Publications by authors named "Holger Kersten"

Zinc oxide has widespread use in diverse applications due to its distinct properties. Many of these applications benefit from controlling the morphology on the nanoscale, where for example gas sensing is strongly enhanced for high surface-to-volume ratios. In this work the formation of novel ZnO nanobrushes by plasma etching treatment as a new approach is presented.

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Background: The aim of this in vitro study was to identify changes in gene expression of proinflammatory cytokines in human whole blood after contact with titanium implant surfaces after plasma treatment.

Materials And Methods: Grade 4 titanium dental implants were conditioned with low-pressure plasma (LPP) and atmospheric-pressure plasma (APP) and submerged in human whole blood in vitro. Unconditioned implants and blood samples without implants served as control and negative control groups, respectively.

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We present one of the first experiments for optically trapping of single microparticles as probes for low temperature plasma diagnostics. Based on the dual laser beam, counter-propagating technique, SiO microparticles are optically trapped at very large distances in low-temperature, low-pressure rf plasma. External forces on the particle are measured by means of the displacement of the probe particle in the trap.

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Understanding the science and engineering of thin films using plasma assisted deposition methods with controlled growth and microstructure is a key issue in modern nanotechnology, impacting both fundamental research and technological applications. Different plasma parameters like electrons, ions, radical species and neutrals play a critical role in nucleation and growth and the corresponding film microstructure as well as plasma-induced surface chemistry. The film microstructure is also closely associated with deposition energy which is controlled by electrons, ions, radical species and activated neutrals.

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The characterization of plasma and atomic radical parameters along with the energy influx from plasma to the substrate during plasma enhanced chemical vapor deposition (PECVD) of Si quantum dot (QD) films is presented and discussed. In particular, relating to the Si QD process optimization and control of film growth, the necessity to control the deposition environment by inducing the effect of the energy of the key plasma species is realized. In this contribution, we report dual frequency PECVD processes for the low-temperature and high-rate deposition of Si QDs by chemistry and energy control of the key plasma species.

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Objectives: Purpose of this in vitro study was to evaluate the effect of surface modifications on the tensile bond strength between zirconia ceramic and resin.

Methods: Zirconia ceramic surfaces were treated with 150-μm abrasive alumina particles, 150-μm abrasive zirconia particles, argon-ion bombardment, gas plasma, and piranha solution (H2SO4:H2O2=3:1). In addition, slip casting surfaces were examined.

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Statement Of Problem: Creating a rough surface for bonding with airborne-particle abrasion with alumina may damage the surface of zirconia. Other treatment methods for creating a bonding surface without causing damage require investigation.

Purpose: The purpose of this in vitro study was to find ways of treating the zirconia surface without causing flaws, debris, pits, microcracks, or tetragonal to monoclinic phase transformation.

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Controlled self-organized growth of vertically aligned carbon nanocone arrays in a radio frequency inductively coupled plasma-based process is studied. The experiments have demonstrated that the gaps between the nanocones, density of the nanocone array, and the shape of the nanocones can be effectively controlled by the process parameters such as gas composition (hydrogen content) and electrical bias applied to the substrate. Optical measurements have demonstrated lower reflectance of the nanocone array as compared with a bare Si wafer, thus evidencing their potential for the use in optical devices.

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A calorimetric probe for plasma diagnostics is presented, which allows measurements of the power taken by a test substrate. The substrate can be biased and used as an electric probe in order to obtain information about the composition of the total heating power. A new calibration technique for calorimetric probes, which uses monoenergetic electrons at low pressure, has been developed for an improved accuracy.

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A novel experiment for the study of forces on microparticles in ion beams is presented. A broad beam ion source provides a vertically upward directed beam wherein 100 microm hollow glass spheres are injected. The particles are illuminated by a diode laser and recorded with a charge-coupled device camera.

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Temperature sensitive features of particular phosphors were utilized for measuring the temperature T(p) of microparticles, confined in the sheath of a rf plasma. The experiments were performed under variation of argon pressure and rf power of the process plasma. T(p) has been determined by evaluation of characteristic fluorescent lines.

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An interesting aspect in the research of complex (dusty) plasmas is the experimental study of the interaction of nano- and micro-particles with the surrounding plasma for diagnostic purpose. From the behaviour of the particles, local electric fields can be determined ("particles as electrostatic probes"), the energy fluxes towards the particles ("particles as thermal probes"), or reactive processes on surfaces ("particles as micro-substrates") can be studied. The behaviour of particles in front of an adaptive electrode, which allows for an efficient confinement and manipulation of the grains, has been experimentally studied in dependence on the discharge parameters and on different bias conditions of the electrode.

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