Spatially resolved thermal probe measurement for the investigation of the energy influx in an rf-plasma

The total energy influx for a typical radiofrequency process plasma has been measured by means of a simple thermal probe. The procedure is based on the measurement of temporal slope of the substrate temperature during the plasma process. A substrate dummy which is thermally isolated and inserted into the plasma at substrate position served as thermal probe. It can be moved in vertical and horizontal directions in order to measure the different energy influxes and their topology in the reactor vessel. The knowledge of the spatial distribution is important for coating or sputtering processes.Different contributions to the total energy influx can be identified by different orientation of the thermal probe. If the thermal probe is orientated to the rf-electrode (“down”) the energy influx is much higher than in the opposite direction. This difference can be explained by an additional influx due to the secondary electron emission from the powered rf-electrode.     

Plasmaprozesse für funktionelle Polymeroberflächen

Plasma Processes for Functional Polymer Surfaces Plasma‐based processes were originally developed for microelectronics, but have exceeded this limits since then. Today the plasma technology is a key technology with numerous applications. A great technological potential can be seen particularly in the field of surface modification because in a plasma any organic bond can be broken and thus reactions can be initiated which cannot be carried out wet‐chemically. Besides, the small depth effect leaves the bulk properties of the material unchanged. This article points out the fundamental characteristics of non‐thermal low pressure plasmas and shows some procedure examples, which were developed at the Fraunhofer‐Institut für Angewandte Polymerforschung (IAP). Finally analysis methods (XPS, labeling techniques) are presented, which are essential for an effective development of plasma processes.     

A novel thermal probe design for the measurement of energy influx in RF remote plasma

A novel design of a thermal probe to measure the energy influx of RF plasma has been achieved. This probe utilises one-dimensional steady-state conduction through the probe's cylindrical body and has the ability of controlling its exposed surface's temperature. The probe is fully instrumented so that the temperature field within it is known. This temperature field will serve as an indicator of achieving steady-state conduction as well as securing the needed data to calculate the energy influx of the RF plasma. Experimental results show that the plasma energy influx varied from 0.3 kW/m² to 2.2 kW/m² for RF power ranging from 15 W to 300 W, respectively. The variation of the energy influx with the RF power was found to follow a linear profile and a simple relation is proposed to model this variation for the considered plasma. Error analysis has been carried out to estimate the experimental uncertainties in the resulting energy influx values. The resulting uncertainties are found to be within the acceptable range for such applications.     

Modifizierung unpolarer Polymeroberflächen

Modification of non‐polar polymer surfaces In numerous technological relevant processes the adhesion in compound systems is of central importance. It concerns for example surface coatings and the manufacturing of composites. Particular problems result at the compounding of polyolefins, silicones and fluoropolymers due to their very low surface energy. The modification of such polymer surfaces with the aim of functionalisation and with it of increasing the surface energy results in an improvement of adhesion properties of the materials. A well‐established procedure, particularly in the automotive industry, is the flame treatment of the surfaces. However, a defined chemical modification of the surface depends on many parameters and thus is very difficult to standardize. A defined change of the surface can be better achieved through a targeted plasma treatment, in which in our case the surface is stabilized by a subsequent wet chemical process step.     

Holzoberflächenmodifikation mittels Atmosphärendruckplasma

Plasma surface modification of wood and wood‐based materials In this article, plasma technical, analytical and application relevant aspects of the plasma treatment of wood and wood‐based materials are presented. With the help of surface energy determinations and adhesion tests it is shown that the surfaces of wood and wood‐based materials can be changed for specific applications. Surface characteristics, which are application‐technological interesting for a later coating or adhesion, can be specifically generated with the use of air plasma. With surface energy determinations of wood and wood‐based materials, a significantly increased polar part of surface energy could be detected after a plasma treatment. Atomic force microscopy analyses of wood composites show that a plasma treatment with the use of ambient air effects an abrasion and a changed surface roughness. Tensile tests and shear tests of coated or adhered wood‐based materials with a plasma treatment show a clearly increased adherence.     

Nicht‐thermische Plasmen zum Emissionsschutz

Non‐thermal plasma for emission protection: State of the art and future prospects The reduction of emissions from exhaust gas streams is becoming more and more important issue in the highly industrialised society. Due to its impact on air, soil and water exhaust pollutions affect the whole environment and thus human health. Therefore environmental norms and standards are constantly increased by national and international authorities. The possibilities of air‐pollution control by means of non‐thermal plasmas are well known. Plasmas contain active and highly reactive species, in particular electrons, ions, atoms, molecules, and radicals, which can decompose of filter pollutant molecules and particulate matter. This contribution intends to summarize the possibilities or pollution control by means of non‐thermal plasmas. Commercially available plasma based and plasma assisted processes for flue gas treatment and deodorization are described. Current trends and concepts will be discussed.     

The Influence of High Pressure Treatment and Thermal Pasteurization on the Surface of Polymeric Packaging Films

Several common single layer films (PE‐HD, PE‐LD, PP‐BO, PA6‐BO and PET‐BO) and multilayer (PS/PE, PP‐BO/PEpeel and PET‐BO/PE) films were treated by either high pressure (600 MPa) or temperature (80 °C/90 °C) to simulate a high pressure or thermal pasteurization process. The samples were tested by atomic force microscopy (AFM), profile method and surface energy measurements to obtain information about the influence of the treatments on the surface topography and surface energy of the samples and by differential scanning calorimetry and by tensile testing concerning material properties. As key figures arithmetic surface roughness (by AFM at Pulsed Force Mode and profile method), surface energy by surface energy measurement and adhesion between tip and surface by AFM were extracted. Results indicate an influence of both high‐pressure processing and thermal‐processing on the surface roughness of biaxial oriented polymer films as single layer films. Laminated biaxially oriented polymer films showed no changes regardless of which processing was performed. The surface energy was hardly affected by both of the treatments for any stretched, non‐stretched, single or laminated films.     

Großflächige Quellen f�r die industrielle Plasmatechnik

Plasma‐technological processes in modern thin film technologies for the refinement of surfaces are of constantly growing interest. Plasma‐technical procedures for the surface modification and film deposition mainly are contributed to the low pressure regime and use ion and/or plasma techniques. In particular plasma‐technological process concepts in the industrial field require adapted and scalable large area plasma sources. A new source concept, based on a coaxial structure, unites these specifications and permits plasma arrangements of nearly any required size.     

Kalte Normaldruck‐Jetplasmen zur lokalen Oberflächenbehandlung

Cold non‐thermal plasma jets for local surface treatment under normal pressure Plasmas at normal pressure are of considerable interest for surface technology because the industrial application requires no vacuum devices. Among other approaches, cold non‐thermal plasma jets represent an emerging technique to generate plasmas at normal pressure with attractive advantages. They allow ambient process temperatures and require only moderate operating voltages (1.5‐2.5 kV). They offer the advantage that the treated surfaces are not placed between the electrodes thus favoring local treatment of non flat, structured 3D surfaces. Moreover, the dimension of the sources is scalable and their integration into automated processes is simple. A capacitively coupled version (27.12 MHz) of a cold plasma jet suitable for surface treatment at atmospheric pressure is presented along with its plasma physical and technical properties and a series of successful applications, including plasma activation of surfaces for increasing printability, adhesion control, surface cleaning, microfluidics, decontamination, its use in plasmamedicine and for deposition of thin SiO₂ films as protective coatings. The device allows the operation with rare gases (e.g. Ar) and reactive gases as N₂, air or admixtures of silicon‐containing compounds.     

Untersuchung der Verteilung und Intensität filamentierter Barrierenplasmen für die Behandlung von Oberflächen

The application of barrier discharges at atmospheric pressure in air expands on the market of plasma technology, because it is an ecological and cost‐effective alternative to other processes of surface treatment. These plasmas usually consist of a multitude of spatially and temporally localized filaments, whose distribution should be as even as possible for homogeneous treatment. This holds especially for the plasma treatment of sensitive goods such as wool or other textiles. In equipment for continuous pass of material the barrier arrangements often consist of a system cylinder – cylinder or cylinder – plane, whereby the gap width changes locally. Space distribution and intensity of filaments has been investigated by means of short‐time photography and spatially resolved measurement of current distribution and energy distribution derived from it. The local dependency found can be explained by means of a capacitive equivalent circuit.     

Anwendungsfelder moderner Oberflächentechnik bei Anbietern oberflächentechnologischer Dienstleistungen

Concerning the transfer of results from research and development into commercial business practice for small and middle sized enterprises, offering surface‐technological services, the situation is generally better than aspected. This is the conclusion arrived at by the Institut for knowledge transfer at the University of Bremen (IfW) after carrying out a random analysis of the enterprises offering surface technology services. The study is a component of the project “Technology transfer surface technology”, which is accomplished on behalf the Federal Ministry for education and research (BMBF) by the VDI Technologiezentrum. Two thirds of the enterprises asked plan to introduce new procedures or modernize and/or supplement existing procedures in the next two years. All the same one third plans on top of this to use new layer materials. At present the situation regarding the application of modern surface technology, shows that the correct application of the surface and layer technologies bears fruits. The degree to which thermal spraying and the PVD and CVD techniques are applied has increased. Old procedures are rapidly being displaced by innovative and more pollution free procedures – especially in the field of thermal treatment. The technological developments planned for the next two years by the enterprises asked show that the degree with which the technologies specified above are spreading will continue to increase. Also the predication as to, which industries will be ranked in the future as important customers of the surface‐technological services, is changing. While the enterprises evaluate the situation toke restrained in the electro‐technology and electronics industry. An increased demand from air and space industry is expected. Moreover a clear increase in the paper and graphic arts industry is predicted.     

Tailoring the composition of self-assembled Si(1-x)C(x) quantum dots: simulation of plasma/ion-related controls

Precise control of composition and internal structure is essential for a variety of novel technological applications which require highly tailored binary quantum dots (QDs) with predictable optoelectronic and mechanical properties. The delicate balancing act between incoming flux and substrate temperature required for the growth of compositionally graded (Si(1-x)C(x); x varies throughout the internal structure), core-multishell (discrete shells of Si and C or combinations thereof) and selected composition (x set) QDs on low-temperature plasma/ion-flux-exposed Si(100) surfaces is investigated via a hybrid numerical simulation. Incident Si and C ions lead to localized substrate heating and a reduction in surface diffusion activation energy. It is shown that by incorporating ions in the influx, a steady-state composition is reached more quickly (for selected composition QDs) and the composition gradient of a Si(1-x)C(x) QD may be fine tuned; additionally (with other deposition conditions remaining the same), larger QDs are obtained on average. It is suggested that ionizing a portion of the influx is another way to control the average size of the QDs, and ultimately, their internal structure. Advantages that can be gained by utilizing plasma/ion-related controls to facilitate the growth of highly tailored, compositionally controlled quantum dots are discussed as well.     

Controlled Electrodeposition of Gold on Graphene: Maximization of the Defect‐Enhanced Raman Scattering Response

A reliable method to prepare a surface‐enhanced Raman scattering (SERS) active substrate is developed herein, by electrodeposition of gold nanoparticles (Au NPs) on defect‐engineered, large area chemical vapour deposition graphene (GR). A plasma treatment strategy is used in order to engineer the structural defects on the basal plane of large area single‐layer graphene. This defect‐engineered Au functionalized GR, offers reproducible SERS signals over the large area GR surface. The Raman data, along with X‐ray photoelectron spectroscopy and analysis of the water contact angle are used to rationalize the functionalization of the graphene layer. It is found that Au NPs functionalization of the “defect‐engineered” graphene substrates permits detection of concentrations as low as 10^?16 m for the probe molecule Rhodamine B, which offers an outstanding molecular sensing ability. Interestingly, a Raman signal enhancement of up to ≈10⁸ is achieved. Moreover, it is observed that GR effectively quenches the fluorescence background from the Au NPs and molecules due to the strong resonance energy transfer between Au NPs and GR. The results presented offer significant direction for the design and fabrication of ultra‐sensitive SERS platforms, and also open up possibilities for novel applications of defect engineered graphene in biosensors, catalysis, and optoelectronic devices.     

Plasmachemische Gasphasenabscheidung und Plasmaätzen bei Atmosphärendruck

Plasma enhanced Chemical Vapour Deposition and plasma etching at atmospheric pressure Plasma processes are applied for a variety of surface modifications. Examples are, e.g. coatings to achieve an improved corrosion and scratch protection, or surface cleaning and texturising. Since these processes, however, usually take place in vacuum, they are unfortunately not applicable for large area industrial use. Plasma enhanced CVD processes at atmospheric pressure enable the deposition of functional coatings on components and semi‐finished parts with in a continuous air‐to‐air process without the use of expensive vacuum systems. By their integration into in‐line production processes the substrate handling and the coating costs are definitely reduced. A thermal plasma source, basing on a linearly extended DC arc discharge at atmospheric pressure, has been tested for the deposition of silicon nitride at substrate temperature of less than 300° in a continuous PECVD process. Furthermore this source has been tested for plasma‐chemical etching and texturising of silicon as well.     

Abscheidung optisch,elektrisch und akustisch wirksamer Schichten mit dem Doppel‐Ring‐Magnetron

Numerous applications in optics, electronics and sensor technology require thin dielectric films. Conventionally they are deposited by evaporation, activated evaporation, rf‐sputtering or CVD‐techniques. This paper describes the deposition of such films using reactive Pulse Magnetron Sputtering. This technology not only enables a tenfold deposition rate compared to the conventional techniques but also offers new possibilities for influencing film growth. For example it is possible to alter film composition during deposition and hence to deposit complete optical systems without interruption of the plasma process. Furthermore the energetic bombardment of the growing film can be controlled in a wide range by the pulse mode and the pulse parameters. This can be used to either deposit very dense films by strong energetic bombardment or to deposit films at low thermal load onto temperature sensitive substrates. Examples of film deposition for laser optics, electrical insulation applications and surface acoustic wave devices show how these new technological possibilities advantageously can be used for creating innovative layer systems. Film deposition is carried out in stationary mode using a Double Ring Magnetron. This type of magnetron ensures film thickness uniformity better than ± 1 % on 8” substrates by the superposition of the thickness distributions of two concentric discharges.     

用于微机电系统的SiO2/Si3N4驻极体的制备及电荷稳定性

驻极体微型发电机是近期提出的微电子机械系统开发中的一个新领域,驻极体电荷稳定性则是影响驻极体微型发电机性能的关键.用等离子体增强化学气相沉积(PECVD)方法制备SiO2/ Si3N4双层膜,采用电晕充电和热极化方法对材料进行注极形成驻极体,探讨了器件加工工艺及存储环境对双层膜驻极体电荷稳定性的影响.结果表明,电晕充电后SiO2/ Si3N4双层膜的电荷存储稳定性明显优于SiO2单层膜;传统的电晕注极方法仅适用于大面积驻极体的制备,但对微米量级的材料表面不适用;微器件制备的工艺流程对驻极体电荷稳定性有显著影响,但存储环境对热极化驻极体电荷稳定性的影响很小.     

Diagnostic in TCOs CVD processes by IR pyrometry

Infra red pyrometry is a sensitive, simple and low-cost technique commonly used for the measurement of the deposition temperature in CVD processes. We demonstrate in this work that this optical technique can be used as diagnostic tool to provide fruitful informations during the growth under atmospheric pressure of TiO₂ films on various substrates chosen as an example of transparent oxide. Significant variations of the pyrometric signal were observed during the deposition of TiO₂ thin films due to interferences in the growing film resulting from multi-reflections at the interfaces and scattering induced by the surface roughness. Modeling of the time dependence of the IR pyrometric signal allows simultaneously the determination of the layer thickness, the growth rate, surface roughness and refractive index of the thin films under the growth conditions. This diagnostic technique can be used for various transparent thin films grown on opaque substrates and is well adapted to control CVD processes operating either under atmospheric or low pressure and more generally any thermal treatment processes.     

Local thermal property analysis by scanning thermal microscopy of an ultrafine-grained copper surface layer produced by surface mechanical attrition treatment

Scanning thermal microscopy (SThM) was used to map thermal conductivity images in an ultrafine-grained copper surface layer produced by surface mechanical attrition treatment (SMAT). It is found that the deformed surface layer shows different thermal conductivities that strongly depend on the grain size of the microstructure: the thermal conductivity of the nanostructured surface layer decreases obviously when compared with that of the coarse-grained matrix of the sample. The role of the grain boundaries in thermal conduction is analyzed in correlation with the heat conduction mechanism in pure metal. A theoretical approach, based on this investigation, was used to calculate the heat flow from the probe tip to the sample and then estimate the thermal conductivities at different scanning positions. Experimental results and theoretical calculation demonstrate that SThM can be used as a tool for the thermal property and microstructural analysis of ultrafine-grained microstructures.     

Characteristics and applications of plasma enhanced-atomic layer deposition

Atomic layer deposition (ALD) is expected to play an important role in future device fabrication due to various benefits, such as atomic level thickness control and excellent conformality. Plasma enhanced ALD (PE-ALD) allows deposition at significantly lower temperatures with better film properties compared to that of conventional thermal ALD. In addition, since ALD is a surface-sensitive deposition technique, surface modification through plasma exposure can be used to alter nucleation and adhesion. In this paper, characteristics of PE-ALD for various applications in semiconductor fabrication are presented through comparison to thermal ALD. The results indicate that the PE-ALD processes are versatile methods to enable nanoscale manufacturing in emerging applications.     

Verschleißschutz und Korrosionsbeständigkeit von austenitischem Stahl durch Plasmadiffusions behandlung

In this paper, we report on a series of experiments designed to study the influence of plasma nitriding on the mechanical properties and the corrosion resistance of austenitic stainless steel. Plasma nitriding experiments were conducted on AISI 304L steel in a temperature range of 375‐475°C using pulsed‐DC plasma with different N ₂‐H ₂ gas mixtures and treatment times. First of all, the formation and the microstructure of the modified layer will be highlighted followed by the results of hardness measurement, adhesion testing, wear resistance and fatigue life tests. In addition the corrosion resistance of the modified layer is described. The microhardness after plasma nitriding is increased by a factor of five compared to the untreated material. The adhesion is examined by Rockwell indentation and scratch test. No delamination of the treated layer could be observed. The wear rate after plasma nitriding is significantly reduced compared to the untreated material. Plasma nitriding produces compressive stress within the modified layer. This treatment improves the fatigue life which can be raised by a factor of ten at a low stress level. The results show that plasma nitriding of austenitic stainless steel is a suitable process for improving the mechanical and the technological properties without significantly effecting the excellent corrosion resistance of this material.