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Universität Leipzig, Felix Bloch Institute of Solid State Physics, Faculty Member add
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Plasma Physics, Thin Films and Coatings, Plasma Diagnostics, Ion Beam Modifications, Ion beam analyses, Cathodic Arc Deposition, and 9 moreMagnetron Sputtering, Diamond Like Carbon, Optical Coatings, Smart Materials and Structures, Materials Science, Synthesis of nanoparticles, Physical Vapor Deposition, Plasma Immersion Ion Implantation, and Plasma Sources edit
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Andre Anders is Director of the Leibniz Institute of Surface Engineering (IOM) in Leipzig, Germany, and Professor of ... moreAndre Anders is Director of the Leibniz Institute of Surface Engineering (IOM) in Leipzig, Germany, and Professor of Applied Physics at the University of Leipzig. He assumed these positions after working over 25 years at Lawrence Berkeley National Laboratory, Berkeley, California.
His research interests are in the field of plasmas and materials, especially in arc and magnetron plasmas, plasma diagnostics, HiPIMS, thin films, diamond-like carbon, transparent conducting oxides, electrochromic materials, nanoparticles and nanocomposites.
Since 2014, Andre also serves as the Editor-in-Chief of Journal of Applied Physics. edit
We describe the temporal development of the plasma composition of pulsed aluminum plasma streams at various oxygen pressures. The plasma was formed with a vacuum arc plasma source and the time resolved plasma composition was measured with... more
We describe the temporal development of the plasma composition of pulsed aluminum plasma streams at various oxygen pressures. The plasma was formed with a vacuum arc plasma source and the time resolved plasma composition was measured with time-of-flight charge-to-mass spectrometry. The temporal development of the plasma composition as well as the Al average ion charge state was found to be a strong function of the oxygen pressure. Oxygen and hydrogen concentrations of up to 0.36 and 0.32, respectively, were found in the first 50 mus of the pulse at oxygen pressures of >=5×10-5 Torr. The average charge state of aluminum ions was found to vary from +1.2 to +2.5 depending on the oxygen pressure and the time elapsed after ignition of the arc. These results are of fundamental importance for the understanding of the evolution of the composition (through the plasma composition) and microstructure (through the Al ion flux energy) of alumina thin films produced by pulsed, reactive aluminum plasmas.
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Gallium oxide thin films were grown by ion beam sputter deposition (IBSD) at room temperature on Si substrates with systematically varied process parameters: primary ion energy, primary ion species (O2+ and Ar+), sputtering geometry (ion... more
Gallium oxide thin films were grown by ion beam sputter deposition (IBSD) at room temperature on Si substrates with systematically varied process parameters: primary ion energy, primary ion species (O2+ and Ar+), sputtering geometry (ion incidence angle α and polar emission angle β), and O2 background pressure. No substrate heating was applied because the goal of these experiments was to investigate the impact of the energetic film-forming species on thin film properties. The films were characterized with regard to film thickness, growth rate, crystallinity, surface roughness, mass density, elemental composition and its depth profiles, and optical properties. All films were found to be amorphous with a surface roughness of less than 1 nm. The stoichiometry of the films improved with an increase in the energy of film-forming species. The mass density and the optical properties, including the index of refraction, are correlated and show a dependency on the kinetic energy of the film-forming species. The ranges of IBSD parameters, which are most promising for further improvement of the film quality, are discussed.
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This milestone has been met. In the previous quarter (3rd quarter FY2008), the Heavy Ion Fusion Science Virtual National Laboratory (HIFS-VNL) completed the new experimental target chamber facility for future Warm Dense Matter (WDM)... more
This milestone has been met. In the previous quarter (3rd quarter FY2008), the Heavy Ion Fusion Science Virtual National Laboratory (HIFS-VNL) completed the new experimental target chamber facility for future Warm Dense Matter (WDM) experiments [1]. The target chamber is operational and target experiments are now underway, using beams focused by a final focus solenoid and compressed by an improved bunching waveform. Initial experiments have demonstrated the capability of the Neutralized Drift Compression Experiment (NDCX) beam to heat bulk matter in target foils. The experiments have focused on tuning and characterizing the NDCX beam in the target chamber, implementing the target assembly, and implementing target diagnostics in the target chamber environment. We have completed a characterization and initial optimization of the compressed and uncompressed NDCX beam entering the target chamber. The neutralizing plasma has been significantly improved to increase the beam neutralization in the target chamber. Preliminary results from recent beam tests of a gold cone for concentrating beam energy on target are encouraging and indicate the potential to double beam intensity on target. Other advantages of the cone include the large amount of neutralizing secondary electrons expected from the grazing incidence at the cone walls, and the shielding of the target from the edges of the beam pulse. The first target temperature measurements with the fast optical pyrometer were made on Sep. 12, 2008. The fast optical pyrometer is a unique and significant new diagnostic. These new results demonstrate for the first time beam heating of the target to a temperature well over 2000 K. The initial experimental results are suggestive of potentially interesting physics. The rapid initial rise and subsequent decay of the target temperature during the beam pulse indicate changes in the balance of beam heating and target evaporative cooling, a behavior which may be affected by phenomena such as droplet formation and rapid changes in the optical properties of the hot target material. NDCX, possibly uniquely, is capable of studying these changes because of its wide range of diagnostic capabilities. These capabilities include target diagnostics already in place such as the fast pyrometer and streak camera, as well as the ability to measure both ion beam transmission and optical transmission through the foil. Measurements with these diagnostic techniques can help determine the rate at which the target is breaking up into droplets and the rate at which its bulk optical properties are changing.
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Equations of State, Evaporation, High Voltage, Heavy Ions Physics, Evaporative Cooling, and 15 moreHydrodynamics, Electric Fields, Implementation, Heat Conduction, High Speed, Compression, Dynamic Response, Heating, Emissivity, Experimental Data, Electric Field, Equation of State, Functional Form, Brightness temperature, and Current Transformer
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The magnetic field of a magnetron serves to increase the residence time of electrons in the ionization region and thereby enables the discharge to be sustained at low working gas pressures. This hinders the electrons to reach the anode... more
The magnetic field of a magnetron serves to increase the residence time of electrons in the ionization region and thereby enables the discharge to be sustained at low working gas pressures. This hinders the electrons to reach the anode which is necessary to close the electrical circuit. At high atom densities in the ionization region, and in the presence of an electric field, collisions of electrons with heavy species consecutively push electrons across the magnetic field lines, which is known as the classical cross-field transport mechanism. At low atom densities in the ionization region, collisions are rare and the classical cross-field transport mechanism is insufficient to carry the discharge current. This gives rise to plasma instabilities, called spokes, that locally provide pathways for electrons to escape from the near-target region and across the magnetic field lines. Here, we show experimentally, for the case of a high power impulse magnetron sputtering discharge with an aluminum target, how spokes gradually disappear with the increase in local gas density. We present an analytical model that shows that under these high gas density conditions, the classical electron transport mechanism is indeed strong enough to solely carry the discharge current. This highlights the importance of the local gas density in the ionization region for the intensity of spokes in a magnetron sputtering discharge and suggests ways for process optimization.
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The energy distributions of secondary ions for the ion beam sputtering of a Ga2O3 target using O2+ and Ar+ ions are measured in dependence on various process parameters using energy-selective mass spectrometry. The process parameters... more
The energy distributions of secondary ions for the ion beam sputtering of a Ga2O3 target using O2+ and Ar+ ions are measured in dependence on various process parameters using energy-selective mass spectrometry. The process parameters include sputtering geometry (ion incidence angle α, polar emission angle β, scattering angle γ), the energy of incident ions Eion, and the background pressure of O2. The main secondary ion species are identified to be Ga+, O+, O2+, and, when argon is used as a process gas, Ar+. The changes in the sputtering geometry and the primary ion energy have the most impact on the energy distributions of secondary Ga+ and O+ ions, giving control over the high-energy tail, which is attributed to anisotropy effects in sputtering. The formation of O2+ ions is attributed to collisions with background gas molecules, as their energy distributions are not influenced by the sputtering geometry or the primary ion energy. The increase of the O2 pressure leads to a minor decrease of the energy of Ga+ ions due to collisions with the background gas particles. The use of primary Ar+ ions with O2 background pressure does not show any specific effect on energy distributions of Ga+, O+, and O2+ ions except for the case without additional O2 background. In the latter case, much fewer O+ and O2+ ions are produced indicative of oxygen depletion of the surface due to preferential sputtering of oxygen. At all considered O2 pressures, the energy distributions of Ar+ ions have a high-energy peak, attributed to direct scattering events. The trends in experimental data show qualitative agreement to simulations using the Monte Carlo code SDTrimSP.
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Materials Engineering, Condensed Matter Physics, Materials Science, Copper, Tin, and 12 moreThin Film, Superconductors, Magnetron Sputtering, Niobium, Temperature Distribution, Temperature measurement, Heat Capacity, Stoichiometry, Specific Heat, Particle Acceleration, Electrical And Electronic Engineering, and Critical Temperature
Cathode spots in a magnetically steered arc source were studied under low-pressure noble gas (Ar) and reactive gas (N2, O2) atmospheres. The plasma was observed using a streak camera coupled with a long-distance microscope to study the... more
Cathode spots in a magnetically steered arc source were studied under low-pressure noble gas (Ar) and reactive gas (N2, O2) atmospheres. The plasma was observed using a streak camera coupled with a long-distance microscope to study the evolution of cathode spots with high temporal and spatial resolution. We find two well-known types of cathode spots: “type 1” for less bright spots eroding the compound layer on the cathode surface and bright “type 2” spots on (clean) metallic surfaces. Cathode spots are characterized by a sequence of microexplosions that give the impression of a moving spot, which, in the presence of a magnetic field, is generally in the retrograde direction. However, the apparent displacement can also go in the opposite, the Amperian direction, especially when nitrogen is present. In oxygen, spot ignition often happens in approximately the same location repeatedly. For type 2 spots, we detected an apparent motion mainly in the retrograde direction with distinct jumps to new locations. Via the effects of spot appearance, we note the competing effects of cathode cleaning by spot-induced material removal (erosion) and compound formation in the presence of reactive gas. The streak images were analyzed by fast Fourier transformation, and we found that the arc fluctuations are stochastic without specific frequencies. The colored random noise (CRN) index tends to be reduced in the presence of a compound layer, indicating an enhanced spot ignition probability. A reduced CRN index implies reduced feedback (influence) of previously active spots, which is most apparent in the presence of elevated oxygen pressure.
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The properties of cathode spots in a magnetically steered vacuum arc plasma source were investigated. The cathode spots were observed with a long-distance microscope coupled to a streak camera, where the entrance slit of the camera was... more
The properties of cathode spots in a magnetically steered vacuum arc plasma source were investigated. The cathode spots were observed with a long-distance microscope coupled to a streak camera, where the entrance slit of the camera was aligned with one of the linear sections of the steered arc source. This is a key feature that allows the observation of spots as they appear along the erosion racetrack. The trends of spot motion and patterns in the emitted light were observed with different sweep times. The streak images were analysed by fast Fourier transformation to check for the presence or absence of characteristic features like characteristic spot lifetimes, since their existence remains a disputed issue. We found that the power spectrum of the arc spot fluctuations does not show any specific frequencies or related times, rather, the spot fluctuations have a broad spectrum following a power law (spectral power density versus frequency), which is indicative for the fractal (self-similar) nature of spot processes. Moreover, we show that—at about 300 MHz under our conditions—we reach the ultimate temporal resolution limit of the method, which is associated with the finite lifetime of excited atomic and ion states. This is a fundamental limit given by the physics of atoms and ions, not a measurement flaw. The temporal resolution limit of about 3 ns also implies a spatial resolution limit of order of a few μm given that radiating species move laterally to the observation direction with at least 103 m s−1.
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The plasma of a hollow-cathode glow discharge with an additional magnetic field was investigated using probes in the ion saturation regime. It was experimentally shown that the application of a magnetic field leads to the formation of a... more
The plasma of a hollow-cathode glow discharge with an additional magnetic field was investigated using probes in the ion saturation regime. It was experimentally shown that the application of a magnetic field leads to the formation of a rotating region of enhanced plasma density when the field exceeds a threshold value, which depends on the kind of gas. Three gases were used (N2, Ar, and Kr) for the experiments. The experiments showed that the higher the atomic mass the higher the threshold magnetic field. The plasma density in the region of enhanced density is about a factor 4-6 higher than the initial density at threshold for otherwise constant parameters. Plasma rotation was observed when the ion Larmor radius was equal to or smaller than the hollow cathode radius. The rotation frequency is of the order of 10 kHz and could be correlated to the ion cyclotron frequency. The rotation frequency increased linearly with magnetic field and reversed direction when the direction of the magnetic field was reversed. Higher discharge current, higher gas pressure, and heavier working gas reduced the plasmarotation frequency. The plasmarotation caused a modulation of ion current extracted from the anode region. A preliminary analysis of characteristic parameters indicated that not only ion gyration but also ExB drift of the guiding center of magnetized electrons may play a crucial role. In the cylindrical hollow cathode geometry, ion gyration and ExB drift of the guiding center of magnetized electron shave the same sense, and a resonance may develop. The exact nature of such resonance is not clear at this time, and future theoretical investigations are needed to explain collisional and other mechanisms in detail.
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Abstract The cathode spot behavior influences the arc plasma chemistry and film growth conditions during reactive cathodic arc deposition of nitride and oxide films. Cathode spots can be studied using their characteristic craters left... more
Abstract The cathode spot behavior influences the arc plasma chemistry and film growth conditions during reactive cathodic arc deposition of nitride and oxide films. Cathode spots can be studied using their characteristic craters left behind on the cathode surface. The multilayer cathode design used in this study reveals temporal and spatial progress of cathode spots by enabling three-dimensional visualization of the craters. The surface nitridation or oxidation of the cathode, also known as cathode poisoning, was found to give rise to a repeated switching between cathode spots of type 1 and 2. The surface oxide layers, however, more significantly promote the ignition of type 1 spots due to their thermodynamically privileged formation and/or their more favorable physical properties building up a stronger electric field within the insulating layer. The crater depths and their contribution to the surface modification of multilayered cathodes are discussed in detail. These results may contribute to a better understanding of macroparticle generation and arc plasma properties in cathodic arc deposition processes.
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Physical vapor deposition (PVD) refers to the removal of atoms from a solid or a liquid by physical means, followed by deposition of those atoms on a nearby surface to form a thin film or coating. Various approaches and techniques are... more
Physical vapor deposition (PVD) refers to the removal of atoms from a solid or a liquid by physical means, followed by deposition of those atoms on a nearby surface to form a thin film or coating. Various approaches and techniques are applied to release the atoms including thermal evaporation, electron beam evaporation, ion-driven sputtering, laser ablation, and cathodic arc-based emission. Some of the approaches are based on a plasma discharge, while in other cases the atoms composing the vapor are ionized either due to the release of the film-forming species or they are ionized intentionally afterward. Here, a brief overview of the various PVD techniques is given, while the emphasis is on sputtering, which is dominated by magnetron sputtering, the most widely used technique for deposition of both metallic and compound thin films. The advantages and drawbacks of the various techniques are discussed and compared.
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In its simplest implementation, sputtering is done with a container filled with a gas, such as argon. On one side of the container one places a source material, known as the target , and on the other side the so-called substrate, which is... more
In its simplest implementation, sputtering is done with a container filled with a gas, such as argon. On one side of the container one places a source material, known as the target , and on the other side the so-called substrate, which is the surface one wants to process. A high ...