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Ion Bombardment (ion + bombardment)
Selected AbstractsEffect of Ion Bombardment on the Characteristics of Ti Based Biocompatible CoatingsPLASMA PROCESSES AND POLYMERS, Issue S1 2007Alina Vladescu Abstract TiN and TiAlN coatings were deposited on CoCr alloy, 316L stainless steel, and Si substrates by cathodic arc method. Various ion bombardment conditions were obtained by different DC and pulsed bias voltages applied on the substrates. A comparative analysis of the coating characteristics for different substrate biasing conditions was performed. [source] Dynamic Magnetic Properties of Ferroic Films, Multilayers, and Patterned ElementsADVANCED FUNCTIONAL MATERIALS, Issue 15 2010Robert L. Stamps Abstract Modification and control of material properties through careful manipulation of geometry on nano- and sub-nanometer length scales is a cornerstone of modern materials science and technology. An exciting area in which these concepts have provided exceptional advances has been magnetoelectronics and nanomagnetism. Important scales in magnetic metals are conduction spin diffusion lengths and distances over which local moments correlate. Advanced techniques now allow for the creation of structures patterned on these length scales in three dimensions. The focus of this article is on magnetic structures whose dynamic properties can be strongly modified by ion bombardment and lithographic patterning. Examples are given of how microwave frequency properties can be tuned with external fields, how factors controlling magnetic switching can be controlled, and how manipulation of magnetic domain walls can be used to reveal new and surprising phenomena. [source] Heat-Transport Mechanisms in SuperlatticesADVANCED FUNCTIONAL MATERIALS, Issue 4 2009Yee Kan Koh Abstract The heat transport mechanisms in superlattices are identified from the cross-plane thermal conductivity , of (AlN)x,(GaN)y superlattices measured by time-domain thermoreflectance. For (AlN)4.1 nm,(GaN)55,nm superlattices grown under different conditions, , varies by a factor of two; this is attributed to differences in the roughness of the AlN/GaN interfaces. Under the growth condition that gives the lowest ,, , of (AlN)4 nm,(GaN)y superlattices decreases monotonically as y decreases, ,,=,6.35,W m,1 K,1 at y,=,2.2,nm, 35 times smaller than , of bulk GaN. For long-period superlattices (y,>,40,nm), the mean thermal conductance G of AlN/GaN interfaces is independent of y, G,,,620 MW m,2 K,1. For y,<,40,nm, the apparent value of G increases with decreasing y, reaching G,,,2 GW m,2 K,1 at y,<,3,nm. MeV ion bombardment is used to help determine which phonons are responsible for heat transport in short period superlattices. The thermal conductivity of an (AlN)4.1 nm,(GaN)4.9,nm superlattice irradiated by 2.3 MeV Ar ions to a dose of 2,×,1014 ions cm,2 is reduced by <35%, suggesting that heat transport in these short-period superlattices is dominated by long-wavelength acoustic phonons. Calculations using a Debye-Callaway model and the assumption of a boundary scattering rate that varies with phonon-wavelength successfully capture the temperature, period, and ion-dose dependence of ,. [source] Bioimaging TOF-SIMS of tissues by gold ion bombardment of a silver-coated thin sectionMICROSCOPY RESEARCH AND TECHNIQUE, Issue 6 2004Håkan Nygren Abstract The imaging time-of-flight secondary-ion-mass-spectrometry (TOF-SIMS) method was utilized to address the problem of cholesterol localization in rat tissues. Rat kidneys were fixed, cryoprotected by sucrose, frozen, sectioned by cryoultramicrotomy, and dried at room temperature. The samples were either covered with a thin silver layer or analyzed uncovered in an imaging TOF-SIMS instrument equipped with an Au -source. The yield of desorbed secondary ions for some species was up to 600-fold higher after silver coating of the samples. Reference samples of cholesterol were silver-coated and analyzed by TOF-SIMS to define significant peaks, specific for cholesterol. Such peaks were found at m/z = 386 (C27H46O+), m/z = 493 (C27H46O107Ag+), m/z = 495 (C27H46O109Ag+), m/z = 879 (C54H92O2107Ag+), and m/z = 881 (C54H92O2109Ag+). The silver-cationized cholesterol (493 , m/z , 495) signal was localized by imaging TOF-SIMS in the kidney sections and showed a high cholesterol content in the kidney glomeruli. A more diffuse distribution of cholesterol was also found over areas representing the cytoplasm or plasma membrane of the epithelial cells in the proximal tubules of rat kidney. Microsc. Res. Tech. 65:282,286, 2004. © 2005 Wiley-Liss, Inc. [source] Hg3In2Te6 -based photodiodes for fiber optic communicationPHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 2 2009L. A. Kosyachenko Abstract Schottky barrier photodiodes obtained by vacuum evaporation of the semi-transparent film over the surface of single crystalline Hg3In2Te6 substrates pre-treated by Ar ion bombardment. The responsivity maximum of the photodiodes is at the wavelength of 1.55 ,m, corresponding to the transmission window in silica glass fiber with the minimal optical losses. The dark current in the diodes is determined by generation-recombination processes in the space-charge region and quantitatively governed by the Sah,Noyce,Shockley theory. A comparison of the photoelectric parameters of Hg3In2Te6 and Ge photodiodes is reported. The speed of the photodiode response is in the range 10,8 s to 10,7 s. (© 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Silver nanocluster containing diamond like carbonPHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 4 2008F. Schwarz Abstract Applying Diamond Like Carbon (DLC) as medical coating has become well established since large scale plasma processes like Plasma Immersion Ion Implantation and Deposition (PIII&D) are available. Now the focus of research lies on systematic modification of certain biological relevant properties and the most recent field of interest turned to generating antimicrobial behaviour. This is desirable for medical tools as well as for different types of medical implants. Since silver and copper are known to provide a bactericidal effect, one tries to introduce clusters of these noble metals into the carbon matrix. The basic principle of the method presented is to convert a metal containing polymer film into DLC by ion bombardment. In this paper the hydrogenated DLC matrix is characterized and the evolution of the metal particles is studied. By means of film composition (RBS/ERD), bonding structure (Raman spectroscopy) and hardness (nanoindentation), the dependency of these material properties on ion species, energy and fluence is investigated. TEM imaging is used to visualize the film structure. Upon ion irradiation of the polymer films, increased density and considerable loss of hydrogen can be observed, which both are controlled by ion fluence and mass. The crosslinking of the carbon network, caused by hydrogen drive out as well as atomic displacements in collision cascades, results in the formation of a-C:H. The silver particles in the film some ion induced growth, but still remain as nanoclusters in the a-C:H matrix. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Reactive magnetron sputtering of highly (001)-textured WS2,x films: Influence of Ne+, Ar+ and Xe+ ion bombardment on the film growthPHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 3 2006K. Ellmer Abstract Layer-type van der Waals semiconductor WS2,x films were grown by radio frequency reactive magnetron sputtering from a metallic tungsten target onto oxidized silicon substrates. The sputtering atmosphere consisted of 75% hydrogen sulfide and 25% neon, argon or xenon. The substrate voltage and hence the energy of the ions bombarding the growing film, was varied from about 20 V (floating potential) to ,80 V. By in situ energy-dispersive X-ray diffraction the growth of the films was monitored and by elastic recoil detection analysis the film composition was measured. It was found that with xenon in the sputtering atmosphere a substrate voltage of ,20 V is sufficient to suppress the crystalline film growth, while for argon as the sputtering rare gas this occurs only at ,80 V. The disturbed film growth is accompanied by a sulfur loss of the growing WS2,x films down to x = 1.1 for sputtering in Ar + H2S at a substrate potential of ,60 V. The results are tentatively explained by the different momentum transfers to sulfur atoms, which is highest for argon ions. It has also to be taken into account that the low-energy xenon bombardment is a many-body cascade process with a much higher local energy density compared to argon and neon bombardment and leading to a higher defect density and a supression of the crystalline growth. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Characterisation and cleaning of oxide support materials for cavity ring-down spectroscopyPHYSICA STATUS SOLIDI (B) BASIC SOLID STATE PHYSICS, Issue 5 2010Aras Kartouzian Abstract Cavity ring-down spectroscopy (CRDS) has been applied to characterise different oxide materials (amorphous silica, borosilicate and yttria stabilised zirconia YSZ) which are suitable to be used as support material for size-selected metal clusters. The sensitivity of the spectroscopic method was improved by means of transversal mode matching and spatial filtering of the laser beam profile, reducing the relative error by 50%. The high sensitivity of CRDS allows the detection of trace amounts of impurities and defect sites in the samples, based on their absorption properties. In YSZ, traces of Nd have been detected. The optical quality of the substrates was determined qualitatively according to the measured optical losses. CRDS surface maps have been used to monitor the homogeneity of the support materials, and the influence of ion bombardment on the surface has been studied. It is shown that in the case of BK7® substrates, sputtering with low energy Ar+ ions could remove deposited gold clusters almost completely causing very low damage to the surface. These results were confirmed analytically. [source] Effect of growth conditions on grown-in defect formation and luminescence efficiency in Ga(In)NP epilayers grown by molecular-beam epitaxyPHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 2 2008D. Dagnelund Abstract A detailed study of the impact of different growth conditions (i.e. ion bombardment, nitrogen flow and In content) on the defect formation in Ga(In)NP epilayers grown on GaP substrates by solid-source molecular beam epitaxy is performed. Reduced nitrogen ion bombardment during the growth is shown to significantly reduce formation of defects acting as competing recombination centers, such as a Ga interstitial defect and other unidentified defects revealed by optically detected magnetic resonance. Further, high nitrogen flow is found to be even more effective than the ion bombardment in introducing the defects. The incorporation of In by 5.1% is, on the other hand, found not to affect the introduction of defects. The results provide a useful insight into the formation mechanism of the defects that will hopefully shed light on a control of the defect introduction in the alloys by optimizing growth conditions. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Plasma-Assisted Atomic Layer Deposition of Al2O3 at Room TemperaturePLASMA PROCESSES AND POLYMERS, Issue S1 2009Tommi O. Kääriäinen Abstract A new design of plasma source has been used for the plasma-assisted atomic layer deposition (PA-ALD) of Al2O3 films at room temperature. In this PA-ALD reactor the plasma is generated by capacitive coupling directly in the deposition chamber adjacent to the substrate but can be separated from it by a grid to reduce the ion bombardment while maintaining the flow of radicals directly to the substrate surface. During the ALD cycle a mixture of nitrogen and argon was introduced into the reactor to act as a purge gas between precursor pulses and to facilitate the generation of a plasma during the plasma cycle. Sequential exposures of TMA and excited O2 precursors were used to deposit Al2O3 films on Si(100) substrates. A plasma discharge was activated during the oxygen gas pulse to form radicals in the reactor space. The experiments showed that the growth rate of the film increased with increasing plasma power and with increasing O2 pulse length before saturating at higher power and longer O2 pulse length. The growth rate saturated at the level of 1.78 Å·cycle,1. EDS analysis showed that the films were oxygen rich and had carbon as an impurity. This can be explained by the presence of bonds between hydrocarbons from the unreacted TMA precursor and excess oxygen in the film. ATR-FTIR spectroscopy measurements indicated a change in growth mechanism when the distance between the location of the radical generation and the substrate was varied. A similar effect was observed with the use of different plasma power levels. [source] Effect of Substrate Temperature and RF Biasing on the Optical Properties of Titania-Like Thin Films Obtained by Plasma Enhanced Chemical Vapor DepositionPLASMA PROCESSES AND POLYMERS, Issue S1 2009Axel Sonnenfeld Abstract A low pressure radio frequency (RF) discharge (200,W) was operated in argon/oxygen with small admixtures of titanium(IV)isopropoxide (TTIP). By regulating the cooling temperature of the RF driven electrode, the influence of the substrate temperature and of the ion bombardment caused by the negative DC self-bias of the RF electrode was investigated comparatively. Thin titania-like films were obtained and characterized with respect to their cut-off wavelength and their spectral absorption coefficient in the UV range. Accordingly, the cut-off wavelength was found to be higher for films obtained on the DC-self-biased electrode. Here, its value appears independent of the substrate temperature and attained successively its maximum at 340,nm with deposition time. Furthermore, the absorption coefficients of films deposited on the DC self-biased electrode are well superior to those obtained on the grounded substrate holder. [source] Deposition of Cubic Boron Nitride in a Supersonic Plasma Jet Reactor with Secondary DischargePLASMA PROCESSES AND POLYMERS, Issue S1 2007Jami McLaren Abstract We have deposited cubic boron nitride thin films with a supersonic plasma jet chemical vapor deposition system with bipolar pulsed substrate bias. Deposited films were characterized by Fourier transform infrared spectroscopy, micro-X-ray diffraction, and scanning electron microscopy. The cubic boron nitride content is observed to scale well with the degree of ion bombardment of the substrate and growing film, which is affected most drastically by the substrate bias pulse frequency, and positive and negative duty cycle. The magnitude of the negative substrate bias was also critical in depositing cubic boron nitride, with a threshold voltage of approximately 90 V necessary for cubic boron nitride deposition. [source] Molecular depth profiling of multilayer structures of organic semiconductor materials by secondary ion mass spectrometry with large argon cluster ion beamsRAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 20 2009Satoshi Ninomiya In this study, we present molecular depth profiling of multilayer structures composed of organic semiconductor materials such as tris(8-hydroxyquinoline)aluminum (Alq3) and 4,4,-bis[N -(1-naphthyl)- N -phenylamino]biphenyl (NPD). Molecular ions produced from Alq3 and NPD were measured by linear-type time-of-flight (TOF) mass spectrometry under 5.5,keV Ar700 ion bombardment. The organic multilayer films were analyzed and etched with large Ar cluster ion beams, and the interfaces between the organic layers were clearly distinguished. The effect of temperature on the diffusion of these materials was also investigated by the depth profiling analysis with Ar cluster ion beams. The thermal diffusion behavior was found to depend on the specific materials, and the diffusion of Alq3 molecules was observed to start at a lower temperature than that of NPD molecules. These results prove the great potential of large gas cluster ion beams for molecular depth profiling of organic multilayer samples. Copyright © 2009 John Wiley & Sons, Ltd. [source] Cluster ion beam profiling of organics by secondary ion mass spectrometry , does sodium affect the molecular ion intensity at interfaces?RAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 24 2008Felicia M. Green The use of cluster ion beam sputtering for depth profiling organic materials is of growing technological importance and is a very active area of research. At the 44th IUVSTA Workshop on "Sputtering and Ion Emission by Cluster Ion Beams", recent results were presented of a cluster ion beam depth profile of a thin organic molecular layer on a silicon wafer substrate. Those data showed that the intensity of molecular secondary ions is observed to increase at the interface and this was explained in terms of the higher stopping power in the substrate and a consequently higher sputtering yield and even higher secondary ion molecular sputtering yield. An alternative hypothesis was postulated in the workshop discussion which may be paraphrased as: "under primary ion bombardment of an organic layer, mobile ions such as sodium may migrate to the interface with the inorganic substrate and this enhancement of the sodium concentration increases the ionisation probability, so increasing the molecular ion yield observed at the interface". It is important to understand if measurement artefacts occur at interfaces for quantification as these are of great technological relevance , for example, the concentration of drug in a drug delivery system. Here, we evaluate the above hypothesis using a sample that exhibits regions of high and low sodium concentration at both the organic surface and the interface with the silicon wafer substrate. There is no evidence to support the hypothesis that the probability of molecular secondary ion ionisation is related to the sodium concentration at these levels. © Crown copyright 2008. Reproduced with the permission of Her Majesty's Stationery Office. Published by John Wiley & Sons, Ltd. [source] | |||||||||||||