c shows a photo of a glow discharge generated from a discharge having a low electric potential according to the invention, Fig. 3 is an example of selected variants of geometrical solution to the cavity of the slot jet according to the invention and combining several slot jets according to the invention, including combinations with a jet for dosing precursors, especially of aerosol type, Fig. 4 is an example of selected alternatives of mutual geometric arrangement of electrodes for the variants of embodiments from Fig. 3, i.e. selected examples consisting of various combinations of a high-frequency high- voltage electrode and a grounded electrode in relation to the dielectric wall and the slot jet and in

- relation to combining slot jets according to the invention, including combinations with a jet for dosing precursors, Fig. 5 is a detail of Fig. 4d, Fig. 6 is an example of utilization of slot plasma -jets with aerosol precursors according to the invention for the application of thin protective layers.

Examples of embodoment The invention is based on generating high-frequency discharge at atmospheric pressure inside a slot jet, through which flows atomic gas argon - either pure or enriched by at least one admixture and/or at least one precursor, using different types of geometry of the slot jet as well as various arrangements of at least one HVHF (high-voltage and high-frequency) electrode and at least one grounded electrode. The HVHF electrode or electrodes and the grounded electrode or electrodes determine the elementary behaviour of the discharge and its properties.

The very principle of the initialization and the subsequent generating of a discharge inside a slot jet according to the invention is based on making use of the feedback behaviour of plasma after the occurrence of a primary discharge, which is achieved by means of the pre-ionization of the environment on the outlet of the slot jet or by the concentration of space electric charge by a high density of electromagnetic energy in proximity of the electrodes, with the aid of the statistic distribution of the space electric charge and electromagnetic field in the hollow space of the slot, which is influenced as a feedback loop by the discharge itself, since the basic characteristic of the plasma behaviour is a "peculiar" collective behaviour of the charged particles consisting creating their own electromagnetic field, which influences both the charged particles in the plasma and the outer electromagnetic field, which generates plasma in this particular case. The consequence of the facts described above is the spreading of the primary local discharge from the place of its formation in the limited area of the length of the slot to the whole length of the slot, which then may be as many as several tens of centimetres long, depending on the delivered power and other conditions. The discharge, created in this manner along the whole length of the slot in the order of tens of centimetres, is then maintained in accordance with a particular arrangement of the HVHF and the grounded electrodes relatively homogeneously, or in the form of microchannels (see Fig. 2a), or completely homogeneously, when it has a character of afterglow discharge (Fig. 2b) or of a glow discharge actively generated in the outer environment by an auxiliary outer electrode at a floating or ground potential (Fig. 2c) .

Subsequently, the discharge is carried from the slot to the outer environment by a stream of argon gas and outside the slot it either spontaneously flickers, or it is actively generated outside the jet as well, whereby it depends on the arrangement of the HVHF and the grounded electrodes whether the discharge outside the slot flickers, or whether it is there, too, actively generated.

Thus, it is possible to achieve either a discharge consisting of a thick network of statistically oscillating microchannels or it is possible to generate a completely homogeneous glow discharge, namely always on the entire length of the slot in the order of tens of centimetres, merely by means of the arrangement of the electromagnetic field, i.e. by the arrangement of the electrodes as well as by argon gas flowing.

This glow discharge only occurs in special cases:

1.lf outside the slot jet there is another electrode at a floating or ground potential, i.e. metal or metal separated by a thin layer of dielectric is situated there, and at the same time in the discharge space of the slot 3 a discharge of a low electric potential is created, the discharge may be created in two ways: a) with a special arrangement of electrodes (HVHF electrodes 7_and grounded electrodes 8) in at least one„assembly" (see Fig. 4d and Fig. 5), when the ..assembly" of electrodes is immersed in the space of the slot 3, which is thereby divided either into at least two separate discharge spaces of the slot 3 (thus creating, for instance, a double slot, etc.), or at least one ..assembly" is located near the dielectric wall of the slot and the discharge space of the slot is consequently situated only on one side of the particular ..assembly";

b) with a special arrangement of electrodes (Fig. 4c), when inside the slot 3 there is at least one grounded electrode 8 (thus creating for instance, a double slot), whereby at least one HVHF electrode 7 is situated outside the jet behind the dielectric plate 9 (on the level of the grounded electrode 8^ or it is shifted further from the outlet of the slot 3 against the direction of the stream flow of the atomic working gas).

In these particular cases the glow mode of discharge is pulled "capacitively" from a discharge of a low electric potential, namely due to the effect of an auxiliary, relatively weaker electromagnetic field created on the outlet and outside the discharge space of the slot 3, which is formed by a special arrangement of the electrodes 7 and 8 according to the above- mentioned cases a) and b) in relation to another auxiliary electrode at a floating or ground potential situated outside the plasma jet in front of its outlet.

2. If the electrodes are arranged in such a manner that the HVHF electrode 7 and the grounded electrode 8 are located parallel against each other across the slot 3 separated by the dielectric plates 9 forming a slot 3 between each other (i.e. the electrodes 7, 8 constitute the plates of the "condenser" and the discharge space of the slot 3 is positioned between these plates of the "condenser" separated by dielectric in the form of dielectric plates 9), between the electrodes 7, 8 a crosswise (in relation to the stream flow of the atomic working gas) homogeneous electromagnetic field is created, which leads to the occurrence of sufficiently homogeneous glow discharge, which is subsequently blown out of the slot 3 by a stream of atomic working gas, where it flickers (no electric current passes through it). A similar effect can be obtained using different combinations of HVHF electrodes 7 and grounded electrodes 8 located at either outer side of the dielectric plates 9 which form a slot/slots 3, when the grounded electrodes 8 and the HVHF electrodes 7 alternate so that an electromagnetic field crosswise to the direction of atomic working gas flowing is created, or a crosswise and simultaneously longitudinal electromagnetic field is created, whereby it is the crosswise electromagnetic field that must prevail, since a longitudinal electromagnetic field only serves to intensify the discharge and take it to a greater distance away from the outlet of the slot 3. The glow mode of the discharge is preserved upon the plasma touching the surface of the object only in the case of dielectric materials, in the case of metal materials the glow discharge changes into a microchannel discharge or the glow mode of discharge is locally transferred into a microchannel discharge . The glow mode of a discharge of type 1 is suitable for surface treatment of metals or thin dielectric materials positioned between the outlet of the slot jet and the outer electrode made of metal. On the other hand, the glow discharge of type 2 is suitable rather for dielectric material or for treatment of thin dielectric materials positioned between the outlet of the slot jet and the outer electrode made of metal (preferably applied for materials which are thermally sensitive or must not be charged by an electric current passing).

Compared to a glow discharge, a microchannel discharge is considerably more energy-efficient and substantially more economical for surface treatment - in the environment outside the slot 3 the discharge in the microchannels is also actively generated as it is inside the slot 3 (it is bound to the electric capacity of the environment), the electric current flowing through the microchannels. Atomic gas streaming and statistic division of the electromagnetic field inside as well as outside the slot 3 which is as a feedback loop influenced by the formed microchannels, results in the oscillation of the microchannels, which in this manner fill the volume of the slot 3. Individual microchannels interact with each other, whereby a weak diffuse discharge of varying homogeneity occurs mutually between the microchannels, or between them and the wall of the dielectric, i.e. the dielectric plates 9, forming a slot 3. This flowing mixture of the oscillating system of microchannels and the local glow discharge subsequently acts upon the surface of the materials to be treated.

Individual slot plasma jets can be arranged behind each other, thus creating multi-slot systems. Into these multi-slot plasma systems it is then possible to incorporate slot jets with gaseous or aerosol precursors, which due to suitable geometry of the stream of gaseous or aerosol precursors analogous to the plasma stream are without difficulty and homogeneously activated by the plasma stream and, as a result, they can create industrially applicable surface treatment of materials.

The basic simple variant of the slot jet according to the invention is schematically represented in Fig.1 in a front view and in Fig.2 in a cross section of the plane A-A from Fig.1.

A slot jet for generating a high-pressure high-frequency discharge 6, i.e. plasma, according to the invention comprises an oblong hollow body Λ provided with at least one inlet 2 of the working gas and further provided with an outlet orifice of the plasma formed by a slot 3. The basic variant of the hollow body Λ comprises a distributor and homogenizer 4 of the working gas, which serves to divide the working gas evenly along the entire length of the hollow body 1 of the slot 3, in which a high-pressure high-frequency discharge 6 is generated, as will be described below. The slot 3 is created as a hollow space between a pair of parallel plates 9 made of a high-temperature dielectric material. At least one

- high-frequency high-voitage electrode 7 (hereinafter HVHF 7) and at least one grounded electrode 8 are aligned with the plates 9 or at least with one of them. Preferably, especially in order to ensure the stability of the generated stream of high-pressure high-frequency discharge (plasma), the slot 3 has a constant width along its entire length. The slot 3 formed by the gap between a pair of dielectric walls 9 has in the direction R of the working gas flow a constant or varying width, i.e. the dielectric plates 9 are either parallel, or they are arranged in the shape of the letter "V" or "Y" or "X" or they have a generally variable shape of their inner walls, which form the slot 3, namely according to the requirements of creating suitable streaming of the working gas, a stream of high-pressure plasma or dosing admixtures or precursors added to the working gas. Selected examples of mutual arrangements of the plates 9 with respect to their inner walls forming the slot 3 are represented in Fig. 3, which shows

- selected variations of geometric solution to the hollow body Λ and combining several slot jets according to the invention into multislot systems, including combinations with a jet 1 for dosing precursors, especially precursors of aerosol type. The slot 3 has in a direction P of the length of the hollow body 1, or, in other words, in a direction perpendicular to the direction R of flowing of the working gas a greater length than the width of the slot 9, i.e. the mutual distance between the inner walls of the pair of dielectric plates 9. In the illustrated example of embodiment the slot 3 is in a direction of its length, i.e. in a direction P of the length of the hollow body Λ , linear, i.e. planar, nevertheless in essence the slot 3 can be in a direction of its length any general shape, for example, it can be even curved, multiple curved, angular, multiple angular, or different types can be combined on several sections of its length, which means that is linear on part of its length, on another part of its length it is curved, on another part of its length it is angular, etc. Also, the ends of the slot 3 can be mutually connected and that means that the slot forms a shape of a circle or ellipse or another suitable closed shape, etc. Therefore, in principle, it is possible to create a slot 3 of any shape in a direction of its length. In an unillustrated example of ^' embodiment it is possible to embed in the outlet of the slot 3 a constructional feature dividing the slot 3 into two or more parallel channels, where a separate stream of high_^pressure high-frequency plasma exits through each channel of the slot 3. Instead of the constructional feature enabling formation of parallel micro-channels, it is possible to embed into the slot 3 a constructional feature creating an array of orifices (for example in the shape of a grid and the like) where analogically a separate stream of high-pressure high-frequency plasma exits through each channel of the slot 3.

The distributor and homogenizer 4 of the working gas is connected to the dielectric plates 9 of the slot 3 by a limiter 5 of mechanical strain transfer from the slot 3 to the distributor and homogenizer 4 of the working gas, where mechanical strain arises as a result of differences in temperature ductility of the materials of individual parts of the slot jet during generating a discharge 6.

Aligned with at least one dielectric plate 9 or with one slot 3 is at least one HVHF electrode 7 and at least one grounded electrode 8, whereby the grounded electrode 8 is located in proximity of the slot 3 as an outlet orifice of the slot jet. The grounded electrode 8 at the same time facilitates the directing of the created planar stream of high-pressure plasma out of the body 1 through the slot 3. Various arrangements of HVHF electrodes 7 and grounded electrodes 8 are shown in Fig. 4. The electrodes 7, 8 can be switched on and off as a HVHF electrode 7 and the grounded electrode 8 in different combinations and number, or, as the case may be, they may be excluded or left at a floating electric potential, although it is always necessary to maintain at least one HVHF electrode 7 and one grounded electrode 8. That means that for a certain application it is possible to switch on a particular electrode as a HVHF - electrode 7 and for another application the same electrode can be switched on as a grounded electrode 8 or as an electrode at a free or ground electric potential, etc. In the illustrated example of embodiment at. least one HVHF electrode 7 and at least one grounded electrode 8 are aligned with each of the opposite dielectric walls 9 of the slot 3. In an unillustrated example of embodiment at least one HVHF electrode 7 is aligned with one of the dielectric plates 9 of the slot 3 and at least one grounded electrode 8. is aligned with the other dielectric plate_9 of the slot 3. In another unillustrated example of embodiment at least one HVHF electrode 7 and at least one grounded electrode 8 are aligned only with one of the dielectric plates 9 of the slot 3 and none of the electrodes 7, 8 is aligned with the other dielectric plate 9 of the slot 3. In another unillustrated example of embodiment at least one HVHF electrode 7 is aligned with each of the dielectric plates 9 of the slot 3 and at least one grounded electrode 8 is aligned with only one of the dielectric plates 9 of the slot 3. In another unillustrated example of embodiment at least one grounded electrode 8 is aligned with each of the dielectric plates 9 of the slot 3 and at least one HVHF electrode 7 is aligned only with one of the dielectric plates 9 of the slot 3. It is apparent that a concrete type of alignment between different types of electrodes 7, 8, and individual dielectric plates 9 of the slot 3 is according to the invention largely variable. The HVHF electrodes 7 and the grounded electrodes 8 may differ from each other in terms of geometry or material, etc.

A HVHF electrode 7, or HVHF electrodes 7, are always physically separated from the slot 3, i.e. from the empty space in which a stream of the high-pressure plasma is generated by the material of the dielectric plate 9. The grounded electrode 8, or grounded electrodes 8 are also physically separated from the slot 3 or they may be deliberately arranged in the slot 3, i.e. in contact with the generated stream of high-pressure plasma, and so the material of the grounded electrode 8 may be deliberately disrupted by the generated stream of high-pressure plasma and as a precursor it may be carried away by the plasma flow to an unillustrated substrate to be treated, by which means the stream of high-pressure plasma acts together with the material of the corresponding grounded electrode 8. This is made possible, for example, by a through longitudinal groove on the inner side of the dielectric plate 9, in which a corresponding grounded electrode 8 is arranged etc. Another option is inserting a grounded electrode 8 directly into the space of the slot 3, see Fig. 4c, and so - the working gas and the generated high-pressure high-frequency plasma flow around it from both sides. If at least one HVHF electrode 7 separated from the slot 3 by the dielectric wall 9_is situated on the same level as the grounded electrode 8 thus inserted into the slot 3, or it is shifted further away from the outlet of the slot 3 against the direction of the stream flow of the atomic working gas, a discharge at an electric potential approximately as low as that of the grounded electrode 8 occurs in the space of the slot 3. If in the outer environment in front of the slot 3 in the stream of the atomic working gas flowing out of the slot 3 another electrode of a free or ground potential is placed, discharge at a low potential in the slot 3 leads to the occurrence of a secondary homogeneoius glow discharge between the system of the electrodes 7, 8 in the slot 3 and the above-mentioned auxiliary outer electrode.

In the illustrated example of embodiment both the HVHF electrodes 7 and the grounded electrodes 8 are composed of a continuous flat body along the entire length of the slot 3. In an uniilustrated example of embodiment at least one HVHF electrode 7 is composed of a system of autonomous HVHF electrodes 7_which are arranged behind each other in a direction of the length of the slot and along the entire length of the slot 3 and which are shorter than the length of the slot 3. In another uniilustrated example of embodiment with at least one of the dielectic plates 9 of the slot 3 are aligned two (or even more than two) HVHF electrodes 7, arranged behind each other in a direction of the stream flow of the working gas. The same applies to the grounded electrodes 8. The grounded electrode 8 is according to an example of embodiment located in a direction of the stream flow of the working gas already before the HVHF electrode 7 or it alternates successively and repeatedly with the high-frequency high-voltage electrode 7, i.e. the order of the electrodes in a direction of the flow of the plasma is grounded electrode 8 - HVHF electrode 7 - grounded electrode 8 - etc., by which means it is possible to obtain either increase or decrease in the effects of generating a flat stream of high-pressure plasma according to the well-chosen geometry of the arrangement. In an uniilustrated example of embodiment the grounded electrode 8 is further connected to the direct voltage source (bias voltage) for enhancing the process of generating a stream of high- pressure plasma, this voltage (bias voltage) being different from that to which the HVHF electrode 7 is connected.

The electrodes 7, 8 either imitate the oblong shape of the slot 3, whereby they either lie directly on the dielectric plate 9_j or have a constant distance from the dielectric plate 9 or they have a varying distance from the dielectric plate 9, which enables to create suitably differentiated sections of high-pressure plasma in the direction P of the length of the slot 3, or the electrodes 7, 8 lie with a part of their length on the dielectric plate 9 and with the remaining part of their length they are away from the dielectric plate 9 at a constant or varying distance etc. In essence, any combinations of the above-described features of the arrangement of electrodes 7, 8 in relation to the dielectric plates 9 are possible. In an unillustrated example of embodiment at least one of the electrodes 7. § is arranged in a groove in the dielectric plate 9, or, as the case may be, it is mounted in the groove replaceably or irreplaceably and possibly covered with the material of the dielectric plate 9 or with another suitable covering material.

In the example of embodiment shown in Fig.3 e, f and 4 e, f, which represent combining several slot jets together parallel next to each other according to the invention, so that their slots 3 are arranged in such a manner that they are all directed to one substrate 5, whose surface is treated by the action of a flat stream of high-pressure plasma that is generated. The resulting functional unit enables to achieve enhanced results in the treatment of the substrate 5 by a flat stream of high-pressure plasma during one passage of the substrate 5.

In the example of embodiment in Fig.3 c, d another possible solution is represented in which the hollow body provided with at least one common inlet 2 of the working gas is divided in its lower portion by at least one parallel partition into at least two spaces separated from each other having respective outlet orifices of the high-pressure plasma, creating a corresponding number of parallel oblong slots 3, whereby at least one HVHF electrode 7 and at least one grounded electrode 8 are aligned with the created system of the parallel slots 3.

In the case of the parallel system of slots 3 it is possible to utilize at least one slot 3 as a jet for feeding auxiliary material into the outer part of the flat stream of high-pressure plasma, by which means possible undesirable deposition of the auxiliary material on the inner walls of the dielectric plates 9 of the slot 3js prevented.

In the example of embodiment in Fig. 4d and Fig. 5 another constructional solution to the slot plasma jet according to the invention is represented. Normally it is assumed that between the plates of the condenser there is a very strong electromagnetic field (also for a high frequency), outside - these plates the field being practically negligible (the only exception is the space close to the edges of the plates). In the case of the above-mentioned constructional solution the electrodes (indicated by thick dark lines) are arranged in a ..assembly" in the shape of e.g. at least two parallel strips which are separated from each other by a high-temperature dielectric distinctly overlapping the edges of the electrodes (the alternative shown is for a three- electrode system - Fig. 5). The outer parts of the electrodes are also overlapped by the dielectric. This compact ..assembly" of the electrodes (constituting the condenser) is inserted into the slot 3 of the slot jet, which is in this manner divided either into at least two separate discharge spaces of the slot 3 (thus forming, for example, a double slot etc.), or at least one such ..assembly" is positioned near the dielectric wall (plate 9) of the slot 3 and the discharge space of the slot 3 is situated only on one side of the corresponding ^' „assembly"of electrodes (this alternative is not shown). These "assemblies" of electrodes may combine and form either a system of discharge slots, or a wide strip of electrodes in a number of combinations of "assemblies" (this alternative is not shown). In the space of the slot 3 between the„assembly"of electrodes and the outer dielectric plates 9 of the slot 3, or between the individual "assemblies" of electrodes, atomic working gas - such as argon - flows to the outer environment. In the case of the illustrated three-electrode system in a „assembly", in one of the possible variants the central electrode is connected to a HVHF pole of an electricity supply source and the grounding is symmetrically connected to the remaining two electrodes. Thus a symmetrical condenser is created with the central HVHF electrode 7 and the side grounded electrodes 8. Due to preionization of the environment in both slots 3 occurs an intensive discharge, which stays in the vicinity of the whole surface of the flat isolated grounded electrodes 8 (adhering to them), the discharge itself practically does not extend outside the slot 3. This discharge does not react with metals, net even with the impressed metal tip at a grounding potential (a possibility of creating an electromagnetic field of high intensity). That means that the plasma does not react capacitively and has a potential as low (approximately) as the grounded electrode. One can touch the plasma with a finger without„a tingling sensation" or without getting burnt locally. So as to obtain a discharge with these characteristics, the outer electrodes in the„assembly" must be grounded.

If a HVHF electrode 7 is located on the outer part of the "assembly", the discharge will have different properties - it will have a higher electric potential, but it will also burn in the space of the slot 3. Provided the system of electrodes in a„assembly"is arranged in such a manner that one end electrode is a HVHF electrode 7 and the other end electrode is a grounded electrode 8 and at the same time close to both end electrodes there is a discharge space of the slot 3, the discharge will take place from one side of the slot 3 at a low electric potential and the discharge on the other side of the slot 3 will be at a high electric potential (from the HVHF electrode 7). These two discharges may create an electric circuit over the space above the "assembly'Of electrodes, thus forming a new discharge space with a specific type of plasma.

These different variants of arrangement of electrodes allow to verify the principle of generating a discharge and also its behaviour. If the discharge for the shown case in Fig. 4d and Fig. 5 in both created slots 3 did not occur between the„assembly"of electrodes and the side dielectric plates 9 of the slot 3, it would be in accordance with the expected behaviour of the electromagnetic field before burning the discharge (the principle of generating a discharge in a slot would then follow the standard "electrotechnic" approach concerning an electromagnetic field between electrodes). If the discharge occurs and is maintained in the slot 3, when considering the principle of a discharge occurrence in the slot 3 we can come to the conclusion of a primary role of the plasma itself, not only the role played by the electric field between the electrodes of the condenser (as seen by the classical "electrotechnic" concept without the existence of the plasma environment, i.e. without including the feedback of the plasma influence on the environment in which plasma was generated). The electromagnetic field between the electrodes of the condenser would be in this case only a primary source of energy, which the generated plasma (primarily generated, for example, by preionization of the high-voltage environment by the Tesla transformer) is capable of "converting" as a feedback loop the electromagnetic field generated by itself into the energy required for maintaining its own discharge. Preionization of the environment leads to the occurrence of primary plasma channels which subsequently influence the electromagnetic field of the condenser and permit conversion of the electromagnetic energy from the condenser to plasma. This phenomenon is in our opinion based on the feedback of the plasma (free electric charge carriers, moving collectively, creating their own electromagnetic field) and (especially) of the magnetic field created between the plates of the condenser, since the ^•experiment that was carried out afterwards using outer grounded electrodes made of ferromagnetic material and covered by a well-conductive layer from aluminium, whereby these electrodes were supposed to shade at least partially the created magnetic field between the plates of the condenser and at the same time to conduct well the electric current, confirmed this hypothesis, namely by the fact that in this case the discharge inside the slot 3 does not occur or it occurs with great difficulty - it is extremely weak and unstable.

If another electrode of a free or ground electric potential is located in the outer environment behind the ..assembly" of electrodes, the discharge of a low potential in the slot 3 results in a secondary homegeneous discharge formation between the ..assembly" of electrodes and the outer electrode. This secondary discharge is already bound to the electromagnetic field coming from the ..edges" of the ..assembly" of electrodes (condenser) and a suitable arrangement of electrodes in the ..assembly" increases the energy flow to the plasma. If the outer electrode is an object, such as a substrate, it is subjected to surface treatment. Also, the outer electrode may be covered with a layer of dielectric, or a thin strip of dielectric may move on it (a fabric, a film and other similar materials).

In the example of embodiment represented in Fig. 4b, e, f, in which the device is composed of at least two slot jets combined together parallel to each other according to the invention, each of the slot jets comprising a hollow body i fitted with at least one inlet 2 of the working gas and an outlet slot 3 of the stream of high-pressure plasma, whereby at least one HVHF electrods 7 is aligned with the hollow body 1 of one slot jet and at least one grounded electrode 8 is aligned with the hollow body i of the other slot jet, the grounded electrode imitating the oblong shape of the slot 3 or having in a direction of the slot 3 a varying distance from the slot 3. In another example of embodiment these slot jets combined together parallel to each other have a common hollow body 1 , which is provided with at least one common inlet 2 of the working gas and which is in its lower portion divided by at least one parallel partition into at least two spaces with respective slots 3 separated from each other, whereby aligned with each of these parallel slots 3 is either one HVHF electrode 7, and/or at least one grounded electrode 8. In this manner it is possible to obtain a stream of high-pressure plasma simultaneously in all the slot jets combined together parallel to each other in such a manner that a stream of high-pressure plasma, which is generated primarily in the slot jet array with the HVHF electrode 7 , "turns round" outside the slot 3 and„is directed" to the slot 3 array with at least one grounded electrode 8, where it induces a stream of high- pressure plasma which is also directed out of the slot 3 of this array. Thus outside the jets 3 of all the slot jet arrays a high-pressure discharge of high intensity is generated, which subsequently acts upon the substrate to be treated or it first acts upon the auxiliary material and after that on the substrate to be treated. In the example of embodiment according to Fig. 4g a device for generating this highly intensive stream of high-pressure plasma is represented, the plasma being formed by two opposite slot jets directed against each other by their slots 3, so that the stream of high-pressure plasma coming out of both slots 3_colIides in the outer environment between the jets, thus obtaining high intensity. At the point of the collision the substrate surface may be treated by thin dielectric films or textiles etc., the effect occurring simultaneously from both sides of the material or even in the whole volume of the substrate if the substrate comprises holes or pores etc. The direction of the flow stream and adhesion of the high-pressure plasma to the inner wall of one or the other dielectric plate 9 of the slot 3 or to the inner partition in the slot 3 can also be set, modified or further regulated by an unillustrated additional or auxiliary electrode of a different electric potential in relation to the HVHF electrode 7 and the grounded electrode 8, which results in creating an auxiliary or additional electromagnetic field modifying the original high-frequency high-voltage electromagnetic field for generating the high- pressure plasma. Such an additional or auxiliary electrode is positioned, for example, near one or the other dielectric plate 9 of the slot 3 or near the partition in the slot 3, or it is formed by an asymmetric arrangement of electrodes in relation to the slot 3 , etc., or by other methods.

An alternative to the above-mentioned possibility of feeding admixtures and precurses into the plasma with the aid of a grounded electrode 8 arranged in the slot 3 being in contact with the plasma is a possibility of feeding admixtures and precurses, i.e. auxiliary material or auxiliary materials, into the stream of the generated high-pressure plasma either directly to the hollow body 1 collaterally with the working gas, or by using an external source of auxiliary material with sufficient homogeneity of dispersion of particles of the auxiliary material, for example by the technology of atomizing, by which the auxiliary material may be fed directly into the stream of the high-pressure plasma inside the slot 3, i.e. to the working gas before the space where plasma is generated, the auxiliary material from the aerosol generator is fed into the stream of plasma as far as outside the slot 3, or behind the slot 3. Another ^' possibility of feeding auxiliary material into the generated high-pressure plasma is locating a passive source of auxiliary material in the slot 3 so that the stream of the generated high-pressure plasma could flow comfortably around the auxiliary material and disrupt it, as is the case of the above-described possibilities of placing a grounded electrode 8 in the slot 3. Another option of feeding auxiliary material into the created stream of high-pressure plasma is feeding the auxiliary material by means of deliberate erosion of the dielectric material of at least one dielectric plate 9 of the slot 3 by the stream of high- pressure plasma, etc.

Other examples of embodiment, especially the arrangement in which the electrodes 7, 8 are located only in the partition inside the slot, can be explained by demonstrating the example from Fig. 4b, when the electrode E is the grounded electrode 8 and the electrode F is the HVHF electrode 7 (The electrodes A, B, C, D are either not located, or they are connected to a floating potential). In that case the discharge is not generated in both parallel slots. Electrodes can be arranged analogically also for the other variants of the slot jets according to Fig.4.

An example of suitable working conditions used for the application of thin layers by slot plasma jets according to the invention and with an aerosol jet in the arrangements according to Fig. 3f, or Fig. 4f, when the electrodes A, B, E, F are the grounded electrodes 8 and the electrodes C, D, G, H are the HVHF electrodes 7. In the experiment slot jets according to the invention were used, having a length of the slot of 120 mm and a width of the slot of 2 mm. Flowing through both end plasma jets was atomic working gas - argon, having a flow rate of 50 l/min for each of the slot jets. The electrodes were connected to a high-frequency generator on a frequency of 13.56 MHz through a common impendant adaptor. The power delivered to the slot jets ranged between 350 - 650 W at a voltage in the order up to approximately 3 - 5 kV. An ultrasound aerosol generator was used to generate an aerosol precursor (e.g. of water glass, HMDSO and the like), which was carried to the slot plasma jets by argon flowing through a vessel with the generated aerosol (approximately 1-15 l/min). Aerosol and plasma were mixed on the outlets of the slot plasma jets and the outlet of the aerosol jet. Under the slots on a conveyor belt samples were passing and on them a thin layer from precursors activated in the plasma was applied. In Fig.6 there are photos of the surface of the thin layers taken by a scanning electron microscope (SEM) for the precursors water glass (Fig. 6a) and HMDSO (Fig. 6b). The thickness of the layers ranged from several hundreds of nm to a few micrometers. Deposition velocities also ranged in the order of several hundreds of nm/s to several pm/s. Thin layers of water glass consist of S1O2, 2 - 4 % Na and have a fine inner nanostructure (Jittle balls" on the surface are formed by compounds on the basis of Na or C at a higher concentration, are dissoluble and can be easily washed off the surface of the material). The SiO₂ layer is indissoluble and rather hard (resistance to being scratched by steel). Thin layers of HMDSO have no visible inner structure, are smooth and scratch resistant (resistant to being scratched by steel). Also, they display good hydrophobicity. Industrial applicability

The invention can be used for treatments of large surface areas of a substrate by means of highly reactive, high-pressure plasma, for example for creating plasma coatings, for realization of plasma reactions and polyreactions, etc.

Claims

PATENT CLAIMS

1. A method of generating plasma at atmospheric pressure in a slot jet, in which a stream of of working gas flowing through the slot jet is acted upon by an electromagnetic field, characterized in that in the slot jet a high-frequency electromagnetic field created and formed by at least one high-voltage electrode (7) dielectrically separated from the cavity of the slot (3) and by at least one - grounded electrode (8) acts upon the flowing atomic working gas, by which means high-pressure high-frequency plasma is created at a high or low electric potential, by which the original high-frequency electromagnetic field changes as a feedback loop and the high-pressure high-frequency plasma is statistically distributed along the entire length of the slot (3) and is blown out of the entire length of the slot (3) by a stream of atomic working gas.

2. A method according to Claim 1 , characterized in that inside and/or outside the slot jet at least one auxiliary material is introduced into the stream of the high-pressure high-frequency plasma.

3. A method according to Claim 2, characterized in that the auxiliary material is introduced together with the atomic working gas into the slot jet in which high-pressure high-frequency plasma is generated.

4. A method according to Claim 2, characterized in that the auxiliary material is introduced by a deliberate erosion of the material surrounded by the created stream of high-pressure high-frequency plasma.

5. A method according to Claim 2, characterized in that the auxiliary material is introduced into a separate slot jet parallel to the slot jet in which high-pressure high-frequency plasma is generated.

6. A method according to Claim 2, characterized in that the auxiliary material is introduced into the outer space in front of the slot (3) of the slot jet.

7. A method according to Claim 1 , characterized in that in the slot jet the flowing atomic working gas is divided into at least two streams, whereby at least one of them is acted upon by the high-frequency electromagnetic field, by which means this separated stream of atomic working gas is converted into high-pressure high-frequency plasma, which is blown out of the slot (3) by the stream of atomic working gas.

8. A method according to Claim 1 , characterized in that the high- frequency electromagnetic field is applied along the entire length of the slot (3) or it is only applied on part of the length (P) of the slot (3) and at least one other high-frequency electromagnetic field is aligned with the remaining part of the length (P) of the slot (3).

9. A method according to Claim 1 , characterized in that the high- frequency electromagnetic field is only applied on parts of the length (P) of the tslot (3), while the remaining part of the length (P) of the slot (3) is without another high-frequency electromagnetic field.

10. A method according to Claim 1 , characterized in that the high- frequency electromagnetic field has in a direction of the length (P) of the slot (3) a constant or varying intensity.

11. A method according to Claim 1 , characterized in that the working gas is in a direction of its stream flow through the slot (3) is acted upon by one high-frequency electromagnetic field or successively by at least two high- frequency electromagnetic fields.

12. A method according to Claim 1 , characterized in that in different sections of the slot (3) the working gas is acted upon by a different high- frequency electromagnetic field.

13. A method according to Claim 1 , characterized in that the created stream of high-pressure high-frequency plasma is curved in a direction of its movement.

14. A method according to Claim 1 , characterized in that the working gas in the slot jet is acted upon by one high-frequency electromagnetic field, as well as by at least one direct current electromagnetic field by means of direct voltage (bias voltage).

15. A device for generating plasma at atmospheric pressure comprising at least one hollow body (1) provided with at least one inlet (2) of the working gas and further provided with at least one slot (3) which forms the outlet orifice of the plasma, at least one electrode being aligned with the hollow body (1), characterized in that the slot (3) is formed by a gap between a pair of dielectric plates (9), whereby aligned with the slot (3) is at least one high-voltage high- frequency electrode (7), separated from the cavity of the slot (3) by a dialectric plate (9), and at least one grounded electrode (8).

16. A device according to Claim 5, characterized in that the slot (3) is in a direction of its length either planar or three-dimensional.

17. A device according to Claim 15, characterized in that the slot (3) is in a direction of the working gas stream flow either planar or three-dimensional.

18. A device according to Claim 15, characterized in that the HVHF electrode (7) and/or the grounded electrode (8) imitates the oblong shape of the slot (3) or it has in a direction of the length of the slot (3) a varying distance from the slot (3), whereby it is situated along the entire length of the slot (3) or on a part of the length of the slot (3).

19. A device according to Claim 15, characterized in that the HVHF electrode (7) is physically separated from the slot (3).

20. A device according to Claim 15, characterized in that arranged in the slot (3) is at least one dividing partition of the working gas stream.

21. A device according to Claim 15, characterized in that at least one parallel slot (3) is aligned with the slot (3) formed by a gap between a pair of dielectric plates (9), whereby aligned with the slots (3) is at least one separate or common HVHF electrode (7) and at least one separate or common grounded electrode (8), both slots (3) having one common hollow body (1) and one common inlet (2) of the working gas.

22. A device according to Claim 15, characterized in that aligned with the slot (3) formed by a gap between a pair of dielectric plates (9) is at least one parallel slot (3) with a separate hollow body (1) and at least one separate inlet (2) of the working gas, whereby aligned with the slots (3) is at least one separate or common HVHF electrode (7) and at least one separate or common grounded electrode (8).

23. A device according to Claims 21 or 22, characterized in that at least two of the slots (3) are arranged next to each other and/or behind each other.

24. A device according to Claim 15, characterized in that aligned with the slot (3) is a source of the auxiliary material into the generated planar stream of the high-pressure plasma.

25. A device according to Claim 24, characterized in that the source of the auxiliary material into the generated stream of the high-pressure plasma is created by at least one device with an oblong slot for dosing the auxiliary material.

26. A device according to Claim 24, characterized in that the source of the auxiliary material into the generated stream of high-pressure plasma is composed of a body arranged in the path of the generated stream of high- pressure plasma.

27. A device according to Claim 26, characterized in that the body arranged in the path of the generated stream of high-pressure plasma is at least one grounded electrode (8).

28. A device according to Claim 24, characterized in that the source of the auxiliary material into the generated stream of high-pressure plasma is composed of the source of the auxiliary material fed into the stream of working gas before it enters the slot (3)

29. A device according to any of Claims 15 to 24, characterized in that aligned with the slot (3) is at least one auxiliary electrode connected to the source of direct voltage.